Analysis of Shockwave Tolerant Features for Small-Volume Composite Rotorcraft Structure

The capability for candidate shockwave tolerant features to contribute to shockwave attenuation and residual structural integrity of small-volume rotorcraft structures was evaluated in this study. To first understand the shockwave reflection and transmission effects of an explosive event on small-volume enclosed geometry, Finite Element Analysis (FEA) was performed to assess the relationship between the enclosed volume and explosive energy. The FEA techniques included a fluid dynamics based Arbitrary Lagrangian Eulerian (ALE) method as well as an empirically based method. With an understanding of the pressure environment, analysis was then performed to compare the structural response of representative structure with and without shockwave tolerant features. The shockwave tolerant features identified for this study can be classified as attenuating and reinforcing. Attenuating shockwave tolerant features include sandwich structures while reinforcing features include stitched composites, hybrid laminates, tailored ply orientations, and out-of-plane features. Finally, the paper concludes with discussion of a planned small-volume composite test program to validate the analytical findings and demonstrate the benefits of the shockwave tolerant features.