Predicting the Effects of Dent Size on the Stress in Aluminum Honeycomb Aircraft Panels Subject to Low-Velocity Impact Damage

Abstract

Aluminum honeycomb sandwich structures are commonplace in aerospace applications due to their high in-plane strength and bending stiffness-to-weight ratio. A disadvantage of these structures is that they are susceptible to indentation from tool drops, hail, and runway debris occurring during maintenance, taxiing, or takeoff due to their poor out-of-plane resistance to deformation. Current literature states that impact damage can result in significant losses in residual strength, but studies featuring dented metal panels subjected to fatigue loading, tension, and bending are lacking. Furthermore, there are no comprehensive studies that identify the primary damage characteristics affecting the residual strength of metallic sandwich panels. The current work presents a method for predicting post-impact face sheet stresses for a panel loaded in tension using finite element (FE) modelling. Specifically, a two-stage loading simulation consisting of a dynamic impact event followed by an applied tensile load was used for determining the effects of dent diameter and depth on the increases in stress in the dented region of the impacted face sheet. It was determined that it was the degree of core damage associated with the dent and not the dent geometry specifically that had an effect on the face sheet stresses in tension. Material failure in the damaged core caused the tensile load to pass through the dented face sheet rather than the core, resulting in a larger percent increase in stress versus a panel with less core damage.