Investigation of the strength of surface-treated carbon fibres embedded in resin, by means of model composite tests

The strength of single fibres of carbon embedded in epoxy resin has been estimated by continuous monitoring of fragmentation tests on single embedded fibres. These fibres had previously been treated to enhance their adhesion to the resin, and the effect of this treatment on the fibre strength is studied. The data generated have been analysed by using an adapted Weibull model which includes the influence of the ‘ineffective’ length at each fibre break. Weibull parameters determined from this analysis have been compared with those from tests carried out on fibres in free air. Similar Weibull moduli are obtained and, although absolute values of strength differ, similar trends are observed and a peak in strength is observed at an intermediate level of treatment in both sets of results.