Mechanical Properties of Reinforced Plastics

In the past, results of standard tests such as tensile strength, Izod impact strength, and softening point have been major emphases in the technical literature on plastics. More recently, however, with the increasing use of plastics in more critical applications, there has been a growing awareness of the need to supplement such information with data obtained from tests more closely simulating operational conditions. 

In addition, a change in a specific polymer parameter may affect processability and basic physical properties. Both of these factors can interact in governing the behavior of a fabricated article. Comprehensive experimental data are therefore necessary to understand effectively the behavior of plastic materials, and to give a realistic and reliable guide to the selection of material and grade. 

In many applications, plastics are replacing traditional materials. Hence, there is often a natural tendency to apply to plastics tests similar to those that have been found suitable for gauging the performance of the traditional material. Dangers can obviously arise if plastics are selected on the basis of these tests without clearly recognizing that the correlation between values of laboratory performance and field performance may be quite different for the two classes of materials. 

The mechanical properties of polymers can be considerably improved by the incorporation in their formulation of reinforcing agents or fillers. These have been used to improve or alter the mechanical properties of polymers. These include glass fiber, glass beads, calcium carbonate, minerals, mica, talc, clay, carbon fiber, carbon nanotubes, aluminum or other metal powders, silica and silicones, and others [1-16]. 

This is the subject matter of this book. It is believed that the incorporation of such agents in polymer formulations will play an important part in the development of polymers with improved properties, which will play a very important part in the development of applications of plastic material in engineering. 

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The improved mechanical properties of reinforced plastics require that the fiber length exceed a certain minimum value. The aspect ratio (length/diameter) of the fibers should be at least about 100 for the full benefits of reinforcement. This is why particulates like carbon black are reinforcements only for hydrocarbon elastomers, but not for plastics generally. 

Several workers have discussed the mechanical properties of reinforced plastics [2-8]. Keating et al. [3] checked the necessity of high-temperature annealing and the degree of its impact on creep straining glass liber-reinforced polymers polyamide 6,6 and polyethylene terephthalate, which had glass transition temperatures of 58°C and 132°C, respectively. 

Clegg DW, Collyer AA, editors. Mechanical properties of reinforced plastics. Barking, UK Elsevier Applied Science Publishers Ltd 1986. 

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