Failure of solid polymers under pulse tension

Results of tests on specimens of polymethyl methacrylate (PMMC) and epoxy resin ÉD-20 MT GFA which were obtained with the help of a dynamic polarization set-up are presented. It is shown that for the entire stage of propagation of the crack from the instant it starts until it stops, the crack length increases spasmodically. Fracture surfaces were fractographically analyzed with a view to establish the interdependence between the spasmodic character of crack growth and the formation and development of microfailures ahead of the crack front. It is observed that occurrence and development of secondary microcracks cannot appear as jumps of the main crack due to the chaotic formation of the microcracks and triviality of their dimensions in comparison with the magnitude of the jumps.Translated from Problemy Prochnosti, No. 7, pp. 14–17, July, 1992.