Delamination Resistance in Stitched and Unstitched Composite Plates Subjected to Impact Loading

Abstract

The delamination resistance of a composite plate subjected to low-velocity impact is dependent on the interlaminar strengths and the level of interlaminar stress. The former is strongly influenced by the material properties such as matrix toughness and fiber-matrix bonding strength while the latter can be affected by the specimen geometry and loading parameters. In this study, some thin composite plates were fabricated and sub jected to low-velocity impact. The delamination in every specimen was examined. Experi mental results revealed that the delamination area was proportional to the lamina thickness and the difference of fiber angle between adjacent laminae. A Mismatch Theory based on the difference of bending stiffness between adjacent laminae was used to interpret the cause of high interlaminar stress level. The effect of interlaminar strengths on the delami nation resistance was also discussed. It was found that through-the-thickness stitching could reduce the delamination area in a composite plate subjected to low-velocity impact as high as 40%.