WO2000026012A1

WO2000026012A1 - Apparatus and method for providing reinforcement in a composite preform

Info

Publication number: WO2000026012A1
Application number: PCT/US1999/025961
Authority: WO
Inventors: Richard Nathan Olds; Christopher Feeney
Original assignee: Gkn Westland Aerospace, Inc.
Priority date: 1998-11-04
Filing date: 1999-11-04
Publication date: 2000-05-11
Also published as: AU1341600A

Abstract

An apparatus (1) is disclosed for direct insertion of a continuous wire (3) into a fiber preform (21) and for cutting the wire to length, the wire preferably forming a Z-axis reinforcement in the preform. The apparatus includes a motor (6) which drives rollers (5a, 5b) between which the continuous wire is fed, the wire fed through an ultrasonic horn (10) which vibrates the wire to facilitate entry of the wire into the fiber preform. As the wire exits the horn, it passes by a cutter (15, 16) which is only activated after the wire has reached a selected depth. A controller (7) controls the motor and ultrasonic generator and also activates a solenoid (18) which causes the cutter to cut the wire thereby completing the insertion of the metal wire reinforcement into the fiber preform. The apparatus of the invention provides a means for automating the insertion of metal reinforcement in a fiber preform, reducing labor costs and processing time while allowing reinforcement pins of virtually any length and angle to be used.

Description

APPARATUS AND METHOD FOR PROVIDING REINFORCEMENT IN A COMPOSITE PREFORM

Technical Field

This invention relates to the production of fiber preforms for use in resin transfer molding and more particularly to an apparatus and method for incorporating metal wire reinforcement in a fiber preform.

Background of the Invention

In fabricating plastic composite articles, it is typical to assemble a plurality of oriented dry fiber layers or plies in a stack and to shape and debulk them to match the shape of the article. The assembly, known as a "preform," is placed in a net shape mold and resin is injected into the mold, infiltrating the fiber layers. The resin is cured to produce the article. This is known as a "resin transfer molding" (RTM) process.

When assembling and shaping the layers to produce various articles, it is common to encounter various junctions made between a pair of plies which can result in a void or gap. For example, with reference to Figure la, a structural member 101, similar to an I-beam, has an upper flange 102 supported by a web 103. Figure lb shows a cross-section of the member 101, which includes a first plurality of plies 104 and a second plurality of plies 105, which form the web 103, a third plurality of plies 106 placed over a top surface of the first and second plies, to form the flange 102. At a junction 107, where the plies meet, a gap may be

formed.

In U.S. Patent No. 5,650,229, commonly owned by the assignee of this application, a shaped unidirectional fiber preform 108 is used to fill the gap. This avoids the potential for fiber distortion, particularly when the resin is injected into the mold. However, with or without the use of the shaped unidirectional fiber preform, there still exists a potential problem after the part has been cured, as the junction still involves a transition region between the first, second, and third set of plies which is a potential area for initiating delamination.

One proposed method for strengthening this junction is to incorporate metal pins in the Z-axis direction, as illustrated in Fig. lb.

This involves providing a plurality of pre-cut pins 109, held in position using a foam block placed adjacent the junction and then driving the pins through the foam into the preform.

This is an expensive labor-intensive operation which adds significantly to the cost of the part because the number of pins must be predetermined, each pin cut to a specific size, the pins placed in a specific pattern in a foam block and then each pin must be pushed through the foam into the preform.

It is important that the pins be of the proper length as producing parts in a resin transfer molding operation requires fairly precise net shaped molds, and it would be undesirable to have the pin ends contact or damage the mold surface.

Consequently, a method and apparatus which simplifies this process would be a significant advance in the art.

Summary of the Invention It is an object of the present invention to provide an apparatus for direct insertion of a continuous wire into a fiber preform and having means for cutting the wire to a selected length.

It is a further object to provide an apparatus which is automatic, reducing labor requirements and increasing flexibility such that the apparatus can be used with virtually any

size or shape preform. These and other objects of the present invention are achieved by an apparatus for inserting a reinforcement wire into a layered fabric assembly comprising means for directing a continuous wire in a selected direction into a layered fabric assembly, drive means for actuating the directing means, vibration means for vibrating the wire to facilitate entry of the wire into the layered fabric assembly, cutting means for cutting the wire and control means for actuating the drive means and vibration means such that the continuous wire is inserted to a selected depth in the fabric assembly and for actuating the cutting means.

A method for inserting the reinforcement wire into the layered fabric assembly would comprise providing a continuous wire, inserting the continuous wire into the layered fabric assembly to a selected depth while vibrating the wire, stopping the wire insertion and cutting the wire adjacent a top surface of the layered fabric assembly.

Brief Description of the Drawings

Fig. la is a view of a preform for an I-beam member; Fig. lb is a cross-section thereof.

Fig. 2a is an illustration of the apparatus according to the present invention; Fig. 2b is an enlarged view of the wire feed assembly.

Fig. 3a is an enlarged view of the cutter portion of the apparatus of Fig. 2, Fig. 3b is a view taken along the line 3b-3b thereof; Fig. 3c is a further enlarged view of the cutter portion.

Fig. 4 is an alternative embodiment of the present invention.

Detailed Description of the Invention

Referring to Fig. 2a, an apparatus 1 for providing metal reinforcement in a layered fiber assembly known as a preform is shown.

The apparatus 1 has a spool 2 containing a continuous metal wire 3. The wire 3 may be of any suitable size or type and be solid or stiff twisted strand wire. As an example, solid metal wire made of stainless steel and having a diameter of about 0.020" may be used. Of course the invention is not limited by the type, size or composition of the wire and it is only necessary that a continuous strand of wire capable of being cut to length is used. As best seen in Fig. 2b, the wire 3 passes through a feed assembly 4 having two pairs of opposed tension rollers 5a and 5b, the wire being frictionally held by the rollers as it passes between the rollers. Typically, each pair of opposed rollers are biased, by springs 5c, 5d or otherwise, into contact with each other, so as to grip the wire passing therebetween. The degree of bias is normally adjustable so as to adapt to the size of the wire with sufficient bias being applied so as to avoid wire slippage.

The rollers 5a and 5b are driven by a motor 6 which is speed adjustable and also reversible. The motor, when actuated, causes the rollers to turn, thereby driving the wire forward. A controller 7 is used to set the speed of the rollers and thus of the wire feed rate. It may be desirable to operate in the range of about 10 to 60" per minute. In addition, the motor can be chosen to provide constant torque, that is, so that as resistance to travel increases the speed of the wire feed decreases to reduce the likelihood of buckling the wire. This may be particularly important when using the apparatus of the invention with fairly thick fiber preforms.

The apparatus further includes a manipulatable end 8 preferably mounted with an arm 9 which may fully articulate in any direction. The end 8 has an ultrasonic horn 10 connected to an ultrasonic generator 11, the horn having a wire feed passage 12 in an end thereof. The wire is preferably fed through one or more guides 13 as it makes its way to the end and then passes through the passage 12 in the horn. Preferably, the guide is a flexible smooth bore tube 13a, through which the wire passes, though other guides may be used. The passage 12 leads to an opening 14 between a stationary cutter blade 15 and a movable cutter blade 16. The movable cutter blade is pivotably mounted to the arm, the blade located at the end of a lever 17 which translates about a pivot 18. A solenoid 19 acts on the lever and thus, upon a signal from the controller 7, causes the cutter blades to contact each other and thereby cut the wire which passes between the blades.

The wire, as it passes through the horn, is vibrated which facilitates both the initial entry and the continuous passage of the wire into the fiber preform. The ultrasonic generator may generate about 30KHz though of course, other frequencies may be used. The horn may have a separate tip 10a which may be removable to allow tips with different diameter passages to be used, to adapt to different diameter wire. Close tolerances between the wire and the passage facilitate vibration transmission to the wire. Thus, with larger wire diameters, a horn with a corresponding larger passage diameter should be used. In Fig. 3c, the tip 10a is attached by threads to the horn to facilitate removal.

In operation, the end on the arm is placed against a top surface 20 of a preform 21. The motor is actuated as is the ultrasonic generator. The wire then is vibrated as it is driven by the rollers to pierce the preform. When the prescribed amount of wire has been fed, as determined for example by the number of turns of the feed rolls, the motor is stopped and the solenoid actuated to cause the movable blade to cut the wire substantially flush with the top surface of the preform.

Thus, custom sized pins can be rapidly and easily incorporated into a fiber preform in virtually any location. In addition, the direction of pin insertion is readily controlled by simply adjusting the angle of the arm. Consequently, pins can be placed in a preform at from acute to oblique angles relative to the surface of the preform.

The length of the reinforcement wire pin can be determined in several ways. For certain parts, a single size or single pattern for a typical part can be developed and insertion made by controlling the number of turns of the motor relative to a specific location of the arm. Alternatively, a foot type assembly located on the opposite surface of the preform which senses either the proximity of the wire or contact with the wire can be used to stop the motor and possibly also to reverse the motor briefly to pull back the wire and thus avoid an end of the wire sticking through the preform. After the wire is cut, the arm is relocated to the next wire insertion point and the end repositioned for repeating the insertion method.

Such an apparatus substantially simplifies the insertion of metal reinforcement in fiber preforms, reducing labor costs and processing time while allowing pins of virtually any length to be inserted by simply adjusting a controller. A single controller is envisioned for use with the apparatus of the invention, the controller used to actuate the direction, speed and torque of the motor which turns the feed rollers and also to actuate the solenoid which causes the wire to be cut. The controller also is used to actuate the ultrasonic generator for vibrating the wire during insertion. In a preferred embodiment, the controller is a computer that also directs the arm to position the end at the selected location, and to assure that the proper length pin is provided in that location. If sensors or a foot assembly are used with the apparatus for determining the depth of insertion into the preform, these are also integrated with the controller for stopping the insertion of the wire into the preform.

In an alternative embodiment of the present invention, the end further includes a probe 22 fixed adjacent the cutter 16, the probe used to produce a pilot hole 23. In other words, the probe, being more rigid than the wire, first penetrates the preform. The probe is then withdrawn and retracted and the arm repositioned such that the wire insertion passage is directly over the hole made by the probe, the wire then inserted into the preform through the hole produced by the probe. The probe has an extended length less than the thickness of the preform, but should be at least approximately 50% of the depth of the preform. The probe may be retractable or extendible in response to a signal from the controller 7, and be engaged by an actuator 24. By producing an initial pilot hole, insertion of the wire into the preform is facilitated to reduce the likelihood that binding would occur. Such an alternative embodiment may be particularly attractive with very thick preforms so as to increase the ability of the wire to traverse the entire thickness of the preform.

Using the apparatus and method of the present invention, metal wire reinforcements can be readily and rapidly inserted in any direction, across a number of plies and thereby substantially increasing the strength at various junctures within a composite part. Such reinforcement thereby reduces the likelihood that delamination could occur and does so without a significant increase in processing time or expense.

While preferred embodiments of the present invention have been shown and described, it would be understood by those skilled in the art that various changes or modifications can be made without varying from the scope of the invention. For example, while a blade cutter has been shown, it will be understood that there are numerous ways in which the wire can be cut flush with the surface of the preform and that virtually any means for cutting the wire can be used. Similarly, while two pairs of rollers have been shown for feeding the wire, there are numerous methods available in the art which can be adapted for feeding a wire with either continuous speed or continuous torque and the invention is not limited to the apparatus described in the specification as it is merely exemplary.

What we claim is:

Claims

1. An apparatus for inserting a reinforcement wire into a layered fiber assembly comprising:

means for directing a continuous wire in a selected direction into the layered fiber assembly; drive means for actuating the directing means; vibration means for vibrating the wire to facilitate entry of the wire into the fiber assembly; cutting means for cutting the wire; and, control means for actuating the drive means and vibration means such that the continuous wire is inserted to a selected depth in the fiber assembly and for actuating the cutting means.

2. The apparatus of claim 1 wherein the means for directing the continuous wire comprises at least a pair of rollers, the wire passing between the rollers, the rollers activated by the drive means for inserting the reinforcement wire into the layered fabric assembly.

3. The apparatus of claim 1 wherein the cutting means comprise a stationary cutting blade and a movable cutting blade, actuator means connected to the movable cutter so as drive the movable cutter into contact with the stationary cutter.

4. The apparatus of claim 1 wherein the vibration means comprise an ultrasonic generator connected to a horn, the horn having a passage through which the wire passes as it is inserted into the layered fiber assembly.

5. The apparatus of claim 1 further comprising an arm that is fully articulatable, the apparatus provided on the arm for positioning the apparatus at a selected location on the preform.

6. A method for inserting a reinforcement wire into a layered fiber assembly comprising: providing a continuous wire; inserting the continuous wire into the layered fiber assembly to a selected depth while vibrating the wire; stopping the wire and cutting the wire adjacent a top surface of the layered fabric assembly.

7. The method of claim 6 further comprising providing a movable arm, for placing the wire adjacent a selected location on the layered fabric assembly.

8. The method of claim 6 wherein the continuous wire is inserted at either a constant torque or a constant speed into the layered fiber assembly.

9. The method of claim 6 further comprising controlling the speed and depth of insertion using a controller.

10. The method of claim 9 wherein the controller controls the vibration and cutting of

the wire.

11. The method of claim 6 wherein the wire is inserted into the layered fiber assembly at a selected angle from acute to oblique.