PSI - Issue 13

Ahmed Sohail et al. / Procedia Structural Integrity 13 (2018) 1014–1019 Author name / Structural Integrity Procedia 00 (2018) 000 – 000

1018

5

Table 4. Comparison of longitudinal and transverse elastic moduli and strength for 2 nd and third configurations with first configuration Exx (GPa) Eyy (GPa) Sxx (MPa) Syy MPa) Carbon 58.6 74.5 888 1183.8 Hybrid 47.9 57.6 704.2 890 Kevlar 26.9 36 416.5 556

In terms of strength parameters, the knockdown of strength in weft direction for hybrid 3D woven composite as compared to baseline configuration is 24.2% and in the weft direction the knockdown value is 20.6 %. For Kevlar configuration the knockdown value is 53% for both weft and warp directions. It is observed from the knockdown values of the elastic moduli and strengths that they remain same and can be attributed to failure strain of all three configurations also remains the same (Fig 2).

Weft

Warp

1400

0 100 200 300 400 500 600 700 800 900 1000

Carbon Hybrid Kevlar

1200

Carbon Hybrid Kevlar

1000

800

600

400 Stress (MPa)

Stress (MPa)

200

0

0

0.005

0.01

0.015

0.02

0

0.005

0.01

0.015

0.02

Strain

Strain

Fig. 2. Stress-strain curves for all three configurations in the weft (left) and warp (right) directions

4. Conclusion

Hybrid and non-hybrid 3D woven composites consisting different types of fiber tows in terms of their material were examined numerically to determine the effect of hybridization on their tensile response. The effective stiffness and strength in tension in weft and warp directions was investigated. A meso-scale unit cell model was created to simulate the elastic response and damage behavior of the 3D woven composite. The FE model based on unit cell model of 3D woven architecture was modelled in Abaqus 6.14 with each fiber tow modelled as a transversely isotropic homogeneous composite material and the matrix modelled as an isotropic epoxy resin. At first the numerical model was validated through the experimental results presented in the available literature. Secondly the verified model was used to determine the effect of hybridization on elastic moduli and strengths of hybrid unit cell. The elastic moduli and strengths for first (Carbon) configuration studied are predicted well when compared to experimental results. The result for the elastic modulus in longitudinal (warp) direction conforms excellently with experimental data within 4% of the error. For strength in warp direction the error was less than 8%. However, in the weft direction the numerical model predicted higher values for elastic modulus and strength due the geometric approximations of the fiber tows, which can be improved by considering the near actual geometry of the fiber tows. After validating the model, two weft and one warp rows in the unit cell were replaced with Kevlar tows to carry out the analysis for hybrid material and observe the effect of hybridization. The knocking down in elastic moduli and