Use this URL to cite or link to this record in EThOS:
Title: Tough natural-fibre composites
Author: Techapaitoon, Mana
ISNI:       0000 0004 7232 9681
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2015
Availability of Full Text:
Access from EThOS:
Access from Institution:
Natural fibre composites (NFCs) possess relatively good specific strength and stiffness properties. However, natural fibres (NFs) often show relatively poor interfacial adhesion with respect to polymeric matrices, may contain relatively high levels of moisture and have variable mechanical properties due to the route by which they have been harvested and manufactured. These aspects may result in inconsistent mechanical properties of such composites, especially evident in a poor interlaminar fracture toughness. Thus, the present work investigates the mode I interlaminar fracture toughness, of NFCs based upon an anhydride-cured diglycidyl ether of bisphenol-A (DGEBA) epoxy matrix. Further, this matrix was used as a ‘control’ or modified with silica nanoparticles and/or rubbery microparticles. Two types of natural fibres were employed: unidirectional flax fibre (FF) and plain-woven regenerated cellulose fibre (CeF). Two very different routes were explored for the production of the NFCs based upon these materials. One route was via a resin infusion under flexible tooling (RIFT) process and a second route employed a resin transfer moulding (RTM) process. A very low value of the interlaminar fracture energy of about 20 J/m2 was measured for the flax fibre-reinforced plastics (FFRPs), using the ‘control epoxy matrix, produced by the RIFT manufacturing process which was initially employed. However, such composite manufactured via the RTM process possessed fracture energy of about 963 J/m2. Further, this value was found to increase to 1264 J/m2 when the epoxy matrix was modified using a combination of silica nanoparticles and rubbery microparticles. Hence, optimization studies using the RIFT manufacturing process were undertaken which led to a simple modification of this manufacturing route whereby the natural fibres were first oven-dried. This resulted in the final RIFT process giving values of the fracture toughness of the same order as those obtained from the RTM process. Also of note was the observation that the FFRPs manufactured via the RTM or the final RIFT process had similar values of toughness as those measured for glass fibre-reinforced plastics (GFRPs) made using the equivalent type of epoxy matrix. Similar observations were recorded in the case of the cellulose fibre-reinforced plastics (CeFFRPs). The present study has also considered the underlying mechanisms for the above observations and used analytical models to predict the toughening mechanisms and a good agreement between the predictions and the experimental data for the NFCs was obtained.
Supervisor: Kinloch, Anthony ; Taylor, Ambrose Sponsor: Imperial College London
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral