Nonlinear thermal and mechanical analysis of edge effects in angle-ply laminates

Carbon Fibre Reinforced Plastic (CFRP) [ + OJ - 0 is laminates have been analysedfor their thermo-mechanical free edge effects using a quasi-three­ dimensionalfinite element. The laminates were assumed to be stress free at a curing temperature of 132'2°C (180°F) and were cooled to the room temperature of 20°e. Initial thermal stresses resulted in the laminates and were reported. The laminates were then subjected to a uniform applied strain in the inplane direction untilfailure occurred according to a maximum strain Jailure criterion. Results were obtainedJor e = 00, 15°,300,45°,60°,75° and 90°. During the manufacturing process, composite laminates are usually cured at temperatures much higher than their design operating temperatures. It is normal practice to stack up the plies in various fibre orientations to enable the laminate to withstand a general loading pattern. For a composite lamina, the thermal cxpansivity in the transverse direction to the fibres is higher than the longitudinal one. When this effect is coupled with the difference in fibre orientations in the laminate, initial thermal stresses and strains result when these laminates are cooled down from their curing temperature. To complicate the problem further, these initial thermal stresses and strains also vary with the laminate ply orientations. By