Experimental and numerical impact behavior of fully carbon fiber sandwiches for different core types

The aim of this study is to experimentally and numerically examine the impact strength and damage mechanisms of sandwich composites consisting entirely of fiber-reinforced composites for different core geometries. For this purpose, firstly, composite sandwich plates with egg box, lattice and square plate core structures were produced. Low-velocity impact tests were carried out by dropping impactors with hemispherical geometry onto the resulting sandwich structure with three different core geometries, and the effect of the core shape on impact strength was determined. For comparison, the cell width and height of these three different types of core were chosen to be similar. In addition, progressive damage analysis with the finite element method was applied. For this purpose, the MAT-162 material model, which provides three-dimensional progressive damage analysis in composite materials and applies the Hashin damage criterion, was preferred to be used in the LS-DYNA^® program. When specific loads are compared using a square core specimen under the same conditions, it can be said that the contact force of the egg box structure is higher. While the striker rebounded from the square core at the same impact energy, it perforated the sandwich structure in the egg box and completely damaged the lattice core structure.