Modeling of the nonlinear dynamic degradation characteristics of fiber-reinforced composite thin plates in thermal environment

In this research, the nonlinear dynamic degradation characteristics of fiber-reinforced composite plates in thermal environment are investigated through a novel dynamic degradation model, which is established by introducing the thermal and time fitting coefficients simultaneously to express dynamic elastic moduli of such composite materials. Based on the classical laminated plate theory, the improved exponential function method, the complex modulus approach and the Ritz method, the dynamic equations are derived to solve the dynamic parameters. Besides, a particle swarm optimization algorithm is employed to iteratively calculate dynamic elastic moduli, and the nonlinear least squares technique in MATLAB software is utilized to draw the three-dimensional fitted surfaces of dynamic elastic moduli, degradation time and temperature data, so that the concerned fitting coefficients in the model developed can be identified. In order to validate the dynamic degradation model, experimental measurements of E120 carbon fiber/ FRD-YG-03 resin composite thin plates are undertaken. The first three natural frequencies, resonant responses and modal damping ratios obtained from the model are compared with experimental results at different degradation time and stabilized thermal environment, which are shown to be in good agreement. Also, the specific influences with and without consideration of the degradation behavior on the dynamic characteristics are investigated and evaluated.