Creep/Fatigue Response of Resin Infused Biaxial Glass Fabric Laminates in Reversed Loading

Abstract

The creep and fatigue behavior of double bias (±45) glass/epoxy laminates has been explored with a variety of tests, including conventional sine-wave fatigue loading at six loading conditions (R-values), residual property stress-strain tests, square wave fatigue tests, creep tests, and loading-unloading-reloading (LUR) tests. The fatigue results are presented as a strain-based constant life diagram (CLD) representing a 50% strain increase which correlates with a transition to rapid strain increase and failure. Reversed loading effects are explored in detail, and show a substantial creep response during both the tensile and compressive parts of the wave-form, which correlate with creep test data. The baseline epoxy resin is compared with a urethane resin, showing the effects of a tougher but more creep sensitive resin on the creep and fatigue resistance for unidirectional and ±45 laminates.

Review of fatigue of bulk structural adhesives and thick adhesive joints

“…The same observation was reported for an angle-ply composite laminate subjected to similar interrupted fatigue loading patterns in Movahedi-Rad et al [184]. The amount of the accumulated strain depends on the applied cyclic mean stress [27]; the former is diminished under inversed fatigue loading, R = σ min /σ max = −1, while it becomes significant for tension-tension (0< R <1) and compression-compression (1< R <∞) fatigue loadings [185]. The cyclic fatigue behaviour of epoxy resins under uniaxial and biaxial stress states, as well as the mean stress/strain effect on the cyclic response has been investigated in Refs.…”