Mechanical behavior of polyimide filament tows under high strain rate tension

The tensile properties of polyimide (PI) filament tows were measured under quasi-static state and at high strain rates with a universal tensile testing machine and a split Hopkinson tension bar, respectively. Experimental results showed that mechanical behaviors of the tows were rather sensitive to strain rate, with failure stress and modulus increasing distinctly but the elongation at break declining as the strain rate increased. Besides, the PI filament tows exhibited a higher growth rate of fracture stress than para-aramid fiber and aramid III fiber did, and scanning electronic microscopy observation on the fracture surface indicated a ductile fracture mode. With the increase of strain rate, the axial splitting of fiber intensified. Further, strength distributions of the PI filament tows were evaluated by a single Weibull distribution function, and the curve predicted was in good accordance with the experimental data obtained.