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Computational Methods for Debonding in Composites

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11 Prediction of Mechanical Properties of Composite Materials by AEH 233<br />

11.5 Numerical Applications<br />

One of the ma<strong>in</strong> objectives of this work is to validate both the use of the asymptotic<br />

expansion homogenisation method and the use of unstructured f<strong>in</strong>ite element<br />

meshes. The AEH is applied to the prediction of the mechanical properties of composite<br />

materials with cont<strong>in</strong>uous fibre re<strong>in</strong><strong>for</strong>cement. The results are obta<strong>in</strong>ed <strong>for</strong><br />

structured and unstructured f<strong>in</strong>ite element meshes and compared with analytical and<br />

experimental results <strong>in</strong> order to validate the implemented procedures. The authors<br />

start by evaluat<strong>in</strong>g the applicability of the use of unstructured tetrahedral f<strong>in</strong>ite element<br />

meshes with<strong>in</strong> the AEH method. The cont<strong>in</strong>uous parallel fibre re<strong>in</strong><strong>for</strong>cement<br />

composite material studied is schematically illustrated <strong>in</strong> Fig. 11.6, along with the<br />

adopted RUC. The composite material is made of an alum<strong>in</strong>ium (Al) matrix and<br />

boron (B) re<strong>in</strong><strong>for</strong>cement. The mechanical properties of these materials are listed<br />

<strong>in</strong> Table 11.1 [12]. The homogenised elastic properties of the composite material<br />

are calculated <strong>for</strong> a re<strong>in</strong><strong>for</strong>cement volume fraction fr = 47%. Several numerical<br />

simulations are done us<strong>in</strong>g two types of f<strong>in</strong>ite element: (i) l<strong>in</strong>ear tetrahedra and<br />

(ii) l<strong>in</strong>ear hexahedra. For each f<strong>in</strong>ite element type, the authors per<strong>for</strong>med a convergence<br />

analysis [16] <strong>for</strong> the homogenised elasticity matrix D h that results from<br />

the homogenisation procedure applied to the representative unit-cell (see Fig. 11.6).<br />

Six different mesh ref<strong>in</strong>ement levels were considered <strong>for</strong> each f<strong>in</strong>ite element type.<br />

Numerical simulation results show that the homogenised elasticity matrices D h<br />

are orthotropic. The orthotropic character of the composite material lies on the<br />

(a) (b)<br />

Fig. 11.6 Schematic representation of (a) the cont<strong>in</strong>uous parallel fibre re<strong>in</strong><strong>for</strong>cement composite<br />

material and (b) the adopted representative unit-cell<br />

Table 11.1 Elastic properties of the matrix (m) and re<strong>in</strong><strong>for</strong>cement (r) materials of the alum<strong>in</strong>ium<br />

matrix composite re<strong>in</strong><strong>for</strong>ced with boron fibres<br />

Property Value<br />

Matrix elastic modulus, Em [GPa] 68.3<br />

Matrix Poisson coefficient, νm [-] 0.3<br />

Re<strong>in</strong><strong>for</strong>cement elastic modulus, Er [GPa] 379.3<br />

Re<strong>in</strong><strong>for</strong>cement Poisson coefficient, νr [-] 0.1

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