Abstract
The room temperature impact response of DERAKANE 411-350 and 411-C50 vinyl ester (VE) unreinforced resin systems has been investigated as a function of impact energy level, sample thickness, matrix material and catalyst system. The response of unreinforced resin plaques to impact loading was investigated using the impact load histories, impact plots and fractography analysis. The maximum load or peak contact force, energy-to-maximum load, total energy and deflection-at-maximum load increased in a nearly parabolic manner with an increase in impact energy level, whereas time-to-maximum load or impact duration at the peak load decreased linearly. Total energy-to-impact energy ratio, i.e. the non-dimensional energy plots, changed in a step-wise manner with impact energy. The slope of the load-deflection (load-time) traces, which is related to the impact modulus or relative stiffness of the material, increased with impact energy level and sample thickness. The change of slope with impact energy level and sample thickness indicated the dependence of impact modulus on the impact energy level and target geometry. The threshold impact energy levels, which were associated with the onset of catastrophic matrix failure and extensive tensile strength losses, were identified from the impact plots. Multiple radial cracking, perforations in the form of a truncated cone at the point of impact and damage resulting from the supports were identified as the dominant failure characteristics in both resin systems. The DERAKANE 411-350-vinyl ester resin system was found more damage resistant than the 411-C50 system. The impact response and the failure characteristics were insensitive to the catalyst system.