Abstract
Fibres from annual plants are a sustainable alternative for glass fibres in composite manufacturing. However, both synthetic fibres, such as carbon fibres, and cellulosic fibres exhibit heterogeneities along their lengths, which appeared as localized morphological disorientations known as kink-bands. In plant fibres, kink-bands occur due to growing conditions under abiotic stress, during the retting stage and the fibre extraction process. Many studies have been conducted to identify the origin of such kink-bands and their impact on the mechanical behaviour of composites but their characteristics and fine ultrastructure remain unclear. Presence of cavities in transition zones was assessed by SEM and AFM and confirmed by low intensity SHG signal, especially when large size kink-bands are considered. Moreover, transverse indentation modulus is obtained by AFM in Peak force mode; no substantial differences were observed between the kink-band and defect-free regions with average values ranging from 6.2 to 7.3 GPa. Also, important MFA changes are 2 measured through SHG imaging, especially in large kink-bands with local misorientation up to 47°. Thus, this intense investigation of kink-band areas reveals ultrastructure heterogeneities and the presence of local defects.