RATE EFFECT FOR IMPACT DAMAGE INITIATION IN CFRP LAMINATES

In carbon fibre composite laminated plates, impact of a small mass at subordnance velocities resulted in three types of initial fractures: yarn splitting, fibre breakage and delamination. An elastic analysis for stresses developed due to impact against the composite plate has been correlated with observations of fracture initiation in impact experiments. Fractures due to yam splitting developed near the periphery of the contact area due to a tensile radial stress perpendicular to the fibres; this type of fracture also occurred near the distal surface as a result of combined transverse tension and shear on fibres. Under the striker there was fibre breakage and delamination as well. Criteria were obtained for initiation of yarn splitting in composite plates deformed at high rates.