John W. Gillespie

Ballistic Impact Experiments and Quantitative Assessments of Mesoscale Damage Modes in a Single-Layer Woven Composite

In this work, we investigated the mesoscale impact and perforation damage of a single layer, woven composite target transversely impacted below and above the ballistic limit by a rigid projectile sized on the order of a tow width. To visualize mesoscale impact damage in woven composites, a thin translucent composite target was used, which provided access to both impact and back-face surfaces. High-resolution photography was used to visualize mesoscale damage, and impact and residual velocity data relative to the location of projectile impact on weaving architecture were quantified. It was found that impact on a tow-tow crossover requires more energy to perforate than impact on a matrix-rich interstitial site or on adjacent, parallel tows. Mesoscale damage in thin, woven composites was characterized for impact velocities below and above the ballistic limit. Four mesoscale damage modes were identified: transverse tow cracks, tow-tow delamination, 45° matrix cracks, and punch- shear. These damage modes were observed both on the surface and inside the composites. High-resolution images of these damage modes were quantified in digital damage maps whereby the output of color intensity correlated with the quantity and type of material damage. Digital maps generated for select specimens revealed characteristic damage patterns in woven fabric composites including a diamond pattern in matrix cracking and a cross pattern in tow–tow delamination. It was found that the greatest extent and quantity of mesoscale damage occurs for impact velocity just below the ballistic limit.