Improvement of numerical methods for crash analysis in future composite aircraft design

Recent aircraft as well as rotorcraft design technologies include more and mon composite materials. Their high mechanical characteristics and high mas s specific energy absorption capability motivate their use in large primary structures as well as in sub-floor structural and crashworthy components i n preference to metals. Due to the increased performance of computers and n ew explicit finite element (FE) software developments industry now consider s using crash simulation technologies to study the crashworthiness of new a ircraft design. In order to address the crash analysis of composite structu res, which is much more difficult than the behaviour of ductile metallic st ructures, a German/French research co-operation was set up between ONERA an d DLR. This paper summarises results from the first 3 years collaboration a nd some work performed within a European research project on composite fuse lage structures. In the first part of the paper, ONERA presents its contrib ution to the characterisation of composite materials from 10(-5) s(-1) up t o 100 s(-1) on hydraulic machines. Simulations have been undertaken to mode l the tests and evaluate the FE codes. In the second part DLR studies are p resented on the application of a commercial explicit FE code to simulate th e behaviour of generic energy absorbing composite sub-floor elements, repre sentative for helicopters and general aviation aircraft, under low velocity crash conditions (up to 15 m/s). This includes some comparisons between pr edicted structural response and failure modes with observed test results. ( C) 2000 Editions scientifiques et medicales Elsevier SAS.