Effect of Fiber Misalignment on Tensile Response of Unidirectional CFRP Composite Lamina

Abstract

Mechanical responses and failure of fiber-reinforced polymer (FRP) composite laminates could be predicted using the validated finite element (FE) simulation. The material constitutive and damage models employed in the simulation are developed based on the properties of the unidirectional lamina, including those obtained through tension tests. Such computational model assumes perfectly aligned fibers in the lamina. In this respect, this paper examined the effect of fabrication-inherited fiber misalignment on the tensile response of the unidirectional lamina. For this purpose, a series of tension tests are performed on unidirectional carbon fiberreinforced polymer (CFRP) composite lamina specimens with different gage lengths ranging from 50 to 150 mm. Fiber misalignment is quantified to be 7o and represents the nominal deviation of the fibers from the reference longitudinal axis direction. Load-displacement responses of the specimens are compared. Results show that the nominal tensile strength of the lamina is 1089±33 MPa. The elastic modulus, however, increases from 36.96 to 55.93 GPa as the gage lengths vary from 50 to 150 mm, respectively. This is due to the induced bending effects on the reinforcing fibers that is greater for longer gage lengths. Multiple fiber fracture events, each is depicted in a noticeable load drop, are recorded throughout the tensile loading of long lamina specimens. Although the load at fracture is accurately reproduced by the FE simulation using the damage-based mesoscale model, the effect of fiber misalignment could not be captured.