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Handbook of Composites Vol 1—Strong Fibres
such as test temperature and loading rate is emphasized, particularly for toughened composite systems, when developing test standards. An excellent review paper on the current status of various approaches to toughen graphite fibre/polymer composites is provided by Leach (ICI) in his paper 'Tough and damage tolerant composites'. In current generation graphite/epoxy systems, the loss of residualcompression strength following low-energy impact damage is a matter of considerable concern and has hindered application of these materials to primary aircraft structure. Some of the approaches to develop tougher composite systems are reviewed, including: (a) modifying epoxy resins with dispersions of elastomers or thermoplastics, or by changing the cross-link density, (b) interleaving of epoxy matrix composites with tough polymers, incorporated between the plies, (c) using through-thickness reinforcements, in the form of pins or stitches, (d) using lower-modulus composite buffer strips - glass/epoxy or aramid/epoxy, (e) changing to a tougher matrix such as a thermoplastic (for example PEEK), and (f) increasing fibre/matrix bond strength in toughened-matrix systems.
The main test to evaluate the influence of the toughening approach is the 'Post Impact Compression' (PIC) test and Leech correlates the results of these tests on current and toughened systems with the Mode I polymer fracture toughness and the Mode I composite interlaminar fracture toughness. Very interestingly, it is found that while very rapid increases in PIC result from increases in interlaminar fracture toughness up to about 1 kJ m -a further toughness increases (up to 4 kJ m -a) produce little or no further improvement in PIC. However, it is found that the damage size continues to diminish with increasing toughness. (It may be, as inferred by Charentenay et al. that the interlaminar fracture energy for initiation controls the PIC strength and that this is much lower than the fracture energy for growth in the toughened systems.) Nevertheless, the improved composite systems have two to three times the PIC strength of current systems. Unfortunately, indications are that under fatigue conditions the advantages of the toughened systems are not maintained. The review concludes with the statement that further understanding of the fibre-matrix interface and micro-mechanisms of failure are needed to enable further developments to be made.
A. A. Baker
Handbook of Composites Vol l m Strong Fibres Edited by: W. Watt and B. V. Perov
North-Holland Publishing Company, Oxford, 1985 (US $115, Dfl 375) This handbook was edited and authored jointly between individuals primarily from the Soviet Union and England. (One chapter, on silicon carbide fibres, was authored by a researcher from Japan.) The text is divided into three parts: inorganic fibres, carbon fibres, and organic, high modulus fibres. The six chapters on inorganic fibres cover glass, oxide, alumina, boron, and silicon carbide fibres in considerable detail. The eight chapters on carbon fibres include rayon, cellulose, polyacrylonitrile and pitch precursor fibres, and fibre surface treatments designed for polymer matrix composites. The four chapters on organic high modulus fibres cover basic principles, synthesis, manufacturing and properties. Aramid and polyethylene fibres receive particular emphasis.
COMPOSITES. JULY 1988
This extensive treatment (a text of 752 pages) of a very specific topic (strong fibres) by some of the leading researchers in the area makes this a very valuable reference work. Although authors from the United States and elsewhere did not contribute to the writing, their works are well referenced and represented. All chapters contain extensive lists of references to the available literature. All of the chapters are very readable, having been well edited. Although this is the first volume in a 'Handbook of Composites' series, composites are not discussed, with the minor exception of the chapter on fibre surface treatments. This was intentional, of course, as later volumes will presumably cover various aspects of composite materials.
D. F. Adams
327
The main test to evaluate the influence of the toughening approach is the 'Post Impact Compression' (PIC) test and Leech correlates the results of these tests on current and toughened systems with the Mode I polymer fracture toughness and the Mode I composite interlaminar fracture toughness. Very interestingly, it is found that while very rapid increases in PIC result from increases in interlaminar fracture toughness up to about 1 kJ m -a further toughness increases (up to 4 kJ m -a) produce little or no further improvement in PIC. However, it is found that the damage size continues to diminish with increasing toughness. (It may be, as inferred by Charentenay et al. that the interlaminar fracture energy for initiation controls the PIC strength and that this is much lower than the fracture energy for growth in the toughened systems.) Nevertheless, the improved composite systems have two to three times the PIC strength of current systems. Unfortunately, indications are that under fatigue conditions the advantages of the toughened systems are not maintained. The review concludes with the statement that further understanding of the fibre-matrix interface and micro-mechanisms of failure are needed to enable further developments to be made.
A. A. Baker
Handbook of Composites Vol l m Strong Fibres Edited by: W. Watt and B. V. Perov
North-Holland Publishing Company, Oxford, 1985 (US $115, Dfl 375) This handbook was edited and authored jointly between individuals primarily from the Soviet Union and England. (One chapter, on silicon carbide fibres, was authored by a researcher from Japan.) The text is divided into three parts: inorganic fibres, carbon fibres, and organic, high modulus fibres. The six chapters on inorganic fibres cover glass, oxide, alumina, boron, and silicon carbide fibres in considerable detail. The eight chapters on carbon fibres include rayon, cellulose, polyacrylonitrile and pitch precursor fibres, and fibre surface treatments designed for polymer matrix composites. The four chapters on organic high modulus fibres cover basic principles, synthesis, manufacturing and properties. Aramid and polyethylene fibres receive particular emphasis.
COMPOSITES. JULY 1988
This extensive treatment (a text of 752 pages) of a very specific topic (strong fibres) by some of the leading researchers in the area makes this a very valuable reference work. Although authors from the United States and elsewhere did not contribute to the writing, their works are well referenced and represented. All chapters contain extensive lists of references to the available literature. All of the chapters are very readable, having been well edited. Although this is the first volume in a 'Handbook of Composites' series, composites are not discussed, with the minor exception of the chapter on fibre surface treatments. This was intentional, of course, as later volumes will presumably cover various aspects of composite materials.
D. F. Adams
327