A NEW APPROACH TOWARD UNDERSTANDING DAMAGE MECHANISMS AND MECHANICS OF LAMINATED COMPOSITES DUE TO LOW-VELOCITY IMPACT .1. EXPERIMENTS

An investigation comprised of experiments and analysis was performed to study impact damage in laminated composites caused by low-velocity impact. The major objective of the study was to fundamentally understand the failure mechanisms and mechanics of fiber-reinforced composites resulting from impact and to identify the essential parameters governing the impact damage. Matrix cracks and delaminations were the primary concern of the study. This paper emphasizes the experimental work of the study. A unique and special air-pressed impact tester was designed and built for the investigation. The major characteristics of the tester was the design of a rectangular barrel and a rectangular based impactor rather than a small circular barrel and a spherical ball, which are commonly adopted for impact study. This new design allows the user to control the impact damage patterns by appropriately selecting different shapes and sizes of the noses which are mounted to the base of the impactor. In this study, a line-nosed impactor was adopted which could produce a uniformly distributed, transient dynamic load across the specimen's width. Accordingly, the impact damage mode was considerably simplified, and the results of the tests were extensively examined and studied for understanding the basic impact damage mechanisms. The essential parameters governing the impact damage were also identified.