Experimental and numerical study of distortion in flat, L-shaped, and U-shaped carbon fiber-epoxy composite parts

Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical EngineeringIn this work, the effect of different parameters, including stacking sequence, part thickness, and tooling material, on distortion of flat panels was investigated. A Romer arm equipped with a laser scanner was used to obtain the maximum amount of distortion as well as the 3D pattern of distortion for each panel. Among the different stacking sequences, the maximum distortion was observed in the asymmetric and balanced panel, while the least distortion belonged to the symmetric and unbalanced one. Furthermore, thinner panels were more distorted than thicker panels with the same planar size and stacking sequences. This study showed that distortion of the flat panels caused by asymmetry in the stacking sequence was an order of magnitude greater than distortion of the panels due to imbalance in the stacking sequence. L-shaped and U-shaped panels were also fabricated to investigate the effect of stacking sequence on spring-in angle and warpage of the panels. Among all the stacking sequences, the panel with an asymmetric and unbalanced stacking sequence showed the least spring-in angle, while the largest angle was observed in the symmetric and balanced panel. Although asymmetry in the stacking sequences reduced the spring-in angle, significantly more warpage was observed in the panels with asymmetric stacking sequences, as compared to the symmetric ones. MSC Marc was used to predict the distortion of the panels, and the simulation results were compared with the experimental results for several stacking sequences of the flat and the L-shaped panels. An L-shaped panel with the stacking sequence of [0/45/90/-45]4 was simulated to investigate the effect of curve radius and tool geometry on the spring-in angle. The FEA results showed that curing the L-shaped panel on a concave tool led to less spring-in angle, as compared to the panel confined to a convex tool