Fracture behaviour of polypropylene/glass bead elastomer composites by using the essential work-of-fracture method

The plane-stress static fracture response of blends composed of isotactic p olypropylene glass beads (GBs) and an elastomer of styrene/ethylene-butylen e/styrene type (SEBS) in both the ungrafted state and the grafted state wit h maleic acid anhydride (SEBS-g-MA) was studied at room temperature and v = 1 mm min(-1) cross-head speed. The volume fraction of GBs was kept constan t (10 vol%) whereas that of the elastomer was set for 5 and 20 vol%, respec tively. Deeply double edge-notched specimens of different ligaments were cu t from pressed sheets of about 1 mm thickness and subjected to tensile test s at ambient temperature. The development of the plastic and process zone w as studied in situ, i.e., during loading of the specimens, by light microsc opy and infrared thermography. From the specific work of fracture versus li gament length plots, the essential and non-essential work of fracture compo nents were determined. It was established that the essential work-of-fractu re approach works well for these hybrid composites. The specific essential work of fracture, w(e), increased with increasing amount of the rubbery mod ifier but depended on its type. Grafting changed the morphology of the comp osites (SEBS-g-MA covered the GBs, whereas SEES was present as an additiona l dispersed phase) and affected both the essential (slightly) and the non-e ssential or plastic work (considerably) terms. It was established that SEBS -g-MA is a less efficient toughener than SE BS because of the substantial d ifferences in the related failure modes. (C) 1998 Chapman & Hall.