Fracture resistance of unfilled and calcite-particle-filled ABS composites reinforced by short glass fibers (SGF) under impact load

Acrylonitrile-butadiene-styrene (ABS) terpolymer, unfilled and filled with calcium carbonate (calcite) particles, was used as a matrix for reinforcement with short glass fibers (SGF). All of the materials were prepared by injection molding and the fibers in the specimens were oriented preferentially in the flow direction (i.e. the axial direction of the specimens). The composites were studied with respect to the work of fracture (WOF), here the notched Charpy impact energy, determined by the Charpy V-notch impact test. The fracture surfaces of the composites were studied by scanning electron microscopy. The total WOF theory for short-fiber-reinforced composites was used to evaluate the interface energy and the matrix fracture work, whereby the fiber fracture work was neglected because of the brittleness of glass fibers, only a small amount of broken fibers being observed experimentally. It was shown that the interface energy is much higher than the matrix fracture work in the presence of fibers. The results showed that the reduction in WOF caused by adding SGF to pure ABS resin matrix is the consequence of a significant reduction in the matrix fracture work; on the other hand, the incorporation of SGF into calcite-filled ABS resulted to some extent in an increase in the WOF, this is being due to the relatively large interface energy contribution to the WOF of the composite. Moreover, it was observed experimentally that the treated case showed a higher WOF for SGF/ABS composites than for the as-received case, whereas this was not observed for hybrid SGF/calcite/ABS composites. This behavior was explained in terms of the changes in fiber length distribution by using the total WOF theory and the fiber pull-out energy theory. Furthermore, it was pointed out that when investigating the influence of the fiber/matrix interface on the WOF of short-fiber composites, the fiber length distribution must be taken into consideration. (C) 1998 Published by Elsevier Science Limited.