Multi-axial loading failure criterion for isotropic, time-dependent materials

Recently, extensive testing has been conducted to characterize the effects of multi-axial loading, temperature, and time on the failure characteristics of TIGA 321, EA913NA, and EA946 (three filled epoxy adhesives). From the test data a “multi-axial-, temperature-, and time-dependent” (MATT) failure criterion was developed. It is shown that this criterion simplifies, for constant load and constant load rate conditions, to a form that can be easily used for stress analysis. Failures for TIGA 321 and EA913NA are characterized below their glass transition temperatures. Failure for EA946 is characterized for conditions that pass through its glass transition. The MATT failure criterion is shown to be accurate for a wide range of conditions for these adhesives.