Acoustic emission characteristics of micro-failure processes in polymer blends and composites
- Composites Science and Technology, 60(8), p.1213-1226, 2000 .
Acoustic emission (AE)characteristics of micro-failure processes in HDPE/PP blends with and without compatibilizer, single- Žbre composites (glass/epoxy, carbon/epoxy, glass/polycarbonate)and unidirectionally reinforced multi-Žbre composites (glass/ polypropylene)were studied. For blends, the number and the elastic fracture energy release of micro-failure processes are theore- tically approximated and correlated with the number of AE signals and the AE energy. A qualitative correlation of the mechanical energy released from Žbre/matrix debonding and Žbre-fracture processes in single-Žbre pull-out experiments with the measured AE energy is demonstrated. For the single-Žbre fragmentation of glass Žbres and carbon Žbres, a quantitative approximation of the AE amplitudes at locations of the fragmentation sources is achieved. A new method for the selection of single transient acoustic emis- sions and the classiŽcation of failure mechanisms in composites is introduced. Selected emissions are classiŽed into matrix cracking, Žbre breakage and interface processes (Žbre/matrix debonding or Žbre pull-out)from their total power in deŽned frequency inter- vals of the spectral power density. A fracture-mechanics investigation of the delamination behaviour of unidirectional composites accompanied by AE examinations is discussed. The extension of the damage zone around the crack tip is quantiŽed by the location of AE events and compared with the theoretically approximated dimensions. The size of the damage zone is used for theoretical calculations of the mechanical energy release from micro-failure processes. A correlation of the AE energy-release rates with the mechanical energy-release rates from participated failure mechanisms like matrix cacking, Žbre/matrix debonding and Žbre break- age is presented.