ON THE USE OF ACOUSTIC-EMISSION TO INVESTIGATE DAMAGE MECHANISMS IN GLASS-FIBER-REINFORCED POLYPROPYLENE

The study of damage and fracture mechanisms in short-glass-fibre-reinforced thermoplastics is of prime importance to improve the mechanical properties of this range of composite materials. In this experimental study, the damage mechanisms of four short-glass-fibre-reinforced polypropylenes are investigated in tensile, tensile fatigue and crack propagation tests. Two parameters of the material composition are investigated, the fibre length and the quality of the fibre matrix adhesion. These parameters show a great influence on the damage mechanisms, on the mechanical properties and on the fatigue life of these four composite materials. The use of acoustic emission (AE) and scanning electron microscopy (SEM) observations has enabled us to identify several damage mechanisms. Many differences in the damage mechanisms between the tensile and crack propagation tests were observed in the SEM photographs. A good correlation was observed between these mechanisms and several ranges of AE amplitude. The use of both techniques (AE and SEM) is shown to be very useful in the investigation of damage phenomena in composite materials.