PSI - Issue 28

8

KHODJET KESBA Mohamed/ Structural Integrity Procedia 00 (2019) 000–000

Mohamed Khodjet Kesba et al. / Procedia Structural Integrity 28 (2020) 864–872

871

1,00

0,95

 = 45°

0,90

0,85

 = 30°

E x(i) /E x0(i)

0,80

 = 15°

T=22°C T=60°C T=120°C

0,75

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0 0,70

Crack density (1/mm) Fig. 5. Stiffness reduction as a function of crack density for a [0/β 3 ] s graphite/epoxy (T300/5208) laminate with different fibre angle β° in the inner layer. When the inner layer are different to 90° and submitted to hygrothermal effect (Fig. 5), we note that the stiffness is reduced with transverse crack density and deceasing of fibre angle orientation β in the inner layers. The results show also the influence of hygrothermal effect on the stiffness degradation with the variation of the temperature. Finally, the hygrothermal condition has more effect in the stiffness reduction when the cracked layers are different than 90° (Rezoug et al. 2011, Khodjet et al. 2015). 4. Conclusion The stiffness reduction was predicted using simple analytical models for the off-axis ply [0 m /β n ] s composite laminates under uniaxial tension. The results show good agreement between prediction models and experimental data. On the other hand, the material properties are considered to be dependent on temperature and moisture concentration, which are given explicitly in terms of the fibre and matrix properties and fibre volume ratio. The solution methodology is general in nature and may be applicable to the analysis of other types of environmental condition, e.g. including the hygrothermal coupling in the governing equation. The results show that the reduction of stiffness on the off-axis composite laminates largely depend on the crack density, fibre orientation angle of the inner and outer layers, matrix diffusivity in desorption case and operational temperature. Benkhedda A, Tounsi A, Adda bedia E.A., 2008, Effect of temperature and humidity on transient hygrothermal stress during moisture desorption in laminated composite plates. Composite Structure, 82. 629-635. Berthelot, J.M., 1997. Analysis of the transverse cracking of cross-laminates: a generalized approach. J. Compos. Mater. 31. 1780–1805. Katerelos, D.T.G., Kashtalyan, M., Soutis, C., Galiotis, C. 2008, Matrix cracking in polymeric composites laminates: Modelling and experiments. Composites Science and Technology, 68.2310-2317. Khodjet-kesba M, AddaBedia EA, Benkhedda A, Boukert B., 2016. Prediction of Poisson’s ratio degradation in hygrothermal aged and cracked [θm/90n]s composite laminates. Ste.& Comp. Struc. 21. 57-72. Khodjet-kesba M, AddaBedia EA, Benkhedda A, Boukert B., 2015. Hygrothermal effect in [θm/90n]s cracked composite laminates-desorption case. Pro. Eng. 114. 110-117. Rezoug T., Benkhedda A., Khodjet-Kesba M., Adda bedia E.A., 2011, Analysis of the composite patches cracked and aged in hygrothermal conditions. Mechanics and industry, 12.395-398. Shen, C.H. and Springer, G.S. 1981, Moisture absorption and desorption of composite materials. Environmental effects on composites materials, ed. G.S. Springer, Technomic Publishing Co., Lancaster, PA. References