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

Abstract

A model to predict off-axis crack evolution in multidirectional laminates subjected to multiaxial loading is proposed. The model applies multi-scale stress and local fracture mechanics analyses to distinguish between two microscopic damage mechanisms, which govern the damage evolution, as well as determining the magnitude of the damage evolution rate associated with each microscopic damage mechanism. The multi-scale analysis is based on the GLOB-LOC off-axis crack damage model, which is extended to include substantial new capabilities such as the influence of crack face sliding interaction and prediction of variations in the stress field due to the local crack density. The extension of the GLOB-LOC model introduces physically based multiaxial fatigue criteria for off-axis crack initiation and mixed-mode off-axis crack propagation. The extended GLOB-LOC model is implemented and it is demonstrated that good predictions are obtained for the damage evolution under various multiaxial stress conditions. Furthermore it is shown that the model only requires input from two different multiaxial stress states to obtain the material parameters for a given FRP ply.

Experimental Analysis of Matrix Cracking in Glass Fiber Reinforced Composite Off-Axis Plies under Static and Fatigue Loading

“…Great effort has been put into the analysis of cross-ply laminates, which are a special case of fiber alignment rarely used for structural applications. However, the analysis of cross-ply laminates has yielded fundamental findings on the cracking process in FRP laminates, and a variety of models have been developed based on these findings [ 24 , 25 , 26 , 27 ], several of which have accounted for the statistical distribution of critical material properties [ 9 , 28 , 29 , 30 ].…”

“…For each configuration, a unique parameter set for the fracture toughness distribution was found to describe the cracking process for static loading conditions. In [ 9 , 30 , 31 , 32 ], Weibull distributions were applied to SN-curves for crack initiation and to Paris -relations for crack growth in order to account for the stochastic nature of the fatigue cracking process within the models.…”

“…On the contrary, the amount of experimental data for the analysis of the cracking process in laminates comprised of layers with fiber angles , in particular for fatigue loading, remains limited. In recent years, results for several fiber orientations have been published [ 14 , 15 , 16 , 23 , 30 , 31 , 32 , 33 ]. The main drawback is the complicated analysis of crack density in angle-ply laminates, which can be overcome by transmitted white light imaging (TWLI) and direction-dependent image filtering [ 16 ], which is only applicable to glass fiber reinforced plastics (GFRP), or by the use of tubular cross-ply specimens loaded by normal and shear stresses [ 34 ].…”

Fatigue of short‐natural‐fiber‐reinforced high‐density polyethylene: Stochastic modeling of single‐gear‐tooth bending

“…Cracking is the damage mentioned most frequently in the literature and can be quantified in terms of number or length, for example, crack density in fiber‐reinforced polymers, 31 length on tensile aluminum samples, 32 metallic structures, 33–35 or aircraft wings 36 . The crack density index can be deceiving, since it decreases when cracks merge.…”

Optical high dynamic range acquisition of crack density evolution in cyclic loaded GFRP cross-ply laminates affected by stitching

“…Models have been developed where the crack density is used to predict the damage state of an arbitrary lay-up e.g. in ref [22][23][24][25][26][27][28][29]. When these models are further matured, it is possible to accurately predict the stiffness degradation of an arbitrary lay-up based on the crack density in the laminate.…”