ACOUSTIC-EMISSION ANALYSIS AND SMALL-ANGLE X-RAY-SCATTERING FROM MICROCRACKS DURING DEFORMATION OF ETFE COMPOSITES

During the deformation of an unfilled matrix of ethylene tetrafluoroet hylene (ETFE), microcracking was observed by small-angle X-ray scatter ing(SAXS), although it does not cause significant acoustic emission be cause the released energy is too small to be detected (size of microcr acks much less than size of fibres). Fibres induce local stress maxima and increase the formation of microcracks. Fibre delamination process es were monitored by acoustic emission analysis. The use of coupling a gents improves the fibre matrix adhesion and increases the mechanical yield stress and decreases delamination processes. A simple model for estimating the energy released by fibre delamination processes was sug gested. The predicted difference in peak amplitude between the two ext reme processes agrees well with the results of the experiments. The ch aracteristic values of the peak amplitude distributions, however, do n ot show any significant dependence on fibre coating or testing tempera ture. Further investigations by SAXS and acoustic emission analysis, e specially at low strain, will be necessary to obtain more detailed inf ormation about the initial formation of microcracks and fibre delamina tion.