Abstract: Composite laminates are very sensitive to foreign impact because of their anisotropy and good absorbing ability to impact energy. They may exhibit different impact damage behavior in body under impact loading. Two kinds of specimens-RTM-stitched and prepreg composite laminate, are manufactured to investigate their behaviors of impact damages. The specimens are subjected to a given energy impact. An ultrasonic B-scan is arranged to the specimens by using focal system in order to study behaviors of impact damages in cross-sections of the specimen bodies. Experimental results have demonstrated that interior damaged area is much larger than damage on surface; new damages occur in different inetrlaminar layers with impact energy going into specimen body deeper and deeper, and they evolve not only along interfaces of layers; the distribution and orientation of damages between near- and far-impact point are significantly different; a clear difference in damage behavior between RTM-stitched and prepreg composite laminates is demonstrated very well, and the stitching fiber thread in depth direction of RTM-stitched composite laminate has obvious help on restriction to development of damages along interlaminar interfaces. The results provide very helpful and practical understanding of the damage behavior in different composite laminate bodies. That may motivate to find new mechanism to improve damage behavior of composite laminates.

Key words: behavior of impact damage, composites, non-destructive testing, ultrasonic imaging