The present study deals with both experimental and numerical investigation on the free vibration behavior of laminated composite plates subjected to varying temperature and moisture. A simple laminated plate model is developed for the vibration of composite plates subjected to hygrothermal loading. A computer program based on finite element method in the MATLAB environment is developed to perform all necessary computations. The woven fiber glass/epoxy specimens were hygrothermally conditioned in a humidity cabinet where the conditions were maintained at temperatures of 300–425 K and relative humidity ranging from 0% to 1.0% for moisture concentrations. Quantitative results are presented to show the effects of geometry, material and lamination parameters of woven fiber laminate on the free vibration of composite plates for different temperature and moisture concentrations. The numerical and experimental results show that there is reduction in natural frequency in Hz with the increase in temperature and moisture concentration for laminates with simply supported and clamped boundary conditions with different aspect ratio and side-to-thickness ratios.

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Q. Pan, and M. RathThe production of unidirectionaUy fiber-reinforced composites (tapes) consisting of high-strength~high-modulus UHMWPE fibers and LDPE matrix is described. Two production techniques are applied: impregnation by aqueous powder dispersion and dry powder impregnation. The produced composites exhibit excellent mechanical properties. Depending on the fiber volume content which can be obtained: tensile strength (in fiber direction) 460-1100 MPa, elastic modulus 11-22 GPa, and elongation at break 4.9-8.3%. Powder Impregnation ProcessFor the production of fiber-reinforced thermoplastic polymers the following tmpregnation techniques are applied: 9 melt impregnation (pultrusion); 9 polymer solution impregnation; 9 film stacking process; 9 impregnation by commingled thermoplastic fibers; 9 powder impregnation.

The present paper deals with the parametric instability of woven fiber laminated composite plates subjected to in plane periodic loadings in hygrothermal environment. The effects of various parameters like increase in number of layers, aspect ratios, side-to thickness ratios, static load factors, ply-orientations, lamination angle and the degree of orthotropy of simply supported composite plates at elevated temperatures and moisture concentrations on the principal instability regions are investigated using finite element method using Bolotin's approach. The effects of transverse shear deformation and rotary inertia are used to study the anti-symmetric angle-ply rectangular plates. The onset of instability occurs earlier and the width of dynamic instability regions increases with rise in temperature and moisture for different parameters.