A NEW MODEL FOR INTER-FIBRE-FAILURE OF HIGH STRENGTH UNI-DIRECTIONALLY REINFORCED PLASTICS AND ITS RELIABILITY IMPLICATIONS

摘要

A new macro-mechanical, multi-axial criterion for interfibre failure of fiber reinforced plastics by Jeltsch-Fricker based on ideas of Hashin and Puck is presented and experimentally verified. Reliability analysis for stresses in the (σ_(22), τ_(21)) -plane are performed. It is pointed out that both stress components as well as the resistance parameters should be dependent variables. Dependencies of the resistance parameters originate from common factors not captured by the experiments. Depending on the stress combination the reliability index varies slightly. It is largest for stresses where the failure surface starts to rotate about the x_1-axis. Sensitivities and partial safety factors are calculated for typical parameter variations. The reliability calculations can also be performed for general stress states at the expense of some more numerical effort and for time-variant stresses leading to essentially the same general insights. Further research is necessary with respect to two aspects. At the one hand distributional assumptions, especially for the resistance parameters, can affect reliabilities quite significantly. On the other hand, the true uncertainty variables remain unknown in a purely macro-mechanical consideration. Therefore, the macro-mechanical findings have to be supported by micro-mechanical considerations.