Design & Optimization of Composites Skin-stringer Panels Subjected to Barely Visible Impact Damage (BVID) to Accelerate Innovation in Aerospace
D. Goyal, Dassault Systèmes SIMULIAIn the past two decades, air traffic growth has been impressive and is expected to strongly increase in forthcoming years. Today, composite materials are being increasingly deployed in primary structures of large commercial aircrafts, small business jets and military airplanes. The increased use of composite materials is due to their superior strength to weight ratio resulting in potentially lower operational costs as compared to the metal materials traditionally used without compromising flight worthiness. However, multiphase material complexity, anisotropy, damage initiation and progression under different modes make it harder to predict the behavior of composites. To meet certification requirements set up by federal aviation regulatory bodies such as the Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA), aircrafts need to be designed for damage tolerance under different categories of potential damages such as Bird Strike, Hail Damage, Blade-off & Barely Visible Impact Damage (BVID) etc. Physical testing for various combinations of composite ply lay-ups, geometries, material variability & damage scenarios is cost prohibitive and unsustainable. This research addresses the design and optimization of composites skin stringer panels under BVID. Critical CAD and experimental data was provided by an aircraft OEM. The automated workflow developed can potentially save millions of dollars in testing & engineering time and can also be extended to address other types of aircraft structural design needs. In this work, load carrying capacity of aerospace skin-stringer structural panels made of composites is compared before and after barely visible impact damage. This information can potentially be used for regulatory certification. Panel buckling loads, failure loads as well as panel buckling strains and failure strains are predicted. This information can be used for efficient design predictions. Whether BVID also shifts the panel failure modes from symmetric to unsymmetric is also investigated. Both thick and thin panels are simulated to understand if there are any differences in their failure behaviors. This can help designers to rule out some panel thicknesses from design considerations. A design of experiments approach using simulations was used to identify the best and worst designs.