Research On Buckling Behavior And Scattering Of Composite Laminated Plates Under Hygrothermal Environment

Composite Structures are often served in terrible environment, such as rapid temperature change, moist outside space, internal stress and their coupling interaction, which can weaken the mechanical properties, influence the safety and reduce the service life. In addition, the structures made of composite materials have more randomness and variability in the system properties compared to conventional isotropic structures as a large number of parameters are involved with their fabrication and manufacturing processes. Some variations of system parameters are inevitable even for the composite laminates. Uncertainties in system parameters lead to uncertainties in the response behavior of the structure, which can reduce the reliability and limit the application and development of composite laminates. In present paper, several aspects are investigated in the following:1. The present research on the buckling behavior and scattering of composite laminated plates under hygrothermal environment are summarized.2. Based on the classical Von Karman lamination theory in conjunction with the Hamilton’s principle, the governing equations of composite laminated plates under uniform and non-uniform temperature distributions are derived. The critical thermal buckling temperature under uniform and non-uniform temperature distributions were worked out by using MATLAB software. The effects of boundary conditions and laying angles on critical thermal buckling temperature under uniform temperature distributions are investigated. Furthermore, the effects of heat source positions and vibration modes on critical thermal buckling temperature under non-uniform temperature distributions are also analyzed. Numerical results obtained by ANSYS were consistent with that by MATLAB software.3. The governing equations about in-plane critical buckling loads are derived by considering the coupling interaction of temperature and humidity. The correctness of the natural frequencies and in-plane buckling loads are checked with the cases studied by references, therefore the validities of the present analytical method and program are well established. Firstly, the effect of non-uniform hygrothermal distributions on critical buckling humidity and in-plane buckling loads of laminated plates under different boundary conditions are discussed. Secondly, the effect of different hygrothermal distribution situations on critical buckling humidity and in-plane buckling loads are also discussed.4. The governing equations for the mean thermal buckling temperature are deduced from the point view of micro mechanics of the composite materials, moreover, the scattering in thermal buckling temperature are worked out based on first order perturbation technique. The correctness of the mean natural frequencies and the SD/mean of natural frequencies obtained by present MATLAB programs are validated against available results.5. System parameters, such as material properties, thermal expansion coefficients, fiber volume fractions and laying angels, are assumed as independent random variables. A mean-centered first order perturbation technique is used to compute the second-order statistics(mean and standard deviation) of the thermal buckling temperature of TID and TD plates. Some useful discussion was carried out. Firstly, the effect of aspect ratios, laying angels and boundary conditions on the mean thermal buckling temperature are presented. Secondly, the effect of fiber elastic modulus, matrix elastic modulus, fiber volume fraction, fiber thermal expansion coefficients and matrix thermal expansion coefficient on the thermal buckling temperature scattering are investigated. Thirdly, when laying angels are modeled as independent random variables, the effect of the outside layers and inside layers on the buckling temperature scattering for angle-ply [θ/θ/θ/θ] laminated composite plates are analyzed. Finally, the effect of SSSS, CSCS and CCCC boundary conditions on thermal buckling temperature scattering for angle-ply [0/θ/θ/0] laminated composite square plates are discussed, what’s more, the major factors about influencing thermal buckling temperature scattering are concluded.6. All of the numerical results obtained by the present solution approach are validated with those obtained by independent Monte-Carlo simulation about the problem of thermal buckling temperature scattering.