Investigation of the effect mechanism of dislocations on natural fibres mechanical properties

Dislocations are thought the weakest link in natural fibres which have negative effects on the tensile strength of the fibres. With the aim to investigate the effect of dislocations on the mechanical properties of natural fibres (hemp), this paper presented a systematic approach to examine the dislocations in natural fibres firstly by optical microscope (OM) and field emission scanning electron microscope (FEG-SEM) for the morphologies of the dislocations and by X-ray diffraction (XRD) and attenuated total reflection fourier transform infrared spectroscopy (ATR-FTIR) for the crystallinity index. Attenuated total reflection fourier transform infrared spectroscopy (ATR-FTIR) was mainly employed for the examination of hydrogen bonds, removal of hemicellulose and lignin in the dislocation regions of natural fibres. The results showed that the effects of dislocations on the mechanical properties of fibres by the following three ways: 1) debonding of hydrogen bonds in cellulose especially the O(3)H—O(5) hydrogen bonds, which could reduce the crystallinity index and strain energy; 2) removal of hemicellolose, which could separate the different layers in cell wall, intensify amorphous features of natural fibres and reduce transfer of shear stress between cellulose microfibrils and lignin; 3) removal of S-lignin, which could reduce the strength of lignin network and the shear stress transferred from cellulose microfibrils.