Axial and Lateral Impact Prediction of Composite Structures Using Explicit Finite Element Analysis

Abstract

The use of composite materials in the automotive industry is growing since these materials exhibit high stiffness, strength and low weight. As such, analytical capabilities must be developed in order for these materials to be used in more structural applications. Previous work in the area of crush performance has concentrated on experimental and empirical studies that have qualitatively characterized the crush process. These studies have shown that the crush process in composite materials is complex, and is dominated by fiber/matrix microcracking, which is the main energy absorption mechanism. In this study, the crush performance of a set of tubular composite structures were modeled using the explicit code RADIOSS™. Unlike many of the other commercially available codes, the composite material model within RADIOSS uses material input parameters that can be easily extracted from basic material test. These tests would include a 0° and 90° tensile and compressive test, as well as an in-plane shear test. The model can also accommodate strain rate effects. As the structure is loaded, the stresses within each element and ply are calculated. Using a Tsai-Wu failure criterion, the material fracture is simulated by removing a failed ply within a given element. As a consequence, the material degradation within and ahead of the crush front is simulated. The results of the study showed that the steady state crush load could be predicted accurately. However, the exact failure mode with the crushed structure was not as accurately represented in the model. In addition, two other case studies one being a 3-point bending on a hexagonal section and composite sandwich plate impact analysis were also performed. The results showed good agreement with experiments in both load levels and failure modes.