Entity

Time filter

Source Type


Qian C.,Knowledge Center Wind Turbine Materials and Constructions | Westphal T.,Knowledge Center Wind Turbine Materials and Constructions | Kassapoglou C.,Technical University of Delft | Nijssen R.P.L.,Knowledge Center Wind Turbine Materials and Constructions
Composite Structures | Year: 2013

The fatigue behaviour of small scale composite unit cells consisting of seven fibres and surrounding matrix is developed for use in fatigue simulations. The predicted fatigue properties of these 7-fibre unit cells are compared with the fatigue properties of single glass fibres and of unidirectional composite dog-bone specimens. These predicted results provide stochastic fatigue characteristics that can be used as input for modelling the fatigue behaviour of larger composite structures. © 2012 Elsevier Ltd. Source


Zarouchas D.,Technical University of Delft | Zarouchas D.,Knowledge Center Wind Turbine Materials and Constructions | Nijssen R.,Knowledge Center Wind Turbine Materials and Constructions
Journal of Adhesion Science and Technology | Year: 2016

Wind turbine blades are made of integrated composite parts bonded together using structural adhesives. The blades are among the most severely multi-axial fatigue loaded structures and the bonded joints play an important role in their structural integrity. For better understanding of the mechanical performance of the bonded joints, thorough knowledge is required on the multi-axial behaviour of the bulk adhesive. In this study, tubular specimens consisting of glass/epoxy bonding paste were subjected to uniaxial (tension, compression and torsion) and biaxial (tension-torsion and compression-torsion) static tests. Different biaxial ratios were used and the stress-strain responses were recorded using strain-gauges. The imposed biaxial stress ratios influenced the stress-strain behaviour of the material system, especially the compression and the shear stress-strain. A material model was developed based on the experimental observations taking into account the non-linear behaviour and the effects of the biaxial ratios and it was implemented together with a progressive damage scenario into a finite-element model. The experimental failure patterns were compared with the numerical simulations and a good match was found. © 2016 Taylor & Francis. Source


Qian C.,Knowledge Center Wind Turbine Materials and Constructions | Westphal T.,Knowledge Center Wind Turbine Materials and Constructions | Nijssen R.P.L.,Knowledge Center Wind Turbine Materials and Constructions
Computational Materials Science | Year: 2013

A multi-scale numerical fatigue modelling methodology is proposed for the characterization of axial tension-tension fatigue behaviour of unidirectional Glass Fibre Reinforced Polymer (GFRP) composites. The methodology is developed to link the dominant fibre failure mechanism to composite fatigue properties, by a three-step geometrical up-scaling process. This study aims to provide composite fatigue predictions by only using the material properties of fibres and matrix. Compared to the experimental results, the fatigue model over-predicts fatigue lives and gives reasonable estimations of axial stiffness degradation curves of the unidirectional GFRP composite dog-bone specimens. © 2012 Elsevier Ltd. All rights reserved. Source


Sari J.,Knowledge Center Wind Turbine Materials and Constructions | Nijssen R.,Knowledge Center Wind Turbine Materials and Constructions | Westphal T.,Knowledge Center Wind Turbine Materials and Constructions | Stammes E.,Knowledge Center Wind Turbine Materials and Constructions | Van Delft D.R.V.,Knowledge Center Wind Turbine Materials and Constructions
European Wind Energy Conference and Exhibition 2010, EWEC 2010 | Year: 2010

An accurate model for constant amplitude description can be used as a tool to obtain a more reliable life prediction of wind turbine composites under variable amplitude loading. Such a fatigue model describes fatigue behavior under all possible loading conditions. Experimental data are typically only available for selected load types. The accuracy of the model in describing constant amplitude fatigue data can be investigated by testing the fit of the model to the available fatigue test data. Popular ways to model constant amplitude fatigue life of a material are using the S-N curve (load versus life for a particular load case) and combining S-N curves and static properties in the Constant Life Diagram (CLD, describing fatigue life as a function of alternating stress and mean stress). The objective of this paper is to describe parameter estimation from the large fatigue dataset that comes from the UPWIND/INNWIND projects and compare the parameter sets of the models. Parameter estimation is done using regression analysis and statistical evaluation of the results. Two forms of the CLD, namely Linear and Modified Goodman diagrams are coupled with linear-log and log-log S-N curves to obtain a parameterized description of constant amplitude fatigue behavior. The best fit parameter sets of the models to the fatigue test data of UPWIND/INNWIND UD glass/epoxy reference material are generated and compared. Discussion and conclusion on the implementation of the models to the fatigue data of UPWIND/INNWIND reference material is presented. Source

Discover hidden collaborations