Failure mechanismsof low velocity impact for the composite scarf repair

The mechanical and fracture properties of composite scarf repair under low velocity impact were investigated. Impact responses of impact load reveal that four typical phases exist during impact procedure. The impact load has double peak forces. The first peak keeps constant while the second one rises with the increase of impact energy. From the failure investigating on the central section, we find that there are two damage modes of the composites laminates and the adhesive. Composite damage contains the matrix crack on 90° and 45° plies and the delamination between 0° and 90° plies. Adhesive damage appears at the backside of specimen opposite to the impact location. Further study of simulation reveals the whole impact behavior of the composite scarf repair. The composite damage leads to impact load dropping at Phase?, and adhesive damage causes the impact load dropping again at the beginning of phase ?.