Exploiting synchrotron X-ray tomography for a novel insight into flax-fibre defects ultrastructure

TL;DR

This study uses synchrotron X-ray microtomography to investigate the ultrastructure of flax-fibre defects, revealing pore organization and their relation to kink-bands, which impact fibre mechanical properties.

Contribution

The paper introduces a novel application of synchrotron phase-contrast X-ray microtomography to analyze flax-fibre defects at the ultrastructural level, linking pore morphology to kink-band formation.

Findings

Pores are organized concentrically around the lumen.

Pores are located at the interface between cellulose layers.

Increased porosity correlates with severe defect zones.

Abstract

Flax fibres are valuable reinforcements for tomorrow's composites. However, defects called kink-bands, which mainly appear on fibres during the extraction and transformation phases, might affect their mechanical properties. Defects induced pores, within the kink-band are investigated in this work. They were morphologically explored using synchrotron phase-contrast X-ray microtomography, a technique that displays a sharp 3D representation of the pores. The study highlights the link between kink-bands and secondary cell wall ultrastructure. Pores are organised concentrically around the lumen, and their low thickness suggest that they are located at the interface between cellulose layers within S2 (G) layer. Moreover, the pores inclination with reference to the lumen axis follows the typical microfibrillar angle changes observed in the literature in the kink-band region. The volumes of the pores were measured, and a local increase in porosity was revealed in zones where defects are most severe along the fibre.