Patent Application
20080085650
The accompanying drawings incorporated in and forming a part of the specification, illustrate several aspects of the present invention, and together with the description serve to explain certain principles of the invention. In the drawings:
a is a schematical side elevational view illustrating an inline process for making the reinforcement fabric of the present invention;
b is a schematical view illustrating an extruded hot melt process for making the reinforcement fabric of the present invention;
c is a schematical illustration of a dry adhesive web process for making the reinforcement fabric of the present invention;
Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings.
A first embodiment of the reinforcement fabric 10 of the present invention is illustrated in
The first layer 12 of collimated continuous fibers may be selected from a group of materials consisting of glass fibers, carbon fibers, graphite fibers, vitreous carbon fibers, non-graphite carbon fibers, boron monolithic graphite fibers, boron monolithic non-graphite carbon fibers, silicone, aramid, ceramic fibers, thermoset polymer fibers, thermoplastic polymer fibers, natural fibers and mixtures thereof. The collimated continuous fibers have a strand size of between about 100 to about 10,000 tex and a filament diameter of between about 9 to about 30 microns. For typical applications, the collimated continuous fibers usually have a strand size of between about 600 to about 8,000 tex and a filament diameter of between about 12 to about 26 microns.
The second layer 14 is constructed from a material selected from a group of materials consisting of glass fibers, carbon fibers, graphite fibers, vitreous carbon fibers, non-graphite carbon fibers, boron monolithic graphite fibers, boron monolithic non-graphite carbon fibers, silicone, aramid, ceramic fibers, thermoset polymer fibers, thermoplastic polymer fibers, natural fibers and mixtures thereof. Where chopped fibers are utilized, those fibers have a strand size of between about 1,000 to about 8,000 tex and a filament diameter of between about 6 to 30 microns. The chopped fibers have a tex of between about 10 to about 1,000 tex in split strands. Where veil is utilized, the filaments are stranded, fully dispersed or a combination of stranded and fully dispersed.
The fibers utilized in the first layer 12 and second layer 14 may include a size. That size includes reagents selected from a group consisting of water, acetic acid, a lubricant, a film former, a silane coupling agent, a biocide and mixtures thereof.
The surface adhesive 16 is selected or formulated from a group consisting of PE, microcrystalline wax, EVA, modified EVA, ethylene-acrylic ester copolymer, ethylene-acrylic ester-maleic anhydride terpolymers, copolyesters, copolyamides, amorphous polypropylene, synthetic rubbers, acrylic block copolymers, and combinations thereof. Where a web bonded adhesive is utilized, the adhesive has a tack between about 0.5 and about 1 N/m. Where a hot melt adhesive is utilized, the adhesive has an open time of between about 3 seconds and about 10 minutes at application temperatures of about 100 C to 200 C and a shear viscosity of between about 10 Pa*s and about 250 Pa*s.
Advantageously, the surface adhesive 16 securely bonds and holds the individual continuous fibers of the collimated fiber layer 12 in parallel alignment while simultaneously allowing rapid infusion when that layer is subsequently infused with resin. This is because the surface adhesive 16 only penetrates the fibers to a limited extent and leaves an infusion pathway. The surface energy of the adhesive is typically less than 45 dynes/cm. The adhesive cohesive strength of 0.3 MPa to 6 MPa depends on whether pressure sensitive characteristics are desired in the application for flexibility during preparation in mold placement with draping, cutting, splicing and adhering plies of the bonded assembly. Likewise the peel strength of the bonded assembly can range from 40 to 200 N/m for pressure sensitive attributes or from 300 to 3000 N/m for permanent bonded assemblies.
The reinforcement fabric 10 illustrated in
The reinforcement fabric 10 of the present invention may be processed or manufactured in accordance with a number of methods. A process for the inline adhesive web extrusion of the reinforcement fabric 10 is illustrated in
An alternative process for manufacturing the reinforcement fabric 10 of the present invention is illustrated in
The hot melt adhesive may be applied in substantially any pattern including patterns selected from a group consisting of a sinusoidal pattern, a loop pattern, a straight line pattern and combinations thereof. In either embodiment the surface adhesive is provided at an areal density of between about 2 and about 30 gsm.
Up to this point a basic two layer reinforcement fabric 10 has been described. It should be appreciated, however, that the present invention encompasses other embodiments with more than two layers. Examples of these alternative embodiments are presented in
A reinforcement fabric 50 suitable, for example, for truck trailer sidewall applications is illustrated in
The surfacing veil 52 of the reinforcement fabric 50 may, for example, be constructed from glass, carbon, polyester, polyamide, polyolefin, or hybrid fibers thereof with a binder. The continuous filament mat 54 of the reinforcement fabric 50 may, for example, be constructed from glass, carbon, polyester, polyamide, polyolefin, or hybrid strands thereof with a binder. The sheet of collimated continuous fibers 56 substantially corresponds to the first layer 12 described in detail with respect to the embodiment shown in
The reinforcement fabric 70 illustrated in
The surfacing veil 72 is constructed from glass, carbon, polyester, polyamide, polyolefin, or hybrid strands thereof with a binder. The chopped fibers may be constructed from glass or carbon fibers. The chopped fibers have a strand size of between about 1000 to about 8000 tex and a filament diameter of between about 6 to about 30 microns. The chopped fibers also have a tex of between about 10 to about 1000 in split strands. The sheet 76 of collimated continuous fibers substantially corresponds to the first layer 12 in the
The infusion media layer 78 is selected from a group of materials consisting of veil, continuous filament mat, chopped strand mat, direct chopped mat, direct continuous mat, collimated continuous fibers, woven fabric, non-woven fabric, scrim and combinations thereof. Materials utilized for the infusion media layer 78 include, for example, continuous filament mat, scrim or direct continuous mat. The layer of woven fabric, non-woven fabric or chopped fibers 80 is described in greater detail above with respect to the second layer 14 of the
The reinforcement fabric 90 illustrated in
The surfacing veil 92 may be constructed from, for example, glass, carbon, polyester, polyamide, polyolefin, or hybrid fibers thereof with a binder. The infusion media layer is selected from a group of materials consisting of veil, continuous filament mat, chopped strand mat, direct chopped mat, direct continuous mat, collimated continuous fibers, woven fabric, non-woven fabric, scrim and combinations thereof. Materials used include, for example, continuous filament mat. The sheet 96 of collimated continuous fibers corresponds to the first layer 12 described in detail above with respect to the
The first and second reinforcing layers of unidirectional fabric 98, 100 may be made from glass or carbon fibers.
As further illustrated in
In accordance with additional aspects of the
In summary, numerous benefits result from employing the concepts of the present invention. The reinforcement fabric 10, 50, 70, 90, 110 of the present invention incorporates continuous fibers bonded together in a collimated sheet 12, 56, 76, 96, 104, 116 using a hot melt or web bonded adhesive 24, 60, 82, 102, 106, 122. When optimized the architecture and chemistry of the reinforcement fabric of the present invention allows 2-3 X resin infusion rates for complex structures with consolidation under vacuum VIP or pressure assist vacuum RTM-Lite. Further, the reinforcement fabric has enough stiffness to hold vertical mold surfaces and maintain fiber alignment for optimal composite mechanical properties like compressive strength and strain to failure.
The reinforcement fabrics of the present invention provide improved kitting/preforming, conformability to tooling, surface aesthetics and composite structural performance for a wide range of molding processes at optimal levels heretofore unachievable with state of the art reinforcement fabrics utilizing stitching to hold fibers in alignment. Advantageously, the reinforcement fabric of the present invention may be processed inline at rates of between 50-500 m/min. This advantageously eliminates the bottleneck typically associated with stitch bonding processes which reduce processing speeds to as low as 5 to 20 m/min.
Advantageously, the reinforcement fabrics of the present invention combine multi-compatible sizing capability for use in polyester, vinyl ester, epoxy, phenolic and some urethane resin systems. The reinforcement fabric is architecture engineered to structural application load requirements such as bending and compressive strength. The optimized fiber alignment of the collimated fibers maintained by the surface adhesive supplements load requirements and reduces/eliminates stitching defect to improve durability in wet environments and for higher allowable fatigue strength.
The foregoing description of the preferred embodiments of the invention have been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. For example, the collimated continuous fiber layer 12 could include stitching if desired for any reason.
The embodiments were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled. The drawings and preferred embodiments do not and are not intended to limit the ordinary meaning of the claims and their fair and broad interpretation in any way.
