Improved Flexural Impact Properties of Carbon Fiber/Epoxy Golf Shaft Hybridized with Pitch-based Low Modulus Carbon Fiber

Pitch-based low modulus carbon fiber increases the flexural impact properties of PAN-based carbon fiber/epoxy composites when it is used as an outer reinforcing layer. This is due to its larger compressive failure strain, which delays the fiber microbuckling failure of the PAN-based fiber layer on the compression side. In this paper, low modulus fiber was applied to the tip segment of a golf shaft as an outer reinforcing layer to provide higher impact performance. In a model circular composite tube for a golf shaft, a PAN-based fiber layer with a fiber modulus of 300 GPa was reinforced with a low modulus outer layer having a fiber modulus of 55 GPa. A flexural impact test showed that the low modulus fiber increased the flexural impact strength and the energy absorption of the composite tube. A finite element analysis based on damage mechanics indicated that the compressive strength of the PAN-based fiber layer increased from 1, 570 MPa in a monolithic unidirectional laminate to 2, 450 MPa in the hybrid tube. This analytical result suggests that the hydrostatic stress state around the loading point restrained the microbuckling failure of the PAN-based fiber layer and increased its compressive strength.