Assessment and quantification of ballistic impact damage of a single-layer woven fabric composite

A methodology is developed to visually analyze and quantify macroscale and mesoscale impact damage on a single layer of S-2 glass/SC15 toughened epoxy plain weave composite. Specimens were clamped in a 203 mm diameter circular frame and impacted by a 5.5 mm (0.22 caliber) right circular cylindrical steel projectile at impact velocities ranging from 104 to 472 m/s. High-resolution images were obtained at the point of impact and up to the edge of the circular frame using an 80 MP camera. Three types of mesoscale damage were identified: (i) transverse tow cracks, (ii) tow–tow delamination, and (iii) 45° matrix cracks. A MATLAB program was developed to translate the image data into a digital damage map whereby the output of color intensity correlated with the quantity and type of material damage. Digital maps generated for select specimens revealed that characteristic damage patterns arise for woven fabric composites including a diamond pattern in matrix cracking and a cross pattern in tow–tow delamination. The greatest extent of matrix cracks and tow–tow delamination over any specimen was observed for the projectile impact with initial velocity of 174 m/s, which is very close to the calculated ballistic limit velocity of 175 m/s.