The shock wave generated by a planar impact of a flyer plate and propagated along the direction of the fibers of a composite was studied. The sample composite used in the experiments was made of unidirectional aluminum fibers cast in an Epoxy matrix. Both the shock-wave velocity and the free surface velocity were measured by means of an optical technique. The shock front in the composite was found to be steady. The results of the measured Hugoniot also give a satisfactory comparison with those obtained from an analysis proposed earlier. The observation of a steady shock in the present work is significant in treating problems involving composite materials.

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A B S T R A C TThe energy for fully shear fracture in CT tests has been measured for controlled roiled, normalised and also quenched and tempered materials. Equations have been derived relating the energy per unit area for fracture to the ligament length, ( W -a ) , of the test piece, both at ambient temperature and also at lower temperatures; these are of the form:where B is the thickness and R,. and S,. are constants. The first term is the energy absorbed per unit area of fracture whereas the second term is the energy absorbed per unit volume of plastic deformation remote from the fracture surface. Increasing the strain rate or decreasing the temperature slightly increased the energy for fracture; however, there was an increase in the maximum contraction with increasing strain rate whereas there was a decrease with decreasing temperature. This indicated that high strain rate tests could not be correctly simulated by testing at lower temperatures. Similar equation constants were obtained from the results of SENB tests, but for tension tests there was a significantly higher Rc value although the S,. value was similar. Results of impact tests were also found to fit the same expression, with Rc and Sc values greater than for the slow rate tests. A number of sub-thickness CT test pieces were tested, but only a small, if any, decrease in toughness was observed.The energy for fracture was found to be related to the degree of modification of the sulphide inclusions, and hence to the Ce/S ratio of the material; this was reflected in much greater changes in fracture energy values compared to those for tensile properties. Modified values of the nominal stress were found to be independent of ligament length and those at maximum load have been correlated with the tensile strength values. Extension measurements on various test pieces showed a similarity with the energy relationships and mean stress values calculated from these were found to be reasonably similar to those of the yield stress.