Patent Description:
Driveshafts are used to connect components to a drive input. Known applications include but are not limited to driveshafts used to drive propellers in aerospace applications. Driveshafts transmit primarily torque and rotation. Driveshafts are generally cylindrical bodies, which can include multiple flexible elements in series that provide bending and/or axial compliances to accommodate angular and axial misalignment and mass imbalance.

Composite driveshafts can provide increased strength and reduced weight as compared to conventional metal designs. However, driveshaft designs and, particularly, the geometry of flexible elements, are limited by current manufacturing methods.

<CIT> discloses a method of forming composite tubular elements with corrugations.

A process for forming a flexible composite driveshaft is defined in claim <NUM>. A flexible composite driveshaft is formed by modifying the shape of a preliminary composite driveshaft. A fiber tape is applied to a temporary mandrel using automated fiber placement to form a preliminary composite driveshaft having a flexible shaft element with an initial geometry. The temporary mandrel from the preliminary composite driveshaft is removed and the initial geometry of the flexible shaft element is modified to form the flexible composite driveshaft having a flexible shaft element with a final geometry.

The present summary is provided only by way of example, and not limitation. Other aspects of the present disclosure will be appreciated in view of the entirety of the present disclosure, including the entire text, claims, and accompanying figures.

While the above-identified figures set forth embodiments of the present invention, the scope of the invention is defined by the appended claims.

Automated fiber placement (AFP) can be used to produce high performance composite components in which the positioning of fibers or fiber paths can be locally optimized to meet varying load requirements. AFP is ideally suited for the manufacture of complex driveshafts including multiple flexible elements; however, a relatively sharp angle or small corner radius required between flexible elements cannot be produced using currently available AFP technology due to fabrication limitations, such as, for example, the shape and size of the fiber placement head. The disclosed method uses AFP to produce a composite driveshaft with flexible elements, which are subsequently compressed in a post-treatment process to form a sharp angle or small corner radius between adjacent flexible elements, or other necessary shapes otherwise unachievable by direct one-step AFP-based lay-up alone. In some embodiments, a pre-treatment can also be used to reduce the angle or radius between flexible elements.

Flexible driveshafts can have one or more flexible elements, generally defined by a change in a size of an outer diameter or radial extent of the shaft with a transition radius capable of accommodating bending during operation. Shaft axial and bending flexibility can be increased by increasing the number of flexible elements on the shaft. Two or more flexible elements are illustrated in each of the embodiments disclosed herein. However, it will be understood that a composite driveshaft according to the present disclosure can have a single flexible element, defined by an increase and/or a decrease in the outer diameter or radial extent of the shaft. A small radius or sharp corner between flexible elements or on either side of a single flexible element in a transition region where the flexible element meets the shaft can be required to accommodate bending. As used herein, "sharp corner" refers to a minimum, but non-zero radius. A minimum radius size can be limited by a size and orientation of the fibers used to form the composite shaft and can be set to prevent or reduce fibers breakage. The size of the radius can vary widely depending on the application, applied materials, and fabrication specifics. The method of the present disclosure can be used to create constant and/or variable radii of any size limited only by a need to limit fiber breakage, and is not limited to the designs illustrated herein.

<FIG> is a schematic axial cross-sectional representation of a preliminary composite driveshaft during a first phase of a method of the present disclosure in which the preliminary composite driveshaft having flexible elements with an initial geometry is formed on a mandrel. <FIG> illustrates preliminary composite driveshaft <NUM> formed on temporary mandrel <NUM>. An internal surface of preliminary composite driveshaft <NUM> matches an external surface geometry of temporary mandrel <NUM>. Both preliminary composite driveshaft <NUM> and temporary mandrel <NUM> can be generally cylindrical and can include flexible elements <NUM> and <NUM>, defined by regions of increased shaft diameter with elevations <NUM> and <NUM> separated by depression <NUM>. Flexible elements <NUM> and <NUM> can be arranged in series along axis A of preliminary composite driveshaft <NUM>, with elevations <NUM> and <NUM> extending radially outward from axis A and depression <NUM> extending radially inward toward axis A. Depression <NUM> can have a diameter equal to, greater than, or less than a diameter of the shaft. Elevations <NUM> and <NUM> and depression <NUM> can each have an annular shape, extending circumferentially around axis A and separated from one another along axis A. Preliminary composite driveshaft <NUM> can be symmetric in the axial cross-section about axis A or asymmetric. For example, elevations and depressions that extend partially around axis A are also contemplated as are elevations and depressions having varying radial heights or displacements from axis A about a circumference of the generally cylindrical shaft. Elevations <NUM> and <NUM> can form convex or curved protrusions having constant or variable radii that extend from the generally cylindrical preliminary composite driveshaft <NUM>. Elevations with angled peaks are also contemplated. A radius on either side of the each elevation <NUM> and <NUM> and between elevations <NUM> and <NUM> in depression <NUM> (i.e., in a transition region where each side of the elevation <NUM> and <NUM> meets the shaft), is limited by the shape and size of the AFP fiber placement head and therefore is equal to or greater than a value allowed by the technology. As illustrated in <FIG>, depression <NUM> has a radius r<NUM>, which is equal to or greater than a minimum radius for which fibers can be placed using AFP. Radius r<NUM> can set a distance d<NUM>, which separates peaks of adjacent elevations <NUM> and <NUM>. Although, not shown, the radii in the transition regions on opposite sides of elevations <NUM> and <NUM> also are equal to or greater than a minimum radius for which fibers can be placed using AFP. Although illustrated as a single radius, radius r<NUM> (of depression <NUM> or in the transitions regions on either side of elevations <NUM> and <NUM>) can be constant or variable. It will be understood that the number, shape, composite layup, and location of flexible elements <NUM> and <NUM> can be varied and that the geometrical shapes of preliminary composite driveshaft <NUM> and the final flexible composite driveshaft (shown in <FIG>) are not limited to the embodiments shown, but that the disclosed method can be used to form any of a variety of shapes not capable of being formed using current AFP methods alone.

Preliminary composite driveshaft <NUM> is formed by applying a fiber tape to temporary mandrel <NUM>. The fiber tape can be wrapped around temporary mandrel <NUM> or otherwise placed to cover temporary mandrel <NUM>. Multiple layers of fiber tape can be applied to temporary mandrel <NUM> to increase a thickness of preliminary composite driveshaft <NUM>. It will be understood by one of ordinary skill in the art that fiber placement, including fiber direction and layering of fiber tape, can be optimized to meet local load conditions and can vary depending on the intended application. Fiber tape can include but is not limited to carbon, glass, organic fibers, or any of combination thereof, as known in the art. Fiber tape can be pre-impregnated with a thermoset or thermoplastic resin matrix. The material can be fully or partially cured following fiber layup using methods known in the art to provide structural rigidity. When the formation of preliminary composite driveshaft <NUM> is complete, temporary mandrel <NUM> can be removed (e.g., by washing or other methods known in the art), leaving the hollow preliminary composite driveshaft <NUM>.

In some embodiments, a load can be applied to temporary mandrel <NUM> prior to and/or during the application of the fiber tape. As illustrated in <FIG>, axial stress can be applied (load F<NUM>) to elongate temporary mandrel <NUM>. Load F<NUM> can be applied at ends of temporary mandrel <NUM> as shown. When the formation of preliminary composite driveshaft <NUM> is complete, load F<NUM> can be released, which can cause the structure to relax and compress causing the distance di between elevations <NUM> and <NUM> to shrink and radius r<NUM> of depression <NUM> to be reduced. In some instances, radius r<NUM> of depression <NUM> can be reduced to a radius smaller than can be achieved with AFP. When temporary mandrel <NUM> is subsequently removed, preliminary composite driveshaft <NUM> can retain the relaxed geometry. In some embodiments, applying load F<NUM> to temporary mandrel <NUM> can be sufficient to produce the desired final geometry of the flexible composite driveshaft and no further modification is necessary. In other embodiments, applying a load to temporary mandrel <NUM> can be used to produce an intermediate composite driveshaft (not shown) having flexible elements <NUM> and <NUM> of an intermediate geometry different from the initial geometry of preliminary composite driveshaft <NUM> and the final geometry of flexible composite driveshaft (shown in <FIG>).

<FIG> is a schematic axial cross-sectional representation of preliminary composite driveshaft <NUM> during a second phase of the method, illustrating the modification of the shape of preliminary composite driveshaft <NUM> of <FIG> to form flexible composite driveshaft <NUM>. After temporary mandrel <NUM> has been removed (e.g., by washing or other methods known in the art), the initial geometry of flexible elements <NUM> and <NUM> is modified to form flexible composite driveshaft <NUM> with flexible shaft elements <NUM> and <NUM> having a desired final geometry. The initial geometry of flexible elements <NUM> and <NUM> of preliminary composite driveshaft <NUM> can be modified by applying a load F<NUM> to preliminary composite driveshaft <NUM> to reduce radius r<NUM> of depression <NUM> to form a smaller radius r<NUM> or sharp angle between elevations <NUM> and <NUM>, which cannot be formed using direct one-step AFP. Although illustrated as having a concave smooth geometry with constant radius, it will be understood by one of ordinary skill in the art that depression <NUM> can be modified to form a concave sharp angle or any other concave shapes with variable radii and/or linear segments.

Load F<NUM> can be applied axially at ends of preliminary composite driveshaft <NUM> to compress preliminary composite driveshaft <NUM>. In some embodiments, preliminary composite driveshaft <NUM> can be formed from a thermoplastic fiber tape, which can be heated to provide compliance upon application of load F<NUM>. Heat can be applied to preliminary composite driveshaft <NUM> globally or locally (e.g., in the region of flexible elements <NUM> and <NUM> and/or <NUM>). Structural modification of preliminary composite driveshaft <NUM> can be carefully controlled by only applying heat to regions where a change in shape is desired and not to regions where no change in shape is desired. In other embodiments, preliminary composite driveshaft <NUM> can be formed from a thermoset fiber tape that has only been partially cured to provide compliance upon application of load F<NUM>.

In some embodiments, one or more clamps <NUM> can be placed around an outer diameter of preliminary composite driveshaft <NUM> to compress in the radial inward direction preliminary composite driveshaft <NUM> around the full or partial circumference to produce reduced radius r<NUM> or a sharp angle between adjacent elevations <NUM> and <NUM>. A load F<NUM> directed radially inward toward axis A can be applied to clamps <NUM> to compress the outer diameter. In some embodiments, heat can be provided to a thermoplastic preliminary composite driveshaft <NUM> through clamps <NUM> to allow modification of the initial geometry. Clamps <NUM> can be placed in depression <NUM> at the location of radius r<NUM> and/or in transition regions on either side of elevations <NUM> and <NUM>, and can have a geometry that matches a desired final geometry (i.e., r<NUM> or sharp angle) of depression <NUM>.

In some embodiments, a cylindrical mandrel <NUM> can be provided within an inner diameter of preliminary composite driveshaft <NUM> to prevent closure of the inner diameter as the initial geometry of flexible shaft elements <NUM> and <NUM> is modified. Cylindrical mandrel <NUM> can be positioned in contact with depression <NUM>, which can cause a radial height of elevations <NUM> and <NUM> from axis A to increase as preliminary composite driveshaft <NUM> is axially compressed. Alternatively, cylindrical mandrel can be spaced apart from depressions <NUM>, which can cause a depth of depression <NUM> to increase (reduction in radially displacement from axis A) as preliminary composite driveshaft <NUM> is axially compressed. Cylindrical mandrel <NUM> can be removed when the final shape of flexible composite driveshaft <NUM> is provided (upon completion of modifying the initial geometry of flexible elements <NUM> and <NUM>).

It will be understood by one of ordinary skill in the art that one or both loads F<NUM> and F<NUM> can be applied to preliminary composite driveshaft <NUM> to produce a desire final shape of flexible composite driveshaft <NUM>. Loads F<NUM> and F<NUM> can be applied separately or simultaneously. Further, it will be understood that clamps <NUM> can be provided at multiple axial locations along the preliminary composite driveshaft to produce multiple depressions <NUM>.

Once the final desired shape of flexible composite driveshaft <NUM> is achieved through modification, steps can be taken to retain the final geometrical shape of flexible composite driveshaft <NUM>. For thermoplastic materials, retaining of the final shape can be accomplished by removing heat or cooling flexible composite driveshaft <NUM>. For thermoset materials, additional curing steps as known in the art are required. Use of thermoplastic fiber tape may be preferable to reduce manufacturing costs and time.

<FIG> is a schematic representation of an alternative preliminary composite driveshaft during a first phase of the method of the present disclosure in which the alternative preliminary composite driveshaft is formed on a mandrel. <FIG> illustrates preliminary composite driveshaft <NUM> formed on temporary mandrel <NUM>. A geometry of preliminary composite driveshaft <NUM> matches a geometry of temporary mandrel <NUM>. Both preliminary composite driveshaft <NUM> and temporary mandrel <NUM> can be generally cylindrical and can include flexible elements <NUM> and <NUM>, defined by regions of increased shaft diameter or radial extent with elevations <NUM> and <NUM> separated by depression <NUM>. Flexible elements, including elevations <NUM> and <NUM> and depression <NUM>, can be arranged in series along the axial cross-section of preliminary composite driveshaft <NUM>, with elevations <NUM> and <NUM> extending radially outward from axis A and depression <NUM> extending radially inward toward axis A. As illustrated, elevations <NUM> and <NUM> and depression <NUM> can be formed by a helix wrapped around axis A, such that elevation <NUM> is a continuation of elevation <NUM>. The helix wrapping geometry can be defined by non-zero angle α between diametric cross-sections and the slope of the elevations <NUM> and <NUM> and/or depressions <NUM>. The angle α can be constant or variable along the axial direction and/or in the circumferential direction. Elevations <NUM> and <NUM> can form convex or otherwise curved protrusions having single or variable radii that extend from the generally cylindrical preliminary composite driveshaft <NUM>. Elevations having angled peaks are also contemplated. Depression <NUM> can have a radius r<NUM> equal to or greater than a minimum radius for which fibers can be placed using AFP. Radius r<NUM> can set a distance d<NUM>, which separates peaks of adj acent elevations <NUM> and <NUM>. It will be understood that the number, shape, and location of flexible elements <NUM> and <NUM> can be varied and that the geometrical shapes of preliminary composite driveshaft <NUM> and the final flexible composite driveshaft (shown in <FIG>) are not limited to the embodiments shown, but that the disclosed method can be used to form any of a variety of shapes not capable of being formed using current AFP methods alone.

Preliminary composite driveshaft <NUM> is formed in a manner consistent with the formation of preliminary composite driveshaft <NUM> of <FIG>. Fiber tape is applied to temporary mandrel <NUM>. The fiber tape can be wrapped around temporary mandrel <NUM> or otherwise placed to cover temporary mandrel <NUM>. Multiple layers of fiber tape can be applied to temporary mandrel <NUM> to increase a thickness of preliminary composite driveshaft <NUM>. It will be understood by one of ordinary skill in the art that fiber placement, including fiber direction and layering of fiber tape, can be optimized to meet local load conditions and can vary depending on the intended application. Fiber tape can have a thermoset or thermoplastic polymeric matrix. The material can be fully or partially cured following fiber layup using methods known in the art to provide structural rigidity. When the formation of preliminary composite driveshaft <NUM> is complete, temporary mandrel <NUM> can be removed (e.g., by washing or other methods known in the art), leaving the hollow preliminary composite driveshaft <NUM>.

In some embodiments, a load can be applied to temporary mandrel <NUM> prior to and/or during the application of the fiber tape. As illustrated in <FIG>, torsional load (due to applied torque F<NUM>) can be applied to twist temporary mandrel <NUM>. Torque F<NUM> can be applied at one or both ends of temporary mandrel <NUM>, as shown. Torque F<NUM> can be defined in the form of specified angular rotation and/or twisting moment. When applied at both ends of temporary mandrel <NUM>, torque F<NUM> is applied in opposite directions at opposite ends. When the formation of preliminary composite driveshaft <NUM> is complete, load F<NUM> can be released, which can cause the structure to relax and compress causing the distance d<NUM> between elevations <NUM> and <NUM> to shrink and radius r<NUM> of depression <NUM> to be reduced. In some instances, radius r<NUM> of depression <NUM> can be reduced to a radius smaller than can be achieved with AFP. When temporary mandrel <NUM> is subsequently removed, preliminary composite driveshaft <NUM> can retain the relaxed geometry. In some embodiments, applying torque to temporary mandrel <NUM> can be sufficient to produce the desired final geometry of the flexible composite driveshaft and no further modification is necessary. In other embodiments, applying a torque to temporary mandrel <NUM> can be used to produce an intermediate composite driveshaft (not shown) having flexible elements <NUM> and <NUM> of an intermediate geometry different from the initial geometry of preliminary composite driveshaft <NUM> and the final geometry of flexible composite driveshaft (shown in <FIG>).

<FIG> is a schematic representation of the alternative preliminary composite driveshaft during the second phase of the method, illustrating the modification of the shape of the alternative preliminary composite driveshaft of <FIG> to form an alternative flexible composite driveshaft. After temporary mandrel <NUM> has been removed, the initial geometry of flexible elements <NUM> and <NUM> is modified to form flexible composite driveshaft <NUM> with flexible shaft elements <NUM> and <NUM> having a desired final geometry. The initial geometry of flexible elements <NUM> and <NUM> of preliminary composite driveshaft <NUM> can be modified by applying an axial load F<NUM> and torque F<NUM> to preliminary composite driveshaft <NUM> to reduce radius r<NUM> of depression <NUM> to form a smaller radius r<NUM> or sharp angle between elevations <NUM> and <NUM>, which cannot be formed using AFP. Although illustrated as having a concave geometry, it will be understood by one of ordinary skill in the art that depression <NUM> can be modified to form a sharp angle.

Load F<NUM> can be applied axially at one or both ends of preliminary composite driveshaft <NUM> to compress preliminary composite driveshaft <NUM>. Torque F<NUM> can be applied at one or both ends of preliminary composite driveshaft <NUM> to twist preliminary composite driveshaft <NUM>. Torque F<NUM> can be applied in opposite directions at opposite ends of preliminary composite driveshaft <NUM> when applied at both ends. Load F<NUM> and torque F<NUM> can be applied to preliminary composite driveshaft <NUM> separately or simultaneously. As a result of applying of any or both load F<NUM> and torque F<NUM>, the helix orientation can be changed from α to α' in the final shape shown in <FIG>. In some embodiments, preliminary composite driveshaft <NUM> can be formed from a thermoplastic fiber tape, which can be heated to provide compliance upon application of load F<NUM> or torque F<NUM>. Heat can be applied to preliminary composite driveshaft <NUM> globally or locally (e.g., in the region of flexible elements <NUM> and <NUM> to allow for twisting and axial compression). Structural modification of preliminary composite driveshaft <NUM> can be carefully controlled by applying heat only to regions where a change in shape is desired and not to regions where no change in shape is desired. In other embodiments, preliminary composite driveshaft <NUM> can be formed from a thermoset fiber tape that has only been partially cured to provide compliance upon application of loads F<NUM> and F<NUM>.

In some embodiments, one or more clamps (not shown) can be placed around an outer diameter of preliminary composite driveshaft <NUM> to compress preliminary composite driveshaft <NUM> around the full or partial circumference to produce reduced radius r<NUM> or sharp angle between adjacent elevations <NUM> and <NUM>. As described with respect to modification of preliminary composite driveshaft <NUM>, illustrated in <FIG>, a load directed radially inward toward axis A can be applied to the clamps. Additionally, heat can be provided to a thermoplastic preliminary composite driveshaft <NUM> through the clamps to allow modification of the initial geometry. In some embodiments, preliminary composite driveshaft <NUM> can be pressed into one or more molds to form flexible elements <NUM> and <NUM>.

A cylindrical mandrel (not shown) can be provided within an inner diameter of preliminary composite driveshaft <NUM> to prevent closure of the inner diameter as the initial geometry of flexible shaft elements <NUM> and <NUM> is modified. The cylindrical mandrel can be positioned in contact with depression <NUM> or spaced apart from depression <NUM> as described with respect to the modification of preliminary composite driveshaft <NUM>, illustrated in <FIG>. The cylindrical mandrel can be removed when the final shape of flexible composite driveshaft <NUM> is provided.

<FIG> is a schematic side-view representation of another alternative embodiment of a preliminary composite driveshaft. <FIG> illustrates preliminary composite driveshaft <NUM> formed on temporary mandrel <NUM>. The geometry of preliminary composite driveshaft <NUM> matches a geometry of temporary mandrel <NUM> and matches the geometry of preliminary composite driveshaft <NUM>, illustrated in <FIG>, having similar flexible elements <NUM> and <NUM>. Preliminary composite driveshaft <NUM> can have alternative geometrical shapes including, but not limited to, the shape of preliminary composite driveshaft <NUM>, illustrated in <FIG>. Preliminary composite driveshaft <NUM> is distinguished from preliminary composite driveshafts <NUM> and <NUM> by fiber placement. As illustrated in <FIG>, fiber tape <NUM> can be wrapped around temporary mandrel <NUM> to form a web structure with openings <NUM>. Such web structure would be advantageous for very lightweight designs or loads that are very simple, e.g., only torque with little bending or axial forces, therefore not requiring supporting composite layers. It will be understood by one of ordinary skill in the art that the orientation of fiber tape <NUM>, fiber tape overlap or weaving, and size of the openings <NUM> can vary depending on the application and as needed to provide high torsional stiffness with sufficient bending compliance to accommodate angular and axial misalignment and mass imbalance.

Preliminary composite driveshaft <NUM> can be formed with materials consistent with those disclosed for forming preliminary composite driveshafts <NUM> and <NUM>. Axial or torsional stress can be applied to temporary mandrel <NUM> during fiber application as is disclosed with respect to the formation of preliminary composite driveshafts <NUM> and <NUM>. Once preliminary composite driveshaft <NUM> is formed, temporary mandrel can be removed, and the shape of preliminary composite driveshaft <NUM> and flexible elements <NUM> and <NUM> can be modified. For a thermoset composite driveshaft, the preliminary shape can be partially cured and then fully cured once the final desired shape is achieved. For a thermoplastic composite driveshaft, the preliminary shape can be produced by conventional AFP methods with full or partial hardening. The thermoplastic driveshaft can be heated, either partially (e.g., in areas of specified deformation) or fully, to allow for modification and then fully hardened once the desired form is achieved. The shape of flexible elements <NUM> and <NUM> can be modified in a manner consistent with that disclosed with respect to preliminary composite driveshafts <NUM> and <NUM>.

<FIG> is a flow chart of a method for forming the flexible composite driveshafts <NUM> and <NUM>, illustrated in <FIG> and <FIG>, and variations thereof, including a flexible composite driveshaft having a webbed structure as disclosed with respect to <FIG>. As described with respect to the disclosure of <FIG>, <FIG>, method <NUM> includes in a first step providing a temporary mandrel having a shape of a preliminary composite driveshaft (step <NUM>). In some embodiments, an axial load or torque can be applied to the temporary mandrel before fiber tape is applied to the temporary mandrel (optional step <NUM>). Fiber tape is applied to the temporary mandrel using AFP in any manner as disclosed with respect to the formation of preliminary composite driveshafts <NUM>, <NUM>, and <NUM> to provide desired stiffness and compliance (step <NUM>). Upon completion of fiber placement, the fiber tape can be partially cured for thermoset materials or solidified for thermoplastic materials and the temporary mandrel is removed using methods known in the art (step <NUM>). In some embodiments, the preliminary composite driveshaft retains the shape of the temporary mandrel after the temporary mandrel has been removed. If a load has been applied to the temporary mandrel during fiber tape application, the preliminary composite driveshaft can take the shape of an intermediate composite driveshaft once the temporary mandrel is removed. The intermediate composite driveshaft can be formed by the relaxation of the structure once the load has been removed. The intermediate composite driveshaft can have flexible elements with intermediate geometries that are different from the initial geometries of the preliminary composite driveshaft and the final geometries of the flexible composite driveshaft. A load can be applied to the preliminary or intermediate composite driveshaft following removal of the temporary mandrel to further modify the shape of the driveshaft (step <NUM>). Clamps to keep desired shape can also be applied at this step (step <NUM>) if needed. Heat can be applied globally or locally to the preliminary and intermediate composite driveshafts formed from thermoplastic fiber tape to allow the shape of the driveshaft to be modified (optional step <NUM>). Preliminary and intermediate composite driveshafts formed using a thermoset fiber tape can undergo a partial cure to provide structural rigidity while allowing for shape modification upon application of axial load and/or torque. Once the desired final shape of the flexible composite driveshaft is achieved, the material can be cured (e.g., heat can be removed for thermoplastic materials and partially cured thermoset materials can be fully cured) (step <NUM>).

The disclosed method can be used to produce high performance components in which the positioning of fibers or fiber path can be locally optimized to meet varying load requirements while providing flexible elements with a relatively sharp angle or small corner radius to accommodate angular and axial misalignment and mass imbalance.

Claim 1:
A process (<NUM>) for forming a flexible composite driveshaft comprising one or more flexible elements defined by a change in a size of an outer diameter or radial extent of the shaft with a transition radius capable of accommodating bending during operation, the process comprising:
applying (<NUM>) a fiber tape to a temporary mandrel (<NUM>) using automated fiber placement to form a preliminary composite driveshaft (<NUM>) having a shaft element with an initial geometry;
removing (<NUM>) the temporary mandrel (<NUM>) from the preliminary composite driveshaft (<NUM>);
modifying (<NUM>) the initial geometry of the shaft element to form the composite driveshaft having a shaft element with a final geometry, wherein an internal surface of the preliminary composite driveshaft (<NUM>; <NUM>) matches an external surface geometry of the temporary mandrel (<NUM>).