Influence of Water Absorption on Impact Fracture Behavior and Residual Strength after Impact of CFRP/Aramid Honeycomb Core Sandwich Panels

An investigation has been carried out concerning the influence of water absorption on the impact fracture behavior and the residual strength after impact of CFRP/Aramid honeycomb core sandwich panels. Some specimens were manufactured by a hotpress molding method and others by an autoclave one. Low velocity impact tests were conducted using a falling weight tester. When the applied impact energy was higher than the threshold one, below which no damage of honeycomb core was introduced, the percentage of the absorbed energy became large. Although the SEM observation showed the degradation of the fiber/matrix interfacial strength by water absorption, no influence of water absorption on the impact induced delamination area was observed. The residual strength after impact was evaluated by compression test and four point bending test. Due to voids and poor adhesion between facing and core materials of the hotpress specimens, the residual compressive strength of the hotpress specimen was smaller than that of the autoclave one.