Filament interaction during failure in bundles under tension
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Structural-fiber failure-probability data quantifies the spread in strength of the filaments. Rather than testing large numbers of individual filaments, a method for extracting Weibull failure parameters from a single fiber-bundle tensile test through Fourier deconvolution is presented. The fiber bundle test uses gripping techniques that result in distributed filament lengths. The generalized convolution equation eliminates the need for an assumed survival model. Examples of the analysis use experimental data for Thornel T-300 and Kevlar 49 fibers. The widened length distribution shifts the response from catastrophic failure to a more even sequence of filament failures. This effect improves the data quality compared to the traditional test that uses a single filament length. A bundle with filaments varying from 75 to 76.1 mm in length failed with a load/displacement energy 14 percent higher than found with uniform filament length. Weibull parameters of m = 12.3 and ε0 = 0.0305 indicate that filament interactions were reduced and parameters corresponding to single filament testing were obtained rapidly. If deconvolution replaces the tedious testing of individual filaments, it would allow rapid analysis of fiber quality and improve prediction of properties in the composite.
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