Apparatus and methods for bonding laminate structures

Abstract

A composite laminate reinforcing tool may be used to form a reinforced joint at a bond line of a composite laminate structure. The tool may hold one or more clips having posts, and the tool may be positioned along the bond line between at least two composite laminate elements. Joint sections of the clip may be heated to increase a pliability of the joint section, and the tool may be actuated to drive the post through the at least two composite laminate elements. The posts, may deflect toward a base of the clip, thereby to seat the clip. The reinforced composite laminate structure may then be cured.

Claims

1. A method for forming a reinforced joint at a bond line in a composite laminate structure, the method comprising: loading a composite laminate reinforcing tool with a clip, having a first post coupled to a base at a first joint section between the first post and the base, the first post extending at an initial angle relative to the base and defining a first-post inner surface, facing toward the base, and a first-post outer surface, facing away from the base, the first-post outer surface comprising an inwardly tapered section at a tip of the first post; positioning the composite laminate reinforcing tool along the bond line between at least two composite laminate elements; heating the first joint section sufficiently above an ambient temperature to increase a pliability of the first joint section; actuating the composite laminate reinforcing tool so that the first post pierces through the at least two composite laminate elements; and while the first joint section is heated above the ambient temperature and as the first post pierces through the at least two composite laminate elements, engaging the tapered section of the first-post outer surface with a backing surface to deflect the first post toward the base at the first joint section until the first post extends at a deflected angle relative to the base, the deflected angle being different from the initial angle, thereby to seat the clip.

2. The method of claim 1, in which: the clip further comprises a second post, coupled to the base at a second joint section between the second post and the base, the second post extending at a second initial angle relative to the base and defining a second-post inner surface, facing toward the base, and a second-post outer surface, facing away from the base, the second-post outer surface comprising an inwardly tapered section at a tip of the second post; heating the joint section comprises heating the first and second joint sections sufficiently above the ambient temperature to increase pliability of the first and second joint sections; actuating the composite laminate reinforcing tool comprises driving the first and second posts through the at least two composite laminate elements; and deflecting the post comprises, while the first and second joint sections are heated above the ambient temperature and as the first and second posts are driven through the at least two composite elements, engaging the tapered section of the first-post outer surface and the tapered section of the second-post outer surface with a backing surface to deflect the first and second posts at the first and second joint sections, respectively, until the first and second posts extend at first and second deflected angles relative to the base, the first and second deflected angles being different from the first and second initial angles, respectively.

3. The method of claim 1, in which the clip is formed of a clip material, selected from a group of clip materials consisting of uni-directional fiber reinforced thermoplastic, non-oriented chopped fiber thermoplastic, and neat thermoplastic resin.

4. The method of claim 1, in which a plurality of clips is loaded into the composite laminate reinforcing tool and driven into the bond line.

5. The method of claim 4, further comprising coupling adjacent pairs of the plurality of clips with a link.

6. The method of claim 1, in which the initial angle is approximately 90 degrees.

7. The method of claim 1, in which the composite laminate reinforcing tool comprises a plunger head positioned to engage a base of the clip, and in which heating the first joint section comprises heating the plunger head.

8. The method of claim 7, in which the plunger head is movable from a retracted position to an extended position, and in which actuating the composite laminate reinforcing tool comprises actuating the plunger head from the retracted position to the extended position.

9. The method of claim 1, in which at least one of the at least two composite laminate elements comprises a pre-impregnated laminate element.

10. The method of claim 1, further comprising, after deflecting the first post, heating the clip that was seated and the at least two composite laminate elements to cure the composite laminate structure.

11. A method for forming a reinforced joint at a bond line in a composite laminate structure, comprising: loading a composite laminate reinforcing tool with a plurality of clips, each of the plurality of clips having a first post, coupled to a base at a first joint section between the first post and the base, and a second post coupled to the base at a second joint section between the second post and the base, the first and second posts extending at first and second initial angles, respectively, relative to the base, the first and second initial angles being approximately 90 degrees so that each of the plurality of clips has a U-shape, the first post defining a first-post inner surface, facing toward the base, and a first-post outer surface, facing away from the base, with the first-post outer surface comprising an inwardly tapered section at a tip of the first post, and the second post defining a second-post inner surface, facing toward the base, and a second-post outer surface, facing away from the base, with the second-post outer surface comprising an inwardly tapered section at a tip of the second post; positioning the composite laminate reinforcing tool along the bond line between at least two composite laminate elements; heating the first and second joint sections of a selected one of the plurality of clips sufficiently above an ambient temperature to increase a pliability of the first and second joint sections; actuating the composite laminate reinforcing tool so that the first and second posts of the selected one of the plurality of clips pierce through the at least two composite laminate elements; and while the first and second joint sections are heated above the ambient temperature and as the first and second posts pierce through the at least two composite laminate elements, engaging the tapered section of the first-post outer surface and the tapered section of the second-post outer surface with a backing surface to deflect the first and second posts of the selected one of the plurality of clips toward the base at the first and second joint sections, respectively, until the first and second posts extend at first and second deflected angles relative to the base, the first and second deflected angles being different from the first and second initial angles, respectively, thereby to seat the selected one of the plurality of clips.

12. The method of claim 11, further comprising coupling adjacent pairs of the plurality of clips with a link.

13. The method of claim 11, in which each of the plurality of clips is formed of a clip material, selected from a group of clip materials consisting of uni-directional fiber reinforced thermoplastic, non-oriented chopped fiber thermoplastic, and neat thermoplastic resin.

14. The method of claim 11, in which the composite laminate reinforcing tool comprises a plunger head, positioned to engage a base of the clip, and in which heating the first and second joint sections of the selected one of the plurality of clips comprises heating the plunger head.

15. The method of claim 14, in which the plunger head is movable from a retracted position to an extended position, and in which actuating the composite laminate reinforcing tool comprises actuating the plunger head from the retracted position to the extended position.

16. The method of claim 11, in which at least one of the at least two composite laminate elements comprises a pre-impregnated laminate element.

17. The method of claim 11, further comprising, after deflecting the first and second posts, heating the selected one of the plurality of clips that was seated and the at least two composite laminate elements to cure the composite laminate structure.

18. A method for forming a composite laminate structure having a reinforced joint at a bond line, the method comprising: loading a composite laminate reinforcing tool with a clip, the clip having a first post coupled to a base at a first joint section between the first post and the base, the first post extending at an initial angle relative to the base and defining a first-post inner surface, facing toward the base, and a first-post outer surface, facing away from the base, the first post outer surface comprising an inwardly tapered section at a tip of the first post; positioning the composite laminate reinforcing tool along the bond line between at least two pre-cured composite laminate elements; heating the first joint section sufficiently above an ambient temperature to increase a pliability of the first joint section; actuating the composite laminate reinforcing tool so that the first post pierces through the at least two pre-cured composite laminate elements; while the first joint section is heated above the ambient temperature, and as the first post pierces through the at least two pre-cured composite laminate elements, engaging the tapered section of the first-post outer surface with a backing surface to deflect the first post toward the base at the first joint section until the first post extends at a deflected angle relative to the base, the deflected angle being different from the initial angle, thereby to seat the clip; and after deflecting the first post to the deflected angle, heating the clip that was seated and the at least two pre-cured composite laminate elements to cure the composite laminate structure.

19. The method of claim 18, in which at least one of the at least two pre-cured composite laminate elements comprises a pre-impregnated laminate element.

20. The method of claim 18, in which the clip is formed of a clip material, selected from a group of clip materials consisting of uni-directional fiber reinforced thermoplastic, non-oriented chopped fiber thermoplastic, and neat thermoplastic resin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of a composite laminate structure including reinforcing clips, in accordance with an advantageous embodiment;

(2) FIG. 2 is a side elevation view, in cross-section, of a composite laminate structure, taken along line 2-2 of FIG. 1;

(3) FIG. 3 is an enlarged side elevation view of a reinforcing clip, in accordance with an advantageous embodiment;

(4) FIG. 4 is a perspective view of a composite laminate structure including linked reinforcing clips, in accordance with an advantageous embodiment;

(5) FIG. 5 is a side elevation view, in cross-section, of a composite laminate structure taken along line 5-5 of FIG. 4;

(6) FIG. 6 is a side elevation view, in cross-section, of a composite laminate reinforcing tool in accordance with an advantageous embodiment;

(7) FIG. 7 is an end view of the composite laminate reinforcing tool of FIG. 6; and

(8) FIG. 8 is a side elevation view, in cross-section, of the composite laminate reinforcing tool of FIG. 6, with a plunger head in an extended position; and

(9) FIG. 9 is a flow chart illustrating a method for forming a reinforced joint of a composite laminate structure, in accordance with an advantageous embodiment.

(10) It should be understood that the drawings are not necessarily drawn to scale and that the disclosed embodiments are sometimes illustrated schematically. It is to be further appreciated that the following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses thereof. Hence, although the present disclosure is, for convenience of explanation, depicted and described as certain illustrative embodiments, it will be appreciated that it can be implemented in various other types of embodiments and in various other systems and environments.

DETAILED DESCRIPTION

(11) The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.

(12) Referring more particularly to the drawings, FIG. 1 illustrates a composite laminate structure 10 including a first composite laminate element 12 and a second composite laminate element 14. While the composite laminate structure 10 is shown having two elements 12, 14, it may include more than two elements. The first composite laminate element 12 is shown in the form of a laminate skin, while the second composite laminate element is shown in the form of a stringer having a base 16 and a flange 18. It will be appreciated, however, that the first and second composite laminate elements 12, 14 may take the form of other components generally known in the relevant art. For example, the two elements may be: both skin elements; layers of an integral skin element; a skin element and a support element; or both support elements. In the aircraft art, exemplary composite laminate structures include a skin joined to a longeron, bulkhead, stringer, frame or other structure, as well as skin joined to another skin.

(13) The first and second composite laminate elements 12, 14 are shown as being bonded together along first and second bond lines 20, 22. The number and location of the bond lines may be determined based on the type of composite laminate structure to be formed, the expected loading of the composite laminate structure, the application in which the composite laminate structure may be used, and other considerations. Accordingly, the number and orientation of the bond lines may be different than those shown in FIG. 1.

(14) As best shown with reference to FIGS. 1-3, the composite laminate elements 12, 14 are joined together by a plurality of reinforcing clips 24 oriented along the bond lines 20, 22. Each clip 24 may include a base 26 and two posts 28, 30 extending from opposite ends of the base 26. The regions in which the posts 28, 30 are coupled to the base 26 are defined herein as joint sections 32, 34. In FIG. 2, the posts 28, 30 are shown piercing through both the first and second composite laminate elements 12, 14 and deflecting inwardly toward the base 26 so that respective tips 36, 38 of the posts 28, 30 engage a bottom surface 40 of the first composite laminate element 12. When positioned as shown in FIG. 2, the clips 24 are referred to herein as being seated or in a seated configuration.

(15) Prior to being seated, the clips 24 may have an initial configuration, as shown in FIG. 3, to facilitate attachment of the clips 24 to the first and second composite laminate elements 12, 14. FIG. 3 more clearly illustrates the parts of the clip 24, including the base 26, posts 28, 30, joint sections 32, 34, and tips 36, 38. In the initial configuration, the posts 28, 30 may extend at initial angles 1, 2 relative to the base 26. In the illustrated embodiment, the initial angles 1, 2 are approximately ninety degrees to give the clip 24 a U-shape, however other angles may be used.

(16) Additionally, in FIG. 3 the posts 28, 30 are shown as having inner surfaces 42, 44 generally facing the base 26 and outer surfaces 46, 48 generally facing away from the base 26. Each of the outer surfaces 46, 48 may include a tapered section 50, 52 which reduces a thickness of the posts 28, 30 at the tips 36, 38. The tapered sections 50, 52 may facilitate inward deflection of the posts 28, 30 during seating of the clip 24, as will be understood more fully below.

(17) The clips 24 may be formed of a material suitable for use in a composite laminate structure. For aircraft applications, the clip material may have a high strength-to-weight ratio, and may react favorably to heat that may be generated during subsequent curing procedures, if needed. Exemplary clip materials include uni-directional fiber reinforced thermoplastic, non-oriented chopped fiber thermoplastic, and neat thermoplastic resin. In materials using fibers, the fibers may be graphite fibers, aramid fibers, or the like. These materials are merely exemplary, as nearly any material may be used that is capable of being formed into a clip and has advantageous non-corrosive characteristics.

(18) An alternative embodiment of a composite laminate structure 110 is illustrated in FIGS. 4 and 5. Similar to the embodiment of FIGS. 1 and 2, the composite laminate structure 110 includes a first composite laminate element 112 and a second composite laminate element 114 joined by a plurality of clips 124. In this embodiment, however, the clips 124 are coupled to each other by links 125 extending between adjacent pairs of clips 124. The links 125 may be formed of the same material as the clips 124, examples of which are identified above.

(19) A composite laminate reinforcing tool 200 may be used to insert the clips 24 through the first and second composite laminate elements 12, 14 and seat the clips 24. An exemplary tool 200 is illustrated in FIGS. 6-8 as including a base 202 pivotably coupled to a housing 204. The base 202 and housing 204 define a chamber 206 sized to receive a plurality of clips 24. The chamber 206 includes a base end 208 and an outlet end 210 defining an outlet 211, through which clips 24 may be dispensed from the tool 200.

(20) The composite laminate reinforcing tool 200 may further include a guide assembly 212 disposed in the chamber 206 that is configured to hold one or more clips 24 in a pre-determined orientation and to bias the one or more clips 24 toward the chamber outlet end 210. In the illustrated embodiment, the guide assembly 212 includes a slide 214 disposed in the chamber 206 and configured to receive a plurality of clips 24 in the pre-determined orientation. More specifically, and as best seen in FIG. 7, the slide 214 has a rectangular cross-section that is generally complementary to the U-shaped clips 24. A top surface 216 of the slide 214 supports a bottom surface 27 of the clip base 26, and the posts 28, 30 of the clips 24 depend downwardly on opposite side surfaces 218, 220 of the slide 214. Accordingly, the slide 214 holds the clips 24 with the posts 28, 30 oriented toward the chamber outlet 211.

(21) The guide assembly 212 may further include a guide head 222 for engaging the one or more clips 24 disposed on the slide 214. The guide head 222 may also be shaped complementary to the slide 214 to permit the guide head 222 to translate longitudinally along the slide 214. The guide head 222 may further be configured to engage the clip 24 (or a trailing clip of a plurality of clips 24). A guide spring 224 may extend between the chamber base end 208 and a rear face of the guide head 222 to bias the guide head 222 toward the outlet end 210, which in turn biases the clip 24 also toward the outlet end 210.

(22) Finally, the guide assembly 212 may include a guide post 226 for maintaining the guide head 222 on the slide 214 across the entire extent of travel of the guide head 222. In the illustrated embodiment, the guide post 226 extends from the base end 208 to a forward-most extent of travel of the guide head 222. The guide head 222 slidably receives the guide post 226, thereby to retain the guide head 222 in sliding engagement with the slide 214. The slide 214, guide head 222, guide spring 224, and guide post 226 may all have fixed positions relative to the base 202, so that the guide assembly 212 and base 202 both may be pivoted relative to the housing 204.

(23) The composite laminate reinforcing tool 200 may further include a plunger assembly 230 for dispensing the clip 24 out of the chamber outlet 211. In the illustrated embodiment, the plunger assembly 230 includes a plunger head 232 disposed in the chamber 206 and positioned adjacent the chamber outlet end 210. The plunger head 232 is configured to engage a top surface 29 of the clip base 26, and is movable between a retracted position, in which the plunger head is disposed in the chamber 206 (FIG. 6), and an extended position, in which the plunger head 232 is disposed partially or entirely through the chamber outlet 211 to dispense the clip 24 (FIG. 8). The plunger head 232 may be manually actuated as shown in FIGS. 6-8, in which case the plunger assembly 230 may include a plunger rod 234, plunger handle 236, and plunger spring 238. The plunger handle 236 is disposed outside of the chamber 206 and is configured to receive a manual force (represented by arrow 239) sufficient to actuate the plunger head 232 between retracted and extended positions. The plunger spring 238 may be configured to automatically return the plunger head 232 to the refracted position as soon as the manual force 239 is removed. Alternatively, the plunger head 232 may be automatically actuated using a drive system (not shown).

(24) The composite laminate reinforcing tool 200 also may include a heating assembly 240 thermally coupled to the plunger head 232. In the illustrated embodiment, the heating assembly 240 includes a heating element 242 disposed in the housing 204. A heating element wire 244 may extend from the heating element 242 to the plunger head 232, thereby to thermally couple the plunger head 232 to the heating element 242.

(25) The composite laminate reinforcing tool 200 may be used to perform a method for forming a reinforced joint at a bond line in a composite laminate structure 10, as illustrated by a flowchart 300 in FIG. 9. The method may begin at block 302, where the composite laminate reinforcing tool 200 is loaded with a clip 24 having at least one post 28 coupled to a base 26 at a joint section 32. The post 28 may extend at an initial angle 1 relative to the base 26. In some embodiments, the clip 24 may have a U-shape with first and second posts 28, 30 joined to the base at first and second joint sections 32, 34, with the first and second posts 28, 30 extending at first and second initial angles 1, 2 relative to the base 26.

(26) Continuing at block 304, the composite laminate reinforcing tool 200 may be positioned along a bond line 20 or 22 between at least two composite laminate elements 12, 14. At block 306, the joint section 32 of the clip 24 may be heated sufficiently above an ambient temperature to increase a pliability of the joint section 32. The actual temperature to which the joint section 32 is heated depends on the type of clip material used. In some embodiments where the clip 24 includes two posts 28, 30, the heating step includes heating both first and second joint sections 32.

(27) Next, the composite laminate reinforcing tool 200 may be actuated to dispense the clip 24, as indicated at block 308. During actuation of the tool 200, a plunger head 232 may be actuated from a retracted position (FIG. 6) to an extended position (FIG. 8). As the plunger head 232 advances to the extended position, the post 28 (or posts 28, 30) of the clip pierce through the composite laminate elements 12, 14.

(28) At block 310, the post 28 is deflected toward the clip base 26 at the joint section 32 to seat the clip 24. The post 28 is deflected to a deflected angle 1 relative to the base 26, with the deflected angle 1 being different from the initial angle 1. In some embodiments having first and second posts 28, 30, this step includes deflecting the first and second posts 28, 30 at the first and second joint sections 32, 34 until the first and second posts 28, 30 extend at first and second deflected angles 1, 2 relative to the base 26. Both the first and second deflected angles 1, 2 may be different from the first and second initial angles 1, 2, respectively.

(29) Deflection of the posts 28, 30 may be facilitated by the heating of the joint sections 32, 34 and the shape of the clips 24. For example, a backing surface 15 (FIGS. 1 and 2) may be positioned beneath the first and second composite laminate elements 12, 14 that engages the tips 36, 38 of the posts 28, 30 as they pierce through the elements 12, 14. The backing surface 15 may be provided as a lay-up tool or other structure having sufficient hardness to deflect the posts 28, 30. With the joint sections 32, 34 heated to increase pliability, the backing surface 15 will deflect the posts 28, 30. The tapered sections 50, 52 of the clips may be provided to more reliably deflect the posts 28, 30 inwardly toward the base 26.

(30) The method described above may be advantageously used with one or more composite laminate elements that are either pre-impregnated with resin or dry fabric (i.e., not pre-impregnated with resin). If pre-impregnated laminates are used, the method may further include heating the seated clip 24 and the at least two composite laminate elements 12, 14 to cure the composite laminate structure 10. If dry fabric is used, an additional step of infusing resin into the dry fabric laminates may be performed prior to curing the composite laminate structure 10. An optional curing step is illustrated at block 312 in FIG. 9.

(31) The above-described embodiments depict a composite laminate reinforcing tool and a method of reinforcing a composite laminate structure that may advantageously be used with a wide variety of composite laminate elements. The apparatus and methods disclosed herein provide an out-of-plane reinforcement for composite laminates that may be used with dry fabric resin infused laminates and/or pre-impregnated laminates. Once seated in the composite laminate elements, the clips provide mechanical locks along a bond line to provide out-of-plane reinforcement. As noted above, the clips may be installed with a manual or automated tool, and in some embodiments may include links between the clips to provide additional reinforcement.

(32) The description of the different advantageous embodiments has been presented for purposes of illustration and description, and it is not intended to be exhaustive or limited to the embodiments in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different advantageous embodiments may provide different advantages as compared to other advantageous embodiments.

(33) Although the different advantageous embodiments have been described with respect to aircraft, the different advantageous embodiments may be applied to other types of platforms. For example, without limitation, other advantageous embodiments may be applied to a submarine, a personnel carrier, a spacecraft, a surface ship, and/or some other suitable object.

(34) The embodiment or embodiments selected are chosen and described in order to best explain the principles of the embodiments, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.