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

Damage evolution in plaques made of vinyl ester resin systems was investiga ted as a function of specimen thickness, impact energy level and matrix mat erial. Dow DERAKANE vinyl ester 411-350 and 411-C50 resin systems, which ha ve low viscosity and are ideally suited for low-cast liquid processing tech niques like vacuum assisted resin transfer molding (VARTM), were considered for the low velocity instrumented impact testing. Characterization of dama ge evolution was undertaken using optical microscopy and analysis of impact load histories recorded during the Impact event. Radial cracking, perforat ions at the point of impact (in the form of a truncated cone), and damage r esulting from the support constraints were identified as the dominant failu re characteristics in both resin systems. Radial cracking, which originated from the bottom surface, was operative in all failed specimens and was att ributed to the, catastrophic failure due to extensive flexural tensile stre ngth losses, For specimens that could deflect significantly, radial crackin g and support-constraint-induced damage were the operative failure mechanis ms, Radial cracking and through-thickness shearing led to failure in stiffe r plaques, The DERAKANE 411-350-vinyl ester resin system was found more dam age resistant than the 4-11-C50 system.