Experimental investigation of the dynamic response of graphite-epoxy composite laminates under compression

In this study, the dynamic stress-strain response of graphite-epoxy composi te laminates is investigated. The laminates are interposed in a section of a split Hopkinson apparatus. A quasi-rectangular wave is generated at one e nd of the incident bar by striking it with another bar of known length. Thi s bar is accelerated using a compressed air gun. Approximate average stress es and strains can be obtained by measuring the incident, reflected and tra nsmitted waves in the split bar. The dynamic behavior is evaluated for a ra nge of impact velocities. The dependence of the response on impact velocity is analyzed and discussed. Three different specimen thicknesses have been used. These are obtained by increasing the repetition factor of a base stac king sequence: (+45 degrees, -45 degrees, 0 degrees, 90 degrees). This proc ess is called sublaminate scaling; it is preferred to ply scaling since it has been shown that the accumulation of layers of the same orientation decr eases the failure load to such an extent that residual stresses may crack t he specimen before any external load is applied. The laminates considered a re: (+45 degrees, -45 degrees, 0 degrees, 90 degrees)(ns) n = 2, 3, 4. The scale effects observed in the experimental response are analyzed and discus sed. (C) 2001 Elsevier Science Ltd. All rights reserved.