FATIGUE RESPONSE OF CARBON/EPOXY LAMINATES UNDER MULTIAXIAL STRESSES FOR DIFFERENT LAY-UP PARAMETERS

The inherent anisotropy of composites complicates their damage response. The influence of multiaxiality is not thoroughly understood due to obstacles related to damage monitoring during loading. In this study, the response of carbon/epoxy laminates under fatigue is examined through in-situ microscopic observations. [0o/θ]2s, [0o/θ/0ο/-θ]s and [0o/θ/-θ]2s laminates with two off-axis angles, namely 30 and 60 degrees, are tested under fatigue. By varying the orientation of off-axis layers, the impact of multiaxiality on the mechanical and damage response is evaluated. Furthermore, balanced and unbalanced laminates are compared, considering the limited information for the latter. The influence of the number of off-axis layers is finally assessed. The fatigue response is evaluated both from the mechanical and the damage point of view. Significant conclusions are drawn, especially for the benefits of unbalanced laminates and the impact of shear stresses, allowing utilization of the data for the establishment of reliable fatigue models.

Trefwoorden:multiaxial fatigue, damage accumulation, fatigue crack growth, unbalanced laminates