Flax fibre bundle: A remarkable multi-scale unidirectional composite material

This is the authors' abstract. We don't add key points for this paper.

Flax fibre bundles possess a remarkable structure, mainly generated through intrusive growth, that can be likened to a unidirectional composite reinforced with discontinuous fibres, resulting in complex mechanical behaviour . The main objectives of the present work are to provide a detailed description of the microstructure and local mechanical properties of the bundle components to better explain their specific mechanical behaviour. Their tensile behaviour was examined using tensile testing and scanning electron microscopy , revealing disparities in the fracture phenomena. Micro-tomographic and multi-photon microscopy images revealed the presence of fibre ends (tips) with a high fraction of crystalline and oriented cellulose. Additional tests were conducted using atomic force microscopy to estimate the thickness and indentation modulus of the middle lamellae , the primary cell wall as well as the S1 and S2 layers. These observations elucidate the origin of the remarkable multi-scale structure of the flax bundles.