THE EFFECTS OF STRAIN-RATE ON THE MECHANICAL-BEHAVIOR OF KEVLAR FIBER-BUNDLES - AN EXPERIMENTAL AND THEORETICAL-STUDY

The stress-strain curves of kevlar49 aramid fibre bundles under both q uasi-static loading and high rate loading were obtained. The strain ra te ranges from 10(-4)/s to 10(3)/s. Based on a bimodal Weibull distrib ution statistical model of strain-rate dependence of fibres and a test method of determining mechanical properties and Weibull parameters of fibres from fibre bundle test, the rate dependence of kevlar49 fibre strength is studied. Experimental results show that kevlar49 fibre has sensitivity to strain rate. The peculiar 'skin-core' structure of kev lar aramid fibre and experimental Weibull data confirm that there are two types of fracture mode in kevlar fibre and the application of bimo dal Weibull distribution is correct. Consistence of simulated and expe rimental results indicates that the model is valid to explain the mech anical behaviour of kevlar49 fibre and the test method is feasible and reliable. (C) 1998 Published by Elsevier Science Ltd. All rights rese rved.