Abstract

Cavitation in solid polymers can be considered as the most important damage source. However, for rubber-toughened polymers (RTP), i. e. rigid polymer matrix containing rubber particles, cavitation in the soft rubber phase can considerably increase ductility and toughness. The recent models for cavitation and related damage mechanisms allowed to increase the understanding of rubber-toughening. Cavitation is associated to a volume change and whitening of the polymer materials. The scattering of light by cavities renders possible the "count" of these cavities. The use of industrial grades of transparent RTP, toughened by spherical rubber based particles, revealed the competition between plasticity and cavitation. The review of classical cavitatia criterion for large pieces of rubber, the influences of the shape of the rubber domains and of the plastic flow in the polymer matrix complete the analysis. Moreover, experimental evidences indicate that mechanical interaction between particles control the damage process. This motivated the development of specific numerical tools in order to take into account the interaction between large numbers of inhomogeneities. Statistics issued from numerical simulations revealed a transition in the spatial damage organisation in the range 10 % to 20 % of volume fraction of particles. In other respects, tough it is admitted that during a rapid crack propagation (RCP), the crack velocity is related to the available energy, the study of fracture of a RTP showed that, for some materials, it is the total created surface which is related to the available energy, at a constant velocity. This behaviour is associated to materials such that the fracture energy decreases in the RCP regime and this constant velocity corresponds to the macroscopic crack branching velocity, i. e. approximately half of the Rayleigh waves speed. Finally a homogenisation model concerned with finite strains in latex reinforced by rigid particles is proposed for non-linear strain localisation and to predict the strain at which a transition in the cinematic of the local strain occurs.