Numerical modeling of impact-damaged sandwich composites subjected to compression-after-impact loading

Semi-empirical numerical models are developed for predicting the residual strength of impact-damaged sandwich composites comprised of woven fabric carbon epoxy facesheets and Nomex honeycomb cores subjected to compression-after-impact loading. Results from non-destructive inspection and destructive sectioning of damaged sandwich panels are used to establish initial conditions for damage (residual facesheet indentation, core crush dimensions, etc.) in the numerical analyses. Honeycomb core crush test results are used to establish the non-linear constitutive behavior for the Nomex core. The influence of facesheet property degradation on the strain redistribution in damaged sandwich panels is examined. Facesheet strains from material and geometric nonlinear finite element analyses correlate relatively well with experimentally determined values. Moreover, numerical predictions of residual strength are consistent with experimental observations. Similar calculations may prove useful in the development of a damage tolerance plan for sandwich composites that accounts for relevant details of damage morphology and provide conservative estimates of residual strength. (C) 2003 Elsevier Science Ltd. All rights reserved.