An improvement to the single specimen test method for fracture characterization of elastomer materials using DENT specimen

Fracture behavior of elastomer materials is investigated based upon single specimen and multiple specimen test methods using the practically recommended double edge notched tension (DENT) specimen. Combining analytical, experimental, and numerical analysis, the critical J integral is determined based upon eta factor concept. The main challenge with this approach is how to extract the eta (or eta*) factor. For DENT specimen, previous studies have proposed that eta* factor, unlike eta, could be considered approximately constant, and even estimated from its homologous LEFM-based formula (eta(el)). In this paper, it is shown that the values of coefficients eta and eta* may significantly depend on the material type and the constitutive model and even on the load level. Moreover, eta* values deviate significantly from eta(el) predictions. Consequently, the claim of a constant coefficient eta* for DENT specimen is not correct, though numerical estimations of this variable factor by using the appropriate constitutive parameters could still be provided.