SYSTEM AND METHOD FOR PROMOTING INTER-PLY SLIPPAGE

Abstract

A composite part forming system for shaping a composite material blank having a plurality of plies, the composite part forming system comprising opposing tools including shape-forming features, an actuator, and a composite tensioning system. The composite tensioning system is connectable to a periphery of the composite material blank to apply tension to the composite material blank the first and second tools are moved together to cause the composite material blank to conform to the shape-forming features. The composite tensioning system is configured to apply more tension to wrinkle prone plies of the composite material blank than to non-wrinkle prone plies as the composite material blank is caused to conform to the shape-forming features.

Claims

1. A composite part forming system for shaping a composite material blank having a plurality of plies, the composite part forming system comprising: a first tool including shape-forming features; and a composite tensioning system connectable to a periphery of the composite material blank to apply tension to the composite material blank such that the composite tensioning system applies more tension to wrinkle prone plies of the composite material blank than to non-wrinkle prone plies of the composite material blank as the composite material blank is caused to conform to the shape-forming features of the first tool.

2. The composite part forming system of claim 1, further comprising a second tool complementary to the first tool.

3. The composite part forming system of claim 1, wherein the composite tensioning system further comprises: a plurality of clevises including clevis pin holes, the plurality of clevises being configured to be positioned near tension openings in the composite material blank; and a plurality of clevis pins configured to be inserted through the clevis pin holes of the plurality of clevises and the tension openings of the composite material blank to connect the clevises to the composite material blank, the plurality of clevises being configured to be pulled to induce tension in the composite material blank, the plurality of clevis pins being configured to induce more tension to wrinkle prone plies of the composite material blank than to non-wrinkle prone plies when the composite material blank conforms to the shape-forming features of the first tool.

4. The composite part forming system of claim 1, the plurality of clevis pins being oriented diagonally relative to the plurality of clevis pins and the composite material blank.

5. The composite part forming system of claim 1, the plurality of clevis pins including step-down ledges.

6. The composite part forming system of claim 1, wherein the composite tensioning system further comprises: a plurality of clevises each including a clevis pin hole, the plurality of clevises being configured to be positioned near tension openings in the composite material blank; and a plurality of cantilever clevis pins configured to be inserted through the clevis pin holes of the plurality of clevises and partially through the tension openings of the composite material blank to connect the clevises to the composite material blank, the plurality of clevises being configured to be pulled to induce tension in the composite material blank, the plurality of clevis pins being configured to induce more tension to wrinkle prone plies of the composite material blank than to non-wrinkle prone plies when the composite material blank conforms to the shape-forming features of the first tool.

7. The composite part forming system of claim 1, wherein the composite tensioning system comprises a plurality of tension wires connected to the clevises and a biasing element for inducing the tension in the composite material blank via the plurality of tension wires.

8. The composite part forming system of claim 1, wherein the composite tensioning system is movable to control the tension.

9. The composite part forming system of claim 2, wherein: the first tool comprises a male tool, and the second tool comprises an inflatable bladder; and the inflatable bladder causes the composite material blank to conform to the shape-forming features when the inflatable bladder is actuated over the male tool.

10. The composite part forming system of claim 9, wherein the composite tensioning system is configured to initially suspend the composite material blank over the male tool to delay cooling of the composite material blank.

11. The composite part forming system of claim 1, further comprising: a plurality of cantilever pins each including: a neck configured to be inserted through the tension holes of the composite material blank, and a head configured to retain the neck in the tension holes of the composite material blank, the plurality of cantilever pins being configured to induce more tension to wrinkle prone plies of the composite material blank than to non-wrinkle prone plies when the male tool and female tools shape the composite material blank.

12. A method of forming a composite material part, the method comprising steps of: connecting a composite tensioning system to a periphery of a composite material blank; placing the composite material blank between a first tool and a complementary, at least one of the first and second tool including shape-forming features; moving the first tool toward the complementary second tool; and applying tension to the composite material blank via the composite tensioning system so that the composite tensioning system applies more tension to wrinkle prone plies of the composite material blank than to non-wrinkle prone plies of the composite material blank as the composite material blank is caused to conform to the shape-forming features.

13. The method of claim 12, the connecting step including inserting a clevis pin through clevis pin holes of a clevis of the composite tensioning system and through a tension opening of the composite material blank so that the clevis pin is oriented at a non-perpendicular angle to plies of the composite material blank.

14. The method of claim 12, the connecting step including inserting a clevis pin through clevis pin holes of a clevis of the composite tensioning system and through a tension opening of the composite material blank, the clevis pin including step-down ledges.

15. The method of claim 12, the connecting step including inserting a cantilever clevis pin through a clevis pin hole of a clevis of the composite tensioning system and partially through a tension opening of the composite material blank.

16. The method of claim 12, the applying tension step including pulling the composite material blank via a biasing element.

17. The method of claim 12, further comprising a step of moving the composite tensioning system to control the tension.

18. The method of claim 12, wherein the first tool comprises an inflatable bladder and the second tool comprises a male tool, the method further comprising a step of inflating the inflatable bladder.

19. The method of claim 18, further comprising a step of suspending the composite material blank over the male tool to delay cooling of the composite material blank.

20. A hot drape forming system for shaping a composite material blank having a plurality of plies, the hot drape forming system comprising: a male tool including shape-forming features; an inflatable bladder suspended above the male tool; an actuator configured to move the inflatable bladder toward the male tool; and a composite tensioning system comprising: a plurality of tension connectors connectable to a periphery of the composite material blank to apply tension to the composite material blank as the inflatable bladder is moved toward the male tool to cause the composite material blank to conform to the shape-forming features of the at least one of the first and second tools; a biasing element configured to induce the tension in the composite material blank; and a plurality of wires linking the plurality of tension connectors to the biasing element, the composite tensioning system being configured to apply more tension to wrinkle prone plies of the composite material blank than to non-wrinkle prone plies as the composite material blank is caused to conform to the shape-forming features.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0040] Embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein:

[0041] FIG. 1 is an elevation view of a composite part forming system constructed in accordance with an embodiment of the invention;

[0042] FIG. 2 is another elevation view of the composite part forming system of FIG. 1;

[0043] FIG. 3 is an elevation view of a composite part formed by the composite part forming system of FIG. 1;

[0044] FIG. 4 is an enlarged elevation view of certain components of the composite part forming system of FIG. 1;

[0045] FIG. 5 is an enlarged elevation view of certain components of a composite part forming system constructed in accordance with another embodiment of the invention;

[0046] FIG. 6 is an enlarged elevation view of certain components of a composite part forming system constructed in accordance with another embodiment of the invention;

[0047] FIG. 7 is an enlarged elevation view of certain components of a composite part forming system constructed in accordance with another embodiment of the invention;

[0048] FIG. 8 is an enlarged elevation view of certain components of a composite part forming system constructed in accordance with another embodiment of the invention;

[0049] FIG. 9 is an elevation view of a composite part forming system constructed in accordance with another embodiment of the invention; and

[0050] FIG. 10 is another elevation view of the composite part forming system of FIG. 9.

[0051] The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The following detailed description of the invention references the accompanying drawings that illustrate specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. The scope of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

[0053] Turning to FIGS. 1-4, a composite part forming system 10 constructed in accordance with an embodiment of the invention is illustrated. The composite part forming system 10 broadly comprises a female tool 12, an actuator 14, a male tool 16, and composite material tensioning system 18.

[0054] The female tool 12 may be a mold, layup tool, bladder, or the like and may have concave radiused inner corners 20 and convex radiused lead corners 22. The female tool 16 may be made of a substantially rigid material configured for supporting a composite material blank (e.g., composite material 100) during layup and prior to and/or during curing.

[0055] The actuator 14 may be configured to urge the male tool 16 and female tool 12 together. In one embodiment, the actuator 14 supports or suspends the male tool 16 above the female tool 12 and actuates the male tool 16 downward toward the female tool 12.

[0056] The male tool 16 may be a mold, layup tool, bladder, or the like and may have convex radiused inner corners 24 and concave radiused lead corners 26. The male tool 16 may be made of a substantially rigid material configured for shaping the composite material 100 during layup and prior to and/or during curing.

[0057] The composite material tensioning system 18 broadly comprises opposing first and second clevises 28A, B, and opposing first and second clevis pins 30A, B. Two clevises and two clevis pins are shown, but any number of clevises and clevis pins may be used to apply tension in the composite material 100. The composite material tensioning system 18 may also include biasing members, cables, linkages, or similar components for applying tension in the composite material 100.

[0058] The first clevis 28A is U-shaped or C-shaped and includes opposing holes 32A,B for receiving the first clevis pin 30A therethrough. The opposing holes 32A,B loosely align with a tension hole 102 in excess manufacturing portions of the composite material 100. The opposing holes 32A,B may be offset from each other in the direction of applied tension so that the first clevis pin 30A is angled in the tension hole 102.

[0059] The first clevis pin 30A is configured to be inserted through the opposing holes 32A,B and tension hole 102 to link the first clevis 28A to the composite material 100. The first clevis pin 30A may be straight and configured to be oriented diagonally through the tension hole 102 due to the offset positioning of the opposing holes 32A,B. Alternatively, the first clevis pin 30A may have an angled, bent, eccentric, tapered, or diagonal shape. The first clevis pin 30A may also include a head or flange for preventing the first clevis pin 30A from completely passing through the first clevis 28A and tension hole 102. The first clevis pin 30A may be configured to be secured to the composite material 100 via linchpin or similar component.

[0060] The second clevis 28B is U-shaped or C-shaped and includes opposing holes 34A,B for receiving the second clevis pin 30B therethrough. The opposing holes 32 align with another tension hole in excess manufacturing portions of the composite material 100 opposite the tension hole 102. Unlike the opposing holes 32A,B, the opposing holes 34A,B may be axially aligned so that the second clevis pin 30B is perpendicular to the direction of applied tension. Alternatively, the opposing holes 34A,B may be offset from each other similar to the opposing holes 32A,B.

[0061] The second clevis pin 30B may be substantially similar the first clevis pin 30A. The second clevis pin 30B may be configured to extend through the opposing holes 34A,B of the second clevis 28B and the tension hole 102 of the composite material 100. The second clevis pin 30B may be straight or may have an angled, bent, eccentric, or tapered, or diagonal shape.

[0062] In use, the clevises 28A,B are positioned at certain locations along the periphery of the composite material 100 with the opposing holes of the clevises 28A,B aligned with the tension holes of the composite material 100. The clevis pins 30A,B are inserted into the opposing holes 32A, B and 34A, B of the clevises 28A, B and through the tension holes of the composite material 100. To that end, the tension holes may be drilled or machined into the composite material 100.

[0063] The clevises 28A,B may then be pulled in opposite directions from each other to induce tension in plies 104 of the composite material 100 via the clevis pins 30A,B. Various tensioning arrangements are possible for applying force to each of the clevises 28A,B to pull them in opposite directions. One example of a tensioning arrangement having biasing elements for pulling the clevises in opposite directions is described below in connection with FIG. 5. As another example, a lever may be used to produce shear in the periphery outside of the composite part to enforce the displacement to promote laminate booking. Importantly, the diagonally oriented clevis pin 30A induce more tension to some of the plies depending on whether those plies are wrinkle prone or not (based on their position in the completed part). In the illustrated example, the upper plies are more susceptible to wrinkling and thus are engaged with more tension by the diagonally oriented clevis 28A than the lower plies.

[0064] Ply tension may be a function of a ply's position in the composite material 100. For example, a non-curved, diagonal clevis pin may apply linearly decreasing tension from one side of the composite material 100 to the opposing side of the composite material 100. Alternatively, ply tension may increase by larger orders or may increase by a tapered amount.

[0065] The male tool 16 may then be moved by the actuator 14 toward the female tool 12 until the male tool 16 and female tool 12 are fully engaged with each other. The composite material 100 complies with shape-forming features of the male tool 16 and female tool 12 so that the composite material 100 takes a desired shape when the male tool 16 and female tool 12 are fully engaged with each other. The clevis pins 30A, B may pull through the composite material when tension exceeds bearing strength of the composite material.

[0066] The above-described composite part forming system 10 provides several advantages. For example, plies of the composite material 100 that are on the inside of a bend (and thus are more susceptible to wrinkling) are stretched under more tension than plies in the middle or on the outside of the bend. This difference in tension endured by adjacent plies promotes inter-ply slippage, which prevents wrinkling and bridging.

[0067] The composite part forming system 10 can be used in aircraft production, automobile production, and other applications that use thermoplastic composite stamp forming, thermosetting laminate hot drape forming, and the like. The composite part forming system 10 also reduces scrap and tooling costs.

[0068] Turning to FIG. 5, a clevis 200 and clevis pin 202 constructed in accordance with another embodiment is illustrated. The clevis 200 may be U-shaped or C-shaped and includes opposing holes 204 that are aligned with each other.

[0069] The clevis pin 202 may be configured to extend perpendicularly through the aligned opposing holes 204 and a tension hole 302 of composite material 300. The tension hole 302 may be tapered on its outer side. That is, outer edges of the tension hole 302 are initially closer to the clevis pin 202 in plies that are more susceptible to wrinkling and farther away in plies that are less susceptible to wrinkling. To that end, the tension hole 302 may be machined to a desired shape.

[0070] In use, the clevis pin 202 may induce more tension to some of the plies 304 depending on whether those plies are wrinkle prone or not (based on their position in the completed part). In the illustrated example, the upper plies are more susceptible to wrinkling and thus are engaged with more tension by the clevis pin 202 than the lower plies due to the tapered outer sides of the tension holes 302. This difference in tension endured by adjacent plies promotes inter-ply slippage, which prevents wrinkling and bridging.

[0071] Turning to FIG. 6, a clevis 400 and clevis pin 402 constructed in accordance with another embodiment is illustrated. The clevis 400 may be U-shaped or C-shaped and includes opposing holes 404. The opposing holes 404 may have different dimensions to accommodate the clevis pin 402. For example, one hole may have a relatively larger diameter while the opposing hole may have a relatively smaller diameter.

[0072] The clevis pin 402 may include a plurality of step-down ledges 406 and may be configured to be inserted perpendicularly through the opposing holes 404 of the clevis 400 and a tension hole 502 of composite material 500. The clevis pin 402 thus may form a discrete tapered profile.

[0073] The clevis pin 402 may induce more tension to some of plies 504 of composite material 500 depending on whether those plies are wrinkle prone or not (based on their position in the completed part). In the illustrated example, the upper plies are more susceptible to wrinkling and thus are engaged with more tension by more prominent ones of the step-down ledges 406 of the clevis pin 402. The lower plies are less susceptible to wrinkling and thus are engaged with less tension by the less prominent ones of the step-down ledges 406 of the clevis pin 402. This difference in tension endured by adjacent plies promotes inter-ply slippage, which prevents wrinkling and bridging.

[0074] Turning to FIG. 7, a clevis 600 and clevis pin 602 constructed in accordance with another embodiment is illustrated. The clevis 600 may be U-shaped or C-shaped and may include a single hole 604.

[0075] The clevis pin 602 is configured to extend cantilever through the hole 604 of the clevis 600 and at least partially through a tension hole 702 of composite material 700. The clevis pin 602 does not extend fully through the tension hole 702 when fully inserted.

[0076] In use, the clevis pin 602 may engage only some plies 704 of the composite material 700. In this way, the clevis pin 602 may induce more tension to some of the plies depending on whether those plies are wrinkle prone or not (based on their position in the completed part). In the illustrated example, the upper plies are more susceptible to wrinkling and thus are engaged directly by the clevis pin 602. The lower plies are only indirectly under tension via the directly-engaged plies. This difference in tension endured by adjacent plies promotes inter-ply slippage, which prevents wrinkling and bridging.

[0077] Turning to another embodiment of the invention illustrated in FIG. 8, one or both of the tensioning connectors of a tensioning system may comprise a cantilever pin 800 employed without the clevises used in the prior embodiments. Each cantilever pin 800 may include a neck 802 and a head 804. Each cantilever pin 800 may be attached to a wire 806 on a distal end 808 opposite the head 804.

[0078] The neck 802 may be configured to extend through a tension hole 902 of composite material 900. The head 804 may be wider than the neck 802 and may anchor the cantilever pin 800 in the tension hole 902 or prevent the cantilever pin 800 from being pulled through the tension hole 902.

[0079] In use, the wire 806 pulls the cantilever pin 800 via the distal end 808 of the cantilever pin 800. The cantilever load may induce more tension in some of the plies 904 of composite material 900 depending on whether those plies are wrinkle prone or not (based on their position in the completed part). To that end, the cantilever pin 800 may rotate about a midplane. In the illustrated example, the upper plies are more susceptible to wrinkling and are engaged with more tension by the distal end 808 of the cantilever pin 800. The lower plies are less susceptible to wrinkling and thus are engaged with less tension by the cantilever pin 800 or may be pushed into forming process. This difference in tension endured by adjacent plies promotes inter-ply slippage, which prevents wrinkling and bridging.

[0080] Turning to FIGS. 9 and 10, a hot drape forming system 1000 constructed in accordance with another embodiment is illustrated. The hot drape forming system 1000 broadly comprises a mold 1002, an inflatable bladder 1004, an actuator 1006, and a composite tensioning system 1008. The composite tensioning system 1008 may be substantially similar to the composite material tensioning system 18 described previously, and may likewise include clevises as described in connection with FIGS. 1-4 or a system using a cantilever pin without a clevis, as described in connection with FIG. 5.

[0081] The mold 1002 may be a male layup tool, bladder, or the like and may have convex radiused inner corners 1010 and concave radiused lead corners 1012. The mold 1002 may be made of a substantially rigid material configured for shaping the composite material 2000.

[0082] The inflatable bladder 1004 may be positioned above the composite material 2000 opposite the mold 1002 and may be flexible, malleable, or compliant to shape the composite material 2000 around the mold 1002 when the inflatable bladder 1004 is inflated. The inflatable bladder 1004 may have a biasing shape to assist in pressing the composite material 2000 along sides of the mold 1002.

[0083] The actuator 1006 may be positioned above the inflatable bladder 1004 and may be configured to move the inflatable bladder 1004 into engagement with the composite material 2000. The actuator 1006 may be further configured to compress the inflatable bladder 1004 against the mold 1002 so the inflatable bladder 1004 shapes the composite material 2000 around the mold 1002.

[0084] The composite tensioning system 1008 may include a biasing element 1014, optional tension wires, and tension connectors 1016 (clevises and clevis pins or cantilever pins as described above). The composite tensioning system 1008 may be configured to induce tension in the composite material 2000 as the composite material 2000 is draped over the mold 1002 via the inflatable bladder 1004.

[0085] The biasing elements 1014 may be configured to exert a tension force on the tension connectors 1016 via the tension wires and may include springs, weights, pressurized or vacuum systems, or the like. The composite tensioning system 1008 may be configured to move along the axis of movement of the inflatable bladder (e.g., downward) during forming to more effectively control an amount of tension on the composite material 2000.

[0086] The tension wires may connect the biasing elements 1014 to the composite material 2000 via the tension connectors 1016 for transferring the tension force from the biasing elements 1014 to the composite material 2000. The tension wires may be configured to at least partially wrap around the inflatable bladder 1004 as the inflatable bladder 1004 presses down the sides of the mold 1002.

[0087] The tension connectors 1016 (clevises and clevis pins or cantilever pins as described above) may connect the tension wires to the composite material 2000. The tension connectors are configured to distribute tension to each ply in the composite material 2000 according to the ply's susceptibility to wrinkling.

[0088] In use, the composite material 2000 may be connected to the tension wires via the tension connectors 1016. Initial tension may be applied to the tension wires to suspend the composite material 2000 above the mold 1002. This may reduce the need for heating the mold 1002 since cooling of the composite material 2000 can be delayed via the suspension. The initial tension may also assist in blank trellising in certain areas of the composite material 2000.

[0089] The inflatable bladder 1004 may then be inflated. Alternatively, the inflatable bladder 1004 may be pre-inflated or permanently inflated. The actuator 1006 may also press the inflatable bladder 1004 against the composite material 2000.

[0090] The biasing elements 1014 may induce additional tension into the composite material 2000 so that the composite material 2000 is subjected to a forming tension. Furthermore, the biasing elements 1014 and tension wires may be moved to change the origin of the tension force, thereby affecting the direction, intensity, and timing of the tension.

[0091] To promote early tensioning in the forming process, the tension wires may be pulled from a position that causes the inflatable bladder 1004 to quickly contact the tension wires. To promote late tensioning, the tension wires may be pulled from a position where the inflatable bladder 1004 does not contact the tension wires until later in the forming process or not at all.

[0092] The tension connectors 1016 (clevises and clevis pins or cantilever pins as described above) may induce more tension to some of the plies depending on whether those plies are wrinkle prone or not (based on their position in the completed part). In the illustrated example, the lower plies are more susceptible to wrinkling near the convex radiused inner corners 1010 and thus are engaged with more tension than the upper plies. This difference in tension endured by adjacent plies promotes inter-ply slippage, which prevents wrinkling and bridging. The tension connectors 1016 may pull through the composite material 2000 when tension exceeds bearing strength of the composite material 2000, as seen in FIG. 10.

[0093] Although the invention has been described with reference to the embodiments illustrated in the attached drawing figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims.