The room temperature impact response of DERAKANE 411-350 vinyl ester neat resin system (unreinforced matrix) has been investigated as a function of sample thickness and impact energy level. Vinyl ester resins are of interest in ballistic applications such as in armored vehicles. The response of neat resin to impact loading was investigated using the impact load histories (load-time and load-deflection traces), impact plots and fractography analysis. The maximum load or peak contact force, energy to maximum load, total energy and deflection at maximum load were found to increase in a nearly parabolic manner with 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 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 support induced damage were identified as the dominant failure characteristics.

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