PREDICTION OF FIBER STRENGTH AT THE CRITICAL LENGTH - A SIMULATION THEORY AND EXPERIMENTAL-VERIFICATION FOR BIMODALLY DISTRIBUTED CARBON-FIBER STRENGTHS

A computer simulation model of fragment distribution with respect to t he fibre strength in a single-filament composite test is developed usi ng the bimodal Weibull statistics. The predictions of the theory are e xamined with experimental results for AU carbon fibres coated by zirco nium-n-propoxide or a zircoaluminate complex. Weibull analysis reveals a bimodal distribution of fibre strengths, in which the fractions of low- and high-strength populations vary with gauge length, It is seen that the simulation results are in good agreement with experimental da ta if the best fit model of strength distribution is applied. Thus, th e use of a bimodal distribution term in the simulation theory yields a predicted strength at the critical length which is in good agreement with the results of extrapolation of experimental data, while the unim odal distribution term leads to overestimation of the strength.