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Fibre-direction strain measurement in a composite ply under pure bending using Digital Volume Correlation and Micro-focus Computed Tomography

Fibre-direction strain measurement in a composite ply under pure bending using Digital Volume Correlation and Micro-focus Computed Tomography
Fibre-direction strain measurement in a composite ply under pure bending using Digital Volume Correlation and Micro-focus Computed Tomography
This paper presents an experimental demonstration and validation of high-resolution three-dimensional experimental strain measurement using Digital Volume Correlation (DVC) on Carbon-Fibre Reinforced Polymers (CFRPs), via through-thickness strain analysis under a state of pure bending. To permit the application of DVC to displacements and/or strain measurements parallel to the fibre direction in well-aligned unidirectional (UD) materials at high volume fractions, a methodology was developed for the insertion of sparse populations of 400 nm BaTiO3 particles within the matrix to act as displacement trackers (i.e. fiducial markers). For this novel material system, measurement sensitivity and noise are considered, along with the spatial filtering intrinsic to established DVC data processing. In conjunction with Micro-focus Computed Tomography (µCT), the technique was applied to a simple standard specimen subjected to a four-point flexural test, which resulted in a linear strain distribution through the beam thickness. The high-resolution, fibre-level strain distributions (imaged at a voxel resolution of ∼0.64 µm) were compared against the classical beam theory (Euler-Bernoulli) in incrementally decreasing averaging schemes and different sub-set sizes.
Different sampling and averaging strategies are reported, showing that DVC outputs can be obtained that are in very good agreement with the analytical solution. A practical lower limit for the spatial resolution of strain is discerned for the present materials and methods. This study demonstrates the effectiveness of DVC in measuring local strains parallel to the fibre direction, with corresponding potential for calibration and validation of micromechanical models predicting various fibre-dominated damage mechanisms.
Carbon-Fibre Reinforced Polymers (CFRPs),, Microstructures,, Micromechanics, Micro-focus Computed Tomography (μCT), Digital Volume Correlation (DVC),, Strain mapping
0021-9983
Schoberl, E.
eccd55e0-c7fa-4903-8e20-d9dd52c3454a
Mavrogordato, M.N.
f3e0879b-118a-463a-a130-1c890e9ab547
Sinclair, I.
6005f6c1-f478-434e-a52d-d310c18ade0d
Spearing, S.M.
9e56a7b3-e0e8-47b1-a6b4-db676ed3c17a
Schoberl, E.
eccd55e0-c7fa-4903-8e20-d9dd52c3454a
Mavrogordato, M.N.
f3e0879b-118a-463a-a130-1c890e9ab547
Sinclair, I.
6005f6c1-f478-434e-a52d-d310c18ade0d
Spearing, S.M.
9e56a7b3-e0e8-47b1-a6b4-db676ed3c17a

Schoberl, E., Mavrogordato, M.N., Sinclair, I. and Spearing, S.M. (2020) Fibre-direction strain measurement in a composite ply under pure bending using Digital Volume Correlation and Micro-focus Computed Tomography. Journal of Composite Materials. (In Press)

Record type: Article

Abstract

This paper presents an experimental demonstration and validation of high-resolution three-dimensional experimental strain measurement using Digital Volume Correlation (DVC) on Carbon-Fibre Reinforced Polymers (CFRPs), via through-thickness strain analysis under a state of pure bending. To permit the application of DVC to displacements and/or strain measurements parallel to the fibre direction in well-aligned unidirectional (UD) materials at high volume fractions, a methodology was developed for the insertion of sparse populations of 400 nm BaTiO3 particles within the matrix to act as displacement trackers (i.e. fiducial markers). For this novel material system, measurement sensitivity and noise are considered, along with the spatial filtering intrinsic to established DVC data processing. In conjunction with Micro-focus Computed Tomography (µCT), the technique was applied to a simple standard specimen subjected to a four-point flexural test, which resulted in a linear strain distribution through the beam thickness. The high-resolution, fibre-level strain distributions (imaged at a voxel resolution of ∼0.64 µm) were compared against the classical beam theory (Euler-Bernoulli) in incrementally decreasing averaging schemes and different sub-set sizes.
Different sampling and averaging strategies are reported, showing that DVC outputs can be obtained that are in very good agreement with the analytical solution. A practical lower limit for the spatial resolution of strain is discerned for the present materials and methods. This study demonstrates the effectiveness of DVC in measuring local strains parallel to the fibre direction, with corresponding potential for calibration and validation of micromechanical models predicting various fibre-dominated damage mechanisms.

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More information

Accepted/In Press date: 21 March 2020
Keywords: Carbon-Fibre Reinforced Polymers (CFRPs),, Microstructures,, Micromechanics, Micro-focus Computed Tomography (μCT), Digital Volume Correlation (DVC),, Strain mapping

Identifiers

Local EPrints ID: 438944
URI: http://eprints.soton.ac.uk/id/eprint/438944
ISSN: 0021-9983
PURE UUID: c37b2871-5427-4d57-8adf-a4adf6c7393f
ORCID for S.M. Spearing: ORCID iD orcid.org/0000-0002-3059-2014

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Date deposited: 27 Mar 2020 17:30
Last modified: 07 Oct 2020 01:49

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