Use of the polar method to predict the hygroscopic transient stresses for balanced [θ/−θ] nS laminates under asymmetrical environmental loadings

This paper presents an analytical method to assess the transient hygroscopic stresses in laminated composite plates due to asymmetrical constant environmental conditions. The developed method permits us to determine directly the values of such stresses without the calculation of the moisture concentration through laminated plates. The present method is the extension of the method developed by Tounsi and Adda-Bedia [Tounsi, A., Adda-Bedia, E.A.: Appl Compos Mater 10, 1–18 (2003)] which is limited only to the problems with symmetrical environmental conditions. Thus by the present method, we can study the effect of symmetrical and asymmetrical environmental conditions. A validation was made with the results of the same authors [Tounsi, A., Adda-Bedia, E.A.: Appl Compos Mater 10, 1–18 (2003); Sereir, Z., et al.: J. Thermal Stres. 28(9), 889–910 (2005)] for symmetrical environmental conditions and the results of benkeddad [Benkeddad, A., et al.: Compos. Struct. 30(2), 201–215 (1995)] for asymmetrical environmental conditions. In order to evaluate the performances of each balanced [θ/−θ]S laminate proposed for this applications, we use the polar method introduced by Verchery [Vannucci, P., Verchery, G.: Int. J. Solids Struct. 38, 9281–9294 (2001), Vincenti, A., et al.: Composites: Part A, 1525–1532 (2001), Valot, E., et al.: Compos. Struct. 60, 413–429 (2003), Vannucci, P., Verchery, G.: Compos. Sci. Technol. 61, 1465–1473 (2001)]. This method enables us to locate the favourite directions of the mechanical characteristics and to estimate the degree of anisotropy of all stacking sequences. Therefore, we can reduce the transient hygroscopic stresses, particularly at the edges of laminated plates. Through this theoretical study presented here, we hope to contribute to the understanding of hygrothermal behaviour of composite laminated plates.