High Strain-Rate Compressive Behaviour of Plain Weave Fiber/Epoxy Composites: Numerical Simulation and Experimentation

Abstract

Nowadays, fiber-reinforced polymer (FRP) composites often penetrate into various critical and supercritical applications because of their inherent superior properties and performances, which are most often easily engineered to meet the design criteria. It is critical to ascertain the complexity of strain rate implications in FRP composites during static and dynamic modes. Since the split Hopkinson pressure bar (SHPB) testing has been extensively used to examine the dynamic behavior of various materials, the data processing techniques and relevant theories for the SHPB evolution are discussed. In the compressive SHPB experiments, the striker bar's velocity (SV) and the incident bar's impact surface are widely recognized for having a substantial influence in obtaining a clean signal. The beginning of this study includes a parametric investigation of such understudied instances utilizing Abaqus software for finite element analysis (FEA). Symmetrically non-parallel plane impact surface, and the filleted impact surface was also studied. It was found that the absolute value of incidence strain at peak increases with an increase in striker velocity, keeping the rise time almost constant. The peak strain, in contrast, remains the same, but the rise time increases with an increase in symmetrically non-parallel plane surface angle and fillet radius. Before finding the polymer composites' dynamic strength, the effect of specimen geometry was essential to understand. Specimen geometry is one of the essential parameters that can ease sample fabrication and help in-situ analysis when altered as per convenience. As part of the current study, high strain rate tests using a compressive SHPB setup were conducted on plain weave glass/epoxy (GE) laminated composite samples of both square prismatic and cylindrical shapes along the through-thickness direction experimentally. Negligible differences were observed due to the change in specimen geometry. Furthermore, developing a computationally accurate model would reduce the need for multiple experimental iterations, thus saving cost and time. The effect of strain-rate dependency of the yarn was analyzed numerically on Abaqus software using a square prismatic-shaped yarn-level finite element composite model. The bulk epoxy's and yarn's material properties were defined using the Johnson-Cook (JC) constitutive model, and the failure mechanism was defined using the JC damage model. One of the primary reasons for using this model is its availability and ease of implementation in almost every FEA simulation software. It was observed that the completely strain-rate-dependent model showed comparable peak stress and strain values with the experimental result to that of other models. Afterward, the high strain rate (HSR) compressive behavior of GE composite embedded with randomly oriented discontinuous carbon fibers (RODCF) was investigated along the through thickness direction using a compressive SHPB setup. The amount of RODCF dispersion in the sample tested was 0.25% and 0.5% by weight of epoxy. The mean compressive strength of the glass/epoxy (GE) sample was observed to increase by 7.4% and 5.8%, with RODCF addition of 0.25% and 0.5% by weight of epoxy, respectively. Finally, the HSR behavior of hybrid composites of symmetrical epoxy-based carbon/glass (CGE) and carbon/Kevlar (CKE) were analyzed along the through-thickness direction. The stacking sequence used for the hybrid composites was [C5/G5]S and [C5/K5]S. An initial striker velocity of about 25 m/s was used for all experiments. The mean reference strain rate observed for CGE and CKE hybrid composites was 2293 and 2333 s-1 , respectively, with a negligible difference in mean compressive strength. The mean strain to failure of [C5/K5]S was almost 17% higher than [C5/G5]S, and proper stress equilibrium was observed. Finally, conclusions and prospects are presented to emphasize the possible promising polymer composites that may be employed in various applications involving high strain rate loading conditions.