Swelling and mechanical stretching of elastomeric materials

The equilibrium stress-stretch behavior of elastomeric materials can be cap tured by statistical mechanics treatments of rubber elasticity. Gaussian st atistics is known to capture the essence of the stress-strain behavior; how ever, discrepancies between Gaussian theory and experiment are recognized t o occur at both small to moderate stretch levels and at large stretch level s. These discrepancies are further amplified in studies of the effects of s welling on stress-stretch behavior. A brief review of the various approache s used to represent the stress-stretch behavior of elastomers and the effec t of swelling on this behavior is given. Then, a hybrid constitutive model composed of the Flory-Erman constrained chain model and the Arruda-Boyce no n-Gaussian eight-chain model is presented and found to capture the stress-s tretch behavior from small to large stretch levels. Furthermore, the Flory- Erinan/Arruda-Boyce hybrid model is also found to successfully predict the effect of swelling on the stress-stretch behavior from small to large stret ches using only three material constants.