The development of thermal stresses in polyimide matrix composite materials as a consequence of three-dimensional thermal gradients - Analysis and experiment

Composite material parts may experience service exposure to three-dimensional (3D) temperature gradients where temperature differences may exceed 150°C. The effect of these conditions on a glass fabric-reinforced BMI resin laminate has been analyzed as a function of location using a 3D model. According to analysis predictions, in a situation of thermal load and temperature gradients, compression stresses develop in the center of the heated zone, which is surrounded by a tensile-stressed annular region. The stresses and strains developed are small compared to the ultimate mechanical properties of the material. The analysis has been verified by subjecting an instrumented sample to nonuniform heating. This confirmed that in the absence of absorbed moisture, the damage-inducing potential of local heating was small. This observation suggests that less conservative design approaches can be used for thick laminates compared to the current, with a consequent weight saving potential.