Predicting Failure Loads of Impact Damaged Honeycomb Sandwich Panels

Abstract

This article examines the effect of impact damage on minimum gauge sandwich structures. This type of damage can cause panels to fail at significantly lower loads than an equivalent undamaged panel. For this reason, impact damage in sandwich structures has been a focus for numerous studies, including those that examine damage tolerance of structures and also their post-impact residual strength. This study specifically examines thin-gauge Nomex honeycomb panels and is concerned with barely visible impact damage (BVID), the type of damage that can be found on aircraft components. An overview of BVID, including an in-depth examination of the failure modes and failure loads of damaged panels is presented in this article. The study uses nonlinear finite element models to accurately predict failure loads, and understand how this type of damage causes panels to fail at reduced loads. A simplified, closed-form analytical model is developed to predict failure stresses through a complete range of damage sizes and depths. This study finishes by comparing numerical and analytical models against experimental values. Good agreement is seen in all cases for a wide variety of damage sizes.