Reinforced plastic continued performance

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. 

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. 

A product is at the end of its useful life when it no longer fulfils its technical function. But technical performance alone is not enough. To be useful, the product must continue to do its job in a cost-effective way. The criteria for cost effectiveness depend on the application and on the financial situation of the organization concerned, including its available investment capital and its perceptions of likely future return on capital. Such concepts are clearly outside our present terms of reference, but it is worthwhile to remind ourselves that cost effectiveness is inseparable from technical considerations, especially as energy saving features and low maintenance costs, rather than initial outlay, are so often mentioned as reasons for using reinforced plastics products. 

An SMC is a reinforced plastic compound in sheet form. Most SMCs combine glass fiber with a polyester (TS) resin. Any combination of reinforcement and resin can be produced. The reinforcements can have continuous long fibers or any size of chopped fibers laid out in a different orientation from that of the resin. The different orientation makes it feasible to use SMCs on flat to complex-shaped molds. These SMCs will contain various additives and fillers to provide a variety of processing and performance properties (Table 6-1). 

Run n. (1) In experimental or test work, performance of the experiment or test at one set of experimental factors. (2) Resin flow down the vertical or sloping surface of a sprayed-up or laid-up reinforced-plastic fabrication before it can be cured (usually unwanted). (3) Narrow downward movement of a paint or varnish film may be caused by the collection of excess quantities of paint at irregularities in the surface, e.g., cracks, holds, etc., the excess material continuing to flow after the surrounding surface has set. Sometimes called tear. (4)... 

Plastics continue to expand their use in primary and secondary aeronautical structures that include aircraft, helicopters, and balloons, to missiles space structures. Lightweight durable plastics and high performance reinforced plastics (RPs) save on ftiel while resisting all kinds of static and dynamic loads (creep, fatigue, impact, etc.) in different and extreme environments. Certain military planes contain up to 60wt%... 

The high-performance composite. The plastic material is used to encapsulate reinforcing elements (continuous fibers) to produce suitable shapes and structures [4,5]. This is also called unidirectional reinforcement. In this case the plastic material is the minor constituent (20-50% by volume) and the composite is normally in the form of a laminate. 

All TP or TS matrix property can be improved or changed to meet varying requirements by using reinforcements. Typical thermoplastics used include TP polyesters, polyethylenes (PEs), nylons (polyamides/ PAs), polycarbonates (PCs), TP polyurethanes (PURs), acrylics (PMMAs), acetals (polyoxymethylenes/POMs), polypropylenes (PPs), acrylonitrile butadienes (ABSs), and fluorinated ethylene propylenes (FEPs). The thermoset plastics include TS polyesters (unsaturated polyesters), epoxies (EPs), TS polyurethanes (PURs), diallyl phthalates (DAPs), phenolics (phenol formaldehydes/PFs), silicones (Sis), and melamine formaldehydes (MFs). RTSs predominate for the high performance applications with RTFs fabricating more products. The RTPs continue to expand in the electronic, automotive, aircraft, underground pipe, appliance, camera, and many other products. 

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