Polymer Testing 5 (1985) 315-316

Book Review

Meelumieai "l?esting of ~ e s . (2nd edition) By S. Turner. 1984. George Godwin in association with the PRI, London. ISBN 0-7114- 5785-9. 214pp. Price: £22.50.

This book was first published in 1973 and at that time was a significant contribution to the library of people struggling to under- s tand the complexities of mechanical testing of these visco-elastic and non-linear materials with their added complications of frequently being anisotropic after processing and also inhomogeneous. Our understanding has developed significantly during the last decade with Dr Turner being a major contributor to that understanding. Hence this second edition is welcomed, representing as it does a major revision and update of the first edition.

The opening chapter underlines that an evaluation schedule for the mechanical properties of plastics involves at least two tests, for stiffness and for strength, and that the position of material within a two-dimensional field using these coordinates gives a rough measure of its mechanical attributes. Environmental factors such as tempera- ture, or test conditions such as the loading history, might be charac- terised by a third axis. A series of characteristic surfaces are then created, corresponding to each of the processing histories that the plastic undergoes before testing. This preamble gave the author the opportuni ty to introduce his own pragmatic approach to the problem of meaningful testing using min imum effort, by carrying out several tests on unusual (according to current practice) specimens.

Subsequent chapters give readable descriptions (with mathematical underpinning) of the principles of testing. Initially Dr Turner consid- ers the plastic to be a 'black box' responding in an observable manner to a defined input excitation. He predicts the response when the polymer system is defined by various constitutive equations. Hence Chapter 2 contains standard text-book information but it is well presented.

Impor tant statements are made about the experimental difficulties in achieving the mechanical loading excitations of step functions and

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Polymer Testing (5) (1985)--~ Elsevier Applied Science Publishers Ltd, England, 1985. Printed in Northern Ireland

316 Book review

ram functions and other mathematically defined excitations. The principles of various dynamic and quasi-static tests are descr ibed-- free vibrations, force vibrations, creep and stress relaxation. Al- though the subject matter in this part of the book is well covered in other publications, the author 's clear personal views are evident and welcome.

The formality of anisotropy is outl ined together 'with a particularly important commentary on the use of unorthodox test geometries. The description of the principles of fracture mechanics is considera- bly enhanced by the frequent application to typical plastics. At tent ion is also given to conventional impact testing and to aspects of long- term durability under quasi-static and dynamic loading histories. This area of mechanical testing is fraught with difficulties for engineers attempting to design test programmes which are both meaningful and economical. Four pages (172-195) indicate such an approach and for many readers might justify the purchase of the book. That is certainly true if the reader then takes advantage of the rest of the book to understand why the particular test strategy is suggested.

The book concludes with an appendix on both systematic and random errors with a concise statement of the relevant statistical formulae.

In summary this book is a 'must ' for any engineer intending to carry out and understand the true significance of a programme of mechani- cal testing of plastics. In order to get the most out of reading the book, however, the engineer will need to have a sound knowledge of cont inuum mechanics in general and linear visco-elasticity in part icular--not too many engineers have this basic knowledge.

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