Development of High Performance Natural Fibre Composites

Abstract

Jute fibre offers similar properties for use as a reinforcing material in the manufacture of high-performance composites on the grounds of its low cost and mechanical properties which are comparable with other natural fibres like flax, sisal and hemp. However, jute fibre composites have a low fibre volume fraction when created using the vacuum infusion process; this is a result of the coarseness of the fibre which is caused by the presence of non-cellulosic components in the fibre. Mechanical performance of natural fibres and their composites are mainly influenced by their constituents (cellulose, lignin and hemicellulose), where cellulose content is accountable for the tensile strength of the fibre and the stiffness of the fibre is governed by the micro-fibrillar arrangement of the fibre. In this regard, for better load sharing, it is necessary to break the inter-fibrillar network of the fibre. In addition to that, another major problem of natural fibre composites is the incompatibility between the hydrophilic natural fibres and the hydrophobic matrices. Additionally, jute fibre in a traditional preform has twist and crimp that can reduce the mechanical properties of the composites. The primary objective of this research work is to design and develop new jute fibre preform architecture without twist and crimp, to improve the mechanical properties of the composites. Development of the preform involves fibre separation, low concentration alkali treatment of the jute fibre, application of sizing and hydraulic pressing. These highly packed preforms are still drapeable to make composites with almost any desired shape. Alkali treatment was done to increase functional group of fibres. A further intention of the research is to introduce graphene 2-D materials (graphene oxide and graphene flakes) onto the surface of alkali treated jute fibres. A single fibre tensile test and a microbond pull-out test were used to evaluate the performance of graphene deposition on the jute fibres. The mechanical properties of the resulting composites were examined by longitudinal and transverse tensile testing. It was found that 1% alkali concentration with 24 hour time frame enhanced the mechanical properties of the composites, due to the improvement of the fibre-matrix compatibility and fibre packing. New fibrillated jute fibre architecture offers a Young's modulus improved by ~162% compared to that of untreated jute fibre composites. A 0.5% alkali solution further increased the Young’s modulus of the composites by ~34% and the tensile strength by ~31.4%. Finally, Graphene-coated composites exhibit a further 61.5% improvement in Young’s modulus and ~63.5% in the tensile strength of the composite. Graphene oxide coating also increased the transverse tensile strength of the composites by ~369% compared to untreated jute fibre composites. The results also indicate that, with a similar fibre volume fraction of the composites, graphene oxide coated jute fibre can offer similar stiffness to sglass fibre composites in the unidirectional tensile test. Thus, a very low volume fraction of graphene attachment on jute fibre can offer the opportunity of replacing a large proportion of the glass fibre currently used in manufacturing composites.

Date of Award	1 Aug 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Hugh Gong (Supervisor) & Prasad Potluri (Supervisor)