WO2015166479A1

WO2015166479A1 - Combined thermoset and thermoplastic resin infusion apparatus and method

Info

Publication number: WO2015166479A1
Application number: PCT/IL2015/050421
Authority: WO
Inventors: Gadi ADLER
Original assignee: Xenom Ltd
Priority date: 2014-04-30
Filing date: 2015-04-21
Publication date: 2015-11-05
Also published as: IL232401A0

Abstract

A method and apparatus for vacuum resin infusion molding of a product having an external layer made of thermoplastic material and a layer of thermoset material attached to the thermoplastic material by the vacuum resin infusion.

Description

COMBINED THERMOSET AND THERMOPLASTIC RESIN INFUSION

APPARATUS AND METHOD

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of resin infusion, more particularly but not exclusively, the present invention is related to the field of systems and methods for efficient manufacturing of reinforced composite structures, from both thermoset and thermoplastic fibers.

2. Description of Related Art Fiber reinforced composite materials are an important class of engineering materials that offer outstanding mechanical properties and unique design flexibility. Such materials are lightweight, corrosion resistant, impact resistant, and exhibit excellent fatigue strength. Composite materials are used in a wide variety of applications including automotive parts, aviation, marine vessels, offshore structures, containers piping, sporting goods and etc. Liquid resin molding, which includes resin transfer molding, reaction injection molding, and resin vacuum infusion, is one of the most attractive manufacturing solutions for producing high quality, affordable, and environmentally friendly composite materials.

Liquid resin molding requires the incorporation of a resin or other flowable elastic material into a reinforcing fiber. Reinforcing fiber generally takes the form of one or more layers of woven or felted fiber reinforcement, typically comprised of carbon, graphite, or fiberglass. The resin infusion or impregnation process is usually done by either a wet or dry fiber lay-up technique. In the wet fiber lay-up process, the resin "wetted" fiber reinforcement consists of a prepreg which already contains a resin and is laid up on a mold and cured. In the dry lay-up process, the fiber reinforcement is laid up dry on a mold or form which serves as a mold. The form may be incorporated as part and parcel of the finish product. Thereafter, the fiber is sprayed, brushed, impregnated, infused, or otherwise coated or "wetted" with the resin. The resin is then cured to form the fiber reinforced plastic structure. During the curing stage of either process, the structure can be placed in a vacuum to assist the curing process. To this end, vacuum bag techniques have been used to provide such vacuum assistance. In a vacuum technique, a flexible impervious sheet, liner, or bag is used to cover a single mold which contains the dry or wet (resin impregnated) fiber lay-up. In the wet fiber process, the edges of the flexible sheet are clamped against the mold to form an envelope and seal the resin impregnated fiber lay-up to the mold and out of the atmosphere. A vacuum is then applied to consolidate the preform during the cure of the resin. In the dry fiber lay-up, catalyzed liquid plastic or resin is generally introduced into the envelope or bag interior to wet the dry fiber, usually using a vacuum to help push the resin into the bag and wet out the dry fiber. Vacuum is applied to the bag interior via a vacuum line to collapse flexible sheet against the fiber and the surface of the mold, while the plastic wetted fiber is processed, compacted and cured to form the fiber reinforced structure. The vacuum bag used in this process is critical because it provides not only a vacuum seal but also a distribution mechanism for moving the liquid resin over the preform. These flexible bags are difficult to work with and although some are considered to be reusable, are typically inadequate for large volume manufacturing production. Also, flexible bags do not perform adequately when used by themselves for processing complex three dimensional shapes. It has been found that flexible bags do not conform entirely to the reinforced structure around corners and other high radius curves. "Bridging" is a term used to describe this condition. When the flexible bag bridges across corners, a gap or void is created between the bag and the reinforced structure, thereby preventing a continuous, uniform distribution of resin.

An improved resin infusion process is disclosed in PCT publication WO2013105082 to Adler. Adler discloses a method for resin infusion molding using a mold having a cavity partially filled with a liquid resin and an elastic cover placed inside the cavity and pressed against the cavity walls and the liquid resin, thus causing the liquid resin to evenly spread and impregnate a reinforcement placed inside the cavity.

The invention hereof depicts some improvements to Adler especially when producing products combining both thermoplastic resins in their external layer and a thermoset resign internal layer. Thermosetting resins are popular because prior to being cured they are usually in a liquid state. This simplifies impregnation of reinforcing fibers such as fiberglass, carbon fiber, or Kevlar. The traits of thermoset resigns include! heat and corrosion resistance, durability and fin finishing suitable for painting and polishing. Thermoplastic resins usually have no reinforcement providing strength. Many thermoplastic products use short discontinuous fibers as a reinforcement. Most commonly fiberglass, but also carbon fiber. This adds some reinforcement to the composite. The main advantages of thermoplastic composites are increased impact resistance and reshapability. Because thermoplastic resin is naturally in a solid state, it is much more difficult to impregnate a reinforcing fiber by it. The resin must first be heated to the melting point, the melted thermoplastic is then pressed against the fibers (by vacuum for example), and the composite must then be cooled under this pressure. This manufacturing process is considered complex compared to thermoset composite manufacturing. Special tooling, technique, and equipment must be used, many of which is expensive. This is the major disadvantage of thermoplastic composites. SUMMARY OF THE INVENTION

The invention discloses a method for vacuum resin infusion for producing a product having a thermoplastic external layer and a thermoset layer including the steps: a. inserting a thermoplastic layer into a mold! b. placing reinforcement inside the mold over thermoplastic layer! c. casting a thermoset resin inside the mold over the reinforcement; d. placing an elastic cover inside mold cavity over the thermoset resin and the reinforcement! e. creating a vacuum between said mold cavity and said elastic cover, wherein said vacuum causes said elastic cover to be pressed against the walls of said mold cavity, thus causing the thermoset resin to impregnate the reinforcement and attaching the reinforcement to the thermoplastic layer.

Alternatively, the method may include utilizing a pre impregnated reinforcement and placing the pre impregnated reinforcement over the thermoplastic layer, thus eliminating the need to cast a thermoset resin over the reinforcement as performed in step c.

The method may also include placing a thermoplastic internal layer over the thermoset resin and the reinforcement, thus creating a three layer product made of two thermoplastic layers and a thermoset layer between. In this configuration, the thermoplastic internal layer may also be utilized as the elastic cover of step d. In other words, the thermoplastic internal layer is used to perform the vacuum infusion instead of a dedicated elastic cover made by silicone rubber for example, and during the vacuum infusion process that thermoplastic layer is being attached to the thermoset layer thus becoming an integral layer of the finished product.

The invention further discloses an apparatus for producing a product having a thermoplastic external layer and a thermoset layer comprising: a. a mold comprising a vacuum port and a cavity! b. a thermoplastic cover having a port for connecting a conduit to a vacuum source! c. a vacuum pump!

The vacuum pump is used to create a vacuum between the mold cavity and the thermoplastic cover and at least part of the thermoplastic cover may be used as a layer of the finished product.

The thermoplastic cover may also include a lip to reliably attach to the mold by the vacuum source (similar to the lip of an elastic cover). The thermoplastic cover may also include groves to extract the lips and the port for connecting a conduit after the vacuum process is finished.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG.l depicts an apparatus and method for efficient resign infusion as depicted by the prior art.

FIG.2 is a flowchart of a prior art resin infusion method.

FIG.3 depicts an apparatus and method for efficient resin infusion of composites having an external layer of thermoplastic resins and an internal layer of thermoset resigns. FIG.4a and FIG 4b. are perspective views of two embodiment of the resin infusion apparatus of the present invention.

FIG.5 is a flowchart of a method for producing a product having a thermoplastic external layer and a thermoset internal layer.

DETAILED DESCRIPTION OF THE INVENTION

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings. With specific reference to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of preferred embodiments of the present invention only, and are presented for the purpose of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention. From the description taken together with the drawings it will be apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Moreover, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting the scope of the invention hereof. FIG.l depicts an apparatus and method for efficient resign infusion as depicted by the prior art. A mold is provided 11 having a cavity 12 in accordance with the shapes of the product which is to be manufactured. Composite material fabrics 13 are placed over the mold 11 inside the cavity 12, resin 14 is paced over the composite materials. An elastic closure made of silicone 15 is made in the shape of the cavity 12 and placed inside the cavity 12 over the resin 14 and the fabrics. Vacuum applied via a conduit 16 presses the elastic cover 15 against the cavity 12 causing the resin 14 to impregnate the fabrics 13. An inlet \ oulet port is provided to add resin or to remove excess resin as required 16. A pressure sensor 17 is also provided.

FIG.2 is a flowchart of a prior art resin infusion method. The first step 21 of the method 20 is setting up a mold, i.e. providing a mold of the desired shape with a reinforcement already placed inside. The second step 22 is applying a resin into the mold. The third step 23 is covering the mold and the resin by an elastic cover. In the fourth step 24, the vacuum is activated. In the last, fifth step 25, excess resin is removed via a conduit.

FIG.3 depicts an apparatus and method for efficient resin infusion of composites having an external layer of thermoplastic resins and an internal layer of thermoset resigns. In order to create a reinforced composite structure, a mold 31 having a cavity of the shape of the desired product is selected. The product mold 31 is used to produce a product having an external layer made of a thermoplastic material 32; the external thermoplastic layer 32 is produced in advance by a different dedicated mold. The thermoplastic external layer 32 is placed inside the products mold 31. Fabrics (reinforcements) are placed over the thermoplastic external layer 33 and resin 34 is casted over the fabrics 33. An internal thermoplastic layer is placed over the fabrics 35 and the resin 34. An elastic cover 36 is inserted into the products mold 31 over the internal thermoplastic layer 35 vacuum is created between the elastic cover 36 to the products mold 31. The vacuum drives the thermoset resin 34 up the fabrics 33 and the infused fabrics 33 are being attached to the external and internal thermoplastic layers 32 and 35. FIG.4a and FIG 4b. are perspective views of two embodiment of the resin infusion apparatus of the present invention. Figure 4a depicts a perspective cross section of the apparatus for producing a product made of an external thermoplastic layer 41, a thermoset layer 42 and an internal thermoplastic layer 43. An elastic silicon cover 44 is used to introduce the thermoset resin 42 between the external thermoplastic layer 41 and the internal thermoplastic layer 43. A conduit 45 is connected to a vacuum source (nor shown) to introduce vacuum between the elastic silicone cover 44 to the product mold 46. A lid 47 is utilized to create an extra pressure on the elastic cover 44. The elastic cover 44 can be made of any elastic material such as! silicone, rubber, latex or any combination thereof. The mold cavity 46 has an inlet/outlet port 48 which is used for the removal of an excess resin from the mold cavity 46. Alternatively, additional resin may be added to the mold cavity 46, via port 48.

FIG 4b. depicts another embodiment by which an internal thermoplastic layer 49 is utilized as the elastic cover thus eliminating the need to use a dedicated elastic cover. The internal elastic cover 49 includes a lip 50 and a port to connect to a conduit to introduce vacuum as the elastic cover may have mutatis mutandis. The vacuum is therefore introduced between the internal thermoplastic layer 49 to the product mold 46. After the vacuum process is finished, the vacuum conduits are disconnected and the internal thermoplastic layer 49 is an integral layer of the product ready for finishing and coloring. The thermoplastic cover may include precut groves 51 to easily extract the lips and the port for connecting a conduit after the vacuum process is finished to facilitate the finishing and the coloring process.

FIG 5. is a flowchart of a method for producing a product having a thermoplastic external layer and a thermoset internal layer. The external thermoplastic layer is molded in advance by a dedicated mold 51. Alternatively, the thermoplastic layer can be produced by melting a thermoplastic material and casting the melted thermoplastic resin over the product mold. After the thermoplastic layer is inserted into the product mold 52, fabrics (reinforcements) are placed over the thermoplastic layer 53, the fabrics can be for example! carbon fiber, fiberglass, Kevlar etc. After placing the fabric inside the products mold 53 thermoset resin is casted over the fabrics 54. An Additional internal thermoplastic layer is placed inside the product mold over the thermoset resin and the fabrics 55. Alternatively, instead of performing step 54, a wet fabric already infused by a thermoset resin can be placed during step 53. An elastic cover is inserted inside the mold to produce the vacuum infusion process 56! during the vacuum infusion 56 the thermoset resin attaches the fabrics to the external thermoplastic layer and to the internal thermoplastic layer. After the vacuum infusion 56 is over, the elastic cover is removed, and the integral product is extracted from the products mold. The mold is ready for another use as the thermoplastic external layer ensured the mold is kept clean, without needing to remove waxes or other chemicals from the mold which would otherwise be applied. The extracted product includes an external thermoplastic layer which simplifies the finishing and coloring processes and increase the reinforcement of the finished integral product.

In another embodiment were the internal thermoplastic layer is being placed over the thermoset resin and the reinforcement 55, the method may include utilizing the internal thermoplastic layer as the elastic cover for performing the vacuum infusion, thereby eliminating the need to use a dedicated elastic cover such as a vacuum bag or a silicon rubber. In other words, the internal thermoplastic layer is used as a vacuum bag which turns into an integral internal layer of the finished product. Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.

Claims

WHAT IS CLAIMED IS-

1. A method of resin infusion for producing a product having a thermoplastic external layer and a thermoset layer comprising the steps: a. inserting a thermoplastic layer into a mold! b. placing reinforcement inside the mold over thermoplastic layer! c. casting a thermoset resin inside the mold over the reinforcement; d. placing an elastic cover inside mold cavity over the thermoset resin and the reinforcement! e. creating a vacuum between said mold cavity and said elastic cover, wherein said vacuum causes said elastic cover to be pressed against the walls of said mold cavity, thus causing the thermoset resin to impregnate the reinforcement and attaching the reinforcement to the thermoplastic layer.

2. The method of claim 1, wherein placing an impregnated reinforcement inside the mold is performed instead of steps b and c.

3. The method of claim 1, additionally comprising the step of placing a thermoplastic internal layer over the thermoset resin and the reinforcement.

4. The method of claim 3, wherein the thermoplastic internal layer is used as the elastic cover of step d.

5. An apparatus for producing a product having a thermoplastic external layer and a thermoset layer comprising: a. a mold comprising a vacuum port and a cavity! b. a thermoplastic cover having a port for connecting a conduit to a vacuum source! c. a vacuum source! wherein the vacuum source is used to create a vacuum between the mold cavity and the thermoplastic cover and wherein at least part of the thermoplastic cover is used as a layer of the finished product.

6. An apparatus according to claim 5, wherein the thermoplastic cover includes a lip to reliably attach to the mold by the vacuum source.

7. An apparatus according to claim 6, wherein groves are provided to extract the lips and the port for connecting a conduit after the vacuum process is finished.