THEORETICAL ASPECTS OF THE FRAGMENTATION TEST

This paper presents a review of the status of the fragmentation test. The processes occurring during the fragmentation test and especially the modelling of the test are analysed. The limits of one-dimensional models are defined and the quality of bidimensional models is outlined, one-dimensional numerical analysis of the fragmentation process being presented as a powerful tool for understanding the basic interfacial phenomena. Finally, misconceptions in the analysis of some mechanical features of the test are emphasized. The most notable of these are that no analytical relationship between the critical fragment length and the mean fragment length can be established at present and that the ineffective length, which may allow the in-situ Weibull parameters of the fibre to be determined, has to be defined by using a probabilistic criterion. In conclusion, fragmentation phenomena still appear to be poorly understood, but the development of understanding is crucial for the micromechanical analysis of composites because the fragmentation test exhibits the basic damage modes which are present in multifibre composites.