LOW-SPEED IMPACT DAMAGE-INITIATION CHARACTERISTICS OF SELECTED LAMINATED COMPOSITE PLATES

The results of an experimental and analytical study of damage initiati on in laminated composite plates subjected to low-speed impact are pre sented. Here, 8, 16-, 24-, 32-, and 48-ply-thick quasi-isotropic and o rthotropic graphite-epoxy and graphite-bismaleimide laminated plates h ave been impacted with dropped weights and the corresponding plate res ponses have been predicted analytically, Impact damage-initiation thre sholds and damage initiation mechanisms corresponding to a range of im pact-energy levels are identified. Impact-damage initiation for the th icker plates occurs at both the impact site and the plate surface oppo site to the impact site. Impact-damage initiation for the thinner plat es is predominately due to tensile fracture on the plate surface oppos ite to the impact site. Three-dimensional stress states that correspon d to the impact conditions that initiate damage are determined analyti cally to help identify damage-initiation mechanisms and to predict fai lure-initiation modes.