Effective use of transient vibration damping results for non-destructive measurements of fibre-matrix adhesion of fibre-reinforced flax and carbon composites (original) (raw)
Related papers
Damping Performance of Flax Fibre Composites
2014
Dynamic mechanical analysis (DMA) and vibration beam testing (VBT) have been used to assess the damping properties of unidirectional, laminated and woven flax fibre (FF)/epoxy composites. The importance of the impregnation quality, the fibre/matrix adhesion, the quality of the fibres, the twist of the FF yarns and the crimp in the FF fabrics on these properties was investigated. Carbon and glass fibre reinforced epoxy composites were considered as comparison. Unidirectional FF instead of glass fibres led to a damping increase of about 133 %. While the intra fibre friction mechanisms were dominant for damping properties at small deformation (DMA), intra and inter-yarn frictions had more importance at larger deformation (VBT). The damping properties increased with the twist and crimp amount so as with a limited fibre/matrix adhesion. Damping maps revealed that the best compromise between damping and stiffness was obtained with high quality FF.
Prediction of dissipative properties of flax fibers reinforced laminates by vibration analysis
This study proposes an experimental-numeric method to identify the viscoelastic properties of a flax fibres reinforced composite laminate (flax/epoxide). The used method consists in identifying the evolutions of both loss factor and stiffness when vibrational frequency changes. In this way, several free-free symmetrically guided beams are excited on a dynamic range of 10 to 4000 Hz with sweep sine excitation focused around the 4-first’s modes. Fractional derivative Zener model is used to identify the on-axis ply complex moduli and describe the laminate dissipative linear behavior with the classical laminate theory. Results obtained on a quasi-isotropic laminate show that this model adequately predicts the vibrational behavior of the tested laminates.
International Journal of Applied Mechanics, 2016
In this paper, the damping properties of flax fiber reinforced composites were investigated. Throughout a series of resonance vibration tests, the natural frequencies and the modal damping were evaluated. A numerical modelling was also produced by using a finite element model to determine the energies dissipated in each layer of the laminate structure in order to calculate the damping factors. The results obtained for the dynamic properties of flax fiber reinforced composites from experimental data and numerical analysis method show close agreement. The effect of fiber orientations on the damping behavior for this material was investigated. Another part of our work was to insert a thin viscoelastic layer within the flax fiber laminate. The interposition of this viscoelastic layer had a significant influence on the vibration behavior, bending stiffness and damping factors.