Characterizing strain-rate dependent longitudinal compressive property of carbon fiber composite tows using a novel test method

The dynamic mechanical properties of composite tows, which bear the primary external loads and absorb a significant portion of energy, directly influence the impact resistance of textile composites. To the best of our understanding, this is the first exploratory study introducing a dynamic longitudinal compression test method for composite tows, based on a Split Hopkinson Pressure Bar (SHPB) system. The optimal fabrication method for composite tows has been ascertained through comparative analysis and characterization. Following experimental and numerical analyses, a dumbbell-shaped configuration has been validated for compression specimens, as it not only facilitates effective compression failure modes and stress equilibrium but also satisfies the other fundamental requirements of SHPB tests. Additionally, the percent bending of composite tows under compression was assessed utilizing an innovative dual-reflector method. Experimental results indicate that the dynamic compressive strength and failure strain at 700 s⁻¹ exhibit a significant increase of approximately 116% and 110%, respectively, in comparison to the quasi-static condition at 1.5 × 10⁻⁵ s⁻¹. Furthermore, a series of morphological examinations and analyses were performed to comprehend the rationale behind their disparities at diverse strain rates. The results reveal that kink bands and longitudinal splitting constitute the primary failure modes in dynamic compression, while fiber kinking emerges as the predominant mode under quasi-static loadings.