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Experimental validation of bend-twist coupling stiffness predictions Vincent Maes , Terence Macquart, Paul Weaver, Alberto Pirrera 8 th Annual Conference of the CDT in Advanced Composites for Innovation and Science 16 th April 2019 2 Overview

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SLIDE 1

Experimental validation

  • f bend-twist coupling

stiffness predictions

Vincent Maes, Terence Macquart, Paul Weaver, Alberto Pirrera 8th Annual Conference of the CDT in Advanced Composites for Innovation and Science

16th April 2019

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SLIDE 2

Overview

2

  • Introduction
  • Numerical Work:
  • Demonstrator Design
  • Model Comparison
  • Experimental Work:
  • Build & Testing
  • Results
  • Conclusions and Future Work
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SLIDE 3

Introduction

3

  • Literature
  • Bend-Twist Coupling has demonstrated advantages,
  • Modelling techniques disagree on performance [1,2].
  • Industry
  • Design remain unchanged, pending validation.

3.

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SLIDE 4

Numerical Work: Demonstrator Design

4

  • 5 demonstrators:
  • BECAS, VABS, and 3D FEM shows:
  • 100% agreement between BECAS and VABS
  • Primary stiffness coefficients (𝑇44, 𝑇66) within 1%
  • Coupling stiffness coefficients (𝑇46) within 2.5%
  • Strong dependence on input handling
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SLIDE 5

Numerical Work: Model Comparison

5

  • Numerical Studies:
  • Looking into handling of features as suggested by Saravia et al. [4].
  • Tweaking lay-up in corner, differences can be reduced to under 2%

Terms

  • Diff. [%]

𝑇44 326.92E-6 325.30E-6

  • 0.5

𝑇66 433.46E-6 432.07E-6

  • 0.3

𝑇46

  • 75.32E-6
  • 78.91E-6
  • 4.8

Inner corner

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SLIDE 6

Experimental Work: Build & Testing

6

  • Built at the NCC out of 913 E glass
  • Tested at University of Bristol:
  • Using calibrated inclinometers
  • Repeated load cycles
  • Manual displacement loading
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SLIDE 7

Experimental Work: Results

7

  • Initial testing of first two beams:
  • Results repeatable and match well,
  • Material appears less stiff than modelled,
  • Awaiting material characterization for final validation.

0.5 1 1.5 2 2.5 3 0.5 1 1.5 2

Axial twist [deg] Distance along free length of beam [m] Beam (BECAS) Shell (FEM) Shell (FEM) w/ Material Knockdown BEAM (VABS) Experimental Sets Beam (BECAS) w/ Material Knockdown

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SLIDE 8

Conclusions

8

  • Initial numerical studies show good correlation, but:
  • High sensitivity to model generation/inputs,
  • Some sensitivity to model simplifications,
  • Potentially higher sensitivity to manufacturing tolerances.
  • Demonstrators built and being tested.
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SLIDE 9

Future Work

9

  • Complete testing campaign:
  • Confirm material properties
  • Validate model predictions
  • Run extended numerical studies:
  • Further calibration of modelling techniques
  • Assessing sensitivity of stiffness coefficients:
  • To modelling simplifications,
  • Manufacturing tolerances.
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SLIDE 10

Acknowledgements

10

The authors would like to acknowledge Vestas for their support of this research.

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SLIDE 11

Thank you for listening. Questions?

vincent.maes@bristol.ac.uk

References:

1. Chen, H., et al., A critical assessment of computer tools for calculating composite wind turbine blade properties. Wind Energy, 2010. 13: p. 497-516. 2. Lekou, D.J., et al., A Critical Evaluation of Structural Analysis Tools used for the Design of Large Composite Wind Turbine Rotor Blades under Ultimate and Cycle Loading. ICCM20 (Proc.), 2015. 3. Chehouri, A., et al., Review of performance optimization techniques applied to wind turbines. Applied Energy, 2015. 142: p. 361-388. 4. Saravia, C., et al., On the determination of the mechanical properties of wind turbine blades: Geometrical aspects of line based algorithms. Renewable Energy, 2017. 105: p. 55-65.