C Dong I Davies/ Materials and Design 54(2014) 893-899 Constituent materials and selected properties. Tensile strength Tensile modulus S-2 glass unidirectional Unitex plain wave UT-S500 fibre mat (SP System, Newport, Isle of wight, UK) 4890 Toray T700S 12 K carbon fibre(Toray Industries Inc. Tokyo, Japan 230 Kinetix R240 high performance epoxy resin with H160 hardener at a ratio of 4: 1 by weight, as recommended by manufacturer 69.6 3.1 (ATL Composites Pty Ltd, Australia) Experiment FEA 叫 Fig. 1. FEA model for [O2c/Ocl configuration. 10 ,134293119371 -,10445 08952-,074607 ,044764 Fig. 2. Deflections from FEA Fig 4. Flexural moduli from experiments and FEA. B (3)D1 It is seen from Fig. 5 that Mo is not constant, which is zero at two For a test specimen under three point bending, the only non- ends and reaches the maximum,-FS4, at the mid-span. From Eq zero element of N and M is Mxx. Thus, Eq ( 3)becomes bend- D ing, the deflection at the mid-span is the resultant of the curvatures loped along the beam, i.e where The strain [Mx puted as: A6后6kxmx(1-3dx Eo=B,M K= D,M The flexural modulus can be calculated using Eq (1) where 2.3. Parametric study B1=-A B(D-BA B In this study, the effects of two variables, the fibre volu me irac tions of carbon/e nd glass/epoxy laminas, Vfc and Vig. were studied using Response Surface Methodology(RSM). For each var- iable. three levels were chosen as shown in table 2. in order to construct a 32 factorial design. A three-level factorial design was used to model possible curvature in the response function and to handle the case of nominal factors at 3 levels[18. For each fibre volume fraction combination, nine stacking con- ed. All the laminates were 2 mm thick and consist of 8 laminas of equal thickness, i.e. the thickness of each lamina is 0.25 mm. The stacking configurations are shown in Fig. 6. From the full carbon/epoxy laminate to the full glass/epoxy minate, the topmost lamina of the carbon/epoxy section is re- placed by a glass/epoxy lamina each time. or the purpose of characterising the degree of hybridisation the hybrid ratio is intre Th Fig 3. Flexural testing being conducted.N M   ¼ A B B D   e0 j ( ) ð3Þ For a test specimen under three point bending, the only non￾zero element of N and M is Mxx. Thus, Eq. (3) becomes: 0 M   ¼ A B B D   e0 j ( ) ð4Þ where ½M ¼ ½ Mxx 0 0 T : The strains are computed as: e0 ¼ B1M ð5aÞ j ¼ D1M ð5bÞ where, B1 ¼ A1 BðD BA1 BÞ 1 D1 ¼ ðD BA1 BÞ 1 : It is seen from Fig. 5 that Mxx is not constant, which is zero at two ends and reaches the maximum, FS/4, at the mid-span. From Eq (5b), the resulting curvature, jxx, is proportional to the moment Mxx. Since jxx ¼ @2w0 @x2 , for a test specimen under three point bend￾ing, the deflection at the mid-span is the resultant of the curvatures developed along the beam, i.e. w0 ¼ R S 0 R S 0 jxx max 1 x S  dx ¼ jxx maxS2 3 ð6Þ The flexural modulus can be calculated using Eq. (1). 2.3. Parametric study In this study, the effects of two variables, the fibre volume frac￾tions of carbon/epoxy and glass/epoxy laminas, Vfc and Vfg, were studied using Response Surface Methodology (RSM). For each var￾iable, three levels were chosen, as shown in Table 2, in order to construct a 32 factorial design. A three-level factorial design was used to model possible curvature in the response function and to handle the case of nominal factors at 3 levels [18]. For each fibre volume fraction combination, nine stacking con- figurations were studied. All the laminates were 2 mm thick and consist of 8 laminas of equal thickness, i.e. the thickness of each lamina is 0.25 mm. The stacking configurations are shown in Fig. 6. From the full carbon/epoxy laminate to the full glass/epoxy laminate, the topmost lamina of the carbon/epoxy section is re￾placed by a glass/epoxy lamina each time. For the purpose of characterising the degree of hybridisation, the hybrid ratio is introduced, which is defined as: rh ¼ 1 1 þ hfcVfc hfgVfg ð7Þ Table 1 Constituent materials and selected properties. Material Tensile strength (MPa) Tensile modulus (GPa) S-2 glass unidirectional Unitex plain wave UT-S500 fibre mat (SP System, Newport, Isle of Wight, UK) 4890 86.9 Toray T700S 12 K carbon fibre (Toray Industries Inc., Tokyo, Japan) 4900 230 Kinetix R240 high performance epoxy resin with H160 hardener at a ratio of 4:1 by weight, as recommended by manufacturer (ATL Composites Pty Ltd., Australia) 69.6 3.1 Fig. 1. FEA model for [02G/03C] configuration. Fig. 2. Deflections from FEA. Fig. 3. Flexural testing being conducted. Fig. 4. Flexural moduli from experiments and FEA. C. Dong, I.J. Davies / Materials and Design 54 (2014) 893–899 895