Influence of conditioning on the high strain rate compression response of Kevlar thermoplastic composites

Kevlar reinforced composite material systems are widely used for personal body armors. Due to aging or minor damage while in service, body armor may get exposed to external weather conditions, including moisture. The present study investigates the effect of moisture on the high strain rate behavior of Kevlar/Polypropylene (K-PP) composite. Flat K-PP composite laminate was manufactured using a vacuum-assisted compression molding followed by laser machining. Dynamic compressive loading tests were performed using split Hopkinson pressure bar setup. The phenomenological modeling approach was adopted to characterize the rate-dependent behavior of dry and wet composites. For identical dynamic compressive loading, different strain rates, strains, and stresses were attained by the dry and wet composite specimens. Macroscopic and microscopic imaging was done to expose the variation in damage behavior as a function of moisture absorption. Significant property reduction as a function of moisture absorption emphasizes the need for moisture proofing and protecting the armor products from minor damages leading to sites for moisture ingress.