Drop-Weight Impact Behaviour of Hybrid Fiber/Epoxy Honeycomb Core Sandwich Composites under Hemi-Spherical Impactor

Low velocity impact test is conducted on hybrid fiber honeycomb core sandwich panels filled with different energy absorbing materials such as Rohacell, wheat husk and polyurethane foam (PUF) using an instrumented drop-weight impact testing machine as per ASTM D3763-93 standard. Low velocity impact characteristics such as peak load, absorbed energy and damage mechanisms of the sandwich panels are investigated at 17.16 J, 25.75 J, 34.33 J and 42.91 J energy levels by varying the height of the dropping weight. Image processing technique is performed to calculate the impact damage area of the specimens using MATLAB 2016 A. To observe the damage and failure mode in the failed specimen, optical microscopic observation method is used. As increasing the impact energy, fiber fracture at face sheets, core fractures, delamination between hybrid fabric-epoxy layers and indentations failures are perceived by the visual inspection. According to the obtained results, the low velocity properties such as energy absorption capacity, load at initial damage are significantly improved and impact damage area is decreased considerably by the PUF filled core sandwich panels. Thus, this analysis puts forward that PUF filled honeycomb core sandwich panel may be a preferable material in the field of composites to overcome delamination and impact damages and to reduce the weight especially for the applications of advanced aerospace structures.