Impact damage resistance of sandwich structure subjected to low velocity impact

The paper aims at evaluating the damage resistance of sandwich structure, composed of Nomex® honeycomb core (thickness: 10 mm and 20 mm) and two kinds of facesheets (carbon/epoxy and glass/epoxy laminates) subjected to low velocity impact. The impact tests are performed using the instrumented impact-testing machine and resulting impact damages are inspected by scanning acoustic microscope (SAM). Based on the force and energy histories, six parameters have been introduced as following: load at incipient damage, energy absorbed at incipient load, maximum load, total energy absorbed during impact, plastic energy absorbed by damage, and impact damage area. The impact resistance of the sandwich structure is greatly influenced by the facesheet type and core thickness. And their impact damages are mainly delamination in the facesheets, which is peanut-shaped with major axis along their lower fiber orientation, and their behavior is dependent on the facesheets.