Adapted anisomorphic model for fatigue life prediction of CFRP laminates under constant amplitude loading

A new constant life diagram (CLD) model is proposed to predict the fatigue life of carbon fibre-reinforced epoxy laminates under constant amplitude (CA) loading. The CLD is asymmetric and non-linear, and it is built upon the anisomorphic CLD model. It consists of two sub-models; one sub-model is applicable to laminates with lay-ups characterised by a larger ultimate tensile strength (UTS) than absolute ultimate compressive strength (UCS): UTS >= vertical bar UCS vertical bar, while the second sub-model can be applied to those exhibiting the opposite tendency: vertical bar UCS vertical bar > UTS. Combined, the sub-models can predict the fatigue life of any carbon-epoxy laminate. The CLD can be constructed using only static strength data and fatigue life data related to one stress ratio (R), defined as either R = 0.1 or R = -1.0. An experimental campaign was conducted on a carbon-epoxy laminate with a lay-up of [90/0/90](2S) to validate the first CLD sub-model. Additionally, a second case study from literature with a lay-up of [45/90/-45/0](2S) was employed for validation. The second CLD sub-model was evaluated using two coupon case studies from literature with lay-ups of [+/- 60](3S) and [45](16). The predicted and experimentally obtained fatigue lives showed agreements for different R-ratios, and the observed prediction errors were in ranges similar to those of the original anisomorphic CLD model. Hence, the presented CLD model allows for fatigue life predictions in scales similar to experimental results while reducing the required experimental efforts with respect to the anisomorphic CLD model.