A new tailoring optimization approach for improving structural response and energy absorption capability of laminated and sandwich composites

Abstract

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.

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“…fibres and matrix) over the plane of the plies. It is also remarked that as shown in [Icardi and Ferrero 2008], even a rough approximation of the elastic coefficients of (19) using patches with a step variation of the orientation can be effective.…”

“…The purpose is to minimize the energy absorbed through unwanted modes (those involving interlaminar strengths) and maximize the energy absorbed through desired modes (those involving membrane strengths). This is done by finding a suited variable distribution of stiffness properties, an extension of the one developed by the authors in [Icardi and Ferrero 2008]. While this former version only dealt with an in-plane variation of properties of laminates, in the current version either a variation of the stiffness properties of the face sheets over their plane, or of the core properties across the thickness of sandwich composites are considered.…”

“…Note that in the applications, pre-existing conventional layers will be substituted with layers that either (i) minimizes bending and maximizes membrane energy, (ii) minimizes bending and maximizes transverse shear, or (iii) maximizes bending and minimizes transverse shear, because for each of these three cases a solution was found in [Icardi and Ferrero 2008] that does not make contradictory these requirements.…”

“…A recently developed optimisation technique [Icardi and Ferrero 2008] is employed for finding the appropriate spatial distribution of the stiffness properties (fibers orientation and core density) that minimize the out-of-plane stresses due to impulsive loading. It is found solving the Euler-Lagrange equations of an optimisation problem in which the absorbed energy due to out-of-plane stresses is minimised, while that due to membrane stresses is maximised.…”

An efficient reanalysis assisted optimization for variable-stiffness composite design by using path functions

“…Lemaire et al presented an optimization method for structures with curved fiber trajectories based on level-sets and a Fast Marching Method (FMM) [34]. Nowadays, various factors can be handled for the variable-stiffness composite optimization, such as rigidity [35], strength [36], thermomechanical design [37], blast pulse loading [38], energy absorption [39] and failure criteria [40].…”