Patent Description:
Fuselages and wings of aircraft can include structural stiffeners, such as stringers, to help the fuselage and wings maintain their shape under various stress and strain conditions. The size, shape, and/or configuration of a stringer can impact one or more performance attribute(s) associated with the stringer. For example, the size, shape, and/or configuration of a stringer coupled to a composite structure of an aircraft such as a skin of a fuselage or wing can affect the impact strength, the crippling strength, and/or the buckling strength associated with the stringer. The size, shape, and/or configuration of the stringer can also affect the potential for thermal cracking and/or wrinkle formation within the stringer. <CIT> states, according to its abstract, systems and methods provide for edge protection and visual damage indication for a composite blade stringer. According to one aspect, an edge protection and visual indication system may be an edge treatment provided over an outer edge of a web of a composite blade stringer. The edge treatment may include a number of material layers encompassing the outer edge of the web and extending from a first <NUM> surface of the web to a second surface of the web. The material layers may include a color contrasting layer and fiberglass layers. The material layers may alternatively include two overlapping, pre-cured angles. <CIT> discloses a stringer comprising a blade and a pair of flanges. The stringer is formed by a process wherein, in a first step, a planar charge is placed on a male forming tool. The charge comprises a laminate structure formed from a stack of sheets, each sheet comprising a plurality of unidirectional carbon fibres impregnated by a thermosetting epoxy resin. These sheets are conventionally known as "prepregs". The charge is then deformed over the mould tool to form a U-shaped part. The U-shaped part is then cut into two L-shaped parts, and the parts are placed back-to-back. Once the L-shaped parts have been placed back-to-back, they are co-cured to harden the stringer and join the parts together.

According to the present disclosure, a method, and a composite blank as defined in the independent claims are provided. Further embodiments of the claimed invention are defined in the dependent claims. Although the claimed invention is only defined by the claims, the below embodiments, examples, and aspects are present for assisting in understanding the background and advantages of the claimed invention. Aircraft stringers having CFRP material reinforced flanges are disclosed. A stringer to be coupled to a skin of an aircraft is disclosed. The stringer comprises a flange. The flange includes a first portion of a first stiffening segment. The flange also includes a first portion of a second stiffening segment coupled to the first portion of the first stiffening segment. The flange also includes a CFRP reinforcement segment coupled to the first portion of the first stiffening segment and to the first portion of the second stiffening segment. The CFRP reinforcement segment is to strengthen the first portion of the first stiffening segment and the first portion of the second stiffening segment. The first stiffening segment and the second stiffening segment are formed from a first composite blank. The CFRP reinforcement segment is formed from a second composite blank. At least one of the first composite blank and the second composite blank, or both, includes a stack and/or layup of plies and has a chordwise ply drop ratio between three and thirty, and a spanwise ply drop ratio between one hundred twenty and three hundred. The chordwise ply drop ratio is calculated as the ratio of a chordwise stagger distance of the plies to a thickness of individual ones of the plies. The spanwise ply drop ratio is calculated as the ratio of a spanwise stagger distance of the plies to the thickness of individual ones of the plies. The chordwise stagger distance and the spanwise stagger distance are implemented between successively-layered ones of the plies.

A method of manufacturing a stringer for an aircraft is disclosed. The method comprises forming first and second stiffening segments from a first composite blank. The method further comprises coupling a first portion of the first stiffening segment to a first portion of the second stiffening segment. The method further comprises forming a CFRP reinforcement segment from a second composite blank. The method further comprises coupling the CFRP reinforcement segment to the first portion of the first stiffening segment and to the first portion of the second stiffening segment. The CFRP reinforcement segment is to strengthen the first portion of the first stiffening segment and the first portion of the second stiffening segment. At least one of the first composite blank and the second composite blank, or both, includes a stack and/or layup of plies and has a chordwise ply drop ratio between three and thirty and a spanwise ply drop ratio between one hundred twenty and three hundred. The chordwise ply drop ratio is calculated as the ratio of a chordwise stagger distance of the plies to a thickness of individual ones of the plies. The spanwise ply drop ratio is calculated as the ratio of a spanwise stagger distance of the plies to the thickness of individual ones of the plies. The chordwise stagger distance and the spanwise stagger distance are implemented between successively-layered ones of the plies.

Certain examples are shown in the above-identified figures and described in detail below. In describing these examples, like or identical reference numbers are used to identify the same or similar elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic for clarity and/or conciseness.

As discussed above, fuselages and wings of aircraft can include stringers to help the fuselage and wings maintain their shape under various stress and strain conditions. <FIG> illustrates an aircraft <NUM> in which one or more stringer(s) can be implemented. The aircraft <NUM> of <FIG> includes a fuselage <NUM>, which can enclose a passenger cabin and/or a cargo area. The fuselage <NUM> can include a skin and stringers coupled to the skin. The stringers provide structural support to the skin of the fuselage <NUM>. The fuselage <NUM> can be a multi-ply composite fuselage <NUM> such as a CFRP fuselage. Alternatively, the fuselage <NUM> can be made of a different type of material.

The aircraft <NUM> of <FIG> further includes wings <NUM> (e.g., a right wing and a left wing) extending laterally outward from the fuselage <NUM>. The wings <NUM> can also include stringers to provide structural support to a skin of the wings <NUM>. The wings <NUM> can be made of substantially the same composite material as the composite fuselage <NUM>. Alternatively, the wings <NUM> can be made of a different type of material.

The size, shape, and/or configuration of a stringer coupled to the skin of the fuselage <NUM> or to the skin of one of the wings <NUM> of the aircraft <NUM> of <FIG> can impact one or more performance attribute(s) associated with the stringer. For example, the size, shape, and/or configuration of the stringer can affect the impact strength, the crippling strength, and/or the buckling strength associated with the stringer. The size, shape, and/or configuration of the stringer can also affect the potential for thermal cracking and/or wrinkle formation within the stringer.

Before describing the details of the disclosed stringers having CFRP material reinforced flanges, a description of a known stringer is provided herein for context. <FIG> illustrates a known stringer <NUM>. The stringer <NUM> of <FIG> is coupled (e.g., joined, bonded, adhered, etc.) to a skin <NUM> of an aircraft (e.g., a skin of the aircraft <NUM> of <FIG>). The stringer <NUM> includes a first stiffening segment <NUM>, a second stiffening segment <NUM>, a base segment <NUM>, a filler area <NUM>, a filler <NUM>, a first flange <NUM>, a second flange <NUM>, a third flange <NUM>, and an end cap <NUM>.

The first stiffening segment <NUM> of the stringer <NUM> of <FIG> includes a first surface <NUM> and a second surface <NUM> located opposite the first surface <NUM>. The first surface <NUM> of the first stiffening segment <NUM> faces and/or is oriented away from the second stiffening segment <NUM> and/or the base segment <NUM> of the stringer <NUM>. The second surface <NUM> of the first stiffening segment <NUM> faces and/or is oriented toward the second stiffening segment <NUM> and/or the base segment <NUM> of the stringer <NUM>. The first stiffening segment <NUM> includes and/or is formed from multiple plies of material sandwiched between the first and second surfaces <NUM>, <NUM> of the first stiffening segment <NUM>.

The first stiffening segment <NUM> of <FIG> further includes a first portion <NUM>, a second portion <NUM> oriented at an angle to the first portion <NUM> of the first stiffening segment <NUM>, and a third portion <NUM> extending between the first portion <NUM> and the second portion <NUM> of the first stiffening segment <NUM>. The second portion <NUM> of the first stiffening segment <NUM> is substantially perpendicular to the first portion <NUM> of the first stiffening segment <NUM>. Based on the orientation of the stringer <NUM> illustrated in <FIG>, the first portion <NUM> of the first stiffening segment <NUM> is oriented vertically, and the second portion <NUM> of the first stiffening segment <NUM> is oriented horizontally. The first and second portions <NUM>, <NUM> of the first stiffening segment <NUM> are substantially linear, and the third portion <NUM> of the first stiffening segment <NUM> is curved and/or non-linear.

The first stiffening segment <NUM> of <FIG> further includes a first end <NUM> formed by the first portion <NUM> of the first stiffening segment <NUM>, and a second end <NUM> formed by the second portion <NUM> of the first stiffening segment <NUM>. The first end <NUM> of the first stiffening segment <NUM> has a flat edge <NUM> (e.g., a zero-degree chamfered edge) extending between the first and second surfaces <NUM>, <NUM> of the first stiffening segment <NUM>. The second end <NUM> of the first stiffening segment <NUM> has an angled edge <NUM> (e.g., a forty-five-degree chamfered edge) extending between the first and second surfaces <NUM>, <NUM> of the first stiffening segment <NUM>.

The third portion <NUM> of the first stiffening segment <NUM> has a curvature defined by a radius of curvature <NUM> measured along the second surface <NUM> of the first stiffening segment <NUM> over the span of the third portion <NUM>. The first stiffening segment <NUM> has a thickness <NUM> measured between the first and second surfaces <NUM>, <NUM> of the first stiffening segment <NUM>. The thickness <NUM> of the first stiffening segment <NUM> is substantially constant and/or uniform among and/or over the first, second and third portions <NUM>, <NUM>, <NUM> of the first stiffening segment <NUM>. The radius of curvature <NUM> of the first stiffening segment <NUM> of <FIG> is approximately twelve millimeters (<NUM>). The thickness <NUM> of the first stiffening segment <NUM> of <FIG> is approximately six millimeters (<NUM>).

The second stiffening segment <NUM> of the stringer <NUM> of <FIG> is constructed and/or implemented as a mirror image of the first stiffening segment <NUM> of the stringer <NUM>. The second stiffening segment <NUM> of <FIG> includes a first surface <NUM> and a second surface <NUM> located opposite the first surface <NUM>. The first surface <NUM> of the second stiffening segment <NUM> faces and/or is oriented away from the first stiffening segment <NUM> and/or the base segment <NUM> of the stringer <NUM>. The second surface <NUM> of the second stiffening segment <NUM> faces and/or is oriented toward the first stiffening segment <NUM> and/or the base segment <NUM> of the stringer <NUM>. The second stiffening segment <NUM> includes and/or is formed from multiple plies of material sandwiched between the first and second surfaces <NUM>, <NUM> of the second stiffening segment <NUM>.

The second stiffening segment <NUM> of <FIG> further includes a first portion <NUM>, a second portion <NUM> oriented at an angle to the first portion <NUM> of the second stiffening segment <NUM>, and a third portion <NUM> extending between the first portion <NUM> and the second portion <NUM> of the second stiffening segment <NUM>. The second portion <NUM> of the second stiffening segment <NUM> is substantially perpendicular to the first portion <NUM> of the second stiffening segment <NUM>. Based on the orientation of the stringer <NUM> illustrated in <FIG>, the first portion <NUM> of the second stiffening segment <NUM> is oriented vertically, and the second portion <NUM> of the second stiffening segment <NUM> is oriented horizontally. The first and second portions <NUM>, <NUM> of the second stiffening segment <NUM> are substantially linear, and the third portion <NUM> of the second stiffening segment <NUM> is curved and/or non-linear.

The second stiffening segment <NUM> of <FIG> further includes a first end <NUM> formed by the first portion <NUM> of the second stiffening segment <NUM>, and a second end <NUM> formed by the second portion <NUM> of the second stiffening segment <NUM>. The first end <NUM> of the second stiffening segment <NUM> has a flat edge <NUM> (e.g., a zero-degree chamfered edge) extending between the first and second surfaces <NUM>, <NUM> of the second stiffening segment <NUM>. The second end <NUM> of the second stiffening segment <NUM> has an angled edge <NUM> (e.g., a forty-five-degree chamfered edge) extending between the first and second surfaces <NUM>, <NUM> of the second stiffening segment <NUM>.

The third portion <NUM> of the second stiffening segment <NUM> has a curvature defined by a radius of curvature <NUM> measured along the second surface <NUM> of the second stiffening segment <NUM> over the span of the third portion <NUM>. The second stiffening segment <NUM> has a thickness <NUM> measured between the first and second surfaces <NUM>, <NUM> of the second stiffening segment <NUM>. The thickness <NUM> of the second stiffening segment <NUM> is substantially constant and/or uniform among and/or over the first, second and third portions <NUM>, <NUM>, <NUM> of the second stiffening segment <NUM>. The radius of curvature <NUM> of the second stiffening segment <NUM> of <FIG> is approximately twelve millimeters (<NUM>). The thickness <NUM> of the second stiffening segment <NUM> of <FIG> is approximately six millimeters (<NUM>). Thus, the radius of curvature <NUM> and the thickness <NUM> of the second stiffening segment <NUM> of <FIG> are equal to corresponding ones of the radius of curvature <NUM> and the thickness <NUM> of the first stiffening segment <NUM> of <FIG> described above.

The base segment <NUM> of the stringer <NUM> of <FIG> includes a first surface <NUM> and a second surface <NUM> located opposite the first surface <NUM>. The first surface <NUM> of the base segment <NUM> faces and/or is oriented toward the first stiffening segment <NUM> and/or the second stiffening segment <NUM> of the stringer <NUM>. The second surface <NUM> of the base segment <NUM> faces and/or is oriented away from the first stiffening segment <NUM> and/or the second stiffening segment <NUM> of the stringer <NUM>. The base segment <NUM> includes and/or is formed from multiple plies of material sandwiched between the first and second surfaces <NUM>, <NUM> of the base segment <NUM>.

The base segment <NUM> of <FIG> further includes a first portion <NUM>, a second portion <NUM> located opposite the first portion <NUM> of the base segment <NUM>, and a third portion <NUM> extending between the first portion <NUM> and the second portion <NUM> of the base segment <NUM>. The first, second and third portions <NUM>, <NUM>, <NUM> of the base segment <NUM> are aligned and/or are substantially parallel to one another. Based on the orientation of the stringer <NUM> illustrated in <FIG>, each of the first, second and third portions <NUM>, <NUM>, <NUM> of the base segment <NUM> is oriented horizontally.

The base segment <NUM> of <FIG> further includes a first end <NUM> formed by the first portion <NUM> of the base segment <NUM>, and a second end <NUM> formed by the second portion <NUM> of the base segment <NUM>. The first end <NUM> of the base segment <NUM> has an angled edge <NUM> (e.g., a forty-five-degree chamfered edge) extending between the first and second surfaces <NUM>, <NUM> of the base segment <NUM>. The second end <NUM> of the base segment <NUM> also has an angled edge <NUM> (e.g., a forty-five-degree chamfered edge) extending between the first and second surfaces <NUM>, <NUM> of the base segment <NUM>.

The base segment <NUM> has a thickness <NUM> measured between the first and second surfaces <NUM>, <NUM> of the base segment <NUM>. The thickness <NUM> of the base segment <NUM> is substantially constant and/or uniform among and/or over the first, second and third portions <NUM>, <NUM>, <NUM> of the base segment <NUM>. The thickness <NUM> of the base segment <NUM> of <FIG> is approximately six millimeters (<NUM>). Thus, the thickness <NUM> of the base segment <NUM> is equal to corresponding ones of the thickness <NUM> of the first stiffening segment <NUM> and the thickness <NUM> of the second stiffening segment <NUM> of <FIG> described above.

The filler area <NUM> of the stringer <NUM> of <FIG> includes a cross-sectional area <NUM> that is generally defined and/or bounded by the third portion <NUM> of the first stiffening segment <NUM>, the third portion <NUM> of the second stiffening segment <NUM>, and the third portion <NUM> of the base segment <NUM> of <FIG> described above. The filler <NUM> is located within the filler area <NUM> and is retained therein. The cross-sectional area <NUM> of the filler area <NUM> and/or the filler <NUM> of <FIG> is approximately sixty-two square millimeters (<NUM><NUM>).

The first portion <NUM> of the second stiffening segment <NUM> of <FIG> is coupled (e.g., joined, bonded, adhered, etc.) to the first portion <NUM> of the first stiffening segment <NUM> of <FIG> described above. More specifically, the second surface <NUM> of the second stiffening segment <NUM> over the span of the first portion <NUM> of the second stiffening segment <NUM> of <FIG> is coupled to the second surface <NUM> of the first stiffening segment <NUM> over the span of the first portion <NUM> of the first stiffening segment <NUM> of <FIG>.

The first portion <NUM> of the base segment <NUM> of <FIG> is coupled (e.g., joined, bonded, adhered, etc.) to the second portion <NUM> of the first stiffening segment <NUM> of <FIG> described above. More specifically, the first surface <NUM> of the base segment <NUM> along the span of the first portion <NUM> of the base segment <NUM> of <FIG> is coupled to the second surface <NUM> of the first stiffening segment <NUM> over the span of the second portion <NUM> of the first stiffening segment <NUM> of <FIG>.

The second portion <NUM> of the base segment <NUM> of <FIG> is coupled (e.g., joined, bonded, adhered, etc.) to the second portion <NUM> of the second stiffening segment <NUM> of <FIG> described above. More specifically, the first surface <NUM> of the base segment <NUM> along the span of the second portion <NUM> of the base segment <NUM> of <FIG> is coupled to the second surface <NUM> of the second stiffening segment <NUM> along the span of the second portion <NUM> of the second stiffening segment <NUM> of <FIG>.

The first, second and third portions <NUM>, <NUM>, <NUM> of the base segment <NUM> of <FIG> are coupled (e.g., joined, bonded, adhered, etc.) to the skin <NUM> of <FIG> described above. More specifically, the second surface <NUM> of the base segment <NUM> along the span of the first, second and third portions <NUM>, <NUM>, <NUM> of the base segment <NUM> of <FIG> is coupled to the skin <NUM> along a corresponding span of the skin <NUM> of <FIG>.

The first flange <NUM> of the stringer <NUM> of <FIG> includes and/or is formed by the first portion <NUM> of the first stiffening segment <NUM> and the first portion <NUM> of the second stiffening segment <NUM> of <FIG>. The second flange <NUM> of the stringer <NUM> of <FIG> includes and/or is formed by the second portion <NUM> of the first stiffening segment <NUM> and the first portion <NUM> of the base segment <NUM> of <FIG>. The third flange <NUM> of the stringer <NUM> of <FIG> includes and/or is formed by the second portion <NUM> of the second stiffening segment <NUM> and the second portion <NUM> of the base segment <NUM> of <FIG>. The first flange <NUM> is substantially perpendicular to the second and third flanges <NUM>, <NUM>. The second and third flanges <NUM>, <NUM> are aligned and/or are substantially parallel to one another. Based on the orientation of the stringer <NUM> illustrated in <FIG>, the first flange <NUM> is oriented vertically, and the second and third flanges <NUM>, <NUM> are oriented horizontally.

The first flange <NUM> of <FIG> has a thickness <NUM> that is equal to the sum of the thickness <NUM> of the first stiffening segment <NUM> and the thickness <NUM> of the second stiffening segment <NUM> of <FIG>. The thickness <NUM> of the first flange <NUM> of <FIG> is accordingly approximately twelve millimeters (<NUM>). The second flange <NUM> of <FIG> has a thickness <NUM> that is equal to the sum of the thickness <NUM> of the first stiffening segment <NUM> and the thickness <NUM> of the base segment <NUM> of <FIG>. The thickness <NUM> of the second flange <NUM> of <FIG> is accordingly approximately twelve millimeters (<NUM>). The third flange <NUM> of <FIG> has a thickness <NUM> that is equal to the sum of the thickness <NUM> of the second stiffening segment <NUM> and the thickness <NUM> of the base segment <NUM> of <FIG>. The thickness <NUM> of the third flange <NUM> of <FIG> is accordingly approximately twelve millimeters (<NUM>). Thus, the respective thicknesses <NUM>, <NUM>, <NUM> of corresponding ones of the first, second and third flanges <NUM>, <NUM>, <NUM> of the stringer <NUM> of <FIG> are equal.

The end cap <NUM> of the stringer <NUM> of <FIG>. includes a first surface <NUM> and a second surface <NUM> located opposite the first surface <NUM>. The first surface <NUM> of the end cap <NUM> faces and/or is oriented away from the first flange <NUM> of the stringer <NUM>. More specifically, the first surface <NUM> of the end cap <NUM> of <FIG> faces and/or is oriented away from the first portion <NUM> of the first stiffening segment <NUM> of <FIG>, and away from the first portion <NUM> of the second stiffening segment <NUM> of <FIG>. The second surface <NUM> of the end cap <NUM> faces and/or is oriented toward the first flange <NUM> of the stringer <NUM>. More specifically, the second surface <NUM> of the end cap <NUM> of <FIG> faces and/or is oriented toward the first portion <NUM> of the first stiffening segment <NUM> of <FIG>, and toward the first portion <NUM> of the second stiffening segment <NUM> of <FIG>.

The end cap <NUM> of <FIG> includes and/or is formed mostly by a single ply of fiberglass material. The end cap <NUM> is removably positioned on and/or over an end portion of the first flange <NUM> of <FIG> (e.g., an end portion defined by the first end <NUM> of the first stiffening segment <NUM> of <FIG> and the first end <NUM> of the second stiffening segment <NUM> of <FIG>). When positioned on and/or over the end portion of the first flange <NUM> as shown in <FIG>, the end cap <NUM> functions as an indicator with respect to low energy impact damage that can be incurred by the first flange <NUM>. The end cap <NUM> does not structurally strengthen and/or reinforce the first flange <NUM>.

Wrinkles can form and/or develop in the stringer <NUM> of <FIG> during formation and curing of the stringer <NUM>. For example, as shown in <FIG>, wrinkles <NUM> can form and/or develop at various locations within and/or between any of the first stiffening segment <NUM>, the second stiffening segment <NUM>, the base segment <NUM>, the first flange <NUM>, the second flange <NUM>, and/or the third flange <NUM> of the stringer <NUM>. The formation of such wrinkles <NUM> can be attributable to the design and/or configuration of the stringer <NUM> of <FIG> as described above. For example, the formation of such wrinkles <NUM> can be attributable to the size of the cross-sectional area <NUM> of the filler area <NUM> of the stringer <NUM>. The presence of wrinkles <NUM> within the stringer <NUM> of <FIG> can negatively impact one or more performance characteristic(s) (e.g., impact strength, crippling strength, buckling strength, etc.) of the stringer <NUM>.

<FIG> illustrates a stringer <NUM> constructed in accordance with the teachings of this disclosure. The stringer <NUM> of <FIG> is coupled (e.g., joined, bonded, adhered, etc.) to a skin <NUM> of an aircraft (e.g., a skin of the aircraft <NUM> of <FIG>). The stringer <NUM> includes a first stiffening segment <NUM>, a second stiffening segment <NUM>, a base segment <NUM>, a filler area <NUM>, a filler <NUM>, a reinforcement segment <NUM>, a first flange <NUM>, a second flange <NUM>, and a third flange <NUM>.

The first stiffening segment <NUM> of the stringer <NUM> of <FIG> includes a first surface <NUM> and a second surface <NUM> located opposite the first surface <NUM>. The first surface <NUM> of the first stiffening segment <NUM> faces and/or is oriented away from the second stiffening segment <NUM> and/or the base segment <NUM> of the stringer <NUM>. The second surface <NUM> of the first stiffening segment <NUM> faces and/or is oriented toward the second stiffening segment <NUM> and/or the base segment <NUM> of the stringer <NUM>. The first stiffening segment <NUM> includes and/or is formed from multiple plies of material sandwiched between the first and second surfaces <NUM>, <NUM> of the first stiffening segment <NUM>. For example, the first stiffening segment <NUM> can be formed by separate plies of CFRP material that are stacked and/or laid up relative to one another.

The first stiffening segment <NUM> of <FIG> further includes a first end <NUM> formed by the first portion <NUM> of the first stiffening segment <NUM>, and a second end <NUM> formed by the second portion <NUM> of the first stiffening segment <NUM>. The first end <NUM> of the first stiffening segment <NUM> has a flat edge <NUM> (e.g., a zero-degree chamfered edge) extending between the first and second surfaces <NUM>, <NUM> of the first stiffening segment <NUM>. The flat edge <NUM> of the first end <NUM> of the first stiffening segment <NUM> reduces the difficulty associated with coupling the reinforcement segment <NUM> to the first stiffening segment <NUM>, as further described below. The second end <NUM> of the first stiffening segment <NUM> has an angled edge <NUM> (e.g., a chamfered edge) extending between the first and second surfaces <NUM>, <NUM> of the first stiffening segment <NUM>. The angled edge <NUM> of the second end <NUM> of the first stiffening segment <NUM> can be implemented as a chamfered edge having a chamfer angle of between twelve and eighteen degrees relative to the first surface <NUM> of the first stiffening segment <NUM> along the second portion <NUM> of the first stiffening segment <NUM>. Implementation of the angled edge <NUM> as a chamfered edge having a chamfer angle of between twelve and eighteen degrees reduces (e.g., prevents) delamination.

The third portion <NUM> of the first stiffening segment <NUM> has a curvature defined by a radius of curvature <NUM> measured along the second surface <NUM> of the first stiffening segment <NUM> over the span of the third portion <NUM>. The first stiffening segment <NUM> has a thickness <NUM> measured between the first and second surfaces <NUM>, <NUM> of the first stiffening segment <NUM>. The thickness <NUM> of the first stiffening segment <NUM> is substantially constant and/or uniform among and/or over the first, second and third portions <NUM>, <NUM>, <NUM> of the first stiffening segment <NUM>. The constant and/or uniform thickness of the first stiffening segment <NUM> provides for a part that is relatively easy to form and/or manufacture. The radius of curvature <NUM> of the first stiffening segment <NUM> of <FIG> is approximately ten millimeters (<NUM>) in the illustrated example. The thickness <NUM> of the first stiffening segment <NUM> of <FIG> is approximately four millimeters (<NUM>) in the illustrated example.

The second stiffening segment <NUM> of the stringer <NUM> of <FIG> is constructed and/or implemented as a mirror image of the first stiffening segment <NUM> of the stringer <NUM>. The second stiffening segment <NUM> of <FIG> includes a first surface <NUM> and a second surface <NUM> located opposite the first surface <NUM>. The first surface <NUM> of the second stiffening segment <NUM> faces and/or is oriented away from the first stiffening segment <NUM> and/or the base segment <NUM> of the stringer <NUM>. The second surface <NUM> of the second stiffening segment <NUM> faces and/or is oriented toward the first stiffening segment <NUM> and/or the base segment <NUM> of the stringer <NUM>. The second stiffening segment <NUM> includes and/or is formed from multiple plies of material sandwiched between the first and second surfaces <NUM>, <NUM> of the second stiffening segment <NUM>. For example, the second stiffening segment <NUM> can be formed by separate plies of CFRP material that are stacked and/or laid up relative to one another.

The second stiffening segment <NUM> of <FIG> further includes a first end <NUM> formed by the first portion <NUM> of the second stiffening segment <NUM>, and a second end <NUM> formed by the second portion <NUM> of the second stiffening segment <NUM>. The first end <NUM> of the second stiffening segment <NUM> has a flat edge <NUM> (e.g., a zero-degree chamfered edge) extending between the first and second surfaces <NUM>, <NUM> of the second stiffening segment <NUM>. The flat edge <NUM> of the first end <NUM> of the second stiffening segment <NUM> reduces the difficulty associated with coupling the reinforcement segment <NUM> to the second stiffening segment <NUM>, as further described below. The second end <NUM> of the second stiffening segment <NUM> has an angled edge <NUM> (e.g., a chamfered edge) extending between the first and second surfaces <NUM>, <NUM> of the second stiffening segment <NUM>. The angled edge <NUM> of the second end <NUM> of the second stiffening segment <NUM> can be implemented as a chamfered edge having a chamfer angle of between twelve and eighteen degrees relative to the first surface <NUM> of the second stiffening segment <NUM> along the second portion <NUM> of the second stiffening segment <NUM>. Implementation of the angled edge <NUM> as a chamfered edge having a chamfer angle of between twelve and eighteen degrees reduces (e.g., prevents) delamination.

The third portion <NUM> of the second stiffening segment <NUM> has a curvature defined by a radius of curvature <NUM> measured along the second surface <NUM> of the second stiffening segment <NUM> over the span of the third portion <NUM>. The second stiffening segment <NUM> has a thickness <NUM> measured between the first and second surfaces <NUM>, <NUM> of the second stiffening segment <NUM>. The thickness <NUM> of the second stiffening segment <NUM> is substantially constant and/or uniform among and/or over the first, second and third portions <NUM>, <NUM>, <NUM> of the second stiffening segment <NUM>. The constant and/or uniform thickness of the second reinforcement segment <NUM> provides for a part that is relatively easy to form and/or manufacture. The radius of curvature <NUM> of the second stiffening segment <NUM> of <FIG> is approximately ten millimeters (<NUM>) in the illustrated example. The thickness <NUM> of the second stiffening segment <NUM> of <FIG> is approximately four millimeters (<NUM>) in the illustrated example. Thus, the radius of curvature <NUM> and the thickness <NUM> of the second stiffening segment <NUM> of <FIG> are equal to corresponding ones of the radius of curvature <NUM> and the thickness <NUM> of the first stiffening segment <NUM> of <FIG> described above.

The base segment <NUM> of the stringer <NUM> of <FIG> includes a first surface <NUM> and a second surface <NUM> located opposite the first surface <NUM>. The first surface <NUM> of the base segment <NUM> faces and/or is oriented toward the first stiffening segment <NUM> and/or the second stiffening segment <NUM> of the stringer <NUM>. The second surface <NUM> of the base segment <NUM> faces and/or is oriented away from the first stiffening segment <NUM> and/or the second stiffening segment <NUM> of the stringer <NUM>. The base segment <NUM> includes and/or is formed from multiple plies of material sandwiched between the first and second surfaces <NUM>, <NUM> of the base segment <NUM>. For example, the base segment <NUM> can be formed by separate plies of CFRP material that are stacked and/or laid up relative to one another.

The base segment <NUM> of <FIG> further includes a first end <NUM> formed by the first portion <NUM> of the base segment <NUM>, and a second end <NUM> formed by the second portion <NUM> of the base segment <NUM>. The first end <NUM> of the base segment <NUM> has an angled edge <NUM> (e.g., a chamfered edge) extending between the first and second surfaces <NUM>, <NUM> of the base segment <NUM>. The second end <NUM> of the base segment <NUM> also has an angled edge <NUM> (e.g., a chamfered edge) extending between the first and second surfaces <NUM>, <NUM> of the base segment <NUM>. The angled edge <NUM> of the first end <NUM> of the base segment <NUM>, and/or the angled edge <NUM> of the second end <NUM> of the base segment <NUM>, can be implemented as a chamfered edge having a chamfer angle of between twelve and eighteen degrees relative to the first surface <NUM> of the base segment <NUM>. Implementing the angled edge <NUM> and/or the angled edge <NUM> as a chamfered edge having a chamfer angle of between twelve and eighteen degrees reduces (e.g., prevents) delamination. In the illustrated example of <FIG>, the angled edge <NUM> of the first end <NUM> of the base segment <NUM> of <FIG> is flush with the angled edge <NUM> of the second end <NUM> of the first stiffening segment <NUM> of <FIG>, and the angled edge <NUM> of the second end <NUM> of the base segment <NUM> of <FIG> is flush with the angled edge <NUM> of the second end <NUM> of the second stiffening segment <NUM> of <FIG>. Implementing the angled edge <NUM> to be flush with the angled edge <NUM>, and further implementing the angled edge <NUM> to be flush with the angled edge <NUM>, reduces (e.g., prevents) delamination.

The base segment <NUM> has a thickness <NUM> measured between the first and second surfaces <NUM>, <NUM> of the base segment <NUM>. The thickness <NUM> of the base segment <NUM> is substantially constant and/or uniform among and/or over the first, second and third portions <NUM>, <NUM>, <NUM> of the base segment <NUM>. The constant and/or uniform thickness of the base segment <NUM> provides for a part that is relatively easy to form and/or manufacture. The thickness <NUM> of the base segment <NUM> of <FIG> is approximately four millimeters (<NUM>) in the illustrated example. Thus, the thickness <NUM> of the base segment <NUM> is equal to corresponding ones of the thickness <NUM> of the first stiffening segment <NUM> and the thickness <NUM> of the second stiffening segment <NUM> of <FIG> described above.

The filler area <NUM> of the stringer <NUM> of <FIG> includes a cross-sectional area <NUM> that is generally defined and/or bounded by the third portion <NUM> of the first stiffening segment <NUM>, the third portion <NUM> of the second stiffening segment <NUM>, and the third portion <NUM> of the base segment <NUM> of <FIG> described above. The filler <NUM> is located within the filler area <NUM> and is retained therein. The cross-sectional area <NUM> of the filler area <NUM> and/or the filler <NUM> of <FIG> is approximately forty-three square millimeters (<NUM><NUM>) in the illustrated example. The filler <NUM> of <FIG> can be implemented as a CFRP filler.

The reinforcement segment <NUM> of the stringer <NUM> of <FIG>. includes a first surface <NUM> and a second surface <NUM> located opposite the first surface <NUM>. The first surface <NUM> of the reinforcement segment <NUM> faces and/or is oriented away from the first portion <NUM> of the first stiffening segment <NUM> of <FIG>, and away from the first portion <NUM> of the second stiffening segment <NUM> of <FIG>. The second surface <NUM> of the reinforcement segment <NUM> faces and/or is oriented toward the first portion <NUM> of the first stiffening segment <NUM> of <FIG>, and toward the first portion <NUM> of the second stiffening segment <NUM> of <FIG>.

The reinforcement segment <NUM> of <FIG> includes and/or is formed by multiple plies of CFRP material. The multiple plies of CFRP material increase the impact strength of the first flange <NUM> of the stringer <NUM> of <FIG> relative to the first flange <NUM> of the known stringer <NUM> of <FIG>. The reinforcement segment <NUM> includes at least four plies to facilitate the increase in impact strength. The reinforcement segment <NUM> has a thickness <NUM> measured between the first and second surfaces <NUM>, <NUM> of the reinforcement segment <NUM>. The thickness <NUM> of the reinforcement segment <NUM> is substantially constant and/or uniform among and/or over the span of the reinforcement segment <NUM>. The constant and/or uniform thickness of the reinforcement segment <NUM> provides for a part that is relatively easy to form and/or manufacture. The thickness <NUM> of the reinforcement segment <NUM> of <FIG> is approximately two millimeters (<NUM>) in the illustrated example.

The reinforcement segment <NUM> of <FIG> extends over and/or along the first portion <NUM> and the first end <NUM> of the first stiffening segment <NUM>, and further extends over and/or along the first portion <NUM> and the first end <NUM> of the second stiffening segment <NUM>. The reinforcement segment <NUM> extends over and/or along the first portion <NUM> of the first stiffening segment <NUM> toward the second portion <NUM> of the first stiffening segment <NUM>, and further extends over and/or along the first portion <NUM> of the second stiffening segment <NUM> toward the second portion <NUM> of the second stiffening segment <NUM>. The reinforcement segment <NUM> can extend along between thirty five percent (<NUM>%) and eighty five percent (<NUM>%) of a height dimension (labeled as "H" on <FIG>) of the stringer <NUM> measured orthogonally from the first end <NUM> of the first stiffening segment <NUM> to the portion of the first surface <NUM> of the first stiffening segment <NUM> located at the second portion <NUM> of the first stiffening segment <NUM>. The height dimension (H) of the stringer <NUM> can alternatively be measured orthogonally from the first end <NUM> of the second stiffening segment <NUM> to the portion of the first surface <NUM> of the second stiffening segment <NUM> located at the second portion <NUM> of the second stiffening segment <NUM>. In the illustrated example of <FIG>, the reinforcement segment <NUM> covers approximately seventy five percent (<NUM>%) of the height dimension (H) of the stringer <NUM>. Implementing the reinforcement segment <NUM> to extend along between thirty five percent (<NUM>%) and eighty five percent (<NUM>%) of the height dimension (H) of the stringer <NUM> increases the crippling strength and/or buckling strength of the first flange <NUM> of the stringer <NUM> of <FIG> relative to the first flange <NUM> of the known stringer <NUM> of <FIG>, while at the same time reducing the weight and/or material volume of the stringer <NUM> of <FIG> relative to the known stringer <NUM> of <FIG>.

The reinforcement segment <NUM> of <FIG> is coupled (e.g., joined, bonded, adhered, etc.) to the first portion <NUM> of the first stiffening segment <NUM> of <FIG> described above, and to the first portion <NUM> of the second stiffening segment <NUM> of <FIG> described above. More specifically, the second surface <NUM> of the reinforcement segment <NUM> of <FIG> is coupled to the first surface <NUM> of the first stiffening segment <NUM> of <FIG> along the span of the first portion <NUM> of the first stiffening segment <NUM>, and to the first surface <NUM> of the second stiffening segment <NUM> of <FIG> along the span of the first portion <NUM> of the second stiffening segment <NUM>. The second surface <NUM> of the reinforcement segment <NUM> of <FIG> is further coupled to the first end <NUM> (e.g., along the flat edge <NUM>) of the first stiffening segment <NUM> of <FIG>, and to the first end <NUM> (e.g., along the flat edge <NUM>) of the second stiffening segment <NUM> of <FIG>. The multi-ply structure of the CFRP reinforcement segment <NUM> of the stringer <NUM> of <FIG> increases the impact strength of the first flange <NUM> of the stringer <NUM> relative to the impact strength associated with the first flange <NUM> and the single-ply fiberglass end cap <NUM> of the known stringer <NUM> of <FIG> described above.

The first, second, and third portions <NUM>, <NUM>, <NUM> of the base segment <NUM> of <FIG> are coupled (e.g., joined, bonded, adhered, etc.) to the skin <NUM> of <FIG> described above. More specifically, the second surface <NUM> of the base segment <NUM> along the span of the first, second and third portions <NUM>, <NUM>, <NUM> of the base segment <NUM> of <FIG> is coupled to the skin <NUM> along a corresponding span of the skin <NUM> of <FIG>.

The first flange <NUM> of the stringer <NUM> of <FIG> includes and/or is formed by the first portion <NUM> of the first stiffening segment <NUM>, the first portion <NUM> of the second stiffening segment <NUM>, and the reinforcement segment <NUM> of <FIG>. The second flange <NUM> of the stringer <NUM> of <FIG> includes and/or is formed by the second portion <NUM> of the first stiffening segment <NUM> and the first portion <NUM> of the base segment <NUM> of <FIG>. The third flange <NUM> of the stringer <NUM> of <FIG> includes and/or is formed by the second portion <NUM> of the second stiffening segment <NUM> and the second portion <NUM> of the base segment <NUM> of <FIG>. The first flange <NUM> is substantially perpendicular to the second and third flanges <NUM>, <NUM>. The second and third flanges <NUM>, <NUM> are aligned and/or are substantially parallel to one another. Based on the orientation of the stringer <NUM> illustrated in <FIG>, the first flange <NUM> is oriented vertically, and the second and third flanges <NUM>, <NUM> are oriented horizontally.

The first flange <NUM> of <FIG> has a thickness <NUM> that is equal to the sum of the thickness <NUM> of the first stiffening segment <NUM>, the thickness <NUM> of the second stiffening segment <NUM>, a first instance of the thickness <NUM> of the reinforcement segment <NUM> (e.g., adjacent the first stiffening segment <NUM>), and a second instance of the thickness <NUM> of the reinforcement segment <NUM> (e.g., adjacent the second stiffening segment <NUM>) of <FIG>. The thickness <NUM> of the first flange <NUM> of <FIG> is accordingly approximately twelve millimeters (<NUM>) in the illustrated example. The second flange <NUM> of <FIG> has a thickness <NUM> that is equal to the sum of the thickness <NUM> of the first stiffening segment <NUM> and the thickness <NUM> of the base segment <NUM> of <FIG>. The thickness <NUM> of the second flange <NUM> of <FIG> is accordingly approximately eight millimeters (<NUM>) in the illustrated example. The third flange <NUM> of <FIG> has a thickness <NUM> that is equal to the sum of the thickness <NUM> of the second stiffening segment <NUM> and the thickness <NUM> of the base segment <NUM> of <FIG>. The thickness <NUM> of the third flange <NUM> of <FIG> is accordingly approximately eight millimeters (<NUM>) in the illustrated example. Thus, the thickness <NUM> of the first flange <NUM> is greater than the thickness <NUM> of the second flange <NUM> and greater than the thickness <NUM> of the third flange <NUM>, the thickness <NUM> of the second flange <NUM> is less than the thickness <NUM> of the first flange <NUM> and equal to the thickness <NUM> of the third flange <NUM>, and the thickness <NUM> of the third flange <NUM> is less than the thickness <NUM> of the first flange <NUM> and equal to the thickness <NUM> of the second flange <NUM>.

The stringer <NUM> of <FIG> differs structurally from the known stringer <NUM> of <FIG> in several respects. For example, while the thickness <NUM> of the first flange <NUM> of the stringer <NUM> of <FIG> is equal to the thickness <NUM> of the first flange <NUM> of the known stringer <NUM> of <FIG>, the thickness <NUM> of the second flange <NUM> and the thickness <NUM> of the third flange <NUM> of the stringer <NUM> of <FIG> are respectively less than corresponding ones of the thickness <NUM> of the second flange <NUM> and the thickness <NUM> of the third flange <NUM> of the known stringer <NUM> of <FIG>. As another example, the thickness <NUM> of the first stiffening segment <NUM>, the thickness <NUM> of the second stiffening segment <NUM>, and the thickness <NUM> of the base segment <NUM> of the stringer <NUM> of <FIG> are respectively less than corresponding ones of the thickness <NUM> of the first stiffening segment <NUM>, the thickness <NUM> of the second stiffening segment <NUM>, and the thickness <NUM> of the base segment <NUM> of the known stringer <NUM> of <FIG>. As another example, the cross-sectional area <NUM> of the filler area <NUM> of the stringer <NUM> of <FIG> is less than the cross-sectional area <NUM> of the filler area <NUM> of the known stringer <NUM> of <FIG>.

The above-described structural differences between the stringer <NUM> of <FIG> and the known stringer <NUM> of <FIG> result in the stringer <NUM> having numerous benefits and/or advantages relative to the known stringer <NUM>. For example, the above-described reduced thicknesses of the first stiffening segment <NUM>, second stiffening segment <NUM>, base segment <NUM>, second flange <NUM>, and third flange <NUM> of the stringer <NUM> of <FIG> relative to the corresponding thicknesses of the first stiffening segment <NUM>, second stiffening segment <NUM>, base segment <NUM>, second flange <NUM>, and third flange <NUM> of the known stringer <NUM> of <FIG> result in the stringer <NUM> of <FIG> having a reduced material volume, a reduced weight, and/or a reduced production cost relative to the material volume, the weight, and/or the production cost of the known stringer <NUM> of <FIG>.

As another example, the above-described reduced cross-sectional area <NUM> of the filler area <NUM> of the stringer <NUM> of <FIG> relative to the cross-sectional area <NUM> of the known stringer <NUM> of <FIG> reduces (e.g., minimizes and/or prevents) thermal cracking and/or the formation of wrinkles (e.g., the wrinkles <NUM> of <FIG> described above) within the stringer <NUM>. Such a reduction in thermal cracking and/or in the formation of wrinkles results in an increase in the performance characteristic(s) (e.g., impact strength, crippling strength, buckling strength, etc.) of the stringer <NUM> of <FIG> relative to the known stringer <NUM> of <FIG>. Furthermore, as discussed above, the multi-ply structure of the CFRP reinforcement segment <NUM> of the stringer <NUM> of <FIG> independently increases the impact strength of the first flange <NUM> of the stringer <NUM> relative to the impact strength associated with the first flange <NUM> and the single-ply fiberglass end cap <NUM> of the known stringer <NUM> of <FIG>.

<FIG> is a perspective view of a composite blank <NUM> from which the reinforcement segment <NUM> of the stringer <NUM> of <FIG> can be fabricated. The composite blank <NUM> of <FIG> includes a first surface <NUM> and a second surface <NUM> located opposite the first surface <NUM>. Respective ones of the first and second surfaces <NUM>, <NUM> of the composite blank <NUM> have a generally rectangular shape <NUM> including a chordwise direction <NUM> shown as line A-A in <FIG> and a spanwise direction <NUM> shown as line B-B in <FIG>. The spanwise direction <NUM> of the composite blank <NUM> corresponds to an axial direction of the stringer <NUM> of <FIG>. The chordwise direction <NUM> of the composite blank <NUM> is oriented orthogonally relative to the spanwise direction <NUM> of the composite blank <NUM>. <FIG> is an enlarged cross-sectional view of the composite blank <NUM> of <FIG> taken along line A-A of <FIG> is an enlarged cross-sectional view of the composite blank <NUM> of <FIG> taken along line B-B of <FIG>.

The composite blank <NUM> of <FIG> includes a stack and/or layup of plies <NUM>. Respective ones of the plies <NUM> within the stack and/or layup are formed from CFRP tape or CFRP fabric. The composite blank <NUM> of <FIG> is accordingly a multi-ply CFRP material. In the illustrated example of <FIG>, the composite blank <NUM> includes a total of six plies <NUM>. The composite blank <NUM> can include a stack and/or layup of plies that differs in number (e.g., four plies, eight plies, ten plies, etc.) from the stack and/or layup of plies <NUM> shown in <FIG>. For example, the number of plies <NUM> can be determined based on a thickness of respective ones of the plies <NUM> relative to a desired thickness of the composite blank <NUM> of <FIG>.

The plies <NUM> of the composite blank <NUM> of <FIG> include a first ply <NUM>, a second ply <NUM>, a third ply <NUM>, a fourth ply <NUM>, a fifth ply <NUM>, and a sixth ply <NUM>. The first ply <NUM> can form the first surface <NUM> of the reinforcement segment <NUM> of <FIG>, and the sixth ply <NUM> can form the second surface <NUM> of the reinforcement segment <NUM> of <FIG>. In the illustrated example of <FIG>, the stack and/or layup of plies <NUM> of the composite blank <NUM> is a symmetric layup. As used herein, the term "symmetric layup" means a layup having an equal number of plies located on opposing sides of a symmetry line of the layup. For example, the composite blank <NUM> of <FIG> is a symmetric layup having the first, second and third plies <NUM>, <NUM>, <NUM> located on a first side of a symmetry line <NUM> and having the fourth, fifth and sixth plies <NUM>, <NUM>, <NUM> located on a second side of the symmetry line <NUM> opposite the first side of the symmetry line <NUM>. Implementing the stack and/or layup of plies <NUM> as a symmetric layup increases the crippling strength and/or buckling strength of the stringer <NUM> of <FIG> relative to the known stringer <NUM> of <FIG>, simplifies the manufacturing process associated with forming the stringer <NUM> of <FIG>, and also reduces (e.g., eliminates) the formation of wrinkles, thermal cracks, and/or distortions in the stringer <NUM> of <FIG> relative to the known stringer <NUM> of <FIG>.

The stack and/or layup of plies <NUM> of the composite blank <NUM> of <FIG> can be layered and/or constructed as a traditional layup. As used herein, the term "traditional layup" means a layering and/or build-up of plies oriented at angles of zero degrees (<NUM>°), plus/minus forty-five degrees (+/-<NUM>°), and ninety degrees (<NUM>°) only relative to an axial direction of a stringer. For example, a symmetric traditional layup of eight plies can have a first ply oriented at forty-five degrees, a second ply oriented at ninety degrees, a third ply oriented at minus forty-five degrees, a fourth ply oriented at zero degrees, a fifth ply oriented at zero degrees, a sixth ply oriented at minus forty-five degrees, a seventh ply oriented at ninety degrees, and an eighth ply oriented at forty-five degrees (e.g., a <NUM>°/<NUM>°/-<NUM>°/<NUM>°/<NUM>°/- <NUM>°/<NUM>°/<NUM>° layup). The stack and/or layup of plies <NUM> of the composite blank <NUM> of <FIG> can be layered and/or constructed as a traditional layup having a ply orientation composition including approximately fifty-five percent of the plies oriented at zero degrees, thirty-five percent of the plies oriented at plus/minus forty-five degrees, and ten percent of the plies oriented at ninety degrees (e.g., a <NUM>/<NUM>/<NUM> ply orientation composition). Implementing the stack and/or layup of plies <NUM> as a traditional layup increases the crippling strength and/or buckling strength of the stringer <NUM> of <FIG> relative to the known stringer <NUM> of <FIG>, and also simplifies the manufacturing process associated with forming the stringer <NUM> of <FIG>.

The stack and/or layup of plies <NUM> of the composite blank <NUM> of <FIG> can alternatively be layered and/or constructed as a non-traditional layup. As used herein, the term "non-traditional layup" means a layering and/or build-up of plies oriented relative to the axial direction of the stringer at angles other than the specific angles of a traditional layup, as defined above. For example, a symmetric non-traditional layup of eight plies can have a first ply oriented at sixty degrees, a second ply oriented at five degrees, a third ply oriented at minus sixty degrees, a fourth ply oriented at minus five degrees, a fifth ply oriented at minus five degrees, a sixth ply oriented at minus sixty degrees, a seventh ply oriented at five degrees, and an eighth ply oriented at sixty degrees (e.g., a <NUM>°/<NUM>°/-<NUM>°/-<NUM>°/-<NUM>°/-<NUM>°/<NUM>°/<NUM>° layup). Implementing the stack and/or layup of plies <NUM> as a non-traditional layup increases the crippling strength and/or buckling strength of the stringer <NUM> of <FIG> relative to the known stringer <NUM> of <FIG>, simplifies the manufacturing process associated with forming the stringer <NUM> of <FIG>, and also reduces (e.g., eliminates) the formation of wrinkles, thermal cracks, and/or distortions in the stringer <NUM> of <FIG> relative to the known stringer <NUM> of <FIG>.

In the illustrated example of <FIG>, the first ply <NUM> of the composite blank <NUM> has a thickness <NUM>. The respective thicknesses of corresponding ones of the second, third, fourth, fifth and sixth plies <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the composite blank <NUM> are equal to the thickness <NUM> of the first ply <NUM> of the composite blank <NUM>. The respective thicknesses of corresponding ones of the second, third, fourth, fifth and sixth plies <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the composite blank <NUM> can alternatively differ (e.g., individually or collectively) from the thickness <NUM> of the first ply <NUM> of the composite blank <NUM>.

As shown in <FIG>, the respective lateral extents of corresponding ones of the plies <NUM> along the chordwise direction <NUM> of the composite blank <NUM> successively decrease from the first ply <NUM> through the sixth ply <NUM>. For example, the lateral extent of the second ply <NUM> in the chordwise direction <NUM> is less than the lateral extent of the first ply <NUM> in the chordwise direction <NUM>, the lateral extent of the third ply <NUM> in the chordwise direction <NUM> is less than the lateral extent of the second ply <NUM> in the chordwise direction <NUM>, the lateral extent of the fourth ply <NUM> in the chordwise direction <NUM> is less than the lateral extent of the third ply <NUM> in the chordwise direction <NUM>, the lateral extent of the fifth ply <NUM> in the chordwise direction <NUM> is less than the lateral extent of the fourth ply <NUM> in the chordwise direction <NUM>, and the lateral extent of the sixth ply <NUM> in the chordwise direction <NUM> is less than the lateral extent of the fifth ply <NUM> in the chordwise direction <NUM>.

The above-described differences in the respective lateral extents of corresponding ones of the plies <NUM> along the chordwise direction <NUM> of the composite blank <NUM> are defined by a chordwise stagger distance <NUM> implemented between successively-layered ones of the plies <NUM>. For example, the second ply <NUM> is laterally staggered in the chordwise direction <NUM> relative to the first ply <NUM> by the chordwise stagger distance <NUM>, the third ply <NUM> is laterally staggered in the chordwise direction <NUM> relative to the second ply <NUM> by the chordwise stagger distance <NUM>, the fourth ply <NUM> is laterally staggered in the chordwise direction <NUM> relative to the third ply <NUM> by the chordwise stagger distance <NUM>, the fifth ply <NUM> is laterally staggered in the chordwise direction <NUM> relative to the fourth ply <NUM> by the chordwise stagger distance <NUM>, and the sixth ply <NUM> is laterally staggered in the chordwise direction <NUM> relative to the fifth ply <NUM> by the chordwise stagger distance <NUM>.

In the illustrated example of <FIG>, the chordwise stagger distance <NUM> is the same (e.g., has the same value) between each of the successively-layered ones of the plies <NUM> of the composite blank <NUM>. Implementing the same chordwise stagger distance between each of the successively-layered ones of the plies <NUM> reduces (e.g., prevents) delamination, and also provides for a part that is relatively easy to form and/or manufacture. The chordwise stagger distance <NUM> can alternatively vary (e.g., change in value) from one successively-layered pair of plies (e.g., the first and second plies <NUM>, <NUM>) to the next successively-layered pair of plies (e.g., the second and third plies <NUM>, <NUM>). The composite blank <NUM> of <FIG> has a chordwise ply drop ratio calculated as the ratio of the chordwise stagger distance <NUM> of the plies <NUM> to the thickness <NUM> of individual ones of the plies <NUM>. The chordwise ply drop ratio of the composite blank <NUM> can have a value between three (<NUM>) and thirty (<NUM>). Implementing a chordwise ply drop ratio between three (<NUM>) and thirty (<NUM>) reduces (e.g., prevents) delamination, and also reduces (e.g., eliminates) the need for one or more post-curing trimming steps associated with the manufacture of the stringer <NUM> of <FIG> relative to the known stringer <NUM> of <FIG>.

As shown in <FIG>, the respective lateral extents of corresponding ones of the plies <NUM> along the spanwise direction <NUM> of the composite blank <NUM> successively decrease from the first ply <NUM> through the fourth ply <NUM>, and successively increase from the fourth ply <NUM> through the sixth ply <NUM>. For example, the lateral extent of the second ply <NUM> in the spanwise direction <NUM> is less than the lateral extent of the first ply <NUM> in the spanwise direction <NUM>, the lateral extent of the third ply <NUM> in the spanwise direction <NUM> is less than the lateral extent of the second ply <NUM> in the spanwise direction <NUM>, the lateral extent of the fourth ply <NUM> in the spanwise direction <NUM> is less than the lateral extent of the third ply <NUM> in the spanwise direction <NUM>, the lateral extent of the fifth ply <NUM> in the spanwise direction <NUM> is greater than the lateral extent of the fourth ply <NUM> in the spanwise direction <NUM>, and the lateral extent of the sixth ply <NUM> in the spanwise direction <NUM> is greater than the lateral extent of the fifth ply <NUM> in the chordwise direction <NUM>.

The above-described differences in the respective lateral extents of corresponding ones of the plies <NUM> along the spanwise direction <NUM> of the composite blank <NUM> are defined by a spanwise stagger distance <NUM> implemented between successively-layered ones of the plies <NUM>. For example, the second ply <NUM> is laterally staggered in the spanwise direction <NUM> relative to the first ply <NUM> by the spanwise stagger distance <NUM>, the third ply <NUM> is laterally staggered in the spanwise direction <NUM> relative to the second ply <NUM> by the spanwise stagger distance <NUM>, the fourth ply <NUM> is laterally staggered in the spanwise direction <NUM> relative to the third ply <NUM> by the spanwise stagger distance <NUM>, the fifth ply <NUM> is laterally staggered in the spanwise direction <NUM> relative to the fourth ply <NUM> by the spanwise stagger distance <NUM>, and the sixth ply <NUM> is laterally staggered in the spanwise direction <NUM> relative to the fifth ply <NUM> by the spanwise stagger distance <NUM>.

In the illustrated example of <FIG>, the spanwise stagger distance <NUM> is the same (e.g., has the same value) between each of the successively-layered ones of the plies <NUM> of the composite blank <NUM>. Implementing the same spanwise stagger distance between each of the successively-layered ones of the plies <NUM> reduces (e.g., prevents) delamination, and also provides for a part that is relatively easy to form and/or manufacture. The spanwise stagger distance <NUM> can alternatively vary (e.g., change in value) from one successively-layered pair of plies (e.g., the first and second plies <NUM>, <NUM>) to the next successively-layered pair of plies (e.g., the second and third plies <NUM>, <NUM>). The composite blank <NUM> of <FIG> has a spanwise ply drop ratio calculated as the ratio of the spanwise stagger distance <NUM> of the plies <NUM> to the thickness <NUM> of individual ones of the plies <NUM>. The spanwise ply drop ratio of the composite blank <NUM> can have a value between one hundred (<NUM>) and three hundred (<NUM>). Implementing a spanwise ply drop ratio between one hundred (<NUM>) and three hundred (<NUM>) reduces (e.g., prevents) delamination, and also reduces (e.g., eliminates) the need for one or more post-curing trimming steps associated with the manufacture of the stringer <NUM> of <FIG> relative to the known stringer <NUM> of <FIG>.

<FIG> is a perspective view of a composite blank <NUM> from which the first and second stiffening segments <NUM>, <NUM>, or the base segment <NUM> of the stringer <NUM> of <FIG> can be fabricated. The composite blank <NUM> of <FIG> includes a first surface <NUM> and a second surface <NUM> located opposite the first surface <NUM>. Respective ones of the first and second surfaces <NUM>, <NUM> of the composite blank <NUM> have a generally rectangular shape <NUM> including a chordwise direction <NUM> shown as line A-A in <FIG> and a spanwise direction <NUM> shown as line B-B in <FIG>. The spanwise direction <NUM> of the composite blank <NUM> corresponds to an axial direction of the stringer <NUM> of <FIG>. The chordwise direction <NUM> of the composite blank <NUM> is oriented orthogonally relative to the spanwise direction <NUM> of the composite blank <NUM>. <FIG> is an enlarged cross-sectional view of the composite blank <NUM> of <FIG> taken along line A-A of <FIG> is an enlarged cross-sectional view of the composite blank <NUM> of <FIG> taken along line B-B of <FIG>.

The composite blank <NUM> of <FIG> includes a stack and/or layup of plies <NUM>. In the illustrated example of <FIG>, the composite blank <NUM> includes a total of six plies <NUM>. In examples not presently being claimed, the composite blank <NUM> can alternatively include a stack and/or layup of plies that differs in number (e.g., four plies, eight plies, ten plies, etc.) from the stack and/or layup of plies <NUM> shown in <FIG>. For example, the number of plies <NUM> can be determined based on a thickness of respective ones of the plies <NUM> relative to a desired thickness of the composite blank <NUM> of <FIG>. The plies <NUM> of the composite blank <NUM> of <FIG> include a first ply <NUM>, a second ply <NUM>, a third ply <NUM>, a fourth ply <NUM>, a fifth ply <NUM>, and a sixth ply <NUM>. In the context of fabricating the first stiffening segment <NUM> of <FIG> or the second stiffening segment <NUM> of <FIG>, the first ply <NUM> can form the second surface <NUM> of the first stiffening segment <NUM> and the second surface <NUM> of the second stiffening segment <NUM>, and the sixth ply <NUM> can form the first surface <NUM> of the first stiffening segment <NUM> and the first surface <NUM> of the second stiffening segment <NUM>. In the context of forming the base segment <NUM> of <FIG>, the first ply <NUM> can form the first surface <NUM> of the base segment <NUM>, and the sixth ply <NUM> can form the second surface <NUM> of the base segment <NUM>.

As illustrated in <FIG>, the stack and/or layup of plies <NUM> of the composite blank <NUM> is a symmetric layup. The composite blank <NUM> of <FIG> is a symmetric layup having the first, second and third plies <NUM>, <NUM>, <NUM> located on a first side of a symmetry line <NUM> and having the fourth, fifth and sixth plies <NUM>, <NUM>, <NUM> located on a second side of the symmetry line <NUM> opposite the first side of the symmetry line <NUM>.

The stack and/or layup of plies <NUM> of the composite blank <NUM> of <FIG> can be layered and/or constructed as a traditional layup. The stack and/or layup of plies <NUM> of the composite blank <NUM> of <FIG> can be layered and/or constructed as a traditional layup having a ply orientation composition including approximately fifty percent of the plies oriented at zero degrees, thirty-eight percent of the plies oriented at plus/minus forty-five degrees, and twelve percent of the plies oriented at ninety degrees (e.g., a <NUM>/<NUM>/<NUM> ply orientation composition). Implementing the stack and/or layup of plies <NUM> as a traditional layup increases the crippling strength and/or buckling strength of the stringer <NUM> of <FIG> relative to the known stringer <NUM> of <FIG>, and also simplifies the manufacturing process associated with forming the stringer <NUM> of <FIG>. The stack and/or layup of plies <NUM> of the composite blank <NUM> of <FIG> can alternatively be layered and/or constructed as a non-traditional layup. Implementing the stack and/or layup of plies <NUM> as a non-traditional layup increases the crippling strength and/or buckling strength of the stringer <NUM> of <FIG> relative to the known stringer <NUM> of <FIG>, simplifies the manufacturing process associated with forming the stringer <NUM> of <FIG>, and also reduces (e.g., eliminates) the formation of wrinkles, thermal cracks, and/or distortions in the stringer <NUM> of <FIG> relative to the known stringer <NUM> of <FIG>.

In the illustrated example of <FIG>, the sixth ply <NUM> of the composite blank <NUM> has a thickness <NUM>. The respective thicknesses of corresponding ones of the first, second, third, fourth and fifth plies <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the composite blank <NUM> are equal to the thickness <NUM> of the sixth ply <NUM> of the composite blank <NUM>. The respective thicknesses of corresponding ones of the first, second, third, fourth, and fifth plies <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of the composite blank <NUM> can alternatively differ (e.g., individually or collectively) from the thickness <NUM> of the sixth ply <NUM> of the composite blank <NUM>.

As shown in <FIG>, the respective lateral extents of corresponding ones of the plies <NUM> along the chordwise direction <NUM> of the composite blank <NUM> successively increase from the first ply <NUM> through the sixth ply <NUM>. For example, the lateral extent of the second ply <NUM> in the chordwise direction <NUM> is greater than the lateral extent of the first ply <NUM> in the chordwise direction <NUM>, the lateral extent of the third ply <NUM> in the chordwise direction <NUM> is greater than the lateral extent of the second ply <NUM> in the chordwise direction <NUM>, the lateral extent of the fourth ply <NUM> in the chordwise direction <NUM> is greater than the lateral extent of the third ply <NUM> in the chordwise direction <NUM>, the lateral extent of the fifth ply <NUM> in the chordwise direction <NUM> is greater than the lateral extent of the fourth ply <NUM> in the chordwise direction <NUM>, and the lateral extent of the sixth ply <NUM> in the chordwise direction <NUM> is greater than the lateral extent of the fifth ply <NUM> in the chordwise direction <NUM>.

The above-described differences in the respective lateral extents of corresponding ones of the plies <NUM> along the chordwise direction <NUM> of the composite blank <NUM> are defined by a chordwise stagger distance <NUM> implemented between successively-layered ones of the plies <NUM>. The second ply <NUM> is laterally staggered in the chordwise direction <NUM> relative to the first ply <NUM> by the chordwise stagger distance <NUM>, the third ply <NUM> is laterally staggered in the chordwise direction <NUM> relative to the second ply <NUM> by the chordwise stagger distance <NUM>, the fourth ply <NUM> is laterally staggered in the chordwise direction <NUM> relative to the third ply <NUM> by the chordwise stagger distance <NUM>, the fifth ply <NUM> is laterally staggered in the chordwise direction <NUM> relative to the fourth ply <NUM> by the chordwise stagger distance <NUM>, and the sixth ply <NUM> is laterally staggered in the chordwise direction <NUM> relative to the fifth ply <NUM> by the chordwise stagger distance <NUM>.

As shown in <FIG>, the respective lateral extents of corresponding ones of the plies <NUM> along the spanwise direction <NUM> of the composite blank <NUM> successively decrease from the first ply <NUM> through the fourth ply <NUM>, and successively increase from the fourth ply <NUM> through the sixth ply <NUM>. The lateral extent of the second ply <NUM> in the spanwise direction <NUM> is less than the lateral extent of the first ply <NUM> in the spanwise direction <NUM>, the lateral extent of the third ply <NUM> in the spanwise direction <NUM> is less than the lateral extent of the second ply <NUM> in the spanwise direction <NUM>, the lateral extent of the fourth ply <NUM> in the spanwise direction <NUM> is less than the lateral extent of the third ply <NUM> in the spanwise direction <NUM>, the lateral extent of the fifth ply <NUM> in the spanwise direction <NUM> is greater than the lateral extent of the fourth ply <NUM> in the spanwise direction <NUM>, and the lateral extent of the sixth ply <NUM> in the spanwise direction <NUM> is greater than the lateral extent of the fifth ply <NUM> in the chordwise direction <NUM>.

The above-described differences in the respective lateral extents of corresponding ones of the plies <NUM> along the spanwise direction <NUM> of the composite blank <NUM> are defined by a spanwise stagger distance <NUM> implemented between successively-layered ones of the plies <NUM>. The second ply <NUM> is laterally staggered in the spanwise direction <NUM> relative to the first ply <NUM> by the spanwise stagger distance <NUM>, the third ply <NUM> is laterally staggered in the spanwise direction <NUM> relative to the second ply <NUM> by the spanwise stagger distance <NUM>, the fourth ply <NUM> is laterally staggered in the spanwise direction <NUM> relative to the third ply <NUM> by the spanwise stagger distance <NUM>, the fifth ply <NUM> is laterally staggered in the spanwise direction <NUM> relative to the fourth ply <NUM> by the spanwise stagger distance <NUM>, and the sixth ply <NUM> is laterally staggered in the spanwise direction <NUM> relative to the fifth ply <NUM> by the spanwise stagger distance <NUM>.

In the illustrated example of <FIG>, the spanwise stagger distance <NUM> is the same (e.g., has the same value) between each of the successively-layered ones of the plies <NUM> of the composite blank <NUM>. Implementing the same spanwise stagger distance between each of the successively-layered ones of the plies <NUM> reduces (e.g., prevents) delamination, and also provides for a part that is relatively easy to form and/or manufacture. The spanwise stagger distance <NUM> can alternatively vary (e.g., change in value) from one successively-layered pair of plies (e.g., the first and second plies <NUM>, <NUM>) to the next successively-layered pair of plies (e.g., the second and third plies <NUM>, <NUM>). The composite blank <NUM> of <FIG> has a spanwise ply drop ratio calculated as the ratio of the spanwise stagger distance <NUM> of the plies <NUM> to the thickness <NUM> of individual ones of the plies <NUM>. The spanwise ply drop ratio has a value between one hundred twenty (<NUM>) and three hundred (<NUM>). Implementing a spanwise ply drop ratio between three (<NUM>) and thirty (<NUM>) reduces (e.g., prevents) delamination, and also reduces (e.g., eliminates) the need for one or more post-curing trimming steps associated with the manufacture of the stringer <NUM> of <FIG> relative to the known stringer <NUM> of <FIG>.

<FIG> illustrate a process <NUM> used to manufacture the stringer <NUM> of <FIG>. During a first stage <NUM> of the process <NUM> shown in <FIG>, a first composite blank <NUM> is pre-heated using a heat blanket <NUM>. The first composite blank <NUM> can be implemented via the composite blank <NUM> of <FIG> described above. The first composite blank <NUM> can be heated via the heat blanket <NUM> at a temperature of one hundred fifty degrees Fahrenheit (<NUM>°F, <NUM>,<NUM>) for between twenty and thirty minutes.

The first stage <NUM> of the process <NUM> shown in <FIG> further includes placing the first composite blank <NUM> on a forming block <NUM>. The forming block <NUM> has first and second parts <NUM>, <NUM> that are separable from one another. In the illustrated example of <FIG>, the first and second parts <NUM>, <NUM> of the forming block <NUM> are symmetric to one another. The first composite blank <NUM> can be placed on the forming block <NUM> prior to the first composite blank <NUM> being pre-heated. The first composite blank <NUM> can alternatively be placed on the forming block <NUM> after the first composite blank <NUM> has been pre-heated.

During a second stage <NUM> of the process <NUM> shown in <FIG>, the first composite blank <NUM> is draped over and/or around the forming block <NUM>. One or more roller(s) <NUM> (e.g., one or more robotic roller(s)) can apply force to the first composite blank <NUM> to assist in draping the first composite blank <NUM> over and/or around the forming block <NUM>.

During a third stage <NUM> of the process <NUM> shown in <FIG>, the first composite blank <NUM> is cut and/or divided into first and second stiffening segments <NUM>, <NUM> via a cutting device <NUM>. The cutting device <NUM> can be implemented via an ultrasonic knife. In the illustrated example of <FIG>, the first and second stiffening segments <NUM>, <NUM> are symmetric to one another. The first stiffening segment <NUM> of the first composite blank <NUM> includes a first portion <NUM>, a second portion <NUM> oriented at an angle to the first portion <NUM>, and a third portion <NUM> extending between the first portion <NUM> and the second portion <NUM>. The second stiffening segment <NUM> of the first composite blank <NUM> includes a first portion <NUM>, a second portion <NUM> oriented at an angle to the first portion <NUM>, and a third portion <NUM> extending between the first portion <NUM> and the second portion <NUM>.

During a fourth stage <NUM> of the process <NUM> shown in <FIG>, the first and second parts <NUM>, <NUM> of the forming block <NUM> carrying the first and second stiffening segments <NUM>, <NUM> of the first composite blank <NUM> are separated from one another and reoriented (e.g., rotated) relative to one another such that the first portion <NUM> of the first stiffening segment <NUM> is placed into face-to-face contact with the first portion <NUM> of the second stiffening segment <NUM>. Placing the first portion <NUM> of the first stiffening segment <NUM> into face-to-face contact with the first portion <NUM> of the second stiffening segment <NUM> as shown in <FIG> results in a filler area <NUM> being formed between the third portion <NUM> of the first stiffening segment <NUM> and the third portion <NUM> of the second stiffening segment <NUM>.

The fourth stage <NUM> of the process <NUM> shown in <FIG> further includes coupling (e.g., joining, bonding, adhering, etc.) the first portion <NUM> of the first stiffening segment <NUM> to the first portion <NUM> of the second stiffening segment <NUM>. The first portion <NUM> of the first stiffening segment <NUM> can be coupled to the first portion <NUM> of the second stiffening segment <NUM> in connection with placing the first portion <NUM> of the first stiffening segment <NUM> into face-to-face contact with the first portion <NUM> of the second stiffening segment <NUM>.

During a fifth stage <NUM> of the process <NUM> shown in <FIG>, a filler <NUM> is inserted into the filler area <NUM>. The filler <NUM> of <FIG> can be implemented as a CFRP filler that is formed and subsequently inserted into the filler area <NUM>.

During a sixth stage <NUM> of the process <NUM> shown in <FIG>, a second composite blank <NUM> is placed on and/or over the second portion <NUM> of the first stiffening segment <NUM>, the second portion <NUM> of the second stiffening segment <NUM>, and the filler <NUM>. The second composite blank <NUM> of <FIG> can be implemented via the composite blank <NUM> of <FIG> described above. The second composite blank <NUM> of <FIG> includes a first portion <NUM>, a second portion <NUM> located opposite the first portion <NUM>, and a third portion <NUM> extending between the first and second portions <NUM>, <NUM>. Placing the second composite blank <NUM> relative to the first and second stiffening segments <NUM>, <NUM> and the filler <NUM> during the sixth stage <NUM> of the process <NUM> shown in <FIG> can include placing the first portion <NUM> of the second composite blank <NUM> into face-to-face contact with the second portion <NUM> of the first stiffening segment <NUM>, placing the second portion <NUM> of the second composite blank <NUM> into face-to-face contact with the second portion <NUM> of the second stiffening segment <NUM>, and placing the third portion <NUM> of the second composite blank <NUM> into face-to-face contact with the filler <NUM>.

The sixth stage <NUM> of the process <NUM> shown in <FIG> further includes coupling (e.g., joining, bonding, adhering, etc.) the second composite blank <NUM> to the first and second stiffening segments <NUM>, <NUM> to provide a formed structure <NUM> including the first and second stiffening segments <NUM>, <NUM>, the filler <NUM>, and the second composite blank <NUM>. The formed structure <NUM> can thereafter be removed, released, and/or ejected from the first and second parts <NUM>, <NUM> of the forming block <NUM> for further processing, treatment and/or handling, as described below.

During a seventh stage <NUM> of the process <NUM> shown in <FIG>, a base segment pre-layup <NUM> is placed on a skin <NUM>. The base segment pre-layup <NUM> of <FIG> can include a single ply of material. The base segment pre-layup <NUM> of <FIG> can alternatively include multiple plies of material (e.g., two plies, four plies, etc.) formed in a stack or layup. The seventh stage <NUM> of the process <NUM> shown in <FIG> further includes coupling (e.g., joining, bonding, adhering, etc.) the base segment pre-layup <NUM> to the skin <NUM>. The base segment pre-layup <NUM> can be coupled to the skin <NUM> in connection with placing the base segment pre-layup <NUM> on the skin <NUM>.

During an eighth stage <NUM> of the process <NUM> shown in <FIG>, the formed structure <NUM> is placed on the base segment pre-layup <NUM>. The eighth stage <NUM> of the process <NUM> shown in <FIG> further includes coupling (e.g., joining, bonding, adhering, etc.) the formed structure <NUM> to the base segment pre-layup <NUM>. The formed structure <NUM> can be coupled to the base segment pre-layup <NUM> in connection with placing the formed structure <NUM> on the base segment pre-layup <NUM>.

The eighth stage <NUM> of the process <NUM> shown in <FIG> further includes forming first and second angled edges <NUM>, <NUM> (e.g., first and second chamfered edges) of the formed structure <NUM>. The first and second angled edges <NUM>, <NUM> can be formed in connection with placing the formed structure <NUM> on the base segment pre-layup <NUM>, and/or coupling the formed structure <NUM> to the base segment pre-layup <NUM>.

During a ninth stage <NUM> of the process <NUM> shown in <FIG>, a third composite blank <NUM> is pre-heated using a heat blanket <NUM>. The third composite blank <NUM> can be implemented via the composite blank <NUM> of <FIG> described above. The third composite blank <NUM> can be heated via the heat blanket <NUM> at a temperature of one hundred fifty degrees Fahrenheit (<NUM>°F, <NUM>,<NUM>) for between twenty and thirty minutes.

The ninth stage <NUM> of the process <NUM> shown in <FIG> further includes placing the third composite blank <NUM> on a flange <NUM> of the formed structure <NUM>. The flange <NUM> of the formed structure <NUM> is formed via the first portion <NUM> of the first stiffening segment <NUM> and the first portion <NUM> of the second stiffening segment <NUM> of the formed structure <NUM>. The third composite blank <NUM> can be placed on the flange <NUM> prior to the third composite blank <NUM> being pre-heated. The third composite blank <NUM> can alternatively be placed on the flange <NUM> after the third composite blank <NUM> has been pre-heated.

During a tenth stage <NUM> of the process <NUM> shown in <FIG>, the third composite blank <NUM> is draped over and/or around the flange <NUM>. One or more roller(s) <NUM> (e.g., one or more robotic roller(s)) can apply force to the third composite blank <NUM> to assist in draping the third composite blank <NUM> over and/or around the flange <NUM>. The tenth stage <NUM> of the process <NUM> shown in <FIG> further includes coupling (e.g., joining, bonding, adhering, etc.) the third composite blank <NUM> to the flange <NUM>. The third composite blank <NUM> can be coupled to the flange <NUM> in connection with draping the third composite blank <NUM> over and/or around the flange <NUM>.

During an eleventh stage <NUM> of the process shown in <FIG>, the formed structure <NUM>, the base segment pre-layup <NUM>, and the third composite blank <NUM> are compacted relative to one another and/or relative to the skin <NUM>. One or more caul(s) <NUM> can be placed on and/or around the formed structure <NUM>, the skin <NUM>, and/or the third composite blank <NUM> to assist in the compacting process. A vacuum bag <NUM> can be placed on and/or around the formed structure <NUM>, the skin <NUM>, the third composite blank <NUM>, and/or the caul(s) <NUM> to assist in the compacting process. The compacting process can include applying vacuum force to the formed structure <NUM>, the skin <NUM>, the third composite blank <NUM>, and/or the caul(s) <NUM> via the vacuum bag <NUM>. The caul(s) <NUM> and the vacuum bag <NUM> can be removed following the compacting process. The eleventh stage <NUM> of the process <NUM> shown in <FIG> further includes curing the formed structure <NUM>, the skin <NUM>, and/or the third composite blank <NUM>.

The above-described process <NUM> of <FIG> can be used to manufacture the stringer <NUM> of <FIG>. For example, the first stiffening segment <NUM> of the process <NUM> of <FIG> corresponds to the first stiffening segment <NUM> of <FIG>, with the first, second and third portions <NUM>, <NUM>, <NUM> of the first stiffening segment <NUM> of the process <NUM> of <FIG> corresponding to the first, second and third portions <NUM>, <NUM>, <NUM> of the first stiffening segment <NUM> of <FIG>. The second stiffening segment <NUM> of the process <NUM> of <FIG> corresponds to the second stiffening segment <NUM> of <FIG>, with the first, second and third portions <NUM>, <NUM>, <NUM> of the second stiffening segment <NUM> of the process <NUM> of <FIG> corresponding to the first, second and third portions <NUM>, <NUM>, <NUM> of the second stiffening segment <NUM> of <FIG>. The filler area <NUM> of the process <NUM> of <FIG> corresponds to the filler area <NUM> of <FIG>. The filler <NUM> of the process <NUM> of <FIG> corresponds to the filler <NUM> of <FIG>. The second composite blank <NUM> of the process <NUM> of <FIG>, in combination with the base segment pre-layup <NUM> of the process <NUM> of <FIG>, corresponds to the base segment <NUM> of <FIG>, with the first, second and third portions <NUM>, <NUM>, <NUM> of the second composite blank <NUM> of the process <NUM> of <FIG> corresponding to the first, second and third portions <NUM>, <NUM>, <NUM> of the base segment <NUM> of <FIG>. The skin <NUM> of the process <NUM> of <FIG> corresponds to the skin <NUM> of <FIG>. The third composite blank <NUM> of the process <NUM> of <FIG> corresponds to the reinforcement segment <NUM> of <FIG>.

From the foregoing, it will be appreciated that the stringers disclosed above (e.g., stringers having CFRP material reinforced flanges) provide numerous advantages over known stringers. For example, the above-described structural differences between the stringer of <FIG> and the known stringer of <FIG> result in the stringer of <FIG> having a reduced material volume, a reduced weight, and/or a reduced production cost relative to the material volume, the weight, and/or the production cost of the known stringer of <FIG>. As another example, the above-described reduced cross-sectional area of the filler area of the stringer of <FIG> relative to the cross-sectional area of the known stringer of <FIG> reduces (e.g., minimizes and/or prevents) thermal cracking and/or the formation of wrinkles within the stringer. Such a reduction in thermal cracking and/or in the formation of wrinkles results in an increase in the performance characteristic(s) (e.g., impact strength, crippling strength, buckling strength, etc.) of the stringer of <FIG> relative to the known stringer of <FIG>. Furthermore, as discussed above, the multi-ply structure of the CFRP reinforcement segment of the stringer of <FIG> independently increases the impact strength of the flange of the stringer of <FIG> relative to the impact strength associated with the flange of the known stringer of <FIG>.

A stringer to be coupled to a skin of an aircraft is disclosed. The stringer comprises a flange. The flange includes a first portion of a first stiffening segment. The flange also includes a first portion of a second stiffening segment coupled to the first portion of the first stiffening segment. The flange also includes a CFRP reinforcement segment coupled to the first portion of the first stiffening segment and to the first portion of the second stiffening segment. The CFRP reinforcement segment is to strengthen the first portion of the first stiffening segment and the first portion of the second stiffening segment.

The CFRP reinforcement segment includes multiple plies of CFRP tape or CFRP fabric. The multiple plies of the CFRP reinforcement segment can be configured as a non-traditional layup. The non-traditional layup can be a symmetric layup.

The CFRP reinforcement segment is to increase at least one of an impact strength, a crippling strength, or a buckling strength of the first portion of the first stiffening segment and the first portion of the second stiffening segment.

The first stiffening segment further includes a first surface and a second surface located opposite the first surface of the first stiffening segment. The second stiffening segment further includes a first surface and a second surface located opposite the first surface of the second stiffening segment. The CFRP reinforcement segment includes a first surface and a second surface located opposite the first surface of the first stiffening segment. The second surface of the first stiffening segment along the first portion of the first stiffening segment is coupled to the second surface of the second stiffening segment along the first portion of the second stiffening segment. The second surface of the CFRP reinforcement segment is coupled to the first surface of the first stiffening segment along the first portion of the first stiffening segment and is further coupled to the first surface of the second stiffening segment along the first portion of the second stiffening segment.

The first stiffening segment further includes a second portion oriented orthogonally to the first portion of the first stiffening segment, and a third portion extending between the first and second portions of the first stiffening segment. The second stiffening segment further includes a second portion oriented orthogonally to the first portion of the second stiffening segment, and a third portion extending between the first and second portions of the second stiffening segment.

The CFRP reinforcement segment extends along between thirty five percent and eighty five percent of a height dimension of the stringer measured orthogonally from an end of the first portion of the first stiffening segment to a portion of the first surface of the first stiffening segment located at the second portion of the first stiffening segment.

The stringer further comprises a base segment, a filler area, and a filler. The base segment includes a first portion, a second portion located opposite the first portion of the base segment, and a third portion extending between the first and second portions of the base segment. The first portion of the base segment is coupled to the second portion of the first stiffening segment. The second portion of the base segment is coupled to the second portion of the second stiffening segment. The filler area is defined by the third portion of the first stiffening segment, the third portion of the second stiffening segment, and the third portion of the base segment. The filler is retained within the filler area.

The first stiffening segment has a first thickness, the second stiffening segment has a second thickness equal to the first thickness, the base segment has a third thickness equal to the first thickness and equal to the second thickness, and the CFRP reinforcement segment has a fourth thickness.

The flange comprises a first flange. The stringer further comprises a second flange and a third flange. The second flange and the third flange are oriented orthogonally to the first flange. The second flange includes the second portion of the first stiffening segment and the first portion of the base segment. The third flange includes the second portion of the second stiffening segment and the second portion of the base segment. The first flange has a fifth thickness equal to a sum of the first thickness, the second thickness, and twice the fourth thickness. The second flange has a sixth thickness equal to a sum of the first thickness and the third thickness. The third flange has a seventh thickness equal to a sum of the second thickness and the third thickness. The fifth thickness is greater than the sixth thickness and greater than the seventh thickness.

A method of manufacturing a stringer for an aircraft is disclosed. The method comprises forming first and second stiffening segments from a first composite blank. The method further comprises coupling a first portion of the first stiffening segment to a first portion of the second stiffening segment. The method further comprises forming a CFRP reinforcement segment from a second composite blank. The method further comprises coupling the CFRP reinforcement segment to the first portion of the first stiffening segment and to the first portion of the second stiffening segment. The CFRP reinforcement segment is to strengthen the first portion of the first stiffening segment and the first portion of the second stiffening segment.

The first composite blank has a chordwise ply drop ratio between three and thirty and a spanwise ply drop ratio between one hundred twenty and three hundred. The second composite blank has a chordwise ply drop ratio between three and thirty and a spanwise ply drop ratio between one hundred and three hundred. The CFRP reinforcement segment includes multiple plies of CFRP tape or CFRP fabric. The multiple plies of the CFRP reinforcement segment can be configured as a non-traditional layup. The non-traditional layup can be a symmetric layup.

Claim 1:
A method (<NUM>) of manufacturing a stringer (<NUM>) for an aircraft (<NUM>), the method comprising:
forming first (<NUM>, <NUM>) and second (<NUM>, <NUM>) stiffening segments from a first composite blank (<NUM>, <NUM>);
coupling a first portion (<NUM>, <NUM>) of the first stiffening segment to a first portion (<NUM>, <NUM>) of the second stiffening segment;
forming a carbon fiber reinforced plastic (CFRP) reinforcement segment (<NUM>) from a second composite blank (<NUM>, <NUM>); and
coupling the CFRP reinforcement segment to the first portion of the first stiffening segment and to the first portion of the second stiffening segment, the CFRP reinforcement segment to strengthen the first portion of the first stiffening segment and the first portion of the second stiffening segment,
wherein at least one of the first composite blank and the second composite blank, or both, includes a stack and/or layup of plies (<NUM>, <NUM>) and has a chordwise ply drop ratio between three and thirty and a spanwise ply drop ratio between one hundred twenty and three hundred,
wherein the chordwise ply drop ratio is calculated as a ratio of a chordwise stagger distance (<NUM>, <NUM>) of the plies (<NUM>, <NUM>) to a thickness (<NUM>, <NUM>) of individual ones of the plies (<NUM>, <NUM>), wherein the spanwise ply drop ratio is calculated as a ratio of a spanwise stagger distance (<NUM>, <NUM>) of the plies (<NUM>, <NUM>) to the thickness (<NUM>, <NUM>) of individual ones of the plies (<NUM>, <NUM>), wherein the chordwise stagger distance (<NUM>, <NUM>) and the spanwise stagger distance (<NUM>, <NUM>) are implemented between successively-layered ones of the plies (<NUM>, <NUM>).