Mechanical modelling of solid woven fabric composites 87 the constants F and W refer to the number of weft and warp yarns in the unit cell: kBCm[ABCmn][SBCmI ABCmn] [3.4 Basically,the four-step procedure defined in the foregoing will result directly in the computation of the overall symmetric 3-D compliance matrix of the woven fabric composite unit cell.Moreover,a direct link is estab- lished between the average unit cell stress and the cell stresses at each geo- metric level.This most important result will serve as a solid basis for further strength modelling in the next section. In conclusion,Fig.3.10 and 3.11 present a benchmark parametric study for a glass/epoxy plain weave fabric composite.The analytical model yields elastic moduli predictions comparable to those obtained by 3-D finite element modelling.This fact is put forward as an indication of the appro- 1s60t priateness of the present multilevel,multistep technique. 3.3.5 Conclusion The ability to specify the woven fabric geometry gives the designer control 2102 over the composite material.Many of the properties that influence how a composite can be used are determined by the 'averaged'behaviours of the fibres and the matrix.The'averaged'stiffness properties are shaped by the internal yarn distribution,i.e.yarn orientation and position.With CEM,we now have a fast and efficient tool to predict the effect of each geometric 30 25 20 sninpow 15 s,buno 10 0 40 5060708090123456780.2 0.4 0.6 E fibre(GPa) E resin(GPa) Fibre Fraction V 3.10 Predicted Young's moduli for the benchmark composite: comparing results from an FEM study [24]and our CEM calculations (material:glass-epoxy plain weave).▲Ex=Ev(CEM):●E.(CEM);△Ex =Ey(FEM);O E,(FEM).the constants F and W refer to the number of weft and warp yarns in the unit cell: [3.4] Basically, the four-step procedure defined in the foregoing will result directly in the computation of the overall symmetric 3-D compliance matrix of the woven fabric composite unit cell. Moreover, a direct link is estab￾lished between the average unit cell stress and the cell stresses at each geo￾metric level.This most important result will serve as a solid basis for further strength modelling in the next section. In conclusion, Fig. 3.10 and 3.11 present a benchmark parametric study for a glass/epoxy plain weave fabric composite. The analytical model yields elastic moduli predictions comparable to those obtained by 3-D finite element modelling. This fact is put forward as an indication of the appro￾priateness of the present multilevel, multistep technique. 3.3.5 Conclusion The ability to specify the woven fabric geometry gives the designer control over the composite material. Many of the properties that influence how a composite can be used are determined by the ‘averaged’ behaviours of the fibres and the matrix. The ‘averaged’ stiffness properties are shaped by the internal yarn distribution, i.e. yarn orientation and position. With CEM, we now have a fast and efficient tool to predict the effect of each geometric S kA S A m F n W UC BC BC mn mn mn mn T [ ] = [ ] [ ][ ] BC BC = = ÂÂ1 1 Mechanical modelling of solid woven fabric composites 87 3.10 Predicted Young’s moduli for the benchmark composite: comparing results from an FEM study [24] and our CEM calculations (material: glass-epoxy plain weave).
Ex = Ey (CEM); Ez (CEM); Ex = Ey (FEM);  Ez (FEM). RIC3 7/10/99 7:37 PM Page 87 Copyrighted Material downloaded from Woodhead Publishing Online Delivered by http://woodhead.metapress.com Hong Kong Polytechnic University (714-57-975) Saturday, January 22, 2011 12:30:11 AM IP Address: 158.132.122.9