Graphene/sol–gel modified polyurethane coating for wind turbine blade leading edge protection : properties and performance

The development of two novel elastomeric erosion resistant coatings for the protection of wind turbine blades is presented. The coatings are prepared by modifying polyurethane (PU) with (i) hydroxyl functionalised graphene nanoparticles (f-GNP) and (ii) f-GNP and a hydrophobic silica-based sol–gel (SG). Tensile, monotonic and cyclic compression and tearing tests have been conducted on the neat PU and the two newly developed elastomeric PU nanocomposites (PU + GNP and PU + GNP + SG) to allow their properties to be compared. The test results showed that the mechanical properties of PU and the modified PUs have strong dependency on temperature, strain rate and nanoparticles loading and addition of GNP and SG to PU improved the mechanical properties. Compared to PU, Young’s modulus and modulus of toughness of PU + GNP + SG increased 95% and 124%, respectively. The PU + GNP nanocomposite displayed the highest tearing strength and the PU + GNP + SG nanocomposite showed the highest elongation at break. An investigation of the microstructures of the modified PUs by FTIR, field emission scanning electron microscope (FESEM) and energy-dispersive X-ray spectroscopy (EDX) are discussed. Hydrophobicity of the PU and developed PU nanocomposites are reported by measuring their water droplet contact angles and their free surface energies

Failure Processes in Elastic Fiber Bundles

The fiber bundle model describes a collection of elastic fibers under load. the fibers fail successively and for each failure, the load distribution among the surviving fibers change. Even though very simple, the model captures the essentials of failure processes in a large number of materials and settings. We present here a review of fiber bundle model with different load redistribution mechanism from the point of view of statistics and statistical physics rather than materials science, with a focus on concepts such as criticality, universality and fluctuations. We discuss the fiber bundle model as a tool for understanding phenomena such as creep, and fatigue, how it is used to describe the behavior of fiber reinforced composites as well as modelling e.g. network failure, traffic jams and earthquake dynamics.Comment: This article has been Editorially approved for publication in Reviews of Modern Physic

Root Causes and Mechanisms of Failure of Wind Turbine Blades: Overview

A review of the root causes and mechanisms of damage and failure to wind turbine blades is presented in this paper. In particular, the mechanisms of leading edge erosion, adhesive joint degradation, trailing edge failure, buckling and blade collapse phenomena are considered. Methods of investigation of different damage mechanisms are reviewed, including full scale testing, post-mortem analysis, incident reports, computational simulations and sub-component testing. The most endangered regions of blades include the protruding parts (tip, leading edges), tapered and transitional areas and bond lines/adhesives. Computational models of different blade damage mechanisms are discussed. The role of manufacturing defects (voids, debonding, waviness, other deviations) for the failure mechanisms of wind turbine blades is highlighted. It is concluded that the strength and durability of wind turbine blades is controlled to a large degree by the strength of adhesive joints, interfaces and thin layers (interlaminar layers, adhesives) in the blade. Possible solutions to mitigate various blade damage mechanisms are discussed

Wpływ mikrostruktury na zniszczenie kompozytu - analiza numeryczna

In this paper, microstructural effects on the damage resistance of composite materials are studied numerically using methods of computational mesomechanics of materials and virtual experiments. Several methods and programs for automatic generation of 3D microstructural models of composites based on the geometrical description of microstructures as well as on the voxel array data have been developed and tested. 3D FE (Finite Element) simulations of the deformation and damage evolution in particle reinforced composites are carried out for different microstructures of the composites. Some recommendations for the improvement of the damage resistance of lightweight metal matrix composites with ceramic reinforcements are obtained.W artykule przedstawiono analizę wpływu mikrostruktury materiałów kompozytowych na ich odporność na zniszczenie, przeprowadzając badania symulacyjne oparte na modelach obliczeniowych stosowanych w mezo-mechanice oraz na eksperymentach numerycznych. Opisano zaproponowane i przetestowane programy do automatycznego generowania trójwymiarowych modeli mikrostruktur kompozytowych bazujące na opisie geometrycznym z zastosowaniem techniki wokseli (3-wymiarowych odpowiedników pikseli). Przeprowadzono symulacje deformacji i ewolucji zniszczenia elementów skończonych reprezentujących kompozyty z wtrąceniami punktowymi o różnej mikrostrukturze. Sformułowano pewne wytyczne dla poprawy odporności na zniszczenia lekkich kompozytów zbudowanych z metalicznego lepiszcza wzmacnianego ceramiką