Influence of geometric imperfections and internal damage patterns of thin-walled laminates on failure in Compression-After-Impact testing

Abstract

Geometric imperfections are induced in composite structures due to manufacturing and assembly processes as well as due to accidental impacts. These geometric imperfections have an influence on the strength of thin-walled composite structures when impact damage is present. Therefore, the influence of the geometric imperfection magnitude on the failure mechanisms of thin-walled laminates with initial internal damage patterns under Compression-After-Impact testing is investigated by creating a finite element model based on different experimental validations. These experiments are a set of tensile tests, low energy impact tests with a pendulum system to induce the internal damage patterns, ultrasonic scanning of the damaged samples to characterize the delaminated areas and, finally, a set of Compression-After-Impact tests combined with digital imaging correlation data using an ARAMIS 3D measuring system (Gom mbH, Braunschweig, Germany). Compression-After-Impact tests are carried out with a frame modified for thin-walled laminates enabling a more reliable measurement of thin laminates. All these data collected during the experiments and damage inspections are used to build up and validate the simulations with the Finite Element code Abaqus (Dassault Systèmes SA, Paris, France). Finally, potential interactions between global and local failure mechanisms in Compression-After-Impact testing are analyzed with different imperfection magnitudes and interface damage idealizations based on these models. The results show an increase of the failure strength with the initial imperfection magnitude.