High velocity impact properties of composites reinforced by stitched and unstitched glass woven fabrics

The present research aimed to investigate the effect of stitching angle and stacking sequence of stitched layers on high velocity impact behavior of composites reinforced by glass woven fabrics. To study the effect of stitching angle on ballistic impact behavior, six different angles of (0°), (90°), (45°), (0°,90°), (±45°) and (0°,90°,±45°) were chosen as stitching angles. These stitching angles were applied on eight layers of glass woven fabric. To study the effect of stacking sequence of stitched layers, a different number of layers were stitched together with the angle of 0°. Unstitched and stitched composites were exposed to high velocity impact with 180 m/s using a spherical projectile. The residual velocity of projectile and dimensions of damage area on the composites’ front and back sides were measured. It was found that the sample with the 45° stitching angle had the best behavior against ballistic impact and its energy absorption was significantly higher than the other samples. Stitching also reduces damage area in front and back sides of the composites and inhibits delamination.