Challenges related to testing of composite materials at high strain rates using the split Hopkinson bar technique

MST-DyMaLab research group, EEMMeCS Department, Faculty of Engineering and Architecture, Ghent University, Tech Lane Ghent Science Park – Campus A, 9052 Zwijnaarde, Belgium

^* Corresponding author: ahmed.elmahdy@ugent.be

Published online: 7 September 2018

Abstract

The design of sample geometries and the measurement of small strains are considered the main challenges when testing composite materials at high strain rates using the split Hopkinson bar technique. The aim of this paper is to assess two types of tensile sample geometries, namely dog-bone and straight strip, in order to study the tensile behaviour of basalt fibre reinforced composites at high strain rates using the split Hopkinson bar technique. 2D Digital image correlation technique was used to study the distribution of the strain fields within the gauge section at quasi-static and dynamic strain rates. Results showed that for the current experiments and the proposed clamping techniques, both sample geometries fulfilled the requirements of a valid split Hopkinson test, and achieved uniform strain fields within the gauge section. However, classical Hopkinson analysis tends to overestimate the actual strains in the gauge section for both geometries. It is, therefore, important to use a local deformation measurement when using these 2 geometries with the proposed clamping technique.