Finite element method correlation of damage tolerance tests for composite sandwich structures

In this study, damage tolerance and impact responses of a sandwich composite aircraft radome (radar dome) were determined numerically and experimentally at different energy levels. The sandwich composite was composed of MTM46® Quartz/epoxy prepreg as face-sheets and Flex-Core® Nomex® honeycomb as core material. For the experimental study, test specimens were prepared with the same face-sheet orientation/thickness and core thickness. Drop-weight impact tests were performed on the specimens while the impact energy changed from 10 J to 25 J (10 J, 15 J, 16 J, 18 J, 20 J, 22 J and 25 J). Within the scope of the study, it is aimed to determine and predict the damage tolerance for both the front and back face sheets. Therefore, initial tests were performed at 25 J energy level to see the impact response of test specimens for both sides. Afterward, experimental studies were continued with tests for other energy levels. The damaged regions of the coupons were measured by using image processing tools. Also, results such as force-time, displacement-time and force-displacement were obtained. Subsequently, the same tests were simulated via LS Dyna. During the simulations, the material properties obtained from the previous qualification tests were used. The main purpose of the study was to provide FEM simulation- experimental test correlation for impact energy, damaged area/geometry, force-time, displacement-time and force-displacement results.