A quantitative model for cavitation and consequent dilatational yielding in multiphase plastics (1, 2) is reviewed and new developments are reported and compared with experimental results. According to the model . cavitation can occur by debonding at phase bound aries or by nucleation of voids within a soft polymeric pha se when the stored volumetric strain energy density within the rubber pha se exceeds a criticai value. The mode l rclates the criticaI volume stra in required for cavitation to the propert ies of the particle: its size. shear modulu s. surface energy and failure strain in biaxial ext ension. Subscquent to cavitation of the rubber particles. the yield behavior of the polymer is significantly altered. especially at high triaxiality. and can be modeled by the modified Gurson equation proposed by Lazzeri and Bucknall (1. 2). Part icle cavitation also increases the rate of yielding . On increasing the stra in level in the material, the defonnation will tend to assume an inhomogencous character leading to the fonnation of dilatational band s. The particles located in proximity of a dilatational band will cavitate preferentially due to the hydro static stress concentration near its ends. leading to a propagation of the band. At the same time. the number of dilatational bands will increase and their growth is associated with significant lcvcls of energy absorption, In some semi-crysta lline polymcrs this can lead lO the fonuat ion of microfibrils in the ligaments beiween neighboring part icles .
Recent Developments in the Modeling of Dilatational Yielding in Toughened Plastics
LAZZERI, ANDREA;
2000-01-01
Abstract
A quantitative model for cavitation and consequent dilatational yielding in multiphase plastics (1, 2) is reviewed and new developments are reported and compared with experimental results. According to the model . cavitation can occur by debonding at phase bound aries or by nucleation of voids within a soft polymeric pha se when the stored volumetric strain energy density within the rubber pha se exceeds a criticai value. The mode l rclates the criticaI volume stra in required for cavitation to the propert ies of the particle: its size. shear modulu s. surface energy and failure strain in biaxial ext ension. Subscquent to cavitation of the rubber particles. the yield behavior of the polymer is significantly altered. especially at high triaxiality. and can be modeled by the modified Gurson equation proposed by Lazzeri and Bucknall (1. 2). Part icle cavitation also increases the rate of yielding . On increasing the stra in level in the material, the defonnation will tend to assume an inhomogencous character leading to the fonnation of dilatational band s. The particles located in proximity of a dilatational band will cavitate preferentially due to the hydro static stress concentration near its ends. leading to a propagation of the band. At the same time. the number of dilatational bands will increase and their growth is associated with significant lcvcls of energy absorption, In some semi-crysta lline polymcrs this can lead lO the fonuat ion of microfibrils in the ligaments beiween neighboring part icles .I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
