Material anisotropy induced by strain in filled vulcanized rubbers strongly affects fracture toughness. The influence of carbon black content on fracture phenomenology and fracture toughness was investigated by performing video-recorded tests adopting a suitable grooved notched pure shear test specimen. In such a way, it was possible to analyze the so-called ‘‘knotty tearing’’ deformation mechanism occurring at the crack tip: sideways cracks perpendicular to the notch plane develop before the onset and propagation of a forward crack parallel to the notch plane. The J-integral fracture mechanics approach was adopted and digital image correlation analysis was performed to measure the strain at the crack tip. The presence of carbon black modifies the maximum chain extensibility and strain-induced crystallizability of the rubber matrix in the compound. The formation of sideways cracks occurred in all filled compounds and resulted in a link to the maximum chain extensibility. Nevertheless, toughness enhancement was observed only when strain-induced crystallization took place at the crack tip before the onset of the forward crack.
Fracture phenomenology and toughness of filled natural rubber compounds via the pure shear test specimen
MARANO, CLAUDIA;BOGGIO, MANUELA;CAZZONI, EMANUELE;RINK SUGAR, MARTA ELISABETH
2014-01-01
Abstract
Material anisotropy induced by strain in filled vulcanized rubbers strongly affects fracture toughness. The influence of carbon black content on fracture phenomenology and fracture toughness was investigated by performing video-recorded tests adopting a suitable grooved notched pure shear test specimen. In such a way, it was possible to analyze the so-called ‘‘knotty tearing’’ deformation mechanism occurring at the crack tip: sideways cracks perpendicular to the notch plane develop before the onset and propagation of a forward crack parallel to the notch plane. The J-integral fracture mechanics approach was adopted and digital image correlation analysis was performed to measure the strain at the crack tip. The presence of carbon black modifies the maximum chain extensibility and strain-induced crystallizability of the rubber matrix in the compound. The formation of sideways cracks occurred in all filled compounds and resulted in a link to the maximum chain extensibility. Nevertheless, toughness enhancement was observed only when strain-induced crystallization took place at the crack tip before the onset of the forward crack.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
