Spiral laminated structural cone and manufacturing method

A cone-shaped composite article may include an inner sublaminate containing at least four unidirectional plies having an inner stacking sequence with fiber angles of 0, 90, −45, and +45 degrees such that the inner laminate has a quasi-isotropic layup pattern at any location on the inner laminate. The cone-shaped composite article may also include an outer sublaminate containing at least four unidirectional plies having an outer stacking sequence that is a mirror image of the inner stacking sequence. Each one of the unidirectional plies may be continuous along a ply arclength wrapping 360 degrees around the cone-shaped composite article and may have opposing ply ends terminating at a ply seam.

FIELD

The present disclosure relates generally to composite articles and, more particularly, to cone-shaped articles formed of laminated composite material.

BACKGROUND

Spacecraft such as communications satellites are typically launched into orbit using a launch vehicle, and are typically encapsulated within a fairing mounted on top of the launch vehicle. The fairing protects the spacecraft from the elements as the launch vehicle ascends through the atmosphere. The spacecraft may be coupled to the launch vehicle with a cone-shaped payload attach fitting. The payload attach fitting must be capable of transmitting axial loads, bending loads and torsional loads from the spacecraft into the launch vehicle. Axial loads on the payload attach fitting can be significant during lift-off of the launch vehicle. Bending loads on the payload attach fitting can be relatively high as a result of aerodynamic turbulence acting on the launch vehicle at relatively high altitudes.

Composite materials may be used to fabricate low-weight, high-strength structures or articles such as for a payload attach fitting for coupling a spacecraft loads to a launch vehicle. Unfortunately, conventional methods of fabricating cone-shaped composite structures may require the use of darting of the individual composite plies so that the composite plies will conform to the structure geometry. In addition, conventional methods of fabricating cone-shaped composite structures may require the use of overlap splicing of the composite plies so that the composite plies will conform to the structure geometry. The use of darting and overlap splicing in the composite plies adds to the weight of the composite structure. In addition, the darting and overlap splicing of composite plies increases the risk of the occurrence of voids or wrinkles in the composite structure which may compromise the strength characteristics of the composite structure.

As can be seen, there exists a need in the art for a cone-shaped composite article that may be fabricated without the need for darts or splices and which can be produced in a relatively high strength. Furthermore, there exists a need in the art for a relatively light weight and high-strength cone-shaped composite article capable of transmitting a variety of loads of different direction and magnitude.

SUMMARY

The above-noted needs associated with composite articles are specifically addressed and alleviated by the present disclosure which provides a cone-shaped composite article including an inner sublaminate containing four unidirectional plies having an inner stacking sequence with fiber angles of 0, 90, +45, and −45 degrees such that the inner laminate has a quasi-isotropic layup pattern at any location on the inner laminate. The cone-shaped composite article may also include an outer sublaminate containing four unidirectional plies having an outer stacking sequence that is a mirror image of the inner stacking sequence. Each one of the unidirectional plies may be continuous along a ply arclength wrapping 360 degrees around the cone-shaped composite article and may have opposing ply ends terminating at a ply seam.

In a further embodiment, disclosed is cone-shaped composite article including an inner sublaminate having a cone shape and containing four unidirectional plies having an inner stacking sequence with fiber angles of 0, 90, +45, and −45 degrees such that the inner laminate has a quasi-isotropic layup at any location on the inner laminate. The cone-shaped composite article may also include an outer sublaminate having an outer stacking sequence that is a mirror image of the inner stacking sequence. Each one of the unidirectional plies may be continuous along a ply arclength wrapping 360 degrees around the cone-shaped composite article and having opposing ply ends terminating at a ply seam. Furthermore, the cone-shaped composite article may also include at least one global axial ply laminated with the inner sublaminate and the outer sublaminate. The global axial ply may include a plurality of axial ply wedges arranged in side-by-side relation and extending 360 degrees around the cone-shaped composite article. Each axial ply wedge may have a fiber angle that may be generally aligned with a longitudinal axis of the cone-shaped composite article.

Also disclosed is a method of manufacturing a cone-shaped composite article. The method may include the step of providing unidirectional plies in a continuous arcuate shape in a flat pattern configured to wrap 360 degrees around a cone-shaped mandrel such that opposing ply ends of each unidirectional ply terminate at a ply seam. The method may further include the step of laying up an inner sublaminate on the cone-shaped mandrel. The inner sublaminate may contain four of the unidirectional plies having an inner stacking sequence with fiber angles of 0, 90, +45, and −45 degrees such that the inner laminate has a quasi-isotropic layup at any location of the inner laminate. The method may also include laying up an outer sublaminate in an outer stacking sequence that is a mirror image of the inner stacking sequence.

It should be noted that the four unidirectional plies in a sublaminate may be arranged in any order and are not limited to being arranged in the 0/90/+45/−45 order indicated above. In this regard, the four unidirectional plies in each sublaminate may be arranged in any order containing at least a 0-degree ply, a 90-degree ply, a +45-degree ply, and a −45-degree ply to form a quasi-isotropic layup on one side of a through-thickness mid-plane (i.e., the thickness centerline), and a mirror image quasi-isotropic sublaminate on an opposite side of the mid-plane containing four unidirectional plies in a mirror-image stacking sequence described below. In addition, a composite laminate may be provided with multiple quasi-isotropic sublaminates on one side of the mid-plane and an equal number of quasi-isotropic sublaminates on an opposite side of the mid-plane to form a balanced and symmetric layup as described below. The composite laminate is balanced in the sense that each negative fiber-angle ply (e.g., a −45-degree ply) is balanced by a corresponding positive fiber-angle ply (e.g., a +45-degree ply). The composite laminate is symmetric in the sense that the plies on one side of the mid-plane are a mirror image of the plies on an opposite side of the mid-plane and are located at the same distances from the mid-plane.

DETAILED DESCRIPTION

Referring now to the drawings wherein the showings are for purposes of illustrating preferred and various embodiments of the disclosure, shown inFIG. 1is a sectional illustration of a spacecraft104encapsulated within a fairing102mounted on top of a launch vehicle100. The spacecraft104may be supported by a payload attach fitting112which may couple the spacecraft104to the launch vehicle100. The payload attach fitting112may be configured as a cone-shaped composite article114and may be configured to transmit axial loads106, bending loads108, and torsional loads110from the spacecraft104to the launch vehicle100.

InFIG. 2, shown is a perspective illustration of the cone-shaped composite article114having a longitudinal axis116extending vertically through a center thereof. The cone-shaped composite article114may include an upper edge118and a lower edge122. Although not shown, a metal ring and mechanical hardware (e.g., separation hardware) may be fastened to the upper edge118for coupling the cone-shaped composite article114to the spacecraft104(FIG. 1). A metal ring and mechanical hardware (e.g., separation hardware) may also be fastened to the lower edge122for releasably coupling the cone-shaped composite article114to the launch vehicle100(FIG. 1). The cone-shaped composite article114may be formed as a composite laminate150formed of a plurality of unidirectional plies180.

InFIGS. 3-4, shown is a top view and a sectional view of the cone-shaped composite article114ofFIG. 2. The upper edge118may have an upper edge diameter120that may be complementary to a diameter of an interface (not shown) with the spacecraft104(FIG. 1). The lower edge122may have a lower edge diameter124that may be complementary to a diameter of an interface (not shown) with the launch vehicle100(FIG. 1). In an embodiment of a payload attach fitting112(FIG. 1), the cone-shaped composite article114may have a cone height130(FIG. 4) in the range of from approximately 10 inches to 36 inches or larger, and a half-angle of between approximately 5 degrees to 40 degrees or larger, depending on the interface dimensions at the spacecraft104and at the launch vehicle100.

InFIG. 4, in an embodiment, the upper edge diameter120may be in the range of from approximately 12-48 inches or larger, and the lower edge diameter124may be in the range of from approximately 18-60 inches or larger. The cone-shaped composite article114may have a wall thickness132extending between the cone inner surface126and the cone outer surface128. In an embodiment, the wall thickness132may be in the range of from approximately 0.10 inch to 1.0 inch or larger, depending on the strength and stiffness requirements for coupling the spacecraft104(FIG. 1) to the launch vehicle100(FIG. 1). However, the cone-shaped composite article114may be provided in any one of a variety of different sizes and configurations, without limitation, and is not limited to the above-noted dimensional ranges.

InFIG. 5, shown is schematic illustration of an embodiment of a solid composite laminate150comprising a plurality of unidirectional plies180of composite material. The unidirectional plies180may be laminated together to form the cone-shaped composite article114. The composite laminate of the cone-shaped composite article114may be fabricated by laying up an initial unidirectional ply180on a cone-shaped mandrel300(FIG. 19). The local fiber angle154(FIG. 9) of the unidirectional ply180may continuously change in a spiraling pattern relative to a longitudinal axis116(FIG. 4) of the cone-shaped composite article114. The ply ends200of the unidirectional ply180may be joined or abutted at a ply seam204having a gap208. The gap208is shown exaggerated inFIG. 5to illustrate a ply butt joint206between the ply ends200. In this regard, the gap208in the ply butt joint206in any one of the unidirectional plies180is preferably less than approximately 0.10 inch between the ply ends200although larger gaps208are contemplated. In an embodiment, the ply ends may be generally straight such that the ply butt joints206form a generally straight line that may be aligned with the longitudinal axis116of the cone-shaped composite article114. However, the ply butt joints206may be formed in any shape and are not limited to a straight line configuration that is aligned with the longitudinal axis116. It should also be noted that although the present disclosure illustrates the ply seams204as ply butt joints206, it is contemplated that the ply ends200may be formed as overlap joints (not shown).

InFIG. 5, a second unidirectional ply180may be laid up over the initial unidirectional ply180with the ply seam204of the second unidirectional ply180being angularly clocked 180 degrees relative to the ply seam204of the initial unidirectional ply180and resulting in a 2-ply laminate having a 0/45 degree layup pattern that spirals around the circumference134of the cone-shaped composite article114. Two additional unidirectional plies180may be laid up with local fiber angles oriented 90 degrees relative to the initial two unidirectional plies180resulting in a 4-ply sublaminate having a quasi-isotropic layup pattern168. The orientation of the quasi-isotropic layup pattern168continuously changes in a spiraling manner along a circumferential direction of the cone-shaped composite article114.

InFIG. 5, additional 4-ply quasi-isotropic layup patterns168may be added to the composite laminate150and clocked at different angles around the circumference134of the cone-shaped composite article114to provide a composite laminate150having the desired strength and stiffness characteristics. As indicated above, such additional 4-ply quasi-isotropic layup patterns168are arranged in a balanced layup166that is mirrored about a mid-plane164of the composite laminate150. For example, as illustrated inFIG. 15, for each additional inner sublaminate156, an outer sublaminate160is provided on an opposite side of the mid-plane164with an outer stacking sequence162of the outer sublaminate160mirroring the inner stacking sequence158of the inner sublaminate156, although it not necessary that the additional inner sublaminate156and outer sublaminate160are adjacent to one another, as described in greater detail below. Global axial plies250(FIG. 17) may optionally be added to the composite laminate150to increase the axial strength and stiffness of the cone-shaped composite article114as described below. The system and method disclosed herein advantageously provides for a balanced and symmetric layup which prevents twisting or warping of the composite laminate150during processing such as during cool down after curing the composite laminate150. In addition, the system and method disclosed herein minimizes or eliminates the occurrence of overlap splices which reduces the overall weight of the composite laminate150, increases structural integrity, and significantly decreases or eliminates the potential for the occurrence of wrinkles in the composite laminate150during cure.

InFIG. 6, shown is an exploded schematic illustration of the inner sublaminate156and the outer sublaminate160which make up an embodiment of the composite laminate150of the cone-shaped composite article114. The inner sublaminate156contains four (4) unidirectional plies180formed of fiber-reinforced polymer matrix material and having an inner stacking sequence158with local fiber angles of 0, 90, −45, and +45 degrees or other combinations of the 4-ply quasi-isotropic layup pattern168(e.g., a 0/+45/90/−45 pattern, a +45/0/−45/−90 pattern, a −45/0/+45/90 pattern, and other patterns) as described below. In this regard, the inner stacking sequence158of the inner sublaminate156advantageously provides a quasi-isotropic layup pattern168at any location on the cone shape152, as mentioned above. The outer sublaminate160also contains four (4) unidirectional plies180having an outer stacking sequence162that is a mirror-image (i.e., in the through-thickness direction) of the inner stacking sequence158as described below. In this regard, the outer sublaminate160also provides a quasi-isotropic layup pattern168at any location on the cone shape152.

InFIGS. 7-8, shown are portions of the inner sublaminate156and outer sublaminate160and illustrating the quasi-isotropic layup pattern168at any location on the cone shape152(FIG. 6).FIG. 7illustrates the two outermost plies of the outer sublaminate160having fiber angles154(FIG. 9) that are oriented 90 degrees relative to one another. The two innermost plies of the outer sublaminate160have fiber angles154that are also oriented 90 degrees relative to one another and 45 degrees relative to the two outermost plies resulting in the quasi-isotropic layup pattern168.FIG. 8illustrates the two outermost plies of the inner sublaminate156having fiber angles154oriented 90 degrees relative to one another and two innermost plies with local fiber angles154oriented 90 degrees relative to one another and locally 45 degrees relative to the two outermost plies resulting in the quasi-isotropic layup pattern168. It can be seen that the fiber angles154for the unidirectional plies180inFIG. 8are mirror-images of the fiber angles154of the unidirectional plies180inFIG. 7.

FIGS. 7-8illustrate a balanced layup166(FIG. 9) provided by the inner sublaminate156and the outer sublaminate160about the mid-plane164(FIG. 6) of the composite laminate150(FIG. 6). The mid-plane164is located between the outermost unidirectional ply180of the inner sublaminate156and the innermost unidirectional ply180of the outer sublaminate160, and wherein the mid-plane164represents the through-thickness location about which the fiber angles154of the inner sublaminate156and outer sublaminate160are mirror-imaged. In addition, the composite laminate150may be arranged such that the unidirectional plies180are symmetric about the mid-plane164wherein pairs of mirror-imaged unidirectional plies180of the inner sublaminate156and outer sublaminate160may be located at equal distances from the mid-plane164which may minimize deformation or warping during curing of the composite laminate150. In the present disclosure, inner sublaminates156are located on an inboard side (i.e., nearest the cone inner surface126—FIG. 4) of the cone-shaped composite article114, and outer sublaminates160are located on an outboard side (i.e., nearest the cone outer surface128—FIG. 4) of the cone-shaped composite article114.

InFIG. 9, shown is a chart illustrating an embodiment of a ply stacking sequence for the cone-shaped composite article114ofFIG. 11. InFIG. 9, the ply numbering (e.g., Ply No.) column represents the stacking order of the unidirectional plies180starting with Ply 1 at the tool surface such as the mandrel surface302of the cone-shaped mandrel300illustrated inFIG. 19. InFIG. 9, the Ply Pattern column represents one of two ply patterns (e.g., ply pattern A or ply pattern B—FIGS. 13-14) that may implemented for forming unidirectional plies180for laying up the composite laminate150. The Seam Location column refers to the seam diagram ofFIG. 12which illustrates the seam locations of the ply seams204for each unidirectional ply180. The Fiber Angle column represents the fiber angles of the unidirectional plies180relative to one another at the 0-degree seam location on the cone-shaped composite article114ofFIG. 11. At the 0-degree seam location inFIG. 11, the fiber angles for Ply 1 through Ply 8 is +45/90/0/−45/−45/0/90/+45, corresponding to the Fiber Angle column ofFIG. 9.

InFIG. 9, the chart lists the stacking sequence of the inner sublaminate156which is comprised of a first pair of unidirectional plies182, Ply 1 and Ply 2, and which may both be formed from ply pattern A using unidirectional ply material at the same fiber angle for Ply 1 and Ply 2. For example,FIG. 13illustrates ply pattern A having a 90 degree fiber angle (i.e., relative to the reference end202) for the first pair of unidirectional plies182, Ply 1 and Ply 2. The chart ofFIG. 9also lists a second pair of unidirectional plies186, Ply 3 and Ply 4, which may be formed from ply pattern B using unidirectional ply material having the same fiber angle for Ply 3 and Ply 4. For example,FIG. 13illustrates ply pattern B having a 0 degree fiber angle (i.e., relative to the reference end202) for the first pair of unidirectional plies182, Ply 3 and Ply 4. The chart inFIG. 9also lists the outer stacking sequence of the outer sublaminate160which is also comprised of a first pair of unidirectional plies182and a second pair of unidirectional plies186arranged in mirror-image to the first pair182and second pair186of unidirectional plies of the inner sublaminate156to provide a balanced layup166for the composite laminate150.

InFIG. 10, shown is a fiber angle rosette210illustrating the sign convention for the fiber angles154of the quasi-isotropic layup pattern168(FIG. 9) in the present disclosure. The sign convention represents the relative fiber angle orientations when looking down on a unidirectional ply180(FIG. 9) applied to a tool. In the present disclosure, the tool may comprise a cone-shaped mandrel300as illustrated inFIG. 19. In an embodiment, the unidirectional plies180may be laid up in a manner such that at any location on the cone-shaped composite article114(FIG. 9), the relative fiber angles154may be maintained within an angular tolerance of up to approximately ±2 degrees for the 0/901±45 fiber angles of the quasi-isotropic layup pattern168of the inner sublaminate156(FIG. 9) and the outer sublaminate160(FIG. 9).

InFIG. 11, shown is an exploded perspective illustration of the unidirectional plies180of the inner sublaminate156and the outer sublaminate160corresponding to the ply stacking sequence illustrated inFIG. 9. InFIG. 11, each one of the unidirectional plies180is continuous (except at a ply seam204) along a ply arclength190(FIG. 13) wrapping 360-degrees around the cone-shaped composite article114. Each one of the unidirectional plies180has opposing ply ends200that terminate at a ply seam204. One of the ply ends200may comprise a reference end202(FIG. 13-14) which may comprise the ply end200by which the unidirectional ply180is aligned with a seam location prior to wrapping the unidirectional ply180around a cone-shaped mandrel300(FIG. 19) or over a previously-laid unidirectional ply180. As indicated above, the ply seams204may be formed as ply butt joints206although one or more of the ply seams204may be formed as an overlap joint (not shown). In an embodiment, each one of the unidirectional plies180may be provided in a ply width198(FIG. 13) which may extend at least from an upper edge118(FIG. 5) of the cone-shaped composite article114(FIG. 5) to at least a lower edge122(FIG. 5) thereof. However, one or more of the unidirectional plies180may have a ply width198(FIG. 13) that extends above the upper edge118and/or below the lower edge122of the final cone-shaped composite article114during layup. Excess ply material above the upper edge118and/or below the lower edge122may be trimmed from the cone-shaped composite article114following cure.

InFIG. 11, the inner sublaminate156includes the first pair of unidirectional plies182, Ply 1 and Ply 2, which are both formed using ply pattern A having a first fiber angle184. The ply seams204of Ply 1 and Ply 2 are clocked 180 degrees relative to one another resulting in a 0/45 degree laminate. The inner sublaminate156also includes the second pair of unidirectional plies186, Ply 3 and Ply 4, which are both formed using ply pattern B having a second fiber angle188. InFIG. 14, the fiber angle154for ply pattern B is shown oriented at 90 degrees relative to the reference end202. InFIG. 13, the fiber angle154for ply pattern A is shown oriented at of 0 degrees relative to the reference end202. However, the fiber angle154of ply pattern A and ply pattern B may be oriented at any angle relative to the reference end202, as long as the fiber angle154of ply pattern A is oriented at 90 degrees to the fiber angle154of ply pattern B.

InFIGS. 11-12, the ply seams204of the second pair of unidirectional plies186, Ply 3 and Ply 4, are clocked 180 degrees relative to one another. In addition, the ply seams204of the second pair of unidirectional plies186, Ply 3 and Ply 4, are aligned with the ply seams204of the first pair of unidirectional plies182, Ply 1 and Ply 2, resulting in a quasi-isotropic layup for the inner sublaminate156as illustrated inFIG. 8. For example, at the 0-degree seam location, the inner sublaminate156from Ply 1 to Ply 4 has a quasi-isotropic layup pattern of +45/90/0/−45. As may be appreciated, the unidirectional plies180may be arranged to provide a different quasi-isotropic layup pattern168. For example, the unidirectional plies180may be arranged to provide a 0/+45/90/−45 pattern, a +45/0/−45/−90 pattern, a −45/0/+45/90 pattern, and other patterns. The unidirectional plies180of the outer sublaminate160may be arranged in mirror-image to the unidirectional plies180of the inner sublaminate156as shown inFIG. 11to provide a balanced layup166as indicated above.

InFIGS. 13-14, shown are the arcuate shapes192of ply pattern A and ply pattern B from which the unidirectional plies180may be formed. Ply pattern A and ply pattern B may be formed at the same dimensions such as the same inner radius194, outer radius196, ply width198, and arcuate length between the ply ends200. Each one of the ply patterns A and B represents a continuous arcuate shape192for forming the unidirectional plies180in flat pattern to wrap 360-degrees around a cone-shaped mandrel300such that opposing ply ends200of each unidirectional ply180may terminate at a ply seam204such as a ply butt joint206(FIG. 11). In addition, each one of the ply patterns A and B may be provided in a ply width198such that when a unidirectional ply180is laid up on the cone-shaped mandrel300(FIG. 19), the inner radius194of the arcuate shape192may be substantially aligned with the upper edge118(FIG. 5) of the cone-shape composite article, and the outer radius196of the arcuate shape192may be substantially aligned with the lower edge122(FIG. 5) of the cone-shape composite article114. However, the unidirectional plies180may be formed at an inner radius194and an outer radius196that extend respectively above and below the upper and lower edges118,122of the final cone-shape composite article114, and the cone-shaped composite article114can be trimmed upper and lower edges118,122after curing

InFIGS. 13-14, the unidirectional plies180may be formed by cutting out unidirectional material in the flat pattern arcuate shape192of ply pattern A and ply pattern B. For example, the unidirectional plies180may be formed by cutting an arcuate shape192of ply pattern A or ply pattern B from a single, large piece of unidirectional material. Alternatively, the unidirectional plies180may be formed from a plurality of individual strips or courses232of unidirectional tape230arranged in side-by-side relation to one another. The unidirectional tape230may be available in a tape width234in the range of from approximately 1 to 20 inches or larger. In an embodiment, the unidirectional tape230may comprise pre-impregnated carbon fiber unidirectional tape230in a desired tape width234.

InFIGS. 13-14, a plurality of courses232of unidirectional tape230are arranged in side-by-side relation so that the fiber angle154is parallel to the reference end202of the ply pattern A. For ply pattern B, the unidirectional tape230may be arranged so that the fiber angle154is perpendicular to the reference end202of the ply pattern B. The reference end202of each ply pattern A and B may comprise the ply end200by which the unidirectional ply180is aligned with the seam location on the cone-shaped mandrel300(FIG. 19). The side-by-side courses232of unidirectional tape230may be cut into the arcuate shape192of ply pattern A. The courses232of unidirectional tape230may be individually laid up by aligning the courses232with index marks that may be provided in the mandrel surface302(FIG. 20) for the seam location index marks304(FIG. 20), upper edge index mark306(FIG. 20), and/or lower edge index marks308(FIG. 20). The tape sides236of the courses232of unidirectional tape230may be positioned in side-by-side abutting (e.g., non-overlapping) relation to one another to form a complete, continuous, 360-degree unidirectional ply180.

In an embodiment, the unidirectional plies180may be comprised of unidirectional material comprising fiber-reinforced polymer matrix material as indicated above. For example, the unidirectional material may comprise pre-impregnated composite material such as pre-impregnated unidirectional tape. However, the unidirectional material may also comprise dry fiber material (not shown) such as dry fiber preforms (not shown) that may be cut to the arcuate shapes of ply pattern A and B and laid up on a cone-shaped mandrel300followed by infusing the preforms with liquid resin in a separate step (not shown).

In an embodiment, the unidirectional material may comprise unidirectional fibers pre-impregnated with polymer matrix material. The polymer matrix material may comprise thermoplastic matrix material or thermosetting matrix material. The fibers may be formed of carbon, glass, aramid, metal, and/or any fiber material or combination thereof. In an embodiment, the unidirectional plies180may be provided as relatively thick, high-density, high-modulus, unidirectional carbon fibers pre-impregnated with polymer matrix material. For example, the unidirectional plies180may have a ply thickness of at least approximately 0.002 inch such as a thickness of approximately 0.020 inch. The unidirectional plies180may comprise unidirectional carbon fibers pre-impregnated with polymer matrix material and having a nominal cured ply thickness of approximately 0.010 inch.

As indicated above, the unidirectional plies180may include fibers having a relatively high modulus in the range of approximately 30-70×106pounds per square inch (psi) which may provide the cone-shaped composite article114with relatively high stiffness in all directions. In addition, the unidirectional plies180may have a relatively high aerial density such as an aerial density of approximately 50-350 grams/square meter which, in combination with a relatively large thickness of approximately 0.020 inch, may minimize the total quantity of unidirectional plies180and global axial plies250(described below) required to achieve the necessary wall thickness132(FIG. 4) for supporting the loads to which the cone-shaped composite article114(FIG. 4) may be subjected during service. The use of pre-impregnated polymer matrix material instead of wet layup (e.g., resin-infused dry preforms) may allow for improved control over the fiber volume fraction in the final cone-shaped composite article114. In an embodiment, the cone-shaped composite article114may be manufactured with a fiber volume fraction of between approximately 45-60 percent, such as between approximately 52-56 percent, although larger or smaller fiber volume fractions are contemplated.

InFIG. 15, shown is a chart of a ply stacking sequence for an embodiment of a cone-shaped composite article114(FIG. 11) having a plurality of balanced layups166(FIG. 11) to achieve a desired wall thickness132(FIG. 4). As indicated above, a balanced layup166comprises an inner sublaminate156having an inner stacking sequence158and an outer sublaminate160having an outer stacking sequence162in mirror-image to the inner stacking sequence158.FIG. 15illustrates three (3) balanced layups166comprising three (3) inner sublaminates156on one side of the mid-plane164(i.e., the mid-plane is between Ply 16 and Ply 17) and three (3) outer sublaminates160on an opposite side of the mid-plane164. As indicated above, each inner sublaminate156and each outer sublaminate160include four (4) unidirectional plies180arranged to form a quasi-isotropic layup at any location on the cone-shaped composite article114. For each balanced layup166, the inner sublaminate156and the outer sublaminate160include ply seams204that are clocked 180 degrees relative to one another as described above and shown inFIG. 9. InFIG. 15, for a cone-shaped composite article114having multiple balanced layups166, the ply seams204(FIG. 11) of the balanced layups166may be clocked at different seam locations around the circumference134of the cone-shaped composite article114. Clocking of the seam locations of the balanced layups166may prevent the occurrence of multiple ply seams204at one location which may improve the stress distribution around the circumference134of the cone-shaped composite article114.

InFIG. 15, in an embodiment, the cone-shaped composite article114may optionally include one or more global axial plies250to increase the axial strength and stiffness of the cone-shaped composite article114(FIG. 4). The global axial plies250may be formed of unidirectional material that may be similar to the unidirectional material used for the unidirectional plies180of the inner sublaminate156and outer sublaminate160. The global axial plies250may be arranged such that the fiber angle252(FIG. 18) is generally aligned with the longitudinal axis116(FIG. 4) of the cone-shaped composite article114. One or more global axial plies250may be laminated within an inner sublaminate156and within an outer sublaminate160. For example,FIG. 15illustrates two (2) global axial plies250laminated between Ply 1 and Ply 3 of the inner sublaminate156comprised of Ply 1, 4, 5, and 7, and another global axial ply250laminated between Ply 5 and Ply 7. To provide a balanced layup166(FIG. 11), the outer sublaminate160comprised of Ply 26, 28, 29, and 32 may have an equal number of global axial plies250laminated in mirror image to the global axial plies250in the inner sublaminate156. The cone-shaped composite article114may optionally include one or more global axial plies250laminated between adjacently-disposed inner sublaminates156(e.g., Ply 8) and between adjacently-disposed outer sublaminates160(e.g., Ply 25) to provide a balanced layup166. AlthoughFIG. 15illustrates eight (8) global axial plies250, any number of global axial plies250may be provided in any arrangement within the sublaminates156,160and/or between the sublaminates156,160.

InFIG. 16, shown is a diagram of seam locations of the inner and outer sublaminates156,160for the cone-shaped composite article114represented inFIG. 15. The ply seam204locations may be equiangularly arranged (e.g., in 45-degree increments) to improve the strength characteristics of the cone-shaped composite article114. As mentioned above, the clocking of the ply seams204avoids the occurrence of multiple ply seams204at one location and instead provides a staggered arrangement of ply seams204. In this manner, the unidirectional plies180that overlap a ply butt joint206act as an overlap splice to interconnect the opposing ply ends200of the unidirectional ply180. AlthoughFIG. 16illustrates an equiangular distribution of the ply seams204, the ply seams204may be arranged in a non-equiangular manner.

InFIG. 17, shown is a view looking downwardly at the cone-shaped composite article114and illustrating global axial plies250made up of a plurality of axial ply wedges254.FIG. 17illustrates Ply 32 which is partially cut away to show Ply 30 and Ply 31 which are global axial plies250laminated within the outer sublaminate160. Each one of the global axial plies250may be comprised of a plurality of axial ply wedges254arranged in side-by-side relation to one another and extending 360-degrees around the cone-shaped composite article114. Each one of the axial ply wedge254may have a fiber angle252(FIG. 18) that may be generally aligned (e.g., within ±10 degrees) of the longitudinal axis116(FIG. 18) of the cone-shaped composite article114. The wedge sides262of adjacent axial ply wedges254may be positioned in abutting side-by-side relation to one another to form a plurality of wedge butt joints264.

InFIG. 17, each global axial ply250may be overlapped by at least one continuous unidirectional ply180of an inner sublaminate156or of an outer sublaminate160. The unidirectional ply180may act as an overlap splice for the wedge butt joints264and may interconnect the adjacently-disposed axial ply wedges254. For example, Ply 32 is a unidirectional ply180overlapping global axial ply, Ply 31, such that Ply 32 may serve as an overlap splice to the wedge butt joints264of Ply 31. Although not shown, Ply 29 is also a unidirectional ply180that may serve as an overlap splice to the wedge butt joints264of global axial ply, Ply 30.

InFIG. 17, in an embodiment, the wedge butt joints264in each one of the global axial plies250may be staggered with the wedge butt joints264in one or more of the remaining global axial plies250to avoid the occurrence of two or more wedge butt joints264at one location on the cone-shaped composite article114. For example,FIG. 17illustrates the wedge butt joints264of Ply 30 being staggered with respect to the wedge butt joints264of Ply 31. In an embodiment, the wedge butt joints264in one or more of the global axial plies250may be positioned at a stagger266of at least 0.50 inch relative to the wedge butt joints264in one or more of remaining global axial plies250, although the amount of stagger266may be less than 0.50 inch. In an embodiment, one or more of the wedge butt joints264in one of the global axial plies250may be generally aligned with one or more of the wedge butt joints264in other global axial plies250.

InFIG. 18, shown is an embodiment of ply pattern C for forming an axial ply wedge254. The ply pattern C has an inner radius256and an outer radius258defining a wedge height260of the axial ply wedge254. In an embodiment, the wedge height260of the axial ply wedge254may be substantially equivalent to the ply width198(FIGS. 13-14) of ply pattern A (FIG. 13) and ply pattern B (FIG. 14). In this regard, the wedge height260of the axial ply wedge254may be sized to extend between the upper edge118(FIG. 17) and the lower edge122(FIG. 17) of the cone-shaped composite article114. However, the axial ply wedges254may be provided in a wedge height260that extends above or below the upper edge118and/or lower edge122during layup of the axial ply wedges254.

InFIG. 18, the axial ply wedges254may be provided in an arcuate length that minimizes the number of axial ply wedges254required to from a 360-degree global axial ply250(FIG. 17) around the cone-shaped composite article114. However, the arcuate length may also be minimized to minimize the amount of misalignment of the fiber angles252on the sides of each axial ply wedge254with the longitudinal axis116(FIG. 17) of the cone-shaped composite article114. By minimizing the misalignment of the fiber angles252on the sides of each axial ply wedge254with the longitudinal axis116, the axial load-carrying capability and axial stiffness of the global axial ply250may be maximized. Each axial ply wedge254may be formed of unidirectional material which may be similar to the unidirectional material described above for the unidirectional plies180. The fiber angle252of the unidirectional material may be generally aligned with a radius bisecting the arcuate length of ply pattern C. In an embodiment, the axial ply wedges254may be formed of unidirectional tape230wherein multiple strips or courses232(FIG. 13) of unidirectional tape230may be arranged in side-by-side relation in a manner similar to the above-described process of forming unidirectional plies180from unidirectional tape230.

InFIG. 18, the axial ply wedges254may be configured such that the axial ply fiber angle252at the center of the axial ply wedge254is generally aligned (i.e., having a 0-degree fiber angle) relative to the longitudinal axis116of the cone-shaped composite article114(FIG. 17), and the opposing wedge sides262may be formed at a wedge angle of cut268of a maximum of 8 degrees. For example, the axial ply wedges254may be configured such that each one of the wedge sides262is formed at a wedge angle of cut268of approximately 5 degrees. By minimizing the wedge angle of cut268, the offset (i.e., from vertical) of the axial ply fiber angle252at the wedge sides262may be minimized.

InFIG. 19, shown is an embodiment of a cone-shaped mandrel300for laying up unidirectional plies180and, optionally, global axial plies250(FIG. 17), around a circumference134of the cone-shaped mandrel300. The cone-shaped mandrel300may be formed of a metallic material (e.g., steel, aluminum, Invar™) or composite material (e.g., graphite-epoxy) having compatible characteristics for forming and curing the cone-shaped composite article114. The mandrel surface302may include index marks to facilitate the alignment of the unidirectional plies180and the global axial plies250with the upper edge118and lower edge122(FIG. 17), and for aligning the ply ends200of each unidirectional ply180with a predetermined seam location. The index marks may comprise scribe marks formed directly in the mandrel surface302. For example, the cone-shaped mandrel300may include seam location index marks304, upper edge index marks306, and lower edge index marks308, and which may be provided as scribe marks formed as indentations in the mandrel surface302or other means for marking the ply locations.FIG. 19illustrates a unidirectional ply180with the reference end202tacked onto the mandrel surface302in alignment with the 0-degree seam location, and the unidirectional ply180wrapping around the cone-shaped mandrel300prior to tacking the remaining ply end200to the mandrel surface302back at the 0-degree seam location.

InFIG. 19, in an embodiment not shown, the index marks may be provided by a laser alignment system configured to project laser light at predetermined indexing locations onto the cone-shaped mandrel300or previously-laid plies. For example, such a laser alignment system may be configured to project the seam locations, upper edge118, and lower edge122onto a cone-shaped mandrel300surface. In addition, such a laser alignment system may project the unidirectional ply180geometry, global axial ply250geometry, and stacking sequences onto the cone-shaped mandrel300or onto previously-laid unidirectional plies180or global axial plies250during the layup process to indicate the nominal position of each newly-applied unidirectional ply180and global axial ply250.

InFIG. 20, shown is a flow chart illustrating a method400of manufacturing a cone-shaped composite article114as shown inFIG. 17. The method may include Step402comprising providing unidirectional plies180in a continuous arcuate shape192in a flat pattern configured to wrap 360-degrees around a cone-shaped mandrel300. In an embodiment, the opposing ply end200of one or more unidirectional plies180terminate in a ply butt joint206although the ply ends200may overlap. The method may include forming at least one of the unidirectional plies180from a plurality of courses232of unidirectional tape230arranged in side-by-side relation to one another as mentioned above. The unidirectional plies180may be provided in a ply width198that extends at least from an upper edge118of the cone-shaped composite article114to at least a lower edge122thereof.

Step404of the method400ofFIG. 20may include laying up an inner sublaminate156on the cone-shaped mandrel300. As described above, the inner sublaminate156advantageously contains at least four (4) unidirectional plies180having an inner stacking sequence158with fiber angles of 0, 90, +45, −45 degrees. The fiber angles may be arranged in different orders (e.g., 0/+45/90/−45, 0/−45/90/+45, 90/+45/0/−45, −45/0/90/+45, etc.) in the 4-ply inner sublaminate156. The 4-ply inner sublaminate156may be arranged to provide a quasi-isotropic layup pattern168by providing a first pair of unidirectional plies182each having a first fiber angle184, clocking the ply seams204of the first pair of unidirectional plies182at 180 degrees relative to one another, providing a second pair of unidirectional plies186each having a second fiber angle188oriented 90 degrees relative to the first fiber angle184, and clocking the ply seams204of the second unidirectional plies180degrees relative to one another around the circumference134of the cone-shaped composite article and in alignment with the ply seams204of the first pair of unidirectional plies182as shown inFIGS. 5-6and11.

As indicated above, such additional 4-ply quasi-isotropic layup patterns168are preferably arranged in a symmetric and balanced layup166about a mid-plane164of the composite laminate150. For example, as illustrated inFIG. 15, for each inner sublaminate156, an outer sublaminate160is provided on an opposite side of the mid-plane164with the corresponding outer sublaminate160having an outer stacking sequence162that is a mirror-image of the inner stacking sequence158of the inner sublaminate156. As illustrated inFIG. 15, it not necessary that each inner sublaminate156and corresponding outer sublaminate160are located adjacent to one another. In this regard, each set of inner and outer sublaminates156,160are symmetric about the mid-plane164such the unidirectional plies180of each inner sublaminate156are located at the same distance from the mid-plane164as the unidirectional plies180of the corresponding outer sublaminate160. In this manner, a composite laminate150is provided in a symmetric and balanced layup166which may minimize warpage of the composite laminate150following cure.

In an embodiment, the inner sublaminate156may be formed by laying up the arcuate shape192of each one of the unidirectional plies180so that the ply ends200are aligned with a seam location index mark304on the cone-shaped mandrel300as shown inFIG. 19. In an embodiment, the ply butt joint206of each one of the unidirectional plies180may be provided with a gap208of less than approximately 0.10 inch between the ply ends200. In addition, the process of laying up the arcuate shape192of each one of the unidirectional plies180may include vertically aligning an inner radius194and outer radius196of the arcuate shape192with an upper edge index mark306and a lower edge index mark308on the cone-shaped mandrel300. The process of laying up the unidirectional plies180may be performed manually and/or with an automated fiber placement machine (not shown).

Step406of the method400ofFIG. 20may include laying up an outer sublaminate160over the inner sublaminate156in an outer stacking sequence162that is a mirror image of the inner stacking sequence158. The ply seams204of the outer sublaminate160may be aligned with the ply seams204of the inner sublaminate156. As indicated above, each one of the inner sublaminate156and the outer sublaminate160represents a quasi-isotropic layup at any location on the composite article. The combination of the inner sublaminate156and the outer sublaminate160comprises a composite laminate150having a balanced layup166and symmetrical layup as described above to minimize warpage of the composite laminate150following cure.

The method of manufacturing a cone-shaped composite article114may include applying a plurality of balanced layups166(FIG. 11)166to achieve a desired wall thickness132to accommodate the loads to which the cone-shaped composite article114may be subjected during service. As indicated above, each one of the balanced layups166may comprise an inner sublaminate156paired with an outer sublaminate160. The outer sublaminate160may be provided as a mirror image of the inner sublaminate156. For a composite laminate150having multiple balanced layups166, the composite laminate may include a plurality of inner sublaminates156each being paired with an outer sublaminate160located on an opposite side of the mid-plane164from the corresponding inner sublaminate156. As indicated above, each one of the outer sublaminates160may have a quasi-isotropic outer stacking sequence162that is a mirror image of the quasi-isotropic inner stacking sequence158of the corresponding inner sublaminate156located on the opposite side of the mid-plane164.

Step408of the method400ofFIG. 20may include laying up one or more global axial plies250with the one or more balanced layups166. For example, one or more global axial plies250that may be laminated between the unidirectional plies180of the inner sublaminate156and the outer sublaminate160. The step of laying up global axial plies250may comprise laying up a plurality of axial ply wedges254in side-by-side relation to one another to form a plurality of wedge butt joints264as shown inFIG. 17such that the axial ply wedges254extend 360-degrees around the cone-shaped mandrel300to form a global axial ply250.

The axial ply wedges254may be formed in a flat pattern geometry such as the geometry of ply pattern C (FIG. 18). The fiber angles252of each axial ply wedge254may be generally aligned with the longitudinal axis116of the cone-shaped composite article114. The global axial plies250may add to the axial strength and stiffness of the cone-shaped composite article114. For a cone-shaped composite article114having multiple global axial plies250, the method may include staggering the wedge butt joints264in each one of the global axial plies250by at least 0.50 inch relative to the wedge butt joints264in remaining ones of the global axial plies250to avoid multiple wedge butt joints264at any one location.

Step410of the method400ofFIG. 20may include applying heat and/or pressure to the composite laminate150to consolidate and cure the composite laminate150. For example, following layup, the composite laminate150may be vacuum bagged to debulk and consolidate the unidirectional plies180. Heat may be applied to the composite laminate150such as by positioning the composite laminate150inside an autoclave or oven. The heat may increase the temperature of the matrix material and reduce the viscosity thereof allowing the matrix material in adjacent unidirectional plies180to intermingle. Heat may be removed and the composite laminate150may be allowed to cool and cure or solidify, resulting in the final cone-shaped composite article114.

Although not shown, the present disclosure also contemplates a cone-shaped composite article configured as a sandwich composite structure instead of a solid composite laminate described above. Such a sandwich composite structure may include at least one inner sublaminate having an inner stacking sequence located on one side of a core, and an outer sublaminate located on an opposite side of the core and having an outer stacking sequence that is a mirror image of the inner stacking sequence to provide a balanced layup. The core material may comprise a foam core, a honeycomb core of aluminum, aramid, etc., or other core configurations and materials. The inner and outer sublaminates of such a sandwich composite structure may be fabricated according to the disclosure above.

A significant advantage of the presently disclosed system and method is the ability to fabricate the cone-shaped composite article114without the need for darts or overlap splices. As indicated above, the use of ply patterns extending in a continuous 360-degree wrap around the cone circumference minimizes or eliminates the need for darts to conform to the cone geometry. In addition, the use of ply butt joints206and the avoidance of overlap splices significantly reduces the potential for the occurrence of wrinkles or voids in the cone-shaped composite article114. Furthermore, the use of butt joints throughout the cone-shaped composite article114may result in a ply layup that does not vary by more than approximately ±10% of the wall thickness132which may improve the specific strength of the cone-shaped composite article114relative to a conventional layup with wall thickness variations greater than ±10%. The combination of the above-noted factors advantageously results in a relatively light-weight, high-strength, and high-stiffness cone-shaped composite article114capable of transmitting a variety of loads of different direction and magnitude such as the axial loads106, bending loads108, and torsional loads110(FIG. 1) transmitted by a conical payload attach fitting112(FIG. 1) coupling a spacecraft104(FIG. 1) to a launch vehicle100(FIG. 1).

Referring toFIGS. 21-22, embodiments of the disclosure may be described in the context of an aircraft manufacturing and service method500as shown inFIG. 21and an aircraft502as shown inFIG. 22. During pre-production, exemplary method500may include specification and design504of the aircraft502and material procurement506. During production, component and subassembly manufacturing508and system integration510of the aircraft502takes place. Thereafter, the aircraft502may go through certification and delivery512in order to be placed in service514. While in service by a customer, the aircraft502is scheduled for routine maintenance and service516(which may also include modification, reconfiguration, refurbishment, and so on).

As shown inFIG. 22, the aircraft502produced by exemplary method500may include an airframe518with a plurality of systems520and an interior522. Examples of high-level systems520include one or more of a propulsion system524, an electrical system526, a hydraulic system528, and an environmental system530. Any number of other systems may be included. Although an aerospace example is shown, the principles of the invention may be applied to other industries, such as the automotive industry.

Apparatus and methods embodied herein may be employed during any one or more of the stages of the production and service method500. For example, components or subassemblies corresponding to production process508may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft502is in service. Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during the production stages508and510, for example, by substantially expediting assembly of or reducing the cost of an aircraft502. Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft502is in service, for example and without limitation, to maintenance and service516.

Additional modifications and improvements of the present disclosure may be apparent to those of ordinary skill in the art. Thus, the particular combination of parts described and illustrated herein is intended to represent only certain embodiments of the present disclosure and is not intended to serve as limitations of alternative embodiments or devices within the spirit and scope of the disclosure.