Experimental study of the strength degradation of GFRP laminates subject to ballistic normal impact

This paper is concerned with the damage tolerance of the S-glass/epoxy(Fiberite HY-E 9134B) laminates struck by a blunt or tip-ended cylindrical impactor in the normal incidence. The impactor is fired against composite target with an initial velocity ranging from 20 m/s up to 150 m/s. Three different types of laminates, i.e., [0°₁₅], [0°₅/90°₅/0°₅], and [0°/±45°/90°)₂]_s, are used as targets. A series of tests have been conducted in the Institute of Aeronautics and Astronautics, National Cheng Kung University. Resulting Impact damages and the associated tensile residual strength are carefully examined by utilizing X-radiography, ultrasonic C-scanning, and also optical photography. Experimental results are recorded by a Polaroid film, PC/AT computer, and standard film (35 mm), respectively. The strength degradation is found to be strongly influenced by impact momentum, shape of penetrator, and the layup of the targets. Penetration and perforation phenomena of composite targets differ tremendously from those of metallic ductile targets, such as steel and aluminum. Current research extends those previously reported work by Caprino and Suarez, et al.