Non-destructive evaluation and modelling of unidirectional carbon fiber composite ropes

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

A holistic condition monitoring approach for carbon fiber composite ropes is presented in this dissertation. The concept for the non-destructive evaluation was created considering demanding specifications, while enabling online damage detection, localisation, characterisation, decision and prediction. The commercial eddy current probes tested were unable to detect fiber breaks in the electrically anisotropic material and therefore novel probes optimised for unidirectional carbon fiber inspection were designed and tested to reach high sensitivity to local variations in conductivity. Localisation and high-speed inspection capabilities were demonstrated in field conditions. A defect was detected and localised in a rope moving at 4 m/s. Contactless high-speed inspection is a requirement for uninterrupted operation of a rope and the capabilities presented here have not been published before. X-ray laminography using photon-counting detectors was developed for characterisation, because the state-of-the-art is missing a solution that provides more information than plain 2D digital radiography using photon-counting detectors, but is easier to implement in field conditions than tomography. Near-planar defects like delaminations can be challenging for X-ray inspection, but it was shown that having multiple angles of incidence allows the reconstruction and characterisation of low-volume defects at various orientations. The complex nature of damage evolution in composites makes acceptance criteria difficult to define and therefore a simulation approach is presented in this dissertation. The approach is based on 3D finite element multiscale modelling using forward micromechanics instead of resorting to calibration, inverse micromechanics or microstructure generators to account for the lack of exact microscale inputs. While nanoindentation did not provide a reliable means for determining material properties, image-based meshing from micrographs was successfully used. The simulations were in good agreement with the experimental results and showed the effect of a resin-rich zone. Predicting the remaining service life remains a topic for future research.
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Vilaça, Pedro, Supervisor
  • Hänninen, Hannu, Supervisor
Publisher
Print ISBNs978-952-60-8720-7
Electronic ISBNs978-952-60-8721-4
Publication statusPublished - 2019
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • carbon fiber
  • non-destructive evaluation
  • modelling

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