Interlaminar Fracture Behaviour of Emerging Laminated-Pultruded CFRP Plates for Wind Turbine Blades under Different Loading Modes
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Xi LI (NETHERLANDS), Francisco MONTICELI (NETHERLANDS), John-Alan PASCOE (NETHERLANDS), Yasmine MOSLEH (NETHERLANDS)Abstract :
Driven by the energy transition and the reduction of carbon emissions, wind turbine blades have been designed in increasing sizes for more energy capture. To achieve larger rotors, carbon fibre reinforced polymer (CFRP) composites, due to their outstanding mechanical performance, have been utilized in spar caps to carry and transfer increased loads in the flap direction [1].
Recently, pultruded CFRP plates have emerged as an affordable high performance material for wind turbine design. To enable the creation of thicker laminates, pre-cured plates are bonded together using an epoxy resin. Considering the dominant role of such CFRP composites in load-bearing structures of wind turbine blades, it is necessary to characterize the fracture behaviours of these novel laminates under different modes, and to further establish fracture criteria for numerical simulations towards design allowable and service life.
The research target of present work is ZoltekTM PX35 pultruded plate bonded with SWANCOR 2511-1AL/BL epoxy resin. Specimens were prepared based on the standards for double cantilever beam tests (ASTM D5528), end-loaded split tests (ISO 15114), and mixed-mode bending tests (ASTM D6671). These tests were performed quasi-statically to construct a failure envelope involving the different fracture modes that could occur during the service life of large-scale structures.
Mode-I crack propagation showed stick-slip behaviour, resulting in brittle failure in a few consecutive step. Inspecting the fracture surfaces demonstrates that cohesive failure within the bonded layer is the dominant failure mode, while some local regions exhibit adhesive failure at the interface between the pultruded plate and the bonded layer or substrate failure with peeling-off CFRP strips at the pultruded plate. Mode-II fracture tests on the other hand, presented a more stable crack growth, and cohesive failure within the bonded layer was found to be the main failure mode. By combining mixed-mode bending tests, power law and Benzeggagh-Kenane law criteria were established to numerically describe the fracture behaviours of bonded ZoltekTM PX35 pultruded plates.
Overall, the results show that the available standards for fracture toughness testing are also suitable for these laminated-pultruded composite plate structures, enabling the material characterization needed for design.
Acknowledgements
Funded by the European Union under GA No. 101091409. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them.
Recently, pultruded CFRP plates have emerged as an affordable high performance material for wind turbine design. To enable the creation of thicker laminates, pre-cured plates are bonded together using an epoxy resin. Considering the dominant role of such CFRP composites in load-bearing structures of wind turbine blades, it is necessary to characterize the fracture behaviours of these novel laminates under different modes, and to further establish fracture criteria for numerical simulations towards design allowable and service life.
The research target of present work is ZoltekTM PX35 pultruded plate bonded with SWANCOR 2511-1AL/BL epoxy resin. Specimens were prepared based on the standards for double cantilever beam tests (ASTM D5528), end-loaded split tests (ISO 15114), and mixed-mode bending tests (ASTM D6671). These tests were performed quasi-statically to construct a failure envelope involving the different fracture modes that could occur during the service life of large-scale structures.
Mode-I crack propagation showed stick-slip behaviour, resulting in brittle failure in a few consecutive step. Inspecting the fracture surfaces demonstrates that cohesive failure within the bonded layer is the dominant failure mode, while some local regions exhibit adhesive failure at the interface between the pultruded plate and the bonded layer or substrate failure with peeling-off CFRP strips at the pultruded plate. Mode-II fracture tests on the other hand, presented a more stable crack growth, and cohesive failure within the bonded layer was found to be the main failure mode. By combining mixed-mode bending tests, power law and Benzeggagh-Kenane law criteria were established to numerically describe the fracture behaviours of bonded ZoltekTM PX35 pultruded plates.
Overall, the results show that the available standards for fracture toughness testing are also suitable for these laminated-pultruded composite plate structures, enabling the material characterization needed for design.
Acknowledgements
Funded by the European Union under GA No. 101091409. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them.