Comment on the impact damage tolerance of stitched composites

Fiber reinforced polymer (FRP) laminates are used in highly-loaded structural components on aircraft, bridges, marine craft and automobiles because of their light weight, high specific modulus and specific strength, good fatigue resistance, and excellent corrosion resistance. However, a problem with using FRP laminates in structures is their susceptibility to delamination cracking under transverse impact loading. The low impact damage resistance is due to the laminated fiber structure of FRP composites, that consist of load-bearing fibers aligned along the plane of the laminate (x,y-directions) but without fibers in the through thickness (or z-) direction to support high impact loads.