FRACTURE STATISTICS OF SINGLE-FIBER COMPOSITE SPECIMENS

The failure of unidirectional composite materials is subject to wide d ispersion owing to the occurrence of flaws or imperfections in the fib res. Fracture modelling requires the use of statistical models to deal with this variability in strength. We are currently developing an ori ginal and general approach that combines random models of defects with mechanical models and tests on composite materials. The present study is devoted to the problem of the characterisation of single fibres. T he fragmentation test is used to study the flaw population along the f ibre as a function of applied stress. Each fracture is due to a flaw i n the fibre with a critical stress, sigma(c), less than the applied st ress sigma. We can estimate the flaw distribution as a function of str ess by means of a multifragmentation test. Various density functions a re proposed and tested and good agreement is found between the experim ental data and theoretical results. Following the proposed model, whic h has been verified experimentally, numerical simulations were carried out to study the validity of the parameters of the model.