Elastic coils: deformation micromechanics of coir and celery fibres

Abstract

Natural fibres, such as flax and hemp, are typically chosen as reinforcing elements in composites to replace traditional glass fibres due to their high stiffness, strength and low strain to failure. Some plant fibres such as coir and celery however possess high strains to failure, which could be utilised in a composite to enhance toughness. This paper reports on the use of Raman spectroscopy to follow the molecular deformation of single fibres of coir and celery. The technique is also used to characterise the orientation of the cellulose structure within the fibres. It is shown by mechanical testing of fibres that both celery and coir possess a non-linear stress-strain curve. Coir fibres however exhibit high strain to failure, whereas celery fibres are shown to have a much lower value of this parameter, despite having a similar coiled fibrillar structure. It is shown by using polarised Raman spectroscopy, and rotating the specimens with respect to the polarisation axis of the laser and measuring the intensity of the 1095 cm -1 Raman band, that both celery and coir fibres combine both axial and transverse orientation, due to their coiled structures. This is also confirmed by birefringence measurements. By following the shift in the central position of this Raman band as a function of cyclic deformation of the fibres, it is shown that the coir fibres recover their molecular deformation, whereas the celery does not show the same level of recovery. This difference between the fibres is postulated to be due to the fact that coir possesses an interlaced fibrillar structure, which remains intact, whereas the celery sub-fibrils unravel and orient towards the fibre axis during deformation.

Orientation of cellulose nanocrystals in electrospun polymer fibres

“…The Raman band intensity remained approximately constant with rotation angle for both PS/CNC-and PVA/CNC-based composite fibres. Previous research has shown that more ellipsoidal shapes are obtained for these polar plots when orientation of the cellulose occurs, be it in chain form or emanating from CNCs themselves [18,19]. This result suggests a lack of orientation of CNCs in both PS and PVA fibres.…”

Open Hole Tension of Coir-angustifolia Haw Agave Fibers Reinforced Hybrid Composite after Drilling Process

“…Then, these fibers were dried during 2 days at room temperature followed by oven drying for 2 hours. Coir fibers were manually twisted and then twisted fibers were made as coir fiber mat [2]. Meanwhile, agave fibers were composed manually in mat form.…”

“…Coir/glass hybrid composite has been studied by where coir fiber as core and glass fiber as shell, and woven coir and glass fiber [4]. The tensile strength of coir/glass hybrid composite tends to rise if increasing content of glass fiber in the composite [2]. Then, eco-friendly fibers used as reinforcement of hybrid composite are coir/jute fibers [5], coir/oil palm fibers [6], coir/sisal fibers [7], coir/angustifolia Haw agave fibers [8].…”

Mechanical Properties of Coir Rope-Glass Fibers Reinforced Polymer Hybrid Composites

“…coir fiber. Coir fiber was evaluated its mechanical properties by Kulkarni et al [4], Bakri and Eichhorn [5]. Its fiber has been used for reinforcing thermoset or thermoplastic in composite.…”