Preface

Abstract

This paper describes the derivation and validation of a numerical material model that predicts the highly dynamic behaviour of CFRP (carbon fibre reinforced plastic) under hypervelocity impact. CFRP is widely used in satellites as face sheet material in CFRP-Al/HC sandwich structures (HC = honeycomb) that can be exposed to space debris. A review of CFRP-Al/HC structures typically used in space was performed. Based on this review, a representative structure in terms of materials and geometry was selected for study in the work described here. An experimental procedure for the characterisation of composite materials is documented by Riedel et al. [ADAMMO – advanced material damage models for numerical simulation codes. ESA CR(P) 4397, EMI report I 75/03, Freiburg; October 31, 2003.]. The test results from the CFRP of the current study allow for the derivation of an experimentally based orthotropic continuum material model data set that is capable of predicting the mechanical behaviour of CFRP under hypervelocity impact. Such a data set was not previously available. In the work by Riedel et al. [Hypervelocity impact damage prediction in composites: part II – experimental investigations and simulations. International Journal of Impact Engineering, 2006;33:670–80.] an orthotropic material data set was used for modelling HVI on AFRP (aramid fibre reinforced plastic), which shows relatively high deformability before failure. The enhancements of the modelling approaches in previous studies [Riedel W, Harwick W, White DM, Clegg RA. ADAMMO – advanced material damage models for numerical simulation codes. ESA CR(P) 4397, EMI report I 75/03, Freiburg; October 31, 2003. Hiermaier S, Riedel W, Hayhurst C, Clegg RA, Wentzel C. AMMHIS – advanced material models for hypervelocity impact simulations. Final report, EMI report E 43/98, ESA CR(P) 4305, Freiburg; July 30, 1999.] necessary to model brittle CFRP are specified. An experimental hypervelocity impact campaign was performed at two different two-stage light gas guns which encompassed both normal and oblique impacts for a range of impact velocities and projectile diameters. Validation of the numerical model is provided through comparison with the experimental results. For that purpose measurements of the visible damage of the face sheets and of the HC core are conducted. In addition, the numerically predicted damage within the CFRP is compared to the delamination areas found in ultrasonic scans.