Simultaneous evaluation of tensile strength and interfacial shear strength of short length carbon fibers using fragmentation test

Novel procedure is proposed for simultaneous evaluation of fiber tensile strength and interfacial shear strength of carbon fiber based on fragmentation test. Polyamide 6 was utilized as a matrix polymer. Relation between defect density lambda and fiber strain epsilon(f) was derived. Stepwise strain was applied to the specimen and increment lambda against epsilon(f) was measured at each step. Accumulation of several test results gave smooth increment of lambda till saturation. From the linear region in the double-logarithm plot of lambda against epsilon(f), Weibull parameters for fiber strength were estimated. Somewhat higher fiber strength was observed by the proposed method as compared with that from the single fiber tensile test. The interfacial shear strength estimated from the saturated lambda value (lambda(infinity)) and the measured fiber strength was comparable to the reported values, indicating the versatility of the proposed method. The proposed procedure could also be applied to the short carbon fiber length specimen, showing the applicability for the evaluation of recycled carbon fibers. (C) 2020 Elsevier Ltd. All rights reserved.