Reinforced plastic continued

TABLE 1.29 POLYESTER LAMINATES-HAYSITE REINFORCED PLASTICS (continued)... 

Polyurethane, PVC, and extruded polystyrene provide the bulk of the cellular plastics used for low and cryogenic temperature appHcations. In some cases, eg, the insulation of Hquid hydrogen tanks on space systems, foams have been reinforced with continuous glass fibers throughout the matrix. This improves strength without affecting thermal performance significantly. 

Laminates aie materials made up of plies or laminae stacked up like a deck of cards and bonded together. Plywood is a common example of a laminate. It is made up of thin pHes of wood veneer bonded together with various glues. Laminates ate a form of composite material, ie, they ate constmcted from a continuous matrix and a reinforcing material (1) (see also Reinforced plastics). 

Laminates ate a special form of composite material or reinforced plastic because the continuous reinforcing ply of fibrous material imparts significant strength in the x—j plane. The strength along the axis results from interlaminar bonding of resins. Very few fibers ate oriented in the direction, so it tends to be the weak link in this type of composite. 

For temperatures above 100 C it is recommended to use epoxy insulators/supporls, which can continuously operate up to I25°C. SMC/FRP (fibreglass reinforced plastic) insulators/supports may not withstand I05 C. 

A reinforced plastic sheet is to be made from a matrix with a tensile strength of 60 MN/m and continuous glass fibres with a modulus of 76 GN/m. If the resin ratio by volume is 70% and the modular ratio of the composite is 25, estimate the tensile strength and modulus of the composite. 

In this book no prior knowledge of plastics is assumed. Chapter 1 provides a brief introduction to the structure of plastics and it provides an insight to the way in which their unique structure affects their performance. There is a resume of the main types of plastics which are available. Chapter 2 deals with the mechanical properties of unreinforced and reinforced plastics under the general heading of deformation. The time dependent behaviour of the materials is introduced and simple design procedures are illustrated. Chapter 3 continues the discussion on properties but concentrates on fracture as caused by creep, fatigue and impact. The concepts of fracture mechanics are also introduced for reinforced and unreinforced plastics. 

Tanks made from fiberglass-reinforced plastic are being increasingly used, but a number of failures have occurred. In the United Kingdom 30 catastrophic failures are known to have occurred during the period 1973-1980, and a 1996 report shows that they seem to have been continuing at a similar rate [21J. The following typify the catastrophic failures that have occurred [11] ... 

The term reinforced plastic (RP), also called composites (more accurately plastic composites), refers to combinations of plastic (matrix) and reinforcing materials that predominantly come in fiber forms such as chopped, continuous, woven and nonwoven fabrics, etc. also in other forms such as powder, flake, etc. They provide significant oriented property and/or cost improvements than the individual components (10, 14, 35, 38, 39-43, 62). 

In order for such an extensive project to remain manageable, certain requirements were necessary. Initially the data were confined to TPs, TSs, TPEs, and casting plastics. To be included in this group were the TSEs, reinforced plastics, foams, semifinished products, and others. Polymat completed its initial work in 1989. New plastics products on the market and updated additional information on existing products are continually added. Data no longer available are still accessible to the user in a memory file. 

Glass fibres dominate this field either as long continuous fibres (several centimetres long), which are hand-laid with the thermoset precursors, e.g., phenolics, epoxy, polyester, styrenics, and finally cured (often called fibre glass reinforcement plastic or polymer (FRP)). With thermoplastic polymers, e.g., PP, short fibres (less than 1 mm) are used. During processing with an extruder, these short fibres orient in the extrusion/draw direction giving anisotropic behaviour (properties perpendicular to the fibre direction are weaker). 

Domier has developed a production route for continuous fiber-reinforced ceramics based on the impregnation and pyrolysis of Si-polymers. This process is related to the manufacturing of fiber-reinforced plastics and allows the cost-effective production of large and complex CMC-structures. 

By far the most common form of reinforcement is fiberglass. Products using unsaturated polyester resin as a matrix and fiberglass fiber reinforcements are commonly referred to as composites , laminates or FRPs (fiber-reinforced plastics). The latter reinforcements are sold as continuous roving, which is continuously chopped in place with a liquid resin stream, chopped roving mat, woven... 

The second main ingredient in reinforced plastic is the reinforcement, eg, fibers of glass, carbon, boron, mineral, cellulose, or polymers. Reinforcements can be configured in many ways, such as continuous or chopped strands, milled fibers, rovings, tows, mats, braids, and woven fabrics. 

Acceptance and use of nonwoven fabrics as reinforcement of structural plastics continues to increase. Only with nonwoven fiber sheet... 

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