Fracture toughness-based models for damage simulation of pultruded GFRP materials

This paper presents a numerical study about the efficiency of implementing fracture toughness (G(c)) as an input to the simulation of damage progression in pultruded glass fibre reinforced polymer (GFRP) materials. The G(c) properties implemented in numerical modelling were determined through Compact Tension (CT) and Wide Compact Tension (WCT) fracture experiments conducted recently by the authors. The numerical models of those tests were developed in Abaqus software, using both built-in tools and user-defined material (UMAT) subroutines. The sensitivity of different damage parameters was assessed, taking into account the shape of the cohesive law (linear or exponential) and the ultimate transverse tensile stress, which ranged between the material strength, sigma(u), determined through mechanical characterization tests, and the cohesive stress, sigma(u), determined by assessing the initial slope in WCT fracture toughness results (with respect to the crack tip opening displacement). Validation of the numerical models was performed taking into account the experimental values of ultimate loads, softening slopes and crack growth rates. The experimentally based G(u) results provided a good agreement between numerical and experimental results for all pultruded GFRP materials investigated. The best fit between numerical and experimental results was obtained for two sets of properties: (i) linear cohesive law and material strength; and (ii) exponential cohesive law and cohesive stress.