SYSTEM AND PROCESS FOR PRODUCING A COMPOSITE ARTICLE

Abstract

According to one or more embodiments, a system includes a cutter for cutting a composite material to form composite pieces, an ultrasonic welding device for connecting two or more of the composite pieces to form a composite stack, and a compression molding device for forming a composite article from the composite stack. The system may further include a transfer arm for delivering the composite pieces to the ultrasonic welding device. The system may further include a forming device to generate a composite preform which is then delivered to the compression molding device. Excess material may be trimmed off before, during or after the forming step to deliver a net-shape for the subsequent molding step.

Description

TECHNICAL FIELD

The disclosed inventive concept relates generally to system and method for producing a composite article.

BACKGROUND

In certain existing methods, relatively high tack pre-impregnated fiber materials (or “prepreg materials”) are cut to two dimensional patterns using a table cutting machine. Upon completion of the cutting process, the resultant prepreg plies are removed manually and stored for manufacture of composite parts. Some of the existing prepreg materials tend to contain carrier films on both sides to separate from each other. This is necessary as these relatively high tack prepreg plies tend to stick to each other and be rendered useless if not properly separated. A problem associated with this existing practice is carrier films must be removed for subsequent processes and removal of carrier films can be labor intensive and cost inefficient.

It would thus be advantageous if system and method for producing a composited article may be provided to solve one or more of these identified problems.

SUMMARY

The disclosed inventive concept is believed to have overcome one or more of the problems associated with producing a composite article.

As will be detailed below, the present invention in one or more embodiments is advantageous at least in that two dimensional prepreg blank geometries can be cut from relatively low tack prepregs on a two dimensional cutting table. Due to the relatively low tack, the prepreg material can be readily separated from each other with or without carrier films. The blanks can be robotically removed from the cutting table, optionally using vacuum pick and place technology. The blanks can then be aligned and connected optionally via ultrasonic welding in preparation for downstream forming and/or compression treatment.

According to one or more embodiments, a system includes a cutter for cutting a composite material such as the relatively low tack prepregs to form composite pieces, an ultrasonic welding device for connecting two or more of the composite pieces to form a composite stack, and a compression molding device for forming a composite article from the composite stack. system may further include a transfer arm for delivering the composite pieces to the ultrasonic welding device. The system may further include a forming device to generate a composite preform which is then delivered to the compression molding device. This is particular for the so called net-shape molding where the composite perform is produced by heat assisted forming and trimming to remove unnecessary excess materials, and the composite perform is then ready for molding where no trimming is necessary any more with the molding. The system may further include a trimmer to trim excess materials from the composite preform to generate a trimmed composite preform which is then delivered to the compression molding device.

According to one or more other embodiments, a method producing a composite article includes subjecting a composite material such as the relatively low tack prepregs to a cutter to form composite pieces, subjecting two or more the composite pieces to an ultrasonic welding device for connecting two or more of the composite pieces to form a composite stack, and subjecting the composite stack to a compression molding device to form a composite article from the composite stack.

The above advantages and other advantages and features will be readily apparent from the following detailed description of embodiments when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of embodiments of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples wherein:

FIG. 1 depicts a system for forming a composite article according to one or more embodiments; and

FIG. 2 depicts a non-limiting process for forming the composite article referenced in FIG. 1.

DETAILED DESCRIPTION OF ONE OR MORE EMBODIMENTS

As referenced in the FIG.s, the same reference numerals are used to refer to the same components. In the following description, various operating parameters and components are described for different constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting.

According to one or more embodiments, and as depicted in FIG. 1 in view of FIG. 2, a system generally shown at 100 includes a cutter 102 for cutting a composite material 112 shown at step 202 to form composite pieces 114, an ultrasonic welding device 104 for connecting two or more of the composite pieces 114 shown at step 204 to form a composite stack 130, and a compression molding device 106 for forming a composite article from the composite stack 130 shown at step 208. A forming step 206 may be included to provide a net shaped perform via forming and trimming. In addition, and as detailed herein elsewhere, step 203 may be included to provide ply layup in which the two or more composite pieces 114 may be aligned, optionally via a robot, for step 204.

The composite stack 130 may be provided with one or more of welding areas 132 where a horn 126 of the ultrasonic welding device 104 contacts the composite stack 130. By such a contact, the ultrasonic energy is transferred onto the composite stack 130 to effect the welding. The welding areas 132 may vary in location and/or number. The welding areas 132 may take any suitable shapes, including spots, lines and/or bars. The two or more composite pieces 114 underlining the composite stack 130 are connected via the welding areas 132. The welding areas 132 help maintain alignment of individual composite pieces 114 and function to hold them together to facilitate the downstream forming and compression steps.

Referring back to FIG. 1, the system 100 may further include a transfer arm 118 for delivering the composite pieces 114 to the ultrasonic welding device 104. The transfer arm 118 may be actuated by a robot 116 and in some instances, may be part of the robot 116. The transfer arm 118 may include a receiving end 120 coupled with a number of vacuum cups (not shown) for picking up and dropping off the composite pieces 114. Accordingly the composite pieces 114 may be aligned back-to-back via the use of the robot 116 and the transfer arm 118. The receiving end 120 may be of any suitable shape and be made of any suitable material. In certain instances, the receiving end 120 may be of a generally flat surface with the vacuum cups positioned thereupon.

Referring back to FIG. 1, the ultrasonic welding device 104 may include a platform 122 for receiving the composite pieces 114. The platform 122 may be built as part of the ultrasonic welding device 104 or may be positioned separable and detachable to the ultrasonic welding device 104. The platform 122 may include another number of vacuum cups (not shown) to receive and stabilize the composite pieces 114 placed thereupon. One or more stabilizing arms 124 may also be provided to assist with the positioning and stabilization of the composite pieces 114. The stabilizing arms 124 may be part of the ultrasonic welding device 104 and/or part of the platform 122.

When a third composite piece 114 is placed onto the first two that have been welded, the horn 126 descends and welds the third composite piece to the second composite sheet 114. Dependent upon the ultrasonic energy transferred, the welding bonds between the third and second pieces may not necessarily be confined within the second and/or third sheet, and therefore may go into the first piece. In addition, the horn 126 may be repositioned such that the welding lines/spots between the first and the second, and the welding lines/spots between the second and the third may be different. This is particularly useful when the composite pieces 114 may be of different shapes among themselves.

The horn 126 may be designed to resonate at the frequency of the ultrasonic system. Therefore the ultrasonic energy as imparted from the horn 126 may be varied by adjusting the resonance frequency of the ultrasonic system.

The ultrasonic welding imparts local “stitching” to one or more of the composite sheets 114. Without wanting to be limited to any particular theory, it is believed that ultrasonic welding works to reduce viscosity of the composite pieces 114 locally and renders these locations of the composite pieces 114 tackier. Ultrasonic vibrational energy causes the material to soften and flow in a fraction of a second. When the material is pressed together and resolidifies, the bond is made. No glues or solvents are needed. Heating is confined to the interface area so the assembled part is not too hot to handle. The energy and/or temperature as imparted by the ultrasonic welding should be low enough so as not to impair any downstream steps including, for instance, forming at step 206 and compression at step 208. If too much energy is delivered prior to forming, the composite pieces 114 may become rigid at these high energy imparted locations. These high energy imparted locations may render the composite pieces 114 not flexible enough to conform to certain desirable shapes at or near those high energy imparted locations.

The ultrasonic welding at step 204 may be plunge welding. In plunge welding, the composite pieces 114 are placed under the horn 126; the horn 126 descends to the composite pieces 114 under moderate pressure and the weld cycle is initiated.

As discussed herein elsewhere, any two composite pieces 114 may be placed on the platform 122 prior to ultrasonic welding. In general, no additional force is required to compress the composite pieces 114. This is at least because the composite pieces 114 should not fit too tightly as over-tight joining may inhibit the vibration needed to induce welding.

The composite material 112 may be thermoplastic or thermoset. Under certain instances, the thermoplastics tend to be less tacky than thermoset materials. When being thermoset, the composite material 112 can behave like thermoplastic under room temperatures so as to be responsive to ultrasonic welding. A non-limiting method to accomplish this may be via increasing the uncured material temperature above the corresponding glass transition temperature such that viscosity may be reduced and the matrix is allowed to flow under the heat with the reduced viscosity.

Although the method described herein may be adapted to be used for composite material of relatively high tackiness under limited circumstances, the method described herein is particularly suitable for composite material 112 that is of relatively low tackiness. When too tacky, the composite pieces 114 would stick to each other and become almost inseparable. Unacceptable tackiness will make the piece-by-piece transfer for the ultrasonic welding accordingly almost impossible.

Thermoplastics can be further categorized as amorphous or crystalline. Amorphous resins exhibit random and do not greatly dampen energy introduced into the material. As heat is applied, they soften and do not have a sharply defined melting temperature. Amorphous resins include ABS, acrylic, polycarbonate, polystyrene and polysulfone. Crystalline resins have an orderly pattern, like coiled springs. Just as metal springs dampen vibration, so do crystalline materials. They also have a well-defined melting temperature. Crystalline materials include acetal, nylon, polyester, polyethylene, polypropylene and polyphenylene sulfide. Alloys/blends are combinations of amorphous and/or crystalline polymers and the combinations seem endless.

In certain instances, the composite material 112 may be a material otherwise termed “pre-preg.” As mentioned herein elsewhere, pre-preg is a term for “pre-impregnated” composite material where a resin is included to bond a matrix material together. The resin may or may not be partially cured to allow easy handling.

Referring back to FIG. 1, the cutter 102 may be positioned in connection to a cutting table 108. During a cutting operation, the cutter 102 may be moved in one or more desirable directions via the support frame 110 to deliver the cutting.

Referring back to FIG. 1, the composite material 112 may be provided as a roll wound about a roller 134. The composite material 112 may optionally be separated from each other via one or two carrier films (not shown). In the event the carrier film is used, the carrier film may be retained and prevented from going onto the cutting table 108 via a second roller 136 or alternatively a stop. The second roller 136 or the stop rolls to pull the carrier film away from the composite material 112.

Referring back to FIG. 1, the system 100 may further include a forming device 128 to generate a composite preform which is then delivered to the compression molding device 106. Forming at step 206 may be a necessary step prior to the compression/curing step 208. To assist with the forming, the ultrasonically welded pieces 114 may be pre-heated. The pre-heating step may also help maintain the shape following the forming step.

During forming and trimming, ultrasonically welded pieces 114 are formed using male/female shape tooling to obtain the ultimate product shape. Excess edging materials are trimmed off according to step 206. The forming does not necessarily reduce the total thickness of the composite pieces 114. But the trimming may be necessary as the cavity of the compression mold 106 is often particularly sized. The excess material would not make the sheets fitting well within the mold cavity.

Formed part coming out of step 206 may deform over time as they are not cured. The final compression and curing may occur at step 208 under elevated pressure and/or temperature.

As described herein elsewhere, the composite material 112 is of relatively low tack. The relatively low tackiness of the composite material may be realized using any suitable methods. A non-limiting example of such methods includes selecting a source resin with a temperature glass transition temperature to be near or above ambient temperature. Another non-limiting example of such methods includes selecting a source resin which is a combination of solid and liquid resins for forming the composite material.

For certain existing systems and processes, relatively high tackiness would be helpful during a manual layup, wherein the tack allows the pieces to stick together and maintain position for subsequent manual layup of plies. Therefore the present invention in one or more embodiments presents a departure from some of the existing practices favoring the use of resin materials of relatively high tack. As detailed herein elsewhere, the use of relatively low tack materials effectuates the employment of robotic handling instead of manual handling, which further effectuates the employment of ultrasonic welding to impart localized welding connections. Exposing someone near an ultrasonic operation such as the ultrasonic welding device 104 may not be that practice for health consciousness reasons; the use of relatively less tacky materials coupled with robotic handling reduces or eliminates such health risk to an operator as he or she can be positioned remotely from the ultrasonic source during operation.

The composite material 112 may come in rolls, optionally separated with one sheet of packaging film such as paper. When provided as a sheet, the composite material 112 may be conveyed underneath the cutter 102 and cut into sizes of predetermined shapes. Because of the relatively low tackiness, the composite pieces 114 as cut are not unacceptably tacky on either side and may be stacked onto each other along a thickness direction.

The term “composite” or “composite material” may refer to materials made from two or more constituent components with different physical or chemical, that when combined, produce a material with characteristics different from the individual components. The individual components often remain separate and distinct within the finished structure. The new material may be preferred for many reasons: common examples include materials which are stronger, lighter or less expensive when compared to traditional materials.

In one or more embodiments, the disclosed invention as set forth herein overcomes the challenges faced by known production of composite articles. However, one skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.

Claims

1. A system comprising:

a cutter for cutting a composite material to form composite pieces;

an ultrasonic welding device for connecting two or more of the composite pieces to form a composite stack; and

a compression molding device for forming a composite article from the composite stack.

2. The system of claim 1, further comprising a transfer arm for delivering the composite pieces to the ultrasonic welding device.

3. The system of claim 2, wherein the transfer arm has a receiving end with a number of vacuum cups.

4. The system of claim 1, wherein the ultrasonic welding device includes a platform to receive the two or more of the composite pieces.

5. The system of claim 4, wherein the platform includes a receiving surface with a number of vacuum cups.

6. The system of claim 4, wherein the platform includes one or more stabilizing arms to stabilize one or more the composite pieces as present on the platform.

7. The system of claim 1, further includes one or more stops to separate the composite material from a carrier film prior to entry of composite material to the cutter.

8. The system of claim 1, further comprising a forming device to generate a composite preform which is then delivered to the compression molding device.

9. The system of claim 8, further comprising a trimmer to trim excess materials from the composite preform to generate a trimmed composite preform which is then delivered to the compression molding device.

10. A system comprising:

a cutter for cutting a composite material to form composite pieces;

a transfer arm for delivering the composite pieces to the ultrasonic welding device

an ultrasonic welding device for connecting two or more of the composite pieces to form a composite stack, the ultrasonic welding device including a platform to receive the two or more of the composite pieces; and

a compression molding device for forming a composite article from the composite stack.

11. The system of claim 10, wherein the detachable platform includes one or more stabilizing arms to stabilize one or more the composite pieces as present on the platform.

12. The system of claim 10, further includes one or more stops to separate the composite material from a carrier film prior to entry of composite material to the cutter.

13. The system of claim 10, further comprising a forming device to generate a composite preform which is then delivered to the compression molding device.

14. The system of claim 10, further comprising a trimmer to trim excess materials from the composite preform to generate a trimmed composite preform which is then delivered to the compression molding device.

15. A method of producing a composite article, comprising:

subjecting a composite material to a cutter to form composite pieces;

subjecting two or more the composite pieces to an ultrasonic welding device for connecting two or more of the composite pieces to form a composite stack; and

subjecting the composite stack to a compression molding device to form a composite article from the composite stack.

16. The method of claim 15, further comprising delivering the composite pieces to the ultrasonic welding device via a transfer arm.

17. The method of claim 15, further comprising stabilizing one or more of the composite pieces prior to activating welding operation by the ultrasonic welding device.

18. The method of claim 15, further comprising separating the composite material from a carrier film prior to entry of composite material to the cutter.

19. The method of claim 15, further comprising generating a composite preform from the composite stack via a forming device.

20. The method of claim 19, further comprising trimming excess materials from the composite preform via a trimmer to generate a trimmed composite preform which is then delivered to the compression molding device.