Effect of Fiber Reinforcement Geometry on Single-Shear and Fracture Behavior of Three-Dimensionally Braided Glass/Epoxy Composite Pins

Abstract

Optimization of single-shear properties through controlled microstructure of composite pins was studied. This research established a processing science based con cept for making near-net-shape three-dimensionally braided circular preforms as well as transforming them into composites by impregnating with resin. The effect of fiber rein forcement geometry (FRG) was related to transverse single-shear and fracture behavior of composite pins. Eight different fiber reinforcement geometric variations were chosen. Single-shear properties of three-dimensionally braided composite pins were measured using a single-shear test. Shear strength varied between 144.48 MPa and 182.62 MPa, shear strain varied between 7.26 and 14.7%, and initial modulus varied between 1.47 GPa and 2.98 GPa. The effect of FRG on the shear stress-strain properties was not pronounced, but had an influence on the failure mechanism of the samples. The nature of shear stress- strain curves was mostly linear except for CBLC-2080 and CBLC-5050, where sequential failure was observed. The general appearance of the fractured surfaces depended largely on the FRG. Fiber pullout and hill and valley mechanisms were dominant and were observed on practically all of the fracture surfaces.