Influence of manufacturing parameters on the tensile strengths of hollow and solid glass fibres

Abstract

Composites reinforced with hollow glass fibres (HGF) have been shown to display improved performance in flexural and compressive loading over materials reinforced with solid fibres. A major drawback associated with hollow fibre composites is reduced reinforcement cross-section for a given fibre volume fraction. It is suggested that the use of optimised manufacturing parameters may allow fibre strengths to be increased, offsetting the inherent strength reduction predicted for hollow fibre composites compared to solid fibre composites. Tensile tests have been performed on batches of hollow and solid fibres with a variety of geometry's to investigate the effects of fibre hollow fraction and manufacturing parameters on fibre strength. Hollow and solid glass fibres drawn under a variety of conditions display tensile strengths which reflect their manufacturing history. A mechanism is proposed whereby differential strains may be locked into the fibre during manufacture. This mechanism may provide an explanation for the strength variations observed. Average tensile strengths for solid and hollow glass fibres appear to increase according to the degree of residual strain differential. The principal manufacturing parameters influencing residual strain differential are draw rate and temperature. Further investigation is suggested into methods for determining heat transport mechanisms within the fibre neck-down zone.