Intermediate strain rate characterization of a plastic-bonded explosive composition

Abstract
This paper describes how the dynamic compressive behaviour of a quasi-brittle material has been characterized at medium strain rates (1 to 200 s⁻¹). A servo-hydraulic machine has been used to deform cylindrical samples between a dynamic jack and an instrumented anvil, according to the direct impact method. An update of the experimental method detailed during the previous DYMAT meeting [Quirion Y. and Lesaffre A.S., Hydraulic compression tests for compression of a quasi-brittle material at medium strain rate, 8th Int. Conf. Mech. Phys. Behaviour Mat. Under Dynamic Loading, Dijon (France) September 11-15 2006, éd. EDP Sciences.] is proposed. The main modification is the use of a laser sensor to monitor the displacement of the piston. The main difficulty of brittle material testing is to achieve dynamic equilibrium in the sample before failure because of their low failure strains. In this paper, we present the method used to carry out as homogeneous as possible tests and to simplify data interpretation. This experimental set-up has been used to characterize the behaviour of a pressed HMX-based explosive composition. Data obtained at 23°C are detailed. It is shown that the time to temperature equivalence, obtained using quasi-static measurements, can not be extrapolated to high strain rates.