How geometrical imperfections and thermal gradients affect wrinkle formation during curing of thick composite laminates

This work provides insights into wrinkle formation due to the thermomechanical nature of curing in thick and long monolithic composite laminates. The investigations focus on two main factors: geometrical imperfections and thermal gradients across the mould. Firstly, the effect of geometrical imperfections was examined in terms of imperfection length and amplitude. Although geometrical imperfections showed a little effect on the angle and amplitude of the wrinkle, the geometrical imperfection was found to have no governing influence on the formation of wrinkles. Secondly, the effect of thermal gradients was assessed by varying the length of a non-heated region in the mould. The effect of varying the length of this region was found to be significant and therefore a governing parameter in the occurrence of wrinkles induced by curing. The effects were found to be as high as 63-70% change of the key wrinkle parameters defined by the wrinkle amplitude and resulting change in fibre undulation. Demonstrating that thermal gradients within the mould play a significant role in wrinkle formation during the curing process of composite manufacturing.