Analysis of failure in 'Recoil from tension' of pan-based carbon fibers

Results from a study of the "recoil from tension" method for estimating the compressive strength of the polyacrylonitrile (PAN)-based carbon fibers are reported here. Analysis of the effect of different gauge lengths on the recoil strength distribution and the fracture morphological features of cross sections of the tested filaments imply that both axial recoil and bending influence the recoil failure of PAN-based carbon fibers. The experimental recoil strength distributions have been compared to logistic and weibull models. A universal logistic model that incorporates a dependence on gauge length has been found to provide a good fit to the distributions obtained at different gauge lengths. This analytical expression can be used to obtain a physically meaningful extrapolated average "zero gauge length" recoil strength, which might be appropriate for estimating the true axial compressive strength of fibers.