Effects of specimen length and fiber layup on transverse tensile fracture behavior of pultruded GFRP materials

• Investigation on quasi-brittle Mode I translaminar fracture behavior of pultruded GFRP materials. • Plateau-type R-curve response capturing full crack propagation in longer specimens. • Definition of a new method to selected valid data to determine fracture toughness for shorter specimens. • Exponential correlation between fracture toughness and transverse tensile strength. • Improved prediction of ultimate load using the bilinear damage evolution law. This paper presents an experimental and numerical study on the transverse tensile (Mode I) translaminar fracture behavior of pultruded glass fiber-reinforced polymer (GFRP) materials. First, wide compact tension (WCT) tests were conducted to investigate the effects of specimen length and fiber layup configuration. Failure modes, load–displacement curves and crack growth resistance curves (i.e., R-curves) are presented and analyzed. Some test results were influenced by compression damage at the free end of the specimens (end effect). To minimize its impact on the tensile fracture toughness and enable a more accurate assessment, a criterion is proposed to exclude data affected by this phenomenon. Alongside the experiments, advanced finite element (FE) models incorporating the Hashin failure criteria together with fracture toughness-based bilinear or linear-exponential damage evolution laws were developed to simulate the fracture behavior. The results indicate that pultruded GFRP materials exhibit quasi-brittle Mode I fracture behavior. Longer specimens exhibit a longer crack propagation process, and their corresponding R-curves effectively capture the full crack growth behavior, characterized by a distinct plateau region. In the cases studied, specimen length has a negligible effect on the material’s fracture toughness, but data affected by the end effect needs to be excluded (e.g., following the aforementioned criterion). A clear exponential relationship was also observed between fracture toughness and transverse tensile strength based on the available experimental data. In addition, both damage evolution laws reasonably capture the overall fracture behavior of pultruded GFRP materials, but the bilinear law provides more accurate predictions of ultimate loads.