Composites a general introduction

Mechanical Properties of Solid Polymers, Third Edition. I. M. Ward and J. Sweeney. 2013 John Wiley Sons, Ltd. Published 2013 by John Wiley Sons, Ltd. 

Reinforced concrete has practically a century of use as a building material. Continuous steel rods, prestressed under tension, pass completely through each structural element and enable the material to withstand tensile as well as compressive stresses, to give a combination that combines the desirable features of each component. 

A further form of composite is one where the second component acts as a filler. Carbon black in vehicle tyres is an example of a filler needed to provide the required properties. Each carbon particle provides an anchorage for many rubber molecules, and so assists in the redistribution of stress and the carbon is also essential to obtain the desired hysteresis behaviour and abrasion resistance. A much simpler application of a filler is the use of sawdust or other cheap powder in mouldings made from a thermosetting plastic. Although the mechanical properties of the base material are degraded (except possibly for impact resistance), they are still adequate for the proposed application, and the product cost is reduced. We shall not consider fillers in the discussion that follows. 

Reinforced concrete has practically a century of use as a building material. Continuous steel rods, prestressed under tension, pass completely through each 

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