Investigation of strain rate effects on in-plane shear properties of glass/epoxy composites

Fiber-reinforced polymeric composites exhibit excellent mechanical properties over conventional engineering materials especially due to their great weight saving. Therefore, by considering the specific attributes of these materials, having a proper knowledge of dynamic behavior as well as static behavior of them is necessary. In order to study the effects of strain rate on the behavior of the materials, special testing machines are needed. Most of the researches in this field are focused on applying real loading and gripping boundary conditions on the testing specimens. This paper discusses the experimental study on the in-plane shear behavior of unidirectional glass fiber-reinforced polymeric composite under quasi-static and intermediate strain rate loading conditions. The symmetric and balanced ±45° composite laminates are manufactured for characterization of the in-plane shear properties (modulus and strength) at various strain rates. Specimens are tested under uni-axial tensile loading using a servo-hydraulic testing apparatus. For performing the practical tests, jig and fixture are designed and manufactured. The performance of the test jig is evaluated and found to be adequate for composites testing. Dynamic tests results are compared with static tests carried out on specimens with identical geometry. The experimental results show that the mechanical shear properties are quite sensitive to strain rate. Under dynamic loading, the failure shear strength increased with increasing the strain rate but the shear modulus decreased. Based on the results obtained from the experiments, empirical functions for expressing the mechanical shear properties are proposed in terms of shear strain rate.