The impact response of thin metal plates and lightweight sandwich panels with metallic fibre cores

This body of work has sought to investigate the capacity of sandwich panels containing networks of sintered fibres in the core, to absorb energy when struck at normal incidence by spherical projectiles. Experimental impact tests have been conducted on sandwich panels and monolithic steel plates, over a large range of impact velocity – 80 ≤ V, ≤ 600 m s-1. The absorbed energies have been calculated from measured incident and residual velocities. The experimental impact tests were then simulated using the explicit finite element code in ABAQUS/CAE. Single faceplate FE models and full sandwich panel models were developed. The faceplates were modelled as isotropic, strain and strain-rate dependent shells, using the constitutive plasticity models of Johnson and Cook and von-Mises. Failure of the faceplates was simulated using a strain rate-dependent, critical plastic strain fracture model. In the sandwich panel model, core material plasticity was modelled using a VUMAT sub-routine. The sub-routine considered the plastic compression of an anisotropic crushable continuum. Failure of the core material was simulated using a quadratic shear stress failure criterion. Experimental tests and numerical simulations on single faceplates indicate a transition in material behaviour for strain rates exceeding ~104 s-1. This has been interpreted as a transition in the rate-hardening mechanism from conventional dislocation effects to dislocation-drag phenomena. Minimum perforation energies are closely predicted by the empirical model of Hill, whilst a modified version of the analytical model of Teng and Wierzbicki exhibits close agreement with experimental data at high impact velocities. The numerical model successfully predicts the plastic strain fields and failure modes over the experimental velocity range.EThOS - Electronic Theses Online ServiceGBUnited Kingdo