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Water absorption behaviour and its effect on the mechanical properties of hybrid interwoven cellulosic fibre composites
No full textMaster of Science in Mechanical EngineeringWith aim to fulfill the public need that eager for ‘green product’, natural based fibres started to receive attention to substitute synthetic fibres as reinforcement in composites. Natural fibres is relatively cheap, easy to get, non-toxic, non-abrasive, less harmful to human health and possessed high specific strength and modulus which make them the perfect choice to
reduce the dependence towards the petroleum based fibres. As the extension to the research involving woven and natural fibre hybrid composites, this study investigated the water absorption behaviour and its effect on the mechanical properties of hybrid cellulosic fibre composites. Hybrid composites consists of interwoven kenaf/jute and kenaf/hemp yarns were
prepared by infusion process using epoxy as the matrix. Woven kenaf, jute and hemp
composites were also prepared for comparison. Water absorption test were conducted
according to ASTM D590 standard by immersing the composite samples in tap water at room
temperature until the water content reach saturation. Dry and water immersed samples of
both woven and interwoven hybrid composites then were subjected to tensile and flexural
tests according to ASTM D638 and ASTM D790, respectively. Fractured portion of the
samples were examined using field emission scanning electron microscope (FESEM) to
observe the effect of water absorption towards the fiber/matrix interface. Water uptake was
rapidly increased at the beginning and getting slower until reach saturation at 1400 hours of
immersion time. Among individual woven composites, woven kenaf composite had the
highest water uptake and through hybridization with jute and hemp fibres, water resistance
properties of kenaf fibre were improved by 46 and 64%. At both, dry and wet condition,
mechanical properties of interwoven hybrid composites was found to be greater than their
individual woven composites. In dry condition, tensile and flexural strength of interwoven
kenaf/jute hybrid composite were 11 and 22% higher than woven kenaf composite and 16
and 39% greater than woven jute composite. For dry samples of interwoven kenaf/hemp
hybrid composite, increment of 4 and 17% over woven kenaf composite and 9 and 33% over
woven hemp composite were recorded for their tensile and flexural strength. Similar as the
dry samples, increase of tensile and flexural strength was also observed for the water
immersed samples of the interwoven hybrid composites. Amount of water uptake increased
as the immersion time increased and reduced the strength and modulus (tensile and flexural)
of the water immersed samples. Tensile strength of woven kenaf, jute, hemp, interwoven
kenaf/jute and kenaf/hemp hybrid composites at their saturation state were reduced by 75,
69, 67, 72 and 69% over their strength at dry condition. Following the similar sequence,
flexural strength of the saturated samples also reduced by 73, 64, 57, 69 and 67% than the
dry condition samples. Those reductions attributed by debonding, matrix cracking, and
delamination as shown through the FESEM images
Study on chitosan thin film for vapour sensor application
No full textMaster of Science in Polymer EngineeringThe aim of this project is to analyse the electrical properties of the chitosan film sensor exposed to water, methanol and toluene. Chitosan film has proven to be potential as reliable sensor for methanol and toluene detector. The exposure of methanol and toluene with four concentrations 0.1, 0.5, LO and 2.0cc into chitosan is to study the sensitivity and selectivity of chitosan film sensor upon methanol, toluene and water. Electrochemical deposition method has been chosen as a method to fabricate chitosan
film. Electrical testing was done to study the sensing properties such as sensitivity, respond time, recovery, stability, repeatability, selectivity and reproducibility has been done in order to fulfill a requirement chitosan film sensor as reliable sensor.
Characterization testing which include Atomic Force Microscopy (AFM), Scanning
Electrons Microscopy (SEM) and Fourier Transform Infrared Spectrometry (FT-IR) bas
been performed to study the microstructure of chitosan film sensor. From the results, the
best chitosan concentration to fabricate chitosan film sensor is 1.75 w/v%. Chitosan film
after exposed to methanol shows higher output voltage than chitosan film after exposed
to toluene. It indicates chitosan film is more sensitive to methanol than toluene. SEM and
AFM irnages of chitosan films show compact and smooth surface which indicates
homogeneity of chitosan film surface. FT-IR shows the presence of the domain
functional group in either chitosan film before or after exposed to methanol and toluene.
Thus chitosan film is potential as a reliable sensor because it has high sensitivity, rapid
response, stable, good recovery, repeatable and selective to water, methanol and toluene
Design optimization of the interior vehicle noise and vibration through computational approaches
No full textMaster of Science in Engineering MathematicsNoise and vibration performance is an indispensable criterion in vehicle design and validation processes since it significantly affects the marketing image of automotive vehicles. The primary goal of this study is to assess and optimize the acoustic and vibration levels in the interior vehicle cabin. The study demonstrated experimental design to acquire sound and vibration signals using three local compact Perodua cars namely Axia, Myvi and Viva on idle (stationary) and non-stationary (highway, pavement and urban) driving conditions. The measured sounds and vibrations are analyzed to obtain the sound quality and vibration exposure levels in the interior cabin. Apart from this, the study presents a formulation of Noise Isolation Index (NII) based on categorizing the trends of sound quality into interior and exterior noises. The NII is developed, compared and validated for the three tested cars and the results showed that Axia has the highest comfort and thus optimal isolation criterion toward the exterior noises. Besides conducting clustering to compare the interior comfort of Axia, Myvi and Viva, this study developed Genetic Algorithm to further optimize the noise and vibration in the interior vehicle cabin. The results of GA model revealed that the interior noise is influenced by vibration exposure values in the interior vehicle cabin. Overall findings of this study indicate that the comfort level is factually influenced by factors including type of road surface, engine transmissions and vehicle design characteristics
Performance evaluation of shell-and-double concentric tube heat exchanger
No full textMaster of Science in Mechanical EngineeringShell-and-tube heat exchangers (STHEX) have been used for several decades. Conventionally to increase the thermo-hydraulic performance of classical heat exchangers, overall length of tubes has to be increased. This contributes major disadvantage in term of classical heat exchangers design particularly considering economical aspect. In this study, the thermo-hydraulic performance analysis of a shelland-double concentric tube heat exchanger (SDCTHEX) is carried out using commercially the available Computational Fluid Dynamic (CFD) software ANSYS FLUENT 14.0. A 3D realizable k–ε turbulence model with scalable wall function treatment is used for the whole numerical simulations. Validation on heat transfer coefficient and pressure drop are done, where the Bell-Delaware method, Gnielinski, and Haaland correlations are compared with CFD simulation values of SDCTHEX and classical STHEX. The SDCTHEX model is then compared with classical STHEX model for their thermo-hydraulic performances for different mass flow rates of the hot fluid. Next, the effects of different inner tube diameters and different arrangement (counter and parallel flows) flows of working fluids flows on the performance of SDCTHEX are investigated. Other than that, the effects of the heat transfer and pressure drop of Al2O3/water nanofluid at different Al2O3 nanoparticle volume
concentrations and flow rates flowing inside annulus side of SDCTHEX are also analysed. It is observed that, the percentage of overall heat transfer rate per overall pressure drop of SDCTHEX with inner tube diameter equal to 8/12 mm/mm, is increased nearly 343 % higher than that of STHEX. Also, the overall heat transfer rate per overall pressure drop of SDCTHEX is sensitive to inner tube diameter. It is found that Φ/ΔP for the mass flow rate of 22.5 kg/s is for to be maxed about 400 % higher at inner tube diameter of 12/16 (mm/mm) with respect to the STHEX. On the other hand, the thermo-hydraulic performance for counter flow arrangement of working fluid is also found higher than that of parallel flow arrangement of working fluid at any hot fluid
mass flow rate. For the nanofluid effect, the results obtained showed that at the same Re, the heat transfer performance increases by increasing the nanoparticle volume concentration and it’s valued higher when compared with water. But when compared at the same mass flow rate, the nanofluid at any nanoparticle volume concentration does not show any enhancement on heat transfer when compared with water
