Fatigue damage evolution in GFRP laminates with constrained off-axis plies

Abstract

., "Fatigue damage evolution in GFRP laminates with constrained off-axis plies", Composites Part A, http://dx.doi. org/10.1016/j.compositesa.2017. method with a data mining approach and applying these to large data sets obtained during fatigue tests. It is shown that for a constant stress level, the stochastic nature of off-axis crack initiation and crack growth is accurately modelled by the Weibull distribution, with the distribution parameters being efficiently derived using the developed approach. The data-rich characterisation provides new insight in the crack density evolution process for VA and C-T loading, as well as derived Weibull distribution parameters in combination with the classical S-N curves and Paris' Law relationship.Hence, providing an improved approach that includes the stochastic and deterministic information for physically based modelling of crack density evolution for fatigue loading.Glud, J.A., Dulieu-Barton, J.M., Thomsen, O.T. and Overgaard, L.C.T., "Fatigue damage evolution in GFRP laminates with constrained off-axis plies", Composites Part A, http://dx

A stochastic multiaxial fatigue model for off-axis cracking in FRP laminates

“…The underlying micro material architecture in the form of fibre-bridging, voids, varying fibre-volume fraction and varying layer thickness etc. results in significant levels of scatter of the material data points derived from fatigue tests [20]. In [20] the Weibull distribution was found to model both the stochastic nature of the crack initiation the and crack growth rates well, and provided a means for determining the stochastic material parameters.…”

“…results in significant levels of scatter of the material data points derived from fatigue tests [20]. In [20] the Weibull distribution was found to model both the stochastic nature of the crack initiation the and crack growth rates well, and provided a means for determining the stochastic material parameters. Furthermore, it was shown that crack initiation and crack growth are not represented by a single S-N and Paris' Law master curve, but instead by S-N and crack growth Weibull fields.…”

“…The crack growth rate (CGR) of an isolated off-axis crack growing in a steady-state manner as function of the maximum ERR for a constant load ratio can be modelled deterministically by adopting the Paris' Law relationship [11,12,20,33,34], (CGR is also routinely refered to as da/dN), G represents the ERR and D and n are empirical constants obtained from fitting Paris' Law to crack growth experimental data.…”

“…Stress-ratio effects on the off-axis crack evolution has been reported in [20,23,30]. Based on the reported results, it was proposed in [23] to use the empirical normalisation principle found in [39] to model the stress-ratio effect on offaxis crack initiation as follows:…”

“…The off-axis crack evolution process for laminates subjected to fatigue loading can be described by initiation of off-axis cracks followed by steady state crack growth [11,19,20]. Therefore, the nature of the problem includes full 3D complexity, since the cracks that are initiated can no longer be assumed to span the entire region of uniform stress.…”