Numerical comparison between different strength after impact test procedures

RWTH Aachen University, Department of Aerospace and Lightweight Structures, Wuellnerstr. 7, D-52062 Aachen, Germany

^a e-mail: klaus@ilb.rwth-aachen.de
^b e-mail: reimerdes@ilb.rwth-aachen.de

Abstract

Different procedures are established to investigate the residual properties of sandwich panels after impact damage. Two used procedures for the testing of this properties are compression after impact (CAI) and 4-point bending. In this paper a numerical procedure is presented for a first prediction of the behaviour of pre-damaged sandwich specimens under different boundary conditions (or testing procedures).

A sequence of impact experiments using a drop tower is performed to assess the damage tolerance of sandwich panels with aramid paper foldcores and CFRP skins. The tested impact energy range allowed to investigate a variety of damage scenarios from barely visible damages (BVID) to fibre fractures in all plies of the impacted face sheet. Additionally 4-point bending tests are performed with the panels previously damaged by impact loadings to assess the residual bending strength of these samples. The developed numerical procedure is used to reproduce these experiments (the impact as well as the 4-point bending tests). Also the same procedure is employed in an attempt to predict the behaviour of samples with the same build-up in simulated compression after impact tests.