On the use of an instrumented set-up to characterize the impact behaviour of an epoxy system containing varying fly ash content

The impact response of a varying fly ash bearing epoxy system was studied. It is observed that with the increase in filler volume fraction there is a net reduction in the impact strength, fracture area and time to maximum load. The Ductility Index of the system, on the other hand, shows an increase with filler level. From visual observations on the failed samples, analyses of the crack length, shift of crack and point at which the slope of the crack reaches 45degrees are made. The work clearly shows that a curvilinear path for the crack gives place to straighter ones as the ash content in the matrix increases. Consequently, the crack shift also gets reduced when filler particles are introduced in larger quantities into the resinous system. The SEM pictures unambiguously demonstrate how the initiation, propagation and termination regions have distinct appearances whose features vary with ash content, thereby demonstrating that ash particles do influence the crack at all stages, viz., from its development to final rupture of the test coupon due to impact. The work also throws light on the larger-sized particles playing a role in the furtherance of the crack progression. (C) 2002 Elsevier Science Ltd. All rights reserved.