Numerical models for buckling, postbuckling and failure analysis of pre-damaged thin-walled composite struts subjected to uniform compression

The paper investigates the stability and post-buckling states of compressed thin-walled composite struts with predamage as a result of low-velocity impact. The struts were made of a GFRP composite material with a symmetrical lay-up by the autoclave technique. The produced channel-section struts were subjected to 20 J impact in different areas of the structure: on the web and on the flange. The struts with composite damage were subjected to axial compression to investigate the effect of composite material damage on the stability and operation of the structure in the post-buckling range. A numerical analysis was performed by the finite element method to compare two models of composite material damage: the proposed Simplified Damage Model (SDM) and the model developed by Fardin Esrail and Christos Kassapoglou. The limit load when the structure loses its stability was determined by the progressive failure criterion, according to which damage initiation in the composite material is based on the Hashin criterion while damage evolution is described with the energy criterion.