Simulation of spring-in distortion in composite L-angles through experimentally measured cure induced residual strain using distributed fiber optic sensor

A Distributed Fibre Optic Sensor is embedded into the flat prepreg laminate during layup stage to measure the Cure Residual Strain (CRS), which gets locked into the composite structures during high-temperature curing. The sensor routing is designed such a way that CRS is measured in both fibre and matrix direction at five levels through-the-thickness of the laminate. The experimentally measured CRS is then converted into the fictitious thermal expansion coefficient and subsequently substituted for the predefined thermal expansion coefficient in the lamina property module of the Abaqus® finite element analysis software. The modelling methodology is used to simulate the spring-in in various L-angle composite parts by performing a linear thermo-elastic analysis. Eight configurations of composite L-angle specimens are designed, fabricated and cured to validate the spring-in simulation from FE analysis. The developed methodology provides a practical framework for spring-in simulation for multi-angular composite parts. The method utilizes experimentally measured CRS from unidirectional laminate to develop finite element simulation methodology of spring-in in multi-angular L-angle composite parts. The proposed methodology helps in estimation and compensation of spring-in, which would support precise curing tool design and could significantly reduce dimensional deviations in the final parts.