In-Situ Measurement and Numerical Analysis of Cure Induced Strain in Curved Composites
Process residual deformation is induced in curved composites, resulting in residual stress after assembly or troublesome shimming. Despites previous efforts over the past two decades, the mechanisms are still unclear. This is partially due to the lack of internal state monitoring techniques. The present study aimed to develop a new fiber-optic-based in-situ strain monitoring method and to investigate the mechanisms using the method. First, the principle of the measurement was proposed taking into account the shear-lag effect. L-shaped specimens were fabricated and the internal states were measured using the fiber-optic technique. Numerical analysis was also carried out. The results showed that the deformation changes from shear dominated to bending dominated as cure proceeds. The effects of boundary conditions and thickness were also discussed. Then, the monitoring technique was applied to the U-shaped geometry. The experiment results and numerical analysis revealed that different strain states were induced in the flange and web area. Furthermore, web warpage was shown to occur after gelation, leading to larger spring-in angle than in L-shaped one.
Author: Shu Minakuchi
Conference: SAMPE Seattle 2017