Reducing wrinkles in composite reinforcements with curved contours

Abstract

To provide a method and apparatus for producing a composite laminate reinforcement with a curved profile that reduces or eliminates ply wrinkle formation.SOLUTION: A composite charge is formed into a composite laminate reinforcement between two compression dies. The reinforcement is contoured along its length by contouring the die. A wrinkle diffuser attached to, embedded in, or incorporated into the tool face of the die diffuses the wrinkles formed in the inner round of the reinforcement during contouring.SELECTED DRAWING: None

Description

[Technical Field]

[0001]

[0001] This disclosure relates generally to methods and apparatus for manufacturing composite structures, and more particularly to methods and apparatus for reducing wrinkle formation during contouring of composite laminate reinforcements. [Background technology]

[0002] Fiber-reinforced composite laminate stiffeners, such as stringers, are frequently used to transfer loads in marine, aircraft, and other industries. In some applications, the stiffeners must be contoured along their length to fit the structure to which they are attached, such as an aircraft skin having a curved profile. Difficulties can be encountered in manufacturing composite laminate stiffeners with highly curved profiles because the plies have a tendency to wrinkle when formed to the desired profile. As the stiffener is contoured, the reinforcing fibers at the stiffener's inner radius can become compressed, causing the ply to buckle and form wrinkles. Ply wrinkling is undesirable because it can undesirably affect the stiffener's performance and / or limit the extent to which the stiffener can be contoured without unacceptable wrinkle formation.

[0003]

[0003] It would therefore be desirable to provide a method and apparatus for manufacturing composite laminate reinforcements having curved profiles that reduces or eliminates wrinkling of the plies. Summary of the Invention

[0004]

[0004] The present disclosure relates generally to methods and apparatus for manufacturing composite structures, and more specifically to a compression mold tool that uses a diffuser to reduce wrinkle formation in composite laminate reinforcements as they are contoured along their length.

[0005] According to one aspect, an apparatus for forming a composite laminate reinforcement having a curved profile is provided. The apparatus includes first and second dies between which a multi-ply composite charge can be formed into the reinforcement. The dies are configured to form the profile in the reinforcement. The apparatus further includes at least a first diffuser disposed between the first and second dies and configured to diffuse wrinkles in the reinforcement being formed into the profile.

[0006] According to another aspect, an apparatus for manufacturing a curved, contoured composite laminate stringer having flanges and webs is provided. The apparatus includes a first die and a second die between which a multi-ply composite charge can be formed into a stringer shape having flanges and webs and contoured along its length. A first wrinkle diffuser is attached to the first die, and a second wrinkle diffuser is attached to the second die opposite the first wrinkle diffuser. The first and second wrinkle diffusers are configured to diffuse wrinkles in the flanges and webs as the charge is formed into the contour.

[0007] According to a further aspect, a method for manufacturing a composite laminate reinforcement having a curved profile is provided. A multi-ply composite charge along with at least one wrinkle diffuser is placed between a first die and a second die. The composite charge is formed into a reinforcement having a desired cross-sectional shape by compressing the charge between the dies. The reinforcement is formed into the desired profile having an internal radius. Wrinkling of the reinforcement along the internal radius is controlled using the wrinkle diffuser.

[0008] One advantage of the disclosed method and apparatus is that ply wrinkling of a composite laminate reinforcement during contouring is controlled, resulting in a reduction in undesirable ply wrinkling. Another advantage is that the size and / or other physical characteristics of ply wrinkles, such as frequency and spacing, are controlled to levels that do not substantially affect the performance of the reinforcement. Yet another advantage of the disclosed method and apparatus is that reinforcement scrap and rework caused by unacceptable ply wrinkling is reduced or eliminated. A further advantage is that the diffuser used to reduce ply wrinkling is easily adapted for use with existing tools used to form the reinforcement. Additionally, the diffuser can be easily replaced and / or interchanged, allowing the diffuser to be used with a variety of tools used to form reinforcements of various configurations.

[0009]

[0009] The features, functions, and advantages can be achieved independently in various embodiments of the present disclosure or can be combined in yet other embodiments, where further details can be found by referring to the following description and drawings.

[0010] The novel features believed characteristic of the illustrative embodiments are set forth in the appended claims. However, the illustrative embodiments, together with their preferred modes of use, further objects and advantages, will best be understood by reference to the following detailed description of illustrative embodiments of the present disclosure taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view of an airplane, showing the location of stiffeners with curved profiles indicated by dashed lines. [Figure 2] FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. [Figure 3]FIG. 3 is a perspective view of a blade stringer having a curved profile used in the airplane wing shown in FIGS. 1 and 2. [Figure 4] FIG. 4 is a partial side view of the blade stringer having the curved profile shown in FIG. 3. [Figure 5] FIG. 4 is a partial perspective view of a tool used to form the curved profiled blade stringer of FIGS. 2 and 3. [Figure 6] FIG. 1 is a side view of a former including a die change mechanism used to profile the stringer. [Figure 7] 6A-6C are end views of the tool of FIG. 5 illustrating successive stages in the process of forming the composite charge into a blade stringer. [Figure 8] 6A-6C are end views of the tool of FIG. 5 illustrating successive stages in the process of forming the composite charge into a blade stringer. [Figure 9] 6A-6C are end views of the tool of FIG. 5 illustrating successive stages in the process of forming the composite charge into a blade stringer. [Figure 10] 6A-6C are end views of the tool of FIG. 5 illustrating successive stages in the process of forming the composite charge into a blade stringer. [Figure 11] FIG. 8 is an end view of the tool similar to FIG. 7 but showing the inflatable bladder positioned on the flange portion of the charge. [Figure 12] 11, but showing the upper and lower dies closed relative to one another and the bladder expanding to apply pressure to the flange portion of the stringer. [Figure 13] 1 is a partial side view of a composite laminate charge formed into a contour using an example wrinkle diffuser, the contour not being shown. [Figure 14] 10 is a partial side view of a composite laminate charge contoured using another example wrinkle diffuser, the contour not being shown; [Figure 15]FIG. 6 is a perspective view of the tool of FIG. 5 showing an example of diffusers attached to the upper and lower dies to reduce wrinkling of the plies when forming the stringer into the profile. [Figure 16] FIG. 10 is a perspective view of the front side of one of the upper die diffusers. [Figure 17] FIG. 17 is a perspective view of the back side of the diffuser shown in FIG. 16. [Figure 18] FIG. 17 is a partial plan view of a portion of the diffuser shown in FIG. 16. [Figure 19] FIG. 10 is a partial plan view of another example of a diffuser for the upper die. [Figure 20] 10 is a partial plan view of another example diffuser for the upper die, illustrating various sizes, distributions, and orientations of the diffuser recesses. [Figure 21] FIG. 10 is a partial perspective view of two segments of a diffuser for use with the lower die. [Figure 22] FIG. 22 is a partial perspective view of the back side of the diffuser shown in FIG. 21. [Figure 23] FIG. 9 is a cross-sectional view taken along line 23-23 in FIG. 8. [Figure 24] FIG. 14 is a cross-sectional view taken along line 24-24 in FIG. [Figure 25] FIG. 6 is a perspective view of the tool of FIG. 5 showing another example of a diffuser attached to the die to reduce wrinkling of the plies when forming the stringer into a profile. [Figure 26] FIG. 26 is a perspective view of the front side of one of the diffusers shown in FIG. 25. [Figure 27] FIG. 27 is a partial perspective view of the area designated "27" in FIG. 26. [Figure 28] FIG. 26 is a perspective view of a diffuser of the type attached to the lower die of FIG. 25. [Figure 29] FIG. 29 is a partial enlarged perspective view of the portion designated "29" of the diffuser shown in FIG. 28. [Figure 30]FIG. 24 is a view similar to FIG. 23, but showing the sinusoidal pattern of wrinkles formed in the flange portion of the charge by the diffusers of FIGS. 25-29. [Figure 31] FIG. 31 is a view similar to FIG. 30 but showing the sinusoidal pattern of wrinkles formed in the web portion of the charge. [Figure 32] FIG. 1 is a flow diagram of a method for manufacturing a composite laminate reinforcement having a curved profile with reduced wrinkle formation. [Figure 33] FIG. 1 is a flow diagram of an aircraft production and service methodology. [Figure 34] FIG. 1 is a block diagram of an aircraft. DETAILED DESCRIPTION OF THE INVENTION

[0012]

[0042] Referring initially to FIGS. 1 and 2 , an airplane 30 includes a fuselage 32, wings 34, and a tail with a vertical stabilizer 36 and a horizontal stabilizer 38. Each of these airframe components includes a skin 40 reinforced and stabilized by stiffeners 42, such as stringers 50. For example, as shown in FIG. 2 , each of the wings 34 includes a wing box 44 formed by spars 46, ribs 48, and stringers 50, which are covered by a composite laminate skin 40, such as a carbon fiber reinforced polymer (CFRP) laminate. The wing box 44 includes upper and lower wing panels 52 and 54. In the illustrated example, the stiffeners 42 are blade-type stringers 50, but the principles disclosed herein are applicable to a wide range of other types of stringers, including, but not limited to, I-, J-, Y-, Z-, and hat stringers. Each of the stringers 50 is bonded to the IML (inner mold line) of the skin 40, typically by co-curing or co-bonding.

[0013]

[0043] Depending on the application, stringers 50 can have various out-of-plane features, such as curvatures, pad-ups, and / or joggles, at one or more locations along their length. Contouring of stringers 50 may be necessary to match the contour of the skin 40 to which they are attached. For example, with reference to FIGS. 3 and 4, a blade-shaped stringer 50, such as that used in the wing of FIG. 2, includes a blade 56 (sometimes referred to herein as a web 56) and a flange 58 extending perpendicular to the blade 56. In this example, stringer 50 has a curved contour 60 along its entire length in the XZ plane in the coordinate system shown at 61, although in other examples, stringer 50 may have straight sections and localized curved contours along its length. While the stringers shown in FIGS. 3 and 4 are concave downward, they may also be concave upward in some applications. Additionally, stringer 50 may have one or more curved profiles along its length in the XY plane, and in some examples, stringer 50 may have a compound profile with curved profiles in both the XZ and XY planes. Web 56 and flanges 58 each may have a variable thickness at one or more locations along their length to allow stringer 50 to conform to local features of the structure to which the stringer is attached.

[0014]

[0044] Attention is now directed to FIG. 5 , which illustrates one form of tool 62 employing a compression die for forming a blade-shaped stringer 50 or similar stiffener 42 using a fiber-reinforced composite charge 64 (hereinafter referred to as the “charge”), which in the illustrated example is generally flat and includes multiple plies 66 of fiber-reinforced composite material. The charge 64 may also include a pad-up ply 68. The ply 66 may include a fiber-reinforced polymer, such as, for example, but not limited to, a thermoset or thermoplastic reinforced with continuous fibers, such as carbon fiber. Generally, the tool 62 includes an upper die 70 attached to an upper flexible plate 72 and a lower die 74 attached to a lower flexible plate 76. The upper die 70 includes a punch 78 having a blade-like shape with a slit 80 along its length. The slit 80 segments the punch 78 into multiple punch portions 82, allowing the punch 78 to flex along its length.

[0015]

[0045] The lower die 74 includes a pair of die blocks 84 that are segmented 86 along their lengths. The die blocks 84 are spaced apart from one another to form a die cavity 90 into which the charge 64 can be formed by the punch 78 when the upper die 70 is closed against the lower die 74. The die blocks 84 are laterally slidable 88 toward and away from one another on the lower flexible plate 76. The segmentation 86 of the die blocks 84 allows the die blocks 84 to flex along their lengths.

[0016]

[0046] A pair of L-shaped brackets 92 are attached to the lower flexible plate 76 on either side of the lower die 74 and extend along the length of the lower flexible plate 76. The L-shaped brackets 92 function to both retain the die block 84 on the lower flexible plate 76 and to resist lateral forming forces generated by the die block 84 during the forming operation. A pair of inflatable hoses 94, sometimes referred to as bags or bladders, are sandwiched between the L-shaped brackets 92 and the die block 84 and are adapted to be coupled to a suitable source of pressurized air (not shown). The inflatable hoses 94 can be selectively pressurized to apply lateral forces to the die block 84 during the forming and / or profiling operations. However, other mechanisms for applying lateral forces to the die block 84 can also be provided.

[0017]

[0047] As previously mentioned, the flange 58 of the stringer 50 may have variable thicknesses in localized regions along its length to allow the stringer 50 to conform to the localized curved contours of the structure (such as the skin panel 40) to which it is attached. To accommodate these thickness variations so that a constant and uniform pressure is applied to the composite charge 64 in these localized regions, shims (not shown) may be placed above or below the die blocks 84 along their lengths as needed to conform to the localized curved contours caused by these thickness variations. As the charge 64 is being formed to the desired contour, both of the die blocks 84 flex as needed to maintain a constant forming pressure on the charge 64. As described below, during the forming operation, the charge 64 is placed on the top 96 of the die blocks 84, and the upper and lower dies close against each other at a controlled rate, effectively punching the charge 64 into the desired stringer cross-sectional shape. In the illustrated stringer example, the flange 58 of the stringer 50 is formed between the top 96 of the die block 84 and the upper plate 72, and the blade or web 56 of the stringer 50 is formed between the punch 78 and the side 98 of the die block 84.

[0018]

[0048] FIG. 6 illustrates a former 100 incorporating the tool 62 shown in FIG. 5 with a die change mechanism 101. The die change mechanism 101 may include, for example, without limitation, a press 102 and a plurality of separate, spaced-apart actuators 104. The actuators 104 are respectively attached to opposing press plates 106 of the press 102 that are adapted to move toward and away from each other, as indicated by arrows 108. The tool 62 is positioned between the press plates 106. The press plates 106 may be coupled with any suitable power mechanism, such as a cylinder actuator (not shown), that displaces the press plates 106 to open and close the tool 62 during a charge forming operation.

[0019]

[0049] The die change mechanism 101 contours the partially formed charge 64 by changing the shape of the dies 70, 74. This contouring process places portions of the charge 64 in tension and other portions in compression. Compressing the charge 64 in this manner causes wrinkles to form in the plies 66 of the charge 64, typically along the inner radii 59 of the contour 60. However, in accordance with one aspect of the invention, wrinkle diffusers (not shown in FIG. 6 ), described in more detail below, are attached between the charge 64 and the upper and lower dies 70, 74 and function to control wrinkling and / or buckling of the charge 64 during the contouring operation. Each of the actuators 104 includes a plunger 110 coupled to one of the upper and lower flexible plates 72, 76, which applies a bending force to the two plates to bend them into the desired stringer contour. Bending the upper and lower flexible plates 72, 76 in turn bends the die block 84, thereby contouring the stringer 50 along its length. However, other mechanisms can be used to contour the tool 62 along its length. In some examples, the charge 64 is first punched to the desired stringer cross-sectional shape and then contoured along its length by the die change mechanism 101. In other examples, however, the dies 70, 74 are first contoured by the die change mechanism 101 and then the charge 64 is punched to the desired cross-sectional shape.

[0020]

[0050] The sequential steps for forming the charge 64 into the desired stringer cross-sectional shape are shown in Figures 7-10. Referring first to Figure 7, the upper die 70 includes a pair of first wrinkle diffusers 114a, 114b, also referred to herein as upper diffusers 114a, 114b, attached to either side of the punch 78. A pair of second wrinkle diffusers 116a, 116b, also referred to herein as lower diffusers 116a, 116b, are attached to the die block 84 of the lower die 74. The upper diffusers 114a, 114b and the lower diffusers 116a, 116b function to control wrinkling of the charge 64 as it is formed into the desired stringer profile 60 (Figure 4) by diffusing the wrinkles into a series of small wrinkles having a predetermined length-to-depth ratio.

[0021]

[0051] With the upper die 70 in its raised position ( FIG. 7 ) and the die block 84 in its open, spaced-apart position, a flat multi-ply composite charge 64 is placed on the lower die 74 overlying the flange portions 118 of the lower diffusers 116 a, 116 b. Next, as shown in FIG. 8 , a downward force F is applied to the upper die 70, causing the punch 78 to form the charge 64 into the die cavity 90 while the upper plate 72 compresses the flanges 58 of the charge 64 against the die block 84. With the partially formed charge 64 clamped between the upper and lower dies 70, the charge 64 is contoured along its length using the die change mechanism 101, as described above in connection with FIG. 6 . During this contouring operation, the inner radii 59 of both the web 56 and the flanges 58 are placed in compression, which may cause them to wrinkle or buckle along the contour 60. As will be described below, the wrinkle diffusers 114, 116 are configured to diffuse wrinkles so as to reduce undesirable effects on the performance of the stiffener 42.

[0022]

[0052] Referring to FIG. 9 , following the profiling operation, the upper die 70 is displaced upward and the punch 78 is withdrawn from the die cavity 90. Next, as shown in FIG. 10 , the upper die 70 is replaced with a flat plate 112, which is placed over the flange 58 of the partially formed charge 64. A downward force F is applied to the flat plate 112, forcing the left and right portions of the flange 58 against the die block 84, securing the flange 58. With the flange 58 secured by the flat plate 112, the die blocks 84 are forced 95 toward each other, thereby closing the open web 56 and forming the blade 56. In the example described above in connection with FIGS. 7-10 , the charge 64 is punched to the desired cross-sectional shape before being profiled along its length. However, in other examples, the dies 70, 74 are first changed to the desired profile by the die changing mechanism 101, and then the charge 64 is punched into the dies 70, 74 having the curved profile, thereby simultaneously shaping and shaping the stiffener 42.

[0023]

[0053] The type and placement of the diffusers 114, 116 on the dies 70, 74 vary depending on the application. Depending on the shape of the stiffener 42, the number and severity of the contours, and other factors, diffusers 114, 116 may be attached to some tool faces of the dies 70, 74 but not others. For example, referring to FIG. 11 , the upper die 70 has an upper diffuser 114a attached only to the left side of the punch 78. To ensure equal pressure is applied to both the left and right portions of the flange 58 of the charge 64 during the forming process, an inflatable bladder 121 is positioned on the right portion of the flange 58. When inflated ( FIG. 12 ), the inflatable bladder 121 applies a pressure to the right portion of the flange 58 substantially equal to the pressure applied to the left portion by the upper diffuser 114a. During the forming process, the inflatable bladder 121 is deflated at a controlled rate to reduce the applied pressure sufficiently to allow the right portion of the flange 58 to slide between the upper die 70 and the die block 84, similar to the sliding of the left portion, as the punch 78 forms the charge 64 into the die cavity 90.

[0024]

[0054] As described below, the diffusers 114, 116 function to control the size and shape of wrinkles that form in the charge 64 in areas of the reinforcement 42 that are placed under compression during the forming / contouring process, for example, along the inner radius 59 or other out-of-plane features of the contour 60 in the reinforcement 42. Rather than forcing wrinkles of uncontrolled size, shape, and spacing to form, which could undesirably affect the performance of the reinforcement, wrinkle formation is diffused by forcing the formation of wrinkles of a desired size, shape, and / or spacing, thereby configured to have minimal or no effect on the performance of the reinforcement. This controlled wrinkle formation is achieved by providing depressions in the diffusers 114, 116, into which portions of the charge 64 may distort as a result of compressive stresses in the charge 64 caused by the forming / contouring process.

[0025]

[0055] FIG. 13 shows an example of diffused wrinkles 144 formed by diffusers 114, 116 within charge 64 along inner radius 59 of contour 60 ( FIGS. 3 and 4 ) in reinforcement 42. In this example, wrinkles 144 form a sinusoidal pattern, with each wrinkle 144 having a preselected length L (wavelength) and depth D, resulting in a desired length-to-depth (L / D) ratio. While FIG. 13 shows a sinusoidal pattern of wrinkles, diffusers 114, 116 may be configured to generate various other patterns of wrinkles 144 having desired L / D ratios. To address local reinforcement conditions, such as changes in the shape of reinforcement 42, the wavelength L and / or depth D of the wrinkles 144 may vary along the length of reinforcement 42 depending on the shape of reinforcement 42. Another example of diffused wrinkles 144 that can be formed by wrinkle diffusers 114, 116 is shown in FIG. 14 , where individual wrinkles 144 having a length L and a depth D are formed. In this example, the wrinkles 144 are formed only on one side of the charge 64, e.g., only on the inner radius 59 of the reinforcement 42. However, depending on the shape of the reinforcement 42, wrinkles 144 may be formed on both sides of the charge 64. In the examples shown in FIGS. 13 and 14 , the length L is constant; however, in other examples, the length L of the wrinkles 144 may vary to address local reinforcement conditions, such as changes in the contour 60 of the reinforcement 42. As will become apparent below, wrinkle diffusers 114, 116 can be used to achieve a variety of other controlled wrinkle configurations.

[0026]

[0056] Attention is now directed to Figures 15-18, which illustrate an example of diffusers 114, 116, sometimes referred to herein as first and second diffusers 114, 116, or upper and lower diffusers 114, 116, respectively. Each of the upper diffusers 114 includes a plurality of interconnected plates 117, each of which is formed of a flexible material, such as a metal or composite, and may be removably attached to the upper die 70 by any suitable means, such as magnets or fasteners (not shown). Each of the plates 117 includes a plurality of depressions 122 therein spaced along its length, each of which is configured to form wrinkles having a desired length L and depth D. In the illustrated example, the depressions 122 include first depressions 122a and second depressions 122b in the form of slots or gaps arranged in an alternating relationship with one another. As used herein, the term "depression" includes, without limitation, gaps, slots, cavities, voids, pockets, and similar out-of-plane features in the surface of plate 117 that form spaces into which a portion of charge 64 may distort as a result of compressive stresses within charge 64.

[0027]

[0057] In the example shown in FIGS. 15-18 , the plates 117 are interconnected by interlocks 132, each comprising a tab 134 at one end of the plate 117 that is received in a matching notch 136 at one end of an adjacent plate 117. Other techniques for interconnecting the plates 117 are possible. Also, depending on the length of the stiffener 42 to be formed, each of the plates 117 may comprise a single piece rather than multiple interconnected pieces. As previously mentioned, the upper diffuser 114 can be removably attached to the upper die 70 using any of several techniques, including fasteners or magnets. In one example, a magnet (not shown) attached to the upper die 70 is received in a recess 138 on the backside of the plate 117, thus providing a means for removably holding the plate 117 to the upper die 70 in proper alignment. In other examples, the plate 117 may be permanently attached, embedded, or otherwise incorporated into the upper die 70.

[0028]

[0058] With particular reference to FIG. 18 , the dimensions of the recesses 122a, 122b will vary depending on the application and the length L and depth D of the wrinkle 144 to be formed. In the illustrated example, the recesses 122a, 122b are slot-shaped, although other shapes are possible. Each recess 122a has a length L1 that is longer than the length L2 of the recess 122b. The widths W1, W2 of the recesses 122a, 122b may be the same or different and will depend on the size of the wrinkle 144 to be formed. Finally, the pitch P1 between the recesses 122a, the pitch P2 between the recesses 122b, and the pitch P3 between the recesses 122a, 122b will also vary depending on the size of the wrinkle 144 to be formed. Furthermore, although not shown in FIG. 18 , the depth of the recesses 122a, 122b is selected to achieve the desired depth D of the wrinkle 144.

[0029]

[0059] FIG. 19 shows another example of an upper diffuser 114, in which recesses 122 in the form of slots are evenly spaced and have the same length L, width W, and depth D. As previously mentioned, the size, shape, and frequency of the recesses 122 can vary along the length of the upper diffuser 114. For example, FIG. 20 shows an upper diffuser 114 with recesses 122 of various shapes in different sections 146-156 of the plate 117. The recesses 122 in section 146 have the same width and length as the recesses 122 in adjacent section 148, but have different pitches P1 and P2. The recesses 122 in another section 150 have a larger width W than the recesses 122 in sections 146 and 148. Section 152 is free of recesses 122, while adjacent section 154 includes recesses 122a and 122b of two different lengths. Depending on the local reinforcement geometry, one or more sections 156 of the upper diffuser 114 may include recesses 122 oriented obliquely relative to the longitudinal axis 158 of the diffuser 114 .

[0030]

[0060] 15, 21, and 22, each lower diffuser 116 is attached to the die block 84 and comprises a plurality of diffuser segments 160 interconnected using interlocks 132 similar to those described above in connection with the upper diffuser 114. Like the upper diffuser 114, the diffuser segments 160 are formed of a suitable flexible material, such as a metal or composite. Each diffuser segment 160 has an L-shaped cross-section formed by a flange portion 118 resting on the top of the die block 84 and a web portion 120 that covers the side of the die block 84 within the die cavity 90. As best seen in FIGS. 15 and 22, the flange portion 118 includes a hooked end 166 that extends down past the backside 168 (FIG. 15) of the die block 84 and functions to hold the lower diffuser 116 in proper alignment on the die block 84. The lower diffuser 116 can be removably or permanently attached, embedded, or otherwise incorporated into the lower die block 84. Removably attaching the upper and lower diffusers 114, 116 to the upper and lower dies 70, 74 allows the diffusers to be interchangeable and allows diffusers of different configurations to be used with the same set of dies.

[0031]

[0061] Each lower diffuser 116 includes first and second sets of recesses 124a, 124b in the form of slots of two different lengths that are alternately arranged similarly to the slots in the upper diffuser 114. However, other configurations of the recesses 124a, 124b in the lower diffusers 116 are possible. The recesses 124a, 124b extend transversely to the longitudinal axis of the lower die 74, across the flange portion 118, and down through the web portion 120. In the illustrated example, the recesses 124a, 124b in the flange portion 118 are aligned with the recesses 122a, 122b, although in other examples, the two sets of recesses may be offset from one another. Similarly, the recesses 124a, 124b in the opposing web portions 120 of the lower diffusers 116 are aligned with one another in the illustrated example, but may be offset from one another in other examples.

[0032]

[0062] It should be noted that in the illustrated example described above, the recesses 122 are formed in a plate or similar member attached to the upper and lower dies 70, 74. However, in other examples, the diffusers 114, 116 may include recesses 122 formed in the tool faces of the upper and lower dies 70, 74, such as by machining or other techniques.

[0033]

[0063] Attention is now directed to FIG. 23, which illustrates how the upper and lower diffusers 114, 116 diffuse wrinkles at the flange 58 as the stiffener 42 is contoured along its length. Once the final step of forming the charge 64 into the desired cross-sectional shape of the stiffener 42 is completed (FIG. 10), the stiffener 42 is formed to the desired contour using the die change mechanism 101 described above in connection with FIG. 6. In the illustrated example, the stiffener 42 is contoured downward, as shown in FIG. 4. By contouring the stiffener 42 in this manner, the plies 66 in the upper region 170 of the flange 118 are placed in tension T, and the plies 66 in the lower region 172 are placed in compression C. The recess 122 in the lower diffuser 116 adjacent the lower region 172 provides a space into which the fibers and resin of the plies 66 may strain to form diffused wrinkles 144 having a predetermined length and depth. Because the recesses 122 in the lower diffuser 116 have a uniform depth and pitch, a series of substantially identical wrinkles 144 are formed within the recesses 122. Effectively, wrinkle formation caused by the compressive force C is diffused, avoiding the uncontrolled formation of potentially undesirable wrinkles.

[0034]

[0064] Although not shown, with reference to both FIGS. 3 and 23, if the stiffener 42 shown in FIG. 3 were contoured upward rather than downward, compressive stresses would occur in the upper region 170, causing the ply 66 in this region to distort into the recess 122 in the upper diffuser 114. The exact location within the stiffener where compressive stresses may occur depends on the location and direction of the contouring. Wrinkling of plies within stiffeners 42 with compound curvatures or contours (occurring in both the XY and XZ planes) can be reduced using wrinkle diffusers specifically configured to address the localized stresses caused by these types of contours.

[0035]

[0065] FIG. 24 illustrates how the lower diffuser 116 diffuses wrinkles in the web 56 of the charge 64 when the stiffener 42 is contoured along its length. During contouring of the stiffener 42 into the downwardly concave shape shown in FIG. 4, the upper region 174 of the web 56 is in tension and the lower region 176 is in compression. The cross-section shown in FIG. 23 is through the lower region 176. The compressive forces present in the lower region 176 create compressive stresses in the plies 66, which cause the plies 66 on both sides of the web 56 to distort into the recesses 122, thereby forming wrinkles 144 having a predetermined, uniform length-to-depth ratio. Similar to the diffusion of wrinkles occurring in the flange 58, wrinkle formation caused by compressive stresses in the lower region 176 of the web 56 is diffused, preventing the formation of larger, undesirable wrinkles. If the stiffener 42 shown in FIG. 4 were contoured upward rather than downward, compressive forces would occur in the upper region 174, causing the outer ply 66 in this region to distort into the recess 122 in the upper region 174 of the lower diffuser 116.

[0036]

[0066] Attention is now directed to FIG. 25, which illustrates another example of a diffuser mounted on the tool 62. A pair of first diffusers 178, sometimes referred to herein as upper diffusers 178, are mounted on the upper plate 72, one on each side of the punch 78. A pair of second diffusers 180, sometimes referred to as lower diffusers 180, are mounted on the die blocks 84 of the lower die 74, respectively. Each of the upper diffusers 178, like the upper diffuser 114 described in connection with FIG. 15, includes a diffuser plate 182 removably attached to the upper plate 72 by any suitable means, such as magnets or fasteners (neither shown). As will be described in more detail below, each of the upper and lower diffusers 178, 180 includes features that diffuse wrinkles that form in the reinforcement 42 as it is contoured.

[0037]

[0067] 25, 26, and 27, each of the upper diffusers 178 includes a plurality of groove-like depressions 184 therein that, in the illustrated example, extend parallel to one another and transverse to the longitudinal axis of the upper die 70. However, in other examples, the depressions 184 may extend obliquely relative to the upper die 70 or may not be parallel to one another, depending on the local out-of-plane conditions in the stiffener 42. Each of the depressions 194 includes alternating peaks 186 and valleys 188 that form a serpentine pattern when viewed in cross section. As best seen in FIG. 27, the depressions 194 are formed by flat surfaces in the plate 182; however, in other examples, these surfaces may be curved to form smooth waves having a preselected length L (wavelength) and depth D, similar to the depressions 122 described above in connection with the example shown in FIGS. 15-22. The length L, depth D, and frequency may vary along the length of the upper diffuser 178.

[0038]

[0068] 28 and 29 show additional details of the lower diffusers 180. Each of the lower diffusers 180 is L-shaped in cross section and includes a flange portion 196 and a web portion 198. The flange portion 196 includes a second set of indentations 192 that are substantially identical to the first indentations 184 in the upper diffuser 178. The web portion 198 of the lower diffuser 180 includes second groove-like indentations 192 that are substantially identical in cross section to the indentations 192 in the flange portion 196. In the illustrated embodiment, the indentations 192 in the flange portion 196 and the web portion 198 are aligned with one another, but in other examples, they may be offset from one another. Optionally, the web portion 198 may include slots 190 or similar openings that are located in the peaks and valleys 188 of the indentations 184. The recesses 184, 192 as well as the slot 190 may be formed directly in the tool face of the die block 84 rather than in a member attached to the die block 84.

[0039]

[0069] Figure 30 shows that the web portion of the charge 64 is compressed between the opposing, undulating surfaces 200 of the upper and lower diffusers 178, 180 to create a sinusoidal pattern having the desired length L and depth D. Figure 31 shows how the opposing, undulating surfaces 202 of the opposing web portion 198 form the web portion of the charge 64 into a sinusoidal pattern having the desired length L and depth D. Additionally, the slots 190 provide additional space within the diffuser 180 into which the charge 64 can distort, while also providing the diffuser 180 with additional flexibility to allow for better contouring by the die change mechanism 101.

[0040]

[0070] FIG. 32 broadly illustrates the steps of a method for manufacturing a composite laminate stiffener having a curved profile. Beginning at 204, a multi-ply composite charge 64 is placed between the first and second dies 70, 74. At 206, at least one wrinkle diffuser 114 is placed between the first and second dies 70, 74. At 208, the multi-ply composite charge 64 is formed into a stiffener 42 having a desired cross-sectional shape by compressing the composite charge 64 between the first and second dies 70, 74. At 210, the stiffener 42 is contoured to the desired profile 60 having an internal radius 59. At 212, the wrinkle diffuser 114 is used to control wrinkling of the stiffener 42 during contouring.

[0041]

[0071] Examples of the present disclosure may find use in a variety of potential applications, particularly in the transportation industry, including, for example, aerospace, marine, automotive applications, and other applications in which stiffeners with curved profiles, such as aircraft stringers, may be used. Accordingly, referring now to FIGS. 33 and 34 , examples of the present disclosure may be used in the context of an aircraft manufacturing and service method 214 as shown in FIG. 33 and an aircraft 216 as shown in FIG. 34 . The disclosed example aircraft application may include various elongated stiffeners, such as stringers, that have curved profiles, curvatures, varying thicknesses, or other out-of-plane features along their lengths. During pre-production, the example method 214 may include specification and design 218 of the aircraft 216 and material procurement 220. During production, component and subassembly manufacturing 222 and system integration 224 of the aircraft 216 occur. The aircraft 216 may then undergo certification and delivery 226 for placement in service 228. While in service by a customer, the aircraft 216 is scheduled for periodic maintenance and service 230, which may include modifications, reconfigurations, refurbishments, and the like.

[0042]

[0072] Each of the steps of method 214 may be performed or implemented by a system integrator, a third party, and / or an operator (e.g., a customer). For purposes of this description, a system integrator may include, but is not limited to, any number of aircraft manufacturers and major system subcontractors, a third party may include, but is not limited to, any number of vendors, subcontractors, and suppliers, and an operator may be an airline, a leasing company, the military, a service organization, etc.

[0043]

[0073] 34, an aircraft 216 produced by exemplary method 214 may include an airframe 232 having a number of systems 234 and an interior 236. Examples of high-level systems 234 include one or more of a propulsion system 238, an electrical system 240, a hydraulic system 242, and an environmental system 244. Any number of other systems may also be included. While an aerospace example is provided, the principles of the present disclosure may be applied to other industries, such as the marine and automotive industries.

[0044]

[0074] Systems and methods embodied herein may be used in any one or more of the stages of aircraft manufacturing and service method 214. For example, components or subassemblies corresponding to production operation 222 may be fabricated or manufactured in a manner similar to components or subassemblies produced while aircraft 216 is in service. Also, one or more example apparatus, method, or combination thereof may be utilized in production operations 222 and 224, for example, by substantially expediting or reducing the cost of assembly of aircraft 216. Similarly, one or more of the example apparatus, method, or combination thereof may be utilized in maintenance and service 230 while aircraft 216 is in service, for example, without limitation.

[0045]

[0075] The present disclosure includes exemplary embodiments in accordance with the following provisions.

[0046]

[0076] Article 1. 1. An apparatus for forming a composite laminate reinforcement (42) having a curved profile, comprising: a first die (70) and a second die (74) between which the multi-ply composite charge (64) can be formed into a stiffener (42), the first die (70) and the second die (74) being configured to form a curved profile (60) in the stiffener (42); and An apparatus comprising at least a first diffuser (114, 178) disposed between the first die (70) and the second die (74) and configured to diffuse wrinkles (144) in the reinforcement material (42) along the curved contour (60).

[0047]

[0077] Article 2. 10. The apparatus of claim 1, wherein the first diffuser (114, 178) includes a recess (122, 184) therein, and wherein the plies (66) of the multi-ply charge (64) can distort into the recess (122, 184) in response to compressive stresses in the stiffener (42) caused by forming the stiffener (42) into the curved profile (60).

[0048]

[0078] Article 3. 3. The device of clause 2, wherein the depressions (184) include a plurality of peaks (186) and valleys (188) that form a serpentine pattern.

[0049]

[0079] Article 4. 3. The device of claim 2, wherein the recess (184) comprises a plurality of slots (190) spaced apart from one another.

[0050]

[0080] Article 5. the first diffuser (114, 178) is disposed on the inner radius (59) of the curved profile (60) of the stiffener (42), and when the stiffener (42) is formed into the curved profile (60), compressive stresses are generated in the stiffener (42) at the inner radius (59); The apparatus of any of clauses 1 to 4, wherein the first diffuser (114, 178) includes a recess (122, 184) configured to allow a portion of the multi-ply charge (64) at the inner radius (59) to distort into the recess (122, 184) and form a wrinkle (144) having a predetermined length-to-depth ratio.

[0051]

[0081] Article 6. the first diffuser (114, 178) is a plate (117, 182) having a recess (122, 184) therein, such that when the stiffener (42) is formed into the curved profile (60), a portion of the ply (66) of the multi-ply charge (64) in the curved profile (60) can distort into the recess (122, 184); 6. The apparatus of any of clauses 1 to 5, wherein the plate (117, 182) is removably attached to one of the first die and the second die (70, 74).

[0052]

[0082] Article 7. The apparatus of any one of clauses 1 to 6, further comprising at least a second diffuser (116, 180) disposed between the first die (70) and the second die (74) and facing the first diffuser (114, 178), the second diffuser (116, 180) including recesses (126, 130, 184, 192) therein configured to diffuse wrinkle formation in the plies (66) of the multi-ply charge (64) within the curved contour (60) of the reinforcement (42).

[0053]

[0083] Article 8. 1. An apparatus for manufacturing a curved profile composite laminate stringer (50) having flanges (58) and webs (56), comprising: a first die (70) and a second die (74) between which the multi-ply composite charge (64) can be formed into a flange (58) and a web (56) having a curved profile (60); a first wrinkle diffuser (114, 178) provided on the first die (70); and a second wrinkle diffuser (116, 180) provided on the second die (74) and facing the first wrinkle diffuser (114, 180); The apparatus, wherein the first and second wrinkle diffusers (114, 116, 178, 180) are configured to diffuse wrinkles (144) in the curved contour (60) of the flange (58) and web (56) as the multi-ply composite charge (64) is formed.

[0054]

[0085] Article 9. The device described in clause 8, wherein each of the first wrinkle diffuser (114, 178) and the second wrinkle diffuser (116, 180) includes a plurality of depressions (122, 124, 126, 130, 184, 192) therein, and when the multi-ply composite charge (64) is formed into the curved contour (60), the multi-ply composite charge (64) can distort within the curved contour (60) and enter the depressions.

[0055]

[0086] Article 10. 10. The apparatus of clause 9, wherein the depressions (184, 192) include a plurality of peaks (186) and valleys (188) that form a sinusoidal pattern.

[0056]

[0087] Article 11. 10. The device of clause 9, wherein the recesses (122, 124) comprise a plurality of slots spaced apart from one another.

[0057]

[0088] Article 12. The slots include a set of first slots (122a) each having a length (L1) and a set of second slots (122b) each having a length (L2) that is shorter than the length (L1) of the first slots (122a); 12. The apparatus of clause 11, wherein the first slots (122a) and the second slots (122b) are arranged in alternating relationship with each other.

[0058]

[0089] Article 13. 10. The device of clause 9, wherein the depressions (122) of the first wrinkle diffuser (114) are aligned and face the depressions (124) of the second wrinkle diffuser (116).

[0059]

[0090] Article 14. Each of the first wrinkle diffuser (114) and the second wrinkle diffuser (116) includes a plate (117) attached to a corresponding one of the first die (70) and the second die (74); 14. The apparatus of clause 9 or 13, wherein a recess (122, 124) is formed in each plate (117).

[0060]

[0091] Article 15. Each of the first wrinkle diffuser (114) and the second wrinkle diffuser (116) includes a plurality of plates (117); recesses (122, 124) are disposed in the plate (117); 15. The apparatus of any of clauses 9, 13, or 14, wherein the plates (117) are releasably connected to one another.

[0061]

[0092] Article 16. A method of manufacturing a composite laminate reinforcement (42) having a curved profile, comprising: placing a multi-ply composite charge (64) between a first die and a second die (70, 74); disposing at least one wrinkle diffuser (114, 116) between the first die and the second die (70, 74); forming the multi-ply composite charge (64) into a reinforcement (42) having a desired cross-sectional shape by compressing the multi-ply composite charge (64) between first and second dies (70, 74); Contouring the reinforcement (42) to a desired profile having an internal radius (59); and using wrinkle diffusers (114, 116) to control wrinkling of the reinforcement (42) along the inner radius (59) during contouring.

[0062]

[0093] Article 17. the outlining includes outlining a first die and a second die (70, 74); Clause 17. The method of clause 16, wherein positioning the wrinkle diffuser (114, 116) includes attaching the wrinkle diffuser (114, 116) to one of the first die and the second die (70, 74) in a region along the inner radius (59).

[0063]

[0094] Article 18. 18. The method of claim 16 or 17, wherein controlling wrinkle formation includes forming wrinkles (144) in the multi-ply composite charge (64) having a preselected length-to-depth ratio.

[0064]

[0095] Article 19. The wrinkle diffuser (114, 116) is arranged interconnecting a plurality of diffuser plates (117); 19. The method of any of clauses 16-18, comprising removably attaching a plurality of diffuser plates (117) to at least one of the first die and the second die (70, 74).

[0065]

[0096] Article 20. 20. The method of any of clauses 16-19, wherein controlling wrinkle formation comprises forcing the multi-ply composite charge (64) into recesses (122) in the wrinkle diffuser (114, 116).

[0066]

[0097] As used herein, the phrase "at least one of," when used in conjunction with a list of items, means that various combinations of one or more of the items in the list can be used, and that only one of each item in the list may be required. For example, "at least one of item A, item B, and item C" can include, but is not limited to, item A, item A and item B, or item B. This example could also include item A, item B, and item C, or item B and item C. An item may be a particular object, thing, or category. In other words, "at least one of" means that any combination and number of items from the list can be used, but not all of the items in the list are required.

[0067]

[0098] The description of various exemplary embodiments has been presented for purposes of illustration and description, but is not intended to be exhaustive or to be limited to the embodiments in the form disclosed. Many modifications and variations will be apparent to those skilled in the art. Moreover, different exemplary embodiments may offer different advantages over other exemplary embodiments. The selected embodiments have been chosen and described in order to best explain the principles, practical applications of the embodiments, and to enable others skilled in the art to understand the present disclosure with various modifications as may be suitable for the particular use contemplated.

Claims

1. 1. An apparatus for forming a composite laminate reinforcement (42) having a curved profile, comprising: a first die (70) and a second die (74) between which a multi-ply composite charge (64) can be formed into a stiffener (42), the first die (70) and the second die (74) being configured to form a curved profile (60) in the stiffener (42); and at least a first diffuser (114, 178) disposed between the first die (70) and the second die (74) and configured to diffuse wrinkles (144) within the stiffener (42) along the curved contour (60); An apparatus comprising:

2. 2. The apparatus of claim 1, wherein the first diffuser includes a recess therein, and wherein plies of the multi-ply composite charge can distort into the recess in response to compressive stresses in the stiffener caused by forming the stiffener into the curved profile.

3. The apparatus of claim 2, wherein the depression (184) includes a plurality of peaks (186) and valleys (188) that form a serpentine pattern.

4. The apparatus of claim 2, wherein the recess (184) includes a plurality of spaced apart slots (190).

5. the first diffuser (114, 178) is disposed on an inner radius (59) of the curved profile (60) of the stiffener (42), and compressive stresses are generated in the stiffener (42) at the inner radius (59) when the stiffener (42) is formed into the curved profile (60); 5. The apparatus of claim 1, wherein the first diffuser includes a recess configured to allow a portion of the multi-ply composite charge at the inner radius to distort into the recess and form a wrinkle having a predetermined length-to-depth ratio.

6. the first diffuser (114, 178) is a plate (117, 182) having a recess (122, 184) therein, and a portion of a ply (66) of the multi-ply composite charge (64) in the curved profile (60) can be distorted into the recess (122, 184) when the stiffener (42) is formed into the curved profile (60); The apparatus of claim 1 , wherein the plate (117, 182) is removably attached to one of the first die and the second die (70, 74).

7. 2. The apparatus of claim 1, further comprising at least a second diffuser disposed between the first die and the second die and opposite the first diffuser, the second diffuser including depressions therein, the depressions configured to diffuse wrinkles in the plies of the multi-ply composite charge within the curved profile of the stiffener.

8. 1. An apparatus for manufacturing a curved profile composite laminate stringer (50) having flanges (58) and webs (56), comprising: a first die (70) and a second die (74) between which a multi-ply composite charge (64) can be formed into a flange (58) and a web (56) having a curved profile (60); a first wrinkle diffuser (114, 178) provided in the first die (70); and a second wrinkle diffuser (116, 180) provided on the second die (74) and facing the first wrinkle diffuser (114, 178); Equipped with the first wrinkle diffuser and the second wrinkle diffuser are configured to diffuse wrinkles in the curved contour of the flange and the web as the multi-ply composite charge is formed.

9. 9. The device of claim 8, wherein the first wrinkle diffuser (114, 178) and the second wrinkle diffuser (116, 180) each include a plurality of depressions (122, 124, 126, 130, 184, 192) therein, and the multi-ply composite charge (64) can be distorted within the curved contour (60) into the depressions when the multi-ply composite charge (64) is formed into the curved contour (60).

10. The apparatus of claim 9, wherein the depressions (184, 192) include a plurality of peaks (186) and valleys (188) that form a sinusoidal pattern.

11. The apparatus of claim 9, wherein the recesses (122, 124) comprise a plurality of spaced apart slots.

12. The slots include a set of first slots (122a) each having a length (L1) and a set of second slots (122b) each having a length (L2) that is shorter than the length (L1) of the first slots (122a); The apparatus of claim 11, wherein the first slots (122a) and the second slots (122b) are arranged in alternating relationship with one another.

13. 10. The device of claim 9, wherein the recesses (122) of the first wrinkle diffuser (114) are aligned and opposite the recesses (124) of the second wrinkle diffuser (116).

14. each of the first wrinkle diffuser (114) and the second wrinkle diffuser (116) includes a plate (117) attached to a corresponding one of the first die (70) and the second die (74); 14. Apparatus according to claim 9 or 13, wherein said recesses (122, 124) are formed in each plate (117).

15. each of the first wrinkle diffuser (114) and the second wrinkle diffuser (116) includes a plurality of plates (117); The recesses (122, 124) are disposed in the plate (117), 10. The apparatus of claim 9, wherein the plates (117) are releasably connected to one another.

16. A method of manufacturing a composite laminate reinforcement (42) having a curved profile, comprising: placing a multi-ply composite charge (64) between a first die and a second die (70, 74); disposing at least one wrinkle diffuser (114, 116) between said first die and said second die (70, 74); forming the multi-ply composite charge (64) into a reinforcement (42) having a desired cross-sectional shape by compressing the multi-ply composite charge (64) between the first die and the second die (70, 74); Contouring said reinforcement (42) to a desired profile having an internal radius (59); using the wrinkle diffusers (114, 116) to control wrinkling of the reinforcement (42) along the inner radius (59) during contouring; A method comprising:

17. Contouring includes contouring the first die and the second die (70, 74); 17. The method of claim 16, wherein positioning the wrinkle diffuser includes attaching the wrinkle diffuser to one of the first die and the second die in a region along the inner radius.

18. 18. The method of claim 16 or 17, wherein controlling the wrinkle formation includes forming wrinkles (144) in the multi-ply composite material charge (64) having a preselected length-to-depth ratio.

19. disposing the wrinkle diffuser (114, 116); interconnecting a plurality of diffuser plates (117); removably attaching the plurality of diffuser plates (117) to at least one of the first die and the second die (70, 74); 17. The method of claim 16, comprising:

20. The method of claim 16, wherein controlling wrinkle formation comprises forcing the multi-ply composite charge (64) into recesses (122) in the wrinkle diffuser (114, 116).

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