Damage evolution in low velocity impacted unreinforced vinyl ester 411‐350 and 411‐C50 resin systems

Abstract Damage evolution in plaques made of vinyl ester resin systems was investigated as a function of specimen thickness, impact energy level and matrix material. Dow DERAKANE vinyl ester 411‐350 and 411‐C50 resin systems, which have low viscosity and are ideally suited for low‐cost liquid processing techniques like vacuum assisted resin transfer molding (VARTM), were considered for the low velocity instrumented impact testing. Characterization of damage evolution was undertaken using optical microscopy and analysis of impact load histories recorded during the impact event. Radial cracking, perforations at the point of impact (in the form of a truncated cone), and damage resulting from the support constraints were identified as the dominant failure characteristics in both resin systems. Radial cracking, which originated from the bottom surface, was operative in all failed specimens and was attributed to the catastrophic failure due to extensive flexural tensile strength losses. For specimens that could deflect significantly, radial cracking and support‐constraint‐induced damage were the operative failure mechanisms. Radial cracking and through‐thickness shearing led to failure in stiffer plaques. The DERAKANE 411‐350‐vinyl ester resin system was found more damage resistant than the 411‐C50 system.