Effect of laminate thickness on impact behavior of aramid fiber/vinylester composites

Aramid fiber/vinylester composites were fabricated to investigate the effect of laminate thickness on impact behavior of the composites. The impact energy and the delamination area of composites were examined as a function of laminate thickness and surface treatment of aramid fiber. The laminate thickness and surface treatment changed the impact absorption mode from plate bending stress to local stress. The absorption mechanism of impact energy changed at a thickness between three-layer composites and four-layer composites. The impact energy of thin laminates was dominated by a large displacement and delamination area, whereas that of thick laminates was controlled by maximum load. The trend of total delamination area was similar to that of total impact energy in both untreated and treated composites. In spite of low delamination area, thick composites exhibited the higher impact energy through increase of maximum load.