Hypervelocity impact on CFRP: Testing, material modelling, and numerical simulation

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 in [1]. 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 [2] 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 [1] and [3] 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.

Theoretical prediction of dynamic composite material properties for hypervelocity impact simulations

“…The calculated irreversible, non-linear damage properties of the UMS2526/Krempel BD laminate are listed in Table 7, compared to those determined experimentally in [8]. The theoreticallyderived master curve shows significantly higher effective stress values than the experimentallydetermined values as a result of the higher predicted directional strength.…”

“…where An experimental program (described in [8]) was used to characterise the properties of a spacerepresentative CFRP laminate for implementation in the advanced orthotropic composite material model. Details of the laminate are given in Table 1.…”

“…The experimental values of A2 and A3 were set to zero as it provided the best overall response with all types of planar plate impact tests performed in [8]. Hugoniot reference curves defined by the parameters in Table 5 are shown in Figure 2b.…”

“…Furthermore, recent advances [6] [7] in the modelling of composite materials provide an improvement over existing capabilities by allowing the macromechanical description of orthotropic constitutive behaviour, non-linear equation of state, orthotropic non-linear irreversible strain, and individual material plane interactive failure initiation criteria. Application of these new capabilities in modelling the hypervelocity impact of aluminium fragments on Aramid/epoxy plates [7] and aluminium projectiles on carbon fibre reinforced polymer (CFRP)/Aluminum honeycomb (HC) sandwich panels (SP) [8] has shown the ability to reproduce many of the damage phenomena observed in experiments.…”

“…[7], [8]), material data has been determined through experimental characterisation programs. As the directional performance of a fibre-reinforced polymer can be altered through composition, orientation of the constituents, and fibre packing geometry, full experimental characterisation is required for each new material configuration.…”