ESEM investigations for assessment of damage kinetics of short glass fibre reinforced thermoplastics – Results of in situ tensile tests coupled with acoustic emission analysis

The damage mechanisms of short glass fibre reinforced polypropylene (PP) and polybutene-1 (PB-1) materials were investigated. For this purpose, in situ tensile tests were conducted in the environmental scanning electron microscope (ESEM) while simultaneously recording the acoustic emission (AE). To be able to observe damage mechanisms directly during loading, notched specimens were used. This method allows the direct correlation of the recorded load – elongation data with observed damage mechanisms, as well as correlations with acoustic emission data. Hence, it is possible to describe the damage kinetics of short glass fibre composite.It was found that different bonding conditions of the two investigated materials result in different damage mechanisms as well as in different AE behaviour. For fibre reinforced PP with excellent bonding conditions of the fibres in the polymeric matrix, fibre fracture, slipping of fibres in the delamination area, debonding and pull-out with matrix yielding was observed. The determined AE parameter amplitude Ap and energy EAE for the PB-1 material are lower because of the weak bonding of the fibres to the PB-1-matrix. Hence, energy dissipative damage mechanisms like pull-out with matrix yielding can occur only in a limited part of such materials.