A Consistent Engineering Methodology for the Treatment of Impact in Composite Materials

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Abstract
An approach is formulated to treat the behavior of composites subjected to impact as the sequential effect of a number of events. The sequence for the analysis of im pact presented here is as follows. First, a global analysis of impact of the structure is con ducted. In this study, a plate is analyzed in a time marching scheme to properly account for nonlinearities during the impact event. This provides loads introduced into the struc ture during impact. These loads are then introduced into a local deformation and strain re sponse model just below the impactor to refine the analysis in the local region where damage occurs. Damage is predicted in the laminate on a ply-by-ply basis. Excellent agreement between the models and test data taken during the impact event is found. This is denoted as the Damage Resistance portion of the problem. Given the pre-existing damage, an analysis of the damaged structure is conducted. This entails using an average strain criterion for fiber-dominated fracture around the damage and a sublaminate buck ling analysis for compression loading. Good agreement is found between the analysis and experimental data. This is denoted as the Damage Tolerance portion of the problem. Finally, all of the models are combined to provide combined Damage Resistance/Damage Tolerance curves for useful design data.