Characterization of impact properties and damage process of glass/epoxy composite laminates

This paper investigates the responses of glass/epoxy composite laminates subjected to impact loading. It presents a new technique to characterize the impact properties and to correlate them with the damage process of the composite laminates. The technique, called the energy profiling technique, is based on instrumented impact tests and the least-squares method. The technique gives specific definitions of the penetration and perforation thresholds of the composite laminates. It also defines the range of the penetration process and quantifies the energy absorption efficiency of the composite laminates. The primary damage modes in the damage process of the composite laminates can also be correlated with the impact properties by using the energy profiling technique. The advantages of using this technique to analyze the experimental data obtained from impact tests are demonstrated by investigating the glass/epoxy composite laminates with various impactor sizes, laminate thicknesses, fiber orientations, and a sandwich construction. Results from the energy profiling technique show that the penetration and perforation thresholds increase nearly linearly with the size of the impactor while they increase nonlinearly with the thickness. A sandwich composite made of two glass/epoxy laminates and a foam material is found to have higher energy absorption efficiency than a bonded laminate. Among the five [0(5)/theta(5)/0(5)] composite laminates investigated, where theta = 0, 15, 30, 45, and 90, [0(5)/15(5)/0(5)] has the highest resistance to delamination and has the highest penetration and perforation thresholds. All these results clearly indicate the advantages of using the energy profiling technique for the analysis of composite laminates subjected to impact loading.