INTERLAMINAR AND INTRALAMINAR DAMAGE MECHANISMS OF IMPACT RESISTANT AIRCRAFT MATERIALS UNDER LOW-ENERGY IMPACT

For low-velocity impact, drop-weight impact tests performed by EADS (European Aeronautic Defence and Space Company) Corporate Research Center Germany have been carried out for 2-D woven E-Glass/epoxy composite systems to determine material response as a function of absorbed energy and damaged area. Nondestructive techniques like visual inspection and analysis of impact response of the woven fabric laminates at different energy levels are utilized to assess the initiation and progression of interlaminar and intralaminar damage. The dominant damage modes for woven reinforced composite systems were found to be matrix cracking with branching into the adjacent layers, intralaminar cracking by mixture of localized matrix shear and matrix/fibre interfacial debonding, front face indentation, and back face fibre damage. The use of woven fabrics as opposed to cross-ply unidirectional prepregtapes is specifically discussed from the point view of microstructure and property. In the case of low-energy impact, damage resistance under impact loading of woven and multiaxial non-crimp fabrics is presented and compared. The assumption that shear-response dominated for woven reinforced composite systems was found to be in good agreement with the experimental results.