Abstract: A stitch-reinforced sandwich panel with improved flatwise tensile strength, improved skin to core peel strength, and substantially reduced damage propagation from impact includes a relatively non-compressible foam core, a dry reinforcing layer of fibers placed on each of the opposite faces of the foam core; and high strength thread stitched with a high density of stitches over the entire panel through each of the reinforcing layers and the foam core. The skins are then impregnated with a resin system to complete the structure.

Abstract: A preform resin immersion process (PRIP) for impregnating resin into a preform for the fabrication of composite structures. The resin contains a heatactivated catalyst and a thixotropic agent which maintain the viscosity of the resin at selected low level during the resin immersion process. The dry preform is placed in an impregnation vessel, and the resin is held in a resin storage vessel, with both vessels initially held at vacuum of about 5.0 mm Hg torr to draw off any air or volatiles. Pressure is introduced into the resin storage vessel, causing the resin to flow through a line into the impregnation vessel which is still held at vacuum conditions. When enough resin is in the impregnation vessel to completely immerse the preform, the flow of resin to this tank is stopped. Once the resin has completely permeated the preform, the resin is drawn back into the resin storage vessel, and the saturated preform is raised up from the impregnation vessel so that the excess resin drips off into collection means.

Abstract: Reinforcing members for securement of reinforced plastic composite components in restricted and confined space locations as a substitute for reinforcing stitching. The reinforcing members are highly effective for securing "T" stiffeners and the like to a skin structure in confined and restricted locations where a stitching machine cannot be used. The composite pieces which are reinforced and secured together by the reinforcing members provide excellent damage tolerance, are highly resistant to delamination and are resistant to tensile pulling and plane shear properties. The reinforcing members primarily comprise a plurality of pins or spikes which are effectively formed by sewing through a disposable and eliminatable core such that when the core is removed, all of the pins, which originally constituted threads passing through the core are secured together in an array by an open mesh physical cross-linking of the pins.

Abstract: An improved warp/knit stitch reinforced multi-axial non-crimp layered fabric sheet used in structural applications, as for example, in aircraft and water applications, e.g. the skin of an airplane wing or fuselage structure, in water applications, e.g. skins of surfboards and boats, and in other areas where high strength and relatively light weight is required. The fabric is comprised of a plurality of plies facewise disposed upon one another and knitted or stitched to form a structural sheet. Each fabric ply is made of strands of aligned structural fibers which can be later impregnated and even pre-impregnated with a resin curable matrix. The improved sheet is formed by applying unidirectional non-crimp and non-woven plies of different angular relationship to one another, e.g. a +45.degree., a 90.degree. and a -45.degree. ply and locating 0.degree. plies in essentially any position in the ply arrangement such that the 0.degree.

Abstract: An extrusion assembly for extrusion of a triple walled (plastic/metal/plastic) pipe includesa first extrusion apparatus, for extruding an inner plastics layer of the pipe, having an extruder with a coaxial outer extrusion sleeve and inner extrusion die,a shaping sleeve surrounding and substantially coaxial with the extruder, which shaping sleeve is capable of shaping a U-section form metallic layer passing through it into a tubular configuration and a welder for welding the metallic layer of tubular configuration to provide a metal tube,a conduit for supplying a pressurized gas internally of the pipe whereby extruded plastics material emerging from the first extrusion apparatus is forced against an internal surface of the metal tube, anda second extrusion apparatus, for extruding an outer plastics layer of the pipe, having a body part and a supply channel within the body part for supplying plastics material,which extrusion assembly has at least one of,(a) an essentially annular section recess in the body part

Abstract: Process for vacuum impregnation of a dry fiber reinforcement with a curable resin to produce a resin-fiber composite, by drawing a vacuum to permit flow of curable liquid resin into and through a fiber reinforcement to impregnate same and curing the resin-impregnated fiber reinforcement at a sufficient temperature and pressure to effect final curing. Both vacuum and positive pressure, e.g. autoclave pressure, are applied to the dry fiber reinforcement prior to application of heat and prior to any resin flow to compact the dry fiber reinforcement, and produce a resin-fiber composite of reduced weight, thickness and resin content, and improved mechanical properties. Preferably both a vacuum and positive pressure, e.g. autoclave pressure, are also applied during final curing.

Abstract: A process and system for vacuum impregnation of a fiber reinforcement, such as carbon cloth, with a resin to produce a resin-fiber composite. Liquid resin enters in arrangement or system comprising a fiber reinforcement layer on a tool or mold and is directed via a system of flow paths to impregnate the fiber reinforcement layer uniformly across the width thereof and along the length of the fiber reinforcement layer. According to one embodiment, a fiber reinforcement layer, e.g., carbon cloth, is placed on a tool. A porous paring film is applied over the fiber reinforcement layer and a bleeder layer, e.g., fiberglass, is applied over the parting film. A non-pourous film is placed over the bleeder layer, a breather cloth, e.g., fiberglass, is then applied over the non-porous film, and a vacuum bag is placed over the entire assembly and sealed to the mold surface. Liquid resin is fed to the assembly within the vacuum bag. Resin spreader means, e.g.

Abstract: Individual plies of woven cloth having different fiber orientation patterns are prelocated with respect to each other and by continuous means, such plies are arranged into a stacked package and sewn together to secure the plies in a predetermined position with respect to each other.

Abstract: Three-dimensional non-crimp integral woven reinforcement for structural components formed as an integral woven assembly of warp and fill fibers, e.g. graphite fibers, in a multiplicity of layers, with light weight tie yarn, e.g. of fiberglass, passing from one side of the layered system to the other. Woven reinforcement forms of various shapes such as an I-beam can be produced by using a specified percentage of 0.degree. (warp) fibers and 90.degree. (fill) fibers, e.g. of graphite, to form a plurality of layers comprising the web and flanges of the I-beam reinforcement, and having the desired number of layers and thickness in both the web and flanges, and passing tie yarn, e.g. of fiberglass, back and forth from one side of the web to the other, and in the same manner from one side of the flanges to the other, and extending lengthwise in the warp direction of the material. The woven assembly is then impregnated with resin, e.g.

Abstract: Complex woven material as reinforcement for forming layered resin impregnated articles which are resistant to catastrophic damage from shock or local impact as from a hard object, comprised of woven bands or strips of high modulus fibers such as carbon or graphite fibers, separated in at least one direction of the material, from each other by woven bands or strips of low modulus fibers such as glass fibers, and which in a preferred embodiment are narrower than the strips of high modulus fibers. Superimposed layers of such materials can be formed, wherein the strips of high modulus fibers and low modulus fibers in the respective layers are at different angles. Such woven materials, e.g. in the form of a layered assembly, are impregnated with a suitable thermosetting resin such as an epoxy resin, and cured, to produce a layered resin impregnated article having improved damage tolerant physical and mechanical properties.

Abstract: Process for producing a resin-fiber composite which comprises applying a "B" stage resin film to a mold surface, placing a fiber reinforcement layer over the "B" stage film, applying a porous parting film over the fiber reinforcement layer, applying a bleeder layer over the fiber reinforcement layer and placing a non-porous material over the bleeder layer. A bag is placed over the materials and sealed to or around the mold. A vacuum is applied to the mold and then the assembly is heated to a temperature sufficient to cause the "B" stage resin to flow and to impregnate the reinforcement layer, and pass up through the porous parting film and to impregnate the bleeder layer. The volume of resin provided by the "B" stage resin film is calculated so that saturation of both the fiber reinforcement layer and the bleeder layer occur, assuring uniform impregnation of the fiber reinforcement layer.