tailieunhanh - Hygroscopically induced residual stresses in composite laminates

In this paper the exact moisture concentration function m(z, t) is used to compute the hygroscopic residual stresses in laminated composites. The governing equations were established by using a full higher-order displacement theory. Hygroscopically induced residual stresses in thick graphite-epoxy composite laminates: Cross-ply [0/90] 8 based on this approach were compared with those obtained by assumption: the moisture concentration m is a constant in all plies through the laminates thickness. | Vietnam Journal of Mechanics, NCST of Vietnam Vol. 23, 2001, No 3 (173 - 182) HYGROSCOPICALLY INDUCED RESIDUAL STRESSES IN COMPOSITE LAMINATES TRAN lCH THINH*, NGO NHU KHOA** ** * Hanoi University of Technology Thainguyen Industrial and Technical University ABSTRACT. In this paper the exact moisture concentration function m(z, t) is used to compute the hygroscopic residual stresses in laminated composites. The governing equations were established by using a full higher-order displacement theory. Hygroscopically induced residual stresses in thick graphite-epoxy composite laminates: Cross-ply [0/90] 8 based on this approach were compared with those obtained by assumption: the moisture concentration m is a constant in all plies through the laminates thickness. 1. Introduction When an organic matrix composite is exposed to humid air or to a liquid, the moisture content of the material may change with time. These changes, in turn, affect the decrease in performance of materials [l]. To utilise the full potential of composite materials and structures, their response to hygroscopic environment must be known. Investigations of such problems have been performed by Pipes, Vinson and Chou [1, 2). Ootao et al [3] have used the Laplace transform, method of separation of variables with the classical laminated plate theory to asses the transient stress fields in multilayered anisotropic, laminated slabs. An interesting approach has been recently presented by Benkeddad [4] for the transient absorption of moisture in thin laminated plates. Each ply is divided into "supplies" and the exact moisture concentration distribution is approached by linear segments, thank to a finite difference method. Paul and Vautrin [5] studied hygrothermal stresses in thick laminated cylinders by analytical method, the moisture distribution is approached through a finite difference method. The classical laminated theories are probably the most dominant mainly because they have produced satisfactory