Low Velocity Bird-Like Impact Behavior on Honeycomb Composite Structure

Abstract

Composite materials are widely used in primary aerospace structures such as wing components and fuselage panels; however, their major disadvantage is their vulnerability to transverse impact loads that can lead to internal delamination and fiber/matrix separation. In this study, the effect of a low-velocity impact which simulates bird impact on a honeycomb sandwich composite plates produced by a co-curing technique for a typical unmanned air vehicle (UAV) was studied both experimentally and numerically. The surface plates of the composite samples were produced from carbon fiber/epoxy prepreg material. Nomex honeycomb core material was used to make the composite sandwich structure via an autoclave process. For the bird-like impact test, the tip of the impactor was coated with thick, tough rubber to simulate a bird strike; the diameter of the impactor was 25 mm to ensure similarity with a bird called Pica nuttalli (magpie), which has a mass of 155 g and is the closest bird body to the simulations. Three different predetermined impact scenarios with kinetic energy 380 Joule, 276 Joule, and 224 Joule were applied to the samples with rubber impactors of similar density, to simulate bird impact events with different impact directions. The impact behavior was characterized by velocity-time, force-time, and displacement-time graphs. Different levels of damage were observed in the composite samples, but none of the sandwich test samples were perforated, and it could therefore be concluded that the unmanned air vehicle could land without risk to flight safety. Ultrasound, digital microscope, and tap inspections have been applied for test samples to determine damage area size and types. This low-velocity bird-like impact was also modeled and analyzed using Ansys numerical program to verify the results, and it was concluded that the verified model could also be used for the preliminary design verification of dynamic bird-impact tests within the 10% sensitivity range.