In this paper a technique for tuning the energy absorption properties of laminated
and sandwich composites through a new tailoring concept is presented. The purpose
is to minimize the energy absorbed through unwanted modes (ones involving
interlaminar strengths) and maximize that absorbed through desired modes (ones
involving membrane strengths) by finding a suited in-plane variable distribution of
stiffness properties. Herein mode is intended as a strain energy contribution, such as
bending energy, in-plane and out-of-plane shear energy, etc., and no vibration mode.
This distribution is obtained making extremal certain strain energy contributions of
interest (for example, membrane, bending, in-plane, and out-of-plane shear energies)
under in-plane variation of the plate stiffness properties. The effect of this technique
is to act as an energy absorption tuning, since it minimizes or maximizes
the amount of energy absorbed by specific modes. Although the present
technique could be applied to laminates or to the face sheets of sandwich
composites, in this paper a preliminary application is presented to single plies
with variable stiffness coefficients over their plane. Once incorporated into a
laminate or a sandwich composite, these layers are shown to have beneficial
effects on the strength at the onset of delamination in sample cases where
laminated and sandwich composites are subjected to low velocity, low energy
impacts.
This paper is dedicated to the memory
of Liviu Librescu.
Keywords
optimization of laminated and sandwich composites, impact
induced damage, delamination