Load-Bearing Fibre Composites

Description

This is a thoroughgoing revision and expansion of the earlier book, bringing it up to date with the latest research. The older ideas are presented along with the new, and the experimental evidence is given in outline, and fully referenced. Where practical, illustrations are chosen from key works and the source reference is given in the subtitle as in the first edition. As before, this book is directed toward upper-year university students and graduate students. Ideas that are highlighted include: How the interface governs the transfer of forces between the fibres and the polymer, or metal, or ceramic, which constitutes the other component of the material. The yielding-slip model used almost universally for reinforced polymers is shown to lack any significant experimental support. Instead, ideas originating in the paper industry in the 1950s, which led naturally to the concept of critical fibre length, are shown to fit experimental results quite well. How to design a good laminate. The commonly accepted notion of the weakness of angle ply laminates is shown to be a mistake. (It arose from the incorrect use of testing methods derived from standard practice with metals.) New results, using better tests, are presented. These show that much simpler designs could be used. Why laminates can be unreliable under compression. Earlier treatments oversimplify: important structural imperfections such as fibre waviness are either neglected or given a single parameter. Letting the fibres follow sine waves permits straightforward analysis, which gives good agreement with test results and suggests avenues for improvement. Water and other fluids in reinforced polymers. Many experimental results for absorption and diffusion are presented. These again show that better models are needed. It is shown that the assumptions used hitherto are unnecessary, and an exact solution is presented for diffusion through a simple fibre array. Shear failure. When polymers are sheared, account must be taken of their non-metallic nature. While metals may be treated rather like arrays of ball bearings, polymers are more akin to collections of very long pieces of string, so simple shearing can take place with metals but not with polymers. Instead, the polymer chains align in the same way as they do in tension and shear-induced failure in polymers involves breaking the chains in a tensile mode. This explains why attempts to measure the shear strength of reinforced polymers give inconsistent results - see Chapter 6. It also explains some highly improbable results from work on the fibre-polymer interface strength - see Chapter 8.Each chapter has a set of problems designed to test your knowledge and skill. They are as practical as possible and selected answers are provided. Since this book is concerned with how composites work, and so how they could be made to perform better, a mathematical basis for the subject is provided. This avoids advanced mathematics (first year university course should be all you require). To clarify the concepts, much use is made of non-dimensional constants. Although the treatment is simple, some complication is unavoidable where many different physical processes act simultaneously