Transverse Fracture Behavior of Pultruded GFRP Materials in Tension: Effect of Fiber Layup

This paper presents an experimental study about the transverse tensile fracture properties of several off-the-shelf pultruded glass fiber-reinforced polymer (GFRP) materials, with different fiber layups and geometries and significant variations of elastic and strength properties. Determining these fracture properties should enable more-accurate advanced numerical simulation of the failure behavior of pultruded GFRP materials and members used in civil engineering applications, namely in the analysis of structural connections or members subjected to concentrated loads (web-crippling phenomenon). For the different GFRP materials, based on compact tension (CT) and wide compact tension (WCT) tests, both the critical energy release rate (Gc) and the cohesive law were determined at the laminate level, applying the following four data reduction methods: standardized analytical expressions, J-integral, Compliance Calibration (CC), and Modified Compliance Calibration (MCC). The CT tests were unsuccessful in reaching a stable propagation stage and provided overestimations of Gc. Conversely, the WCT tests were able to achieve a stable propagation stage and thus provided more-consistent estimates of Gc and cohesive laws. Among the various data reduction methods, a good agreement was found between visually based methods. On the contrary, the MCC method was found to provide significantly lower estimates of Gc when compared with the remainder. Different reasons for this variation are identified and discussed. The sample of GFRP materials presented a significant variation of Gc, which was found to be highly dependent on the fiber architecture: (i) for the material with weaker transverse reinforcement layers, consisting only of continuous filament mats, Gc ranged between 6.6 and 10.7 N/mm; (ii) materials presenting cross-ply layers presented intermediate Gc values, ranging from 13.1 and 21.3 N/mm; and (iii) materials comprising quasi-isotropic layups presented the highest overall Gc estimates, ranging from 19.3 N/mm (similar to cross-ply materials) to above 150 N/mm.