Reinforced plastics structures

Measurements on Reinforced Plastics (Structure Effect). Polymeric substrates (Poly-butylterephthalate PBT) with different amount of glass fibers were painted with a typical coating system for plastics. The complete coatings... 

The combination of rigidity and stress resistance that is required in higher plants is provided by the structure of the various layers and lamellae of the cell wall that contain crystalline microfibrils, matrix polysaccharides, and amorphous lignin. According to an early interpretation by Freudenberg, the microfibrils in the cell wall act in the same way as the reinforcing rods in prestressed concrete. A better mathematical model is furnished by filament-wound, reinforced-plastic structures, such as pressure vessels. 

Braids Is used to give high strength three-dimensional (3-D) reinforcement, incorporating more than one type of fiber, if required. Conventional woven fabrics are limited to providing reinforcement at orthogonal orientations, but many reinforced plastics structures are loaded in non-orthogonal fashion. Woven fabrics are, therefore, not necessarily mechanically efficient. 

Thick laminates are obviously much less affected than thin ones in a given period and this explains the durability of many early reinforced plastics structures. It has been calculated that an epoxy-based reinforced plastics material with a typical diffusivity towards moisture of lO m s would require 13 months to reach saturation if left in a tropical climate at 35°C and 95% relative humidity (RH) if the thickness was 2 mm, but a 90 mm thick section would need 1342 years. During the approach to saturation, there is a through-the-thickness variation in moisture content and therefore in properties. 

Adhesive joints in reinforced plastics structures are capable of achieving higher strength than mechanical ones and may be preferred for that reason, but once made, adhesive joints cannot be disconnected and they can be vulnerable to prolonged high humidity. Their durability depends more on the flexibility and toughness of the resin used in the adhesive than on its strength [39]. 

Intrinsically non-flammable polymers are few, but phenolic resins have a good reputation both in Are and smoke performance, which has resulted in their becoming increasingly favoured for reinforced plastics structures, for example, underground transport, where such concerns are greatest. Polyether ether ketone (PEEK) is also a low fire and smoke polymer. Unsaturated polyesters, vinyl esters and epoxy resins bum readily, but modified versions are available with improved behaviour. For example, both bromine and chlorine are used extensively in the form of chlorendic (HET) acid, tetrachlorophthalic anhydride (TCPA) and tetrabromo-phthalic anhydride (TBPA) which can be reacted into the polyester in small quantities and can act as permanent (non-migrating) flame retardants. 

Uses Curing agent for adhesives, high solids coatings, chem. resist, flooring, fiberglass reinforced plastics, structural steet primers and topcoats commonly used to accelerate cycbatiphafic amines Features Provides rapid cure at iow temp. 

Cylindrical weave n. A type of woven, knitted, or braided sleeve generated as reinforcement in tubular reinforced-plastic structures such as pipe. Typically, the rein-... 

Fiber-resin interface (fiber-matrix interface). The surfaces shared by the fibers and the resin in a fiber-reinforced plastic structure. This interface, and the effects of various sizes and chemical treatments on the interfacial bond, are subjects of many past and ongoing studies. Because of the pretreatment of fibers with sizes, the interface has a small but finite thickness. 

Filamentary composite A reinforced-plastic structure in which the reinforcement consists of filaments usually oriented to most efficiently withstand the stresses imposed on the structure. The filaments are not woven and in a single lamina they will all be parallel. Wallenberger FT, Weston NE (eds) (2003) Natural fibers, plastics and composites. Springer-Verlag, New York. 

Multilayer fabric n. A fabric for reinforced-plastic structures formed by braiding to and fro or overlapping in one direction. Layers may be biaxial or triaxial, fibers mixed, and braid angles varied. 

Non-woven mat A mat of glass fibers in random arrangement, hghtiy bonded so as to be able to be handled and cut, used in making reinforced-plastics structures. 

Triaxial-braid performing n. Any braiding technique for fibrous reinforcements by which three-dimensional performs for reinforced-plastics structures are produced. 

Unidirectional laminate - la-m9- nat. A reinforced-plastic structure in which substantially all of the fibers are parallel. The modulus of elasticity ( ) and strength of such a laminate in the direction of reinforcement will be somewhat more than the product of the volume fraction of reinforcing fiber times its corresponding properties. However, properties in the transverse directions are essentially those of the matrix resin. 

Glass beads and microspheres are frequently silane treated, and special grades may have metallic coatings. Glass flakes are promoted by Glassflake Ltd. as constituents of anticorrosion barriers in reinforced plastics structures, including pipe. The company offers a wide range of thicknesses and particle size distributions. 

W. H. Seemann, Plastic transfer molding techniques for the production of fiber reinforced plastic structures. US Patent No. 4902,215 1990. 

Figures 8-3, 8-4 and 8-5 show some of the parts which incorporate the sandwich panel concept to improve stiffness. They range from structural foam molded parts (which come from the mold as completed parts) incorporating low density cores and high density skins of the same materials to parts vacuum formed of a plastics material, the core of which becomes cellular during the heating process for forming. Reinforced plastic structural panels for curtain wall building construction that have honeycomb cores or decorative cores are examples...

Efficiency of Reinforcement n (fiber-efficiency factor) The percentage of fiber in a reinforced-plastic structure or part contributing to the property of concern. For example, in a unidirectionally reinforced bar, the theoretical efficiency for Young s modulus and fiber-direction tensile strength is 100%. For a sheet molded from chopped-strand mat with all fibers randomly oriented in the sheet plane, the efficiency for inplane properties is 37%. With chopped strands randomly oriented in three dimensions, efficiency falls to 20%. 

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