Theses and dissertations (Engineering and Built Environment)
Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/10
Browse
3 results
Search Results
Item Performance of nanoclay infused plant fibre-reinforced hybrid biocomposites under impact loading(2023-05) Moyo, Mufaro; Kanny, Krishnan; Mohan, Turup PanduranganThis study focused on developing sustainable and lightweight plant fibre-reinforced hybrid bionanocomposites with enhanced impact properties. Such biocomposites are envisaged as potential replacements for the non-sustainable conventional synthetic fibre-reinforced polymer composites in applications requiring resistance to impact loading. In this work, the hybrid bionanocomposites were fabricated using polylactic acid (PLA) as the biopolymer, kenaf fibre nonwoven mat as the biofibre and clay nanoparticles of different loadings as fillers. Clay nanoparticle loading of 0, 3, 5, and 7 wt% were used. The resultant kenaf/nanoclay/PLA hybrid bionanocomposites were tested for thermal decomposition, tensile properties, flexural properties, dynamic mechanical properties and impact properties. The medium velocity impact resistance was tested using a high speed gas gun. The structure-property relationships were characterised using a scanning electron microscopy (SEM), energy dispersive x-ray (EDX), fourier transform infrared (FTIR) spectroscopy and x-ray diffraction (XRD) techniques. The resultant kenaf/nanoclay/PLA hybrid bionanocomposites were found to be considerably lightweight with a positive buoyancy. Clay nanoparticle loading of 5 wt% was found to be the optimum. The results showed that the thermal stability and dynamic mechanical properties of the hybrid bionanocomposites improved with the addition of clay nanoparticles. The tensile strength and the flexural strength of the hybrid bionanocomposites improved by 19.1% and 9.8%, respectively, when clay nanoparticles were added. Infusion with clay nanoparticles improved the Young’s modulus and flexural modulus by 41.5% and 34%, respectively. Addition of clay nanoparticles improved the energy absorption capability and impact strength of the hybrid bionanocomposites under low velocity impact loading by 92.9% and 98.7%, respectively. The clay nanoparticles also considerably enhanced the medium velocity impact resistance of the hybrid bionanocomposites as evidenced by improvement of the perforation threshold limit, energy absorption capability and damage resistance. The perforation threshold limit improved to 37 m/s which was equivalent to 42.3% increase, the energy absorption capability improved by 109% and the resistance to damage improved by 26.5%. The dominating damage mechanisms for the kenaf/nanoclay/PLA hybrid bionanocomposites were observed to be shear, matrix cracking, matrix crushing, fibre fracture, fibre/matrix debonding, shear plugging, bulging, interface debonding and delamination. Since the resistance to impact loading was established to be in the medium velocity impact range, the novel hybrid bionanocomposites have a potential to replace the non-biodegradable synthetic fibre-reinforced polymer composites in cushioning against secondary debris or blasts in the medium velocity impact range. They are also suitable for lightweight applications such as in the transportation sector for lightweight mass transit systems and unmanned aerial vehicles (UAV). The novel biodegradable kenaf/nanoclay/PLA hybrid bionanocomposite materials developed in this work are potential materials for the future which can positively contribute to sustainability and attainment of Sustainable Development Goals (SDG’s).Item Low friction hybrid nanocomposite material for brake pad application(2017) Gbadeyan, Oluwatoyin Joseph; Kanny, Krishnan; Mohan, T.P.Despite the huge improvements made in the development of vehicle brake pad materials, problems such long stopping distances, noise pollution, and heat dissipation still continue to persist. In this regard, a novel polymer-based hybrid nanocomposite brake pad (HC) has been developed. Here, a combination of carbon-based materials, including those at a nanoscale, was used to produce the brake pad. The coefficient of friction, wear rate, noise level, and interfacial temperature was investigated and compared with that of a commercial brake pad material (CR). It was found that the brake pad performance varied with the formulation of each pad. Hybrid nanocomposite brake pads material exhibited superior performance in most tests when compared to the commercial brake pad. They exhibited a 65% lower wear rate, 55% lower noise level, 90% shorter stopping distance, and 71 % lower interfacial temperature than the commercial brake pad (CR). Furthermore, mechanical properties such as hardness, compressive strength, shear strength, and impact resistance were also evaluated. The material exhibited a 376% higher shear strength, 100% improved compressive strength, 77% greater modulus and 100% higher impact strength than the commercial brake pad. The hardness of both brake pads material was statistically comparable. Additionally, the thermal stability, degradation, water and oil absorption behaviour were measured. It was found that HC brake pad material exhibited a 100% lower water absorption and 80% oil absorption rate. The brake pads also exhibited a thermal stability within the brake pad standard maximum working temperature of 300 -400 0C. The superior performance of hybrid nanocomposite brake pad material observed was due to synergism between the carbon-carbon additives and uniform dispersion of carbon fiber as shown in Figure 4.16. Scanning electron microscopy study was subsequently performed on fracture and worn surfaces of the brake pads. The micrographs show changes in the structural formation after the incorporation of carbon based fillers. It also shows the smooth structure and uniform dispersion of the carbon fiber. The smooth surface of the worn brake pad is an indicative of a harder structure. No ploughing or score marks were evident. Hence, it was deduced that the reinforced had superior mechanical and tribological properties. These improved properties are suggestive of materials that may be successfully used for brake pad application.Item Fatigue performance of nanoclay filled glass fiber reinforced hybrid composite laminate(2017) Olusanya, John Olumide; Kanny, Krishnan; Mohan, T.P.In this study, the fatigue life of fiber reinforced composite (FRC) materials system was investigated. A nano-filler was used to increase the service life of the composite structures under cyclical loading since such structures require improved structural integrity and longer service life. Behaviour of glass fiber reinforced composite (GFRC) enhanced with various weight percentages (1 to 5 wt. %) of Cloisite 30B montmorillonite (MMT) clay was studied under static and fatigue loading. Epoxy clay nanocomposite (ECN) and hybrid nanoclay/GFRC laminates were characterised using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The mechanical properties of neat GFRC and hybrid nanoclay/GFRC laminates were evaluated. Fatigue study of the composite laminates was conducted and presented using the following parameter; matrix crack initiation and propagation, interfacial debonding, delamination and S–N relationship. Residual strength of the materials was evaluated using DMA to determine the reliability of the hybrid nanoclay/GFRC laminates. The results showed that ECN and hybrid nanoclay/GFRC laminates exhibited substantial improvement in most tests when compared to composite without nanoclay. The toughening mechanism of the nanoclay in the GFRC up to 3 wt. % gave 17%, 24% and 56% improvement in tensile, flexural and impact properties respectively. In the fatigue performance, less crack propagations was found in the hybrid nanoclay/GFRC laminates. Fatigue life of hybrid nanoclay/GFRC laminate was increased by 625% at the nanoclay addition up to 3 wt. % when compared to neat GFRC laminate. The residual strength of the composite materials revealed that hybrid nanoclay/GFRC showed less storage modulus reduction after fatigue. Likewise, a positive shift toward the right was found in the tan delta glass transition temperature (Tg) of 3 wt. % nanoclay/GFRC laminate after fatigue. It was concluded that the application of nanoclay in the GFRC improved the performance of the material. The hybrid nanoclay/GFRC material can therefore be recommended mechanically and thermally for longer usage in structural application.