A model to predict low-velocity impact response and damage in sandwich composites

Composite sandwich structures are susceptible to low-velocity impact damage, but existing elastic impact models cease to be valid after the onset of damage. In this paper, a modified energy-balance model coupled with the law of conservation of momentum is proposed to extend its validity beyond the elastic regime. Three parameters were first derived from the static load-deformation response: the elastic stiffness, the critical load at the onset of damage, and the damaged stiffness. These parameters were then used in the impact model to predict transient load and deflection histories for the plate subjected to impact. A three-dimensional finite element model was also developed to analyse the static indentation problem, and core damage was identified to be one of the damage mechanisms at initial failure. By accounting for the elastic energies absorbed by the plate up to initial failure in the core, the critical load was found to be theoretically predictable. Numerical predictions compared well with experimental results. (c) 2007 Elsevier Ltd. All rights reserved.