Non-linear numerical study of the single-fiber fragmentation test. Part I: Test mechanics

A non-linear finite element method is used to investigate the mechanics of the test procedure of single-fiber fragmentation test of AS4/Epon 828 composite containing an interphase. Stress transfer between the fiber and matrix for fragments created at different matrix strain state is evaluated. The ineffective fiber length was found to vary with the matrix strain state. It is found that the stress transfer and local stress fields remain unchanged for constant, linear and power-law interphase property gradients as long as the average interphase properties are the same. Causes and effects of debonding and debond propagation are examined through the evaluation of the stress fields near the fiber breaks. The effect of thermal residual stresses is examined. Stress transfer for fragments of shorter length than the critical length is studied. Physical meaning of the critical length is discussed.