Using Modal Analysis to Investigate the Validity of Finite Element Models for Simulating the Thermostamping of Woven-Fabric Reinforced Composites

Thermostamping/thermoforming of woven-fabric reinforced composites can produce high-volume low-cost composite parts. Finite element modelling of the forming of such composites allows tailoring the manufacturing process to yield quality parts in the minimal time required and for prediction of the resulting mechanical behavior. Visual methods can be used to compare the final fibre directions from simulation results to that of a physically stamped part for single- and two-ply parts. However, such a visual comparison on three or more plies cannot be done without destructive evaluation of the formed part. Modal analysis is a viable option for doing nondestructive comparison of a physically formed part to that of its corresponding finite element modelling result. In this paper, modal analysis is used to compare the vibration modes between a physically stamped part to the same part “formed” using a finite element simulation. The study explores such a comparison for a two-layer plain-weave flat sheet of glass-fibre fabric with orthogonal yarns and a polypropylene thermoplastic matrix.