Evaluation of Influence of Molding Conditions on Process-Induced Strain of Reinforcements of GFRP by FEM Analysis and In-Situ Strain Measurement

Abstract

FRP(Fiber Reinforced Plastic) is a composite material for glass or carbon reinforcements with resin. In the heat forming method of FRP, residual stress occurs due to discrepancy of different thermal expansion. Since it is known that process-induced residual stress influences behavior of matrix cracks generated in operation, accurate estimation of the residual stress is an important issure for FRP manufacturing. For thermoset-based FRP, the residual stress may result from curing shrinkage as well as thermal deformantion. However, the residual stress caused by cure reaction has been hardly studied and then the effect of molding temperature pattern on the residual stress has not been cleared. In the present syudy, FEM analysis was performed to evaluate the molding processinduced strain occurred in reinforcement fibers on the assumption of viscoelastic properties of resin depending on the degree of cure. In addition, model specimens of glass optical-fiber reinforced polymers were manufactured for in-situ evaluation of process-induced strain by embedded FBG (Fiber Bragg grating) sensors.