Investigation of static and dynamic fracture toughness of short ceramic fiber reinforced polypropylene composites

Short ceramic fiber reinforced polypropylene composites have been investigated to determine their static and dynamic fracture toughness for different reinforcing fiber contents. The composites were reinforced with fibers produced by a carding technique combined with needle-punching. Static fracture toughness (K-c) was measured on single-edge notched tensile (SEN-T) specimens, while dynamic fracture toughness (K-d) was tested by impact strength Charpy specimens. Specimens in both cases were cut transverse (T) and in longitudinal (L) directions. Test results show that dynamic fracture toughness is larger than the static one. During loading of SEN-T specimens the burst-type acoustic emission (AE) signals were monitored. From AE signals it can be concluded that the main damage form is the pull-out in the T specimens, and debonding in L ones. These results were supported by scanning electron microscopy micrographs taken from fracture surfaces.