RESIDUAL BENDING STRENGTHS OF CFRP LAMINATES AFTER IMPACT

In the present work, static and fatigue residual bending strengths of carbon fiber reinforced plastic (CFRP) laminates having impact damage are evaluated with four- and three-point bending tests. A steel ball w as launched from an air gun and impacted upon CFRP laminates to genera te impact damage. The delamination growth during fatigue tests and the fracture surface are observed with a scanning acoustic microscope and scanning electron microscope, respectively. The residual strengths de termined by the four-point bending test are reduced, particularly when the impacted side is compressed. The degree of reduction is influence d by the propagation of surface cracks near the impact impression. The residual strengths determined by the three-point bending test are alm ost the same whether the impacted side is the top or the bottom. It is determined that the degree of reduction of strength is governed by th e slide of the transverse cracks due to the shear force.