A straightforward procedure is described for utilizing experimentally evaluated bridging laws that characterize Mode II fracture growth of composite materials into numerical simulations. Unidirectional glass/epoxy end notch flexure (ENF) coupons have been fabricated and tested. Three data reduction schemes available in the literature were used for the construction of the R-curves together with the J-integral approach for the derivation of the bridging laws. Two traction— separation models have been utilized for the characterization of the fracture process zone (FPZ) developing during the delamination propagation process. The first model considers only the existence of a bridging zone behind the physical crack tip, whereas the proposed model considers both the existence of a bridging zone and of a cohesive zone in front of the physical crack tip. The traction—separation models were implemented into interface elements for the simulation of the ENF tests. Numerical results have shown that the proposed procedure together with the proposed traction— separation model is quite promising for simulations that involve Mode II fracture growth.

This study provides a simple yet effective procedure for the characterization of the fracture process zone (FPZ) developing in the interface of unidirectional laminates under Mode I delamination fracture. Double cantilever beam (DCB) coupons have been manufactured and tested. Three data reduction schemes available in the literature have been utilized for the calculation of the energy release rate (ERR) magnitude as a function of crack extension and the corresponding R-curves have been constructed. The R-curves were then reconstructed in terms of the experimentally registered pre-crack tip opening displacement (δ*) and analytical functions have been used to describe their concatenate trend. The J-integral approach was then applied over the analytical functions to derive the corresponding bridging laws that describe the FPZ. The derived bridging laws were appropriately modified according to three different traction–separation models and implemented into user-developed interface finite elements (UEL) for the simulation of the fracture tests in ABAQUS® commercial software. Comparisons between numerical and experimental results have shown that the proposed straightforward procedure leads to an effective traction–separation law that can be used as a material property of the modeled interface.

The increasing prominence of glass-fibre-reinforced plastics (GFRPs) in the wind energy industry, due to their exceptional combination of strength, low weight, and resistance to corrosion, makes them an ideal candidate for enhancing the performance and durability of wind turbine blades. The unique properties of GFRPs not only contribute to reduced energy costs through improved aerodynamic efficiency but also extend the operational lifespan of wind turbines. By modifying the epoxy resin with carbon nanofillers, an even higher degree of performance can be achieved. In this work, graphene nanoplatelet (GNP)-enhanced GFRPs are produced through industrial methods (filament winding) and coupons are extracted and tested for their mechanical performance after harsh environmental aging in high temperature and moisture. GNPs enhance the in-plane shear strength of GFRP by 200%, while reducing their water uptake by as much as 40%.