Graphene-Enhanced Structural Composites

  • Murniyati Ahmad Mahtar

Student thesis: Phd

Abstract

The use of fibre reinforced polymer (FRP) composites as the primary loadbearing structure has significantly increased in many industries such as oil and gas, aerospace, automotive, marine, and civil infrastructure. The development of advanced forms of FRP materials, for instance, high-performance resin systems and new types of reinforcement, such as nanomaterials (e.g. graphene), are key factors driving the increased applications of this material over the recent years. This study investigated the reinforcement benefit of graphene nanoplatelet (GNP) and functionalised graphene oxide (fGO) in an epoxy matrix and glass fibre reinforced epoxy composites system. This project comprises two parts. The first part was undertaken to fabricate the GNP-epoxy nanocomposites, characterise the GNPs and determine the effect of different aspect ratios, dispersion methods and weight fractions of the commercially available GNP on the thermal, tensile, and flexural properties of the nanocomposites. It was found that the tensile and flexural modulus increased linearly with the incorporation of 25 micrometre GNP (G5). However, tensile strength and strain at fracture were reduced significantly. Based on this result and literature studies, it was necessary to use the chemically modified graphene materials to balance the mechanical properties and obtain higher degrees of reinforcement. Therefore, the second part of the project focused on fabricating hybrid glass fibre epoxy composites using fGO. Experimental observations were carried out on their thermal, tensile, water absorption, creep, and fatigue behaviours at various temperatures. The effects of fGO weight fractions and temperatures on the composites' short-term and long-term properties were investigated. The results obtained from comprehensive investigations demonstrated that all parameters in the tensile properties (i.e., strength, modulus, and strain at fracture) increased with the incorporation of fGO at all test temperatures of 28, 90 and 130 degree celcius. The creep and fatigue life was increased up to 132 and 30 times, respectively, with fGO weight fractions. These positive findings could create a new market opportunity for these hybrid structural composites applications in various sectors. Further analysis of creep and fatigue behaviour in the graphene-based hybrid composite system was conducted using an analytical model and prediction methods. Such an investigation could not be found in most graphene-related composite material literature, thus making this finding a novel approach to comprehensively predicting the creep and fatigue behaviour and the life prediction of the fGO-GFRP composites system. This study used Burger's model and Findley's power laws to represent the creep curve and explain the structure to property relationship in the fGO-GFRP composites. Basquin's model was used to correlate experimental fatigue data and relate the fatigue life dependency to the maximum applied stress, temperatures and fGO contents.
Date of Award31 Dec 2022
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorVenkata Potluri (Supervisor), Arthur Wilkinson (Supervisor) & Mark Bissett (Supervisor)

Keywords

  • nanocomposites
  • Graphene
  • Composites

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