Response of thermoplastic and thermosetting composites under compressive loading—An experimental and finite element study

Abstract

The influence of long-term moisture exposure and temperature on the compressive properties of T-300/epoxy (thermosetting) and APC-2 (thermoplastic) composites has been studied. Specimens of quasi-isotropic configuration [45°/90°/−45°/0°] 5 were designed on the basis of the Euler buckling criterion, and a temperature range of 23–100°C was considered for both dry as well as wet tests. Specimens for wet tests were soaked in distilled water for a period of 360 days, and the effects of moisture absorption on the compressive properties and geometry of the specimens were investigated. The results of the investigation indicated that the moisture absorption rate of T-300/epoxy was higher than that of APC-2. It was noticed that the geometry of the specimen influenced the moisture absorption rate. The thick plate with a smaller surface area absorbed less moisture than the thin plate with a larger surface area. The compressive strength and modulus of APC-2 were found to be comparatively higher than that of T-300/epoxy both in dry and wet conditions. The effect of moisture at 100°C was negligible for both materials. The modes of failure in both materials under compressive load were found to be delamination, interlaminar shear and end brooming. Thick laminates of thermoplastic composites (APC-2) were modeled with isoparametric layered shell elements to predict the responses of the dry laminate at various temperatures under compressive loading. A large-displacement finite element analysis was performed by considering the geometric non-linearities in the composite structure. Multiple load steps with linear material behavior were used to model the load-displacement characteristics found in the experimental study. The compressive response with respect of displacements, normal stresses and interlaminar shear stresses under three different temperatures is presented. The laminate response along the length as well as through the thickness is also presented, to analyze and understand the failure mechanisms under such loading. Experimental data were compared with the FEM results to test the accuracy of the finite element analysis (FEA) using the layered shell element under the assumption of first-order shear-deformation theory. A reasonably good correlation between FEA and experimental results was found.