3-DIMENSIONAL FINITE-ELEMENT ANALYSIS OF THE STRESS-CONCENTRATION AT A SINGLE-FIBER BREAK

A linear elastic analysis is performed of a single broken fibre surrounded by six equally spaced fibres. These fibres and the surrounding epoxy matrix are modelled separately whilst the rest of the composite is treated as a homogeneous, orthotropic material. The distance of the adjacent fibres is fixed based on an assumed fibre volume fraction of 0.60. The analysis shows that the stress concentration in the adjacent fibres is 1.058, much lower than the value of 1.104 predicted by Hedgepeth and van Dyke (J. Comp. Mater., 1 (1967) 294-309). The positively affected length where there is an increase in stress is only about half the ineffective length of the broken fibre. Further away from the break the axial stress in the adjacent fibres actually drops below the nominal axial stress. This results in a very small enhanced probability of failure in the adjacent fibres. Very close local fibre spacing around the broken fibre increases the maximum stress in the adjacent fibres by less than 3%.