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Title: Nano-reinforced epoxy resin for carbon fibre fabric composites
Author: Liu, Yan
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2016
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This thesis reports a study of the effects on processing and properties of incorporating nano-scale reinforcements (multiwall carbon nanotubes, MWCNTs) in the matrix of epoxy- carbon fibre (CF) laminate composites to produce multi-scale composites (M-SC). The main aim of this research was to study the effects of MWCNTs on matrix toughening and the through-thickness properties of M-SCs based on a commonly used aerospace grade epoxy resin — triglycidyl-p-aminophenol (TGPAP) cured with diaminodiphenyl sulphone (DDS). In order to improve resin processing, diglycidyl ether of bisphenol F (DGEBF) was added into the TGPAP/DDS system as a reactive diluent. Factorial experimental design (FED) was used to optimize the composition of this tri-component system to obtain high Tg and low resin viscosity, which gave a TGPAP/DGEBF/DDS system with 30.56 wt.% of DGEBF and a chemical stoichiometry of 0.5. Three types of MWCNTs were used; as-received (AR-), base-washed (BW-) and amine functionalized (NH2-). These were shear-mixed with both the bi- and tri-component systems using a 3-roll mill to produce nanocomposite matrices (NCM). The curing behaviour, dispersion state of MWCNTs in the resin and processability of NCMs were studied to decide upon the preparation method for the final M-SC. The fracture toughness (KIC) and the flexural properties of NCM were affected by both MWCNTs and the matrix type; thus KIC increased by up to 8 % in TGPAP/DDS NCM but decreased by 23% in TGPAP/DGEBF/DDS NCM with 0.5 wt.% AR-CNTs. The addition of both non-functionalized and functionalized MWCNTs increased the flexural modulus. The failure mechanism of NCMs was found to be dominated by the size and distribution of CNT aggregates and the behaviour of MWCNTs, both those dispersed in the matrix and in aggregates. The addition of functionalized MWCNTs increased the interfacial bonding between MWCNT and epoxy resin and thus improved the mechanical properties. All the NCM systems were taken forward to manufacture M-SC using a hybrid resin film infusion (RFI)/hot press process. The fibre volume fraction and the void content could be controlled at 43 ± 5 % for M-SC with TGPAP/DDS NCM and 60 ± 6 % for M-SC with TGPAP/DGEBF/DDS NCM. M-SCs were characterised using a range of tests, including flexural, interlaminar shear strength (ILSS), mode-II interlaminar fracture toughness (GIIC), low velocity impact and compression after impact (CAI). The most obvious improvement occurred for the M-SC with tri-component system with 0.5 wt.% CNTs, whereILSS increased by 16 % upon adding NH2-CNTs and GIIC increased significantly on addition of 0.5 wt.% AR-CNTs and NH2-CNTs, by 85% and 184% respectively. However the effect of MWCNTs on other properties was at best marginal. For example, for the M-SC with TGPAP/DDS, the flexural modulus and ILSS only increased by 4.1 % and 2.3 % with 0.5 wt.% AR-CNT.
Supervisor: Wilkinson, Arthur ; Kinloch, Ian Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: carbon nanotube ; multi-scale composites ; carbon fibre ; fracture toughness ; interlaminar properties ; impact ; rheology