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Publication

The role of sodium surface species on oxygen charge transfer in the Pt/YSZ system

( 2012-08-01)

Naimah Ibrahim

;

Danai Poulidi

;

Maria Elena Rivas

;

Iain D. Baikie

;

Ian S. Metcalfe

The role of sodium surface species in the modification of a platinum (Pt) catalyst film supported on 8 mol% yttria-stabilised-zirconia (YSZ) was investigated under a flow of 20 kPa oxygen at 400°C. Cyclic and linear sweep voltammetry were used to investigate the kinetics of the oxygen charge transfer reaction. The Pt/YSZ systems of both 'clean' and variable-coverage sodium-modified catalyst surfaces were also characterised using SEM, XPS and work function measurements using the Kelvin probe technique. Samples with sodium coverage from 0.5 to 100% were used. It was found that sodium addition modifies the binding energy of oxygen onto the catalyst surface. Cyclic voltammetry experiments showed that higher overpotentials were required for oxygen reduction with increasing sodium coverage. In addition, sodium was found to modify oxygen storage and/or adsorption and diffusion increasing current densities at higher cathodic overpotential. Ex situ XPS measurements showed the presence of sodium hydroxide, carbonate and/or oxide species on the catalyst surface, while the Kelvin probe technique showed a decrease of approximately 250 meV in the work function of samples with more than 50% sodium coverage (compared to a nominally 'clean' sample).

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Publication

An investigation of the processability of natural fibre reinforced polymer composites on shallow and flat thin-walled parts by injection moulding process

( 2013)

Mohd Azaman Md Deros

;

S.M. Sapuan

;

S. Sulaiman

;

E.S. Zainudin

;

K. Abdan

Currently, many industries are trending towards producing products exhibit such properties as small thickness, lightweight, small dimensions, and environmental friendliness. In this project, flat or shallow thin-walled parts were designed to compare the advantages and disadvantages of lignocellulosic polymer composites (PP + 50 wt% wood) in terms of processability. This study focused on the filling, in-cavity residual stresses and warpage parameters associated with both types of thin-walled moulded parts. Thin-walled parts 0.7 mm in thickness were suitably moulded using lignocellulosic composite materials to determine the effects of filling. The analysis showed, the shallow thin-walled part is preferable in moulding lignocellulosic polymer composite material due to the low residual stress and warpage measured. The results also indicate that the shallow thin-walled part is structurally rigid, such that it can be used in applications involving small shell parts, and can be processed more economically using less material than the flat thin-walled part.

Publication

Analysis of accent-sensitive words in multi-resolution mel-frequency cepstral coefficients for classification of accents in Malaysian English

( 2013-06)

M.A. Yusnita

;

M.P. Paulraj

;

Sazali Yaacob

;

R. Yusuf

;

Shahriman Abu Bakar

This paper investigates the most accent-sensitive words for Malaysian English (MalE) speakers in multi-resolution 13 Mel-frequency cepstral coefficients. A text-independent accent system was implemented using different numbers of Mel-filters to determine the optimal settings for this database. Then, text-dependent accent systems were developed to rank the most accent-sensitive words for MalE speakers according to the classification rates. Prior work has also been conducted to test the significance of the wordlist for both gender and accent factors, and to investigate any interaction between these two factors. Experimental results show that male speakers have a higher intensity of accent effects compared with female speakers by 3.91% on text-independent and 3.47% on text-dependent tasks. Another finding has proven that by selecting appropriate words that carry severe accent markers could improve the task of speaker accent classification. An improvement of at most 8.45% and 8.91% was achieved on the male and female datasets, respectively, following vocabulary selection.

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Publication

Shrinkages and warpage in the processability of wood-filled polypropylene composite thin-walled parts formed by injection molding

( 2013-07-01)

Mohd Azaman Md Deros

;

S.M. Sapuan

;

S. Sulaiman

;

E.S. Zainudin

;

A. Khalina

Reducing volumetric shrinkages and warpage during the injection molding process is a challenging problem in the production of molded thin-walled parts. In this study, the injection molding of shallow, thinwalled parts (thickness 0.7 mm), composed of lignocellulosic polymer composites (polypropylene (PP) + 50 wt% wood), was simulated. The volumetric shrinkages and warpage in the thin-walled parts were evaluated under different process conditions, with varying post-filling parameters, such as mold temperature, cooling time, packing pressure and packing time. The analysis showed that the cooling time and packing time had less of an effect on the shrinkage and warpage; nevertheless the optimal levels for both parameters are required in the molding process for the thin-walled part to achieve the best results. The volumetric shrinkage was lower near the gate than at the end-of-fill location along the flow path. The results also showed that the volumetric shrinkage correlates with the warpage measured on the molded part. The optimum parameters ranges is 40–45 C for the mold temperature; 20–30 s for cooling time; 0.85 from injection pressure (Pinject) for packing pressure; and 15–20 s for the packing time to achieve the best results with the least amount of volumetric shrinkage and warpage.

3 21

Publication

Optimization of blending parameters and fiber size of Kenaf-bast-fiber-reinforced the thermoplastic polyurethane composites by Taguchi Method

( 2013-12-16)

Y. A. El-Shekeil

;

S. M. Sapuan

;

M. D. Azaman

;

M. Jawaid

“Kenaf-fibers- (KF-)” reinforced “thermoplastic polyurethane (TPU)” composites were prepared by the melt-blending method followed by compression molding. Composite specimens were cut from the sheets that were prepared by compression molding. The criteria of optimization were testing the specimens by tensile test and comparing the ultimate tensile strength. The aim of this study is to optimize processing parameters (e.g., processing temperature, time, and speed) and fiber size using the Taguchi approach. These four parameters were investigated in three levels each. The L9 orthogonal array was used based on the number of parameters and levels that has been selected. Furthermore, analysis of variance (ANOVA) was used to determine the significance of different parameters. The results showed that the optimum values were 180°C, 50 rpm, 13 min, and 125–300 micron for processing temperature, processing speed, processing time, and fiber size, respectively. Using ANOVA, processing temperature showed the highest significance value followed by fiber size. Processing time and speed did not show any significance on the optimization of TPU/KF.

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Publication

Mechanical characterization and water absorption behaviour of interwoven Kenaf/PET fibre reinforced epoxy hybrid composite

( 2015)

Yakubu Dan-mallam

;

Tan Wei Hong

;

Mohd Shukry Abdul Majid

The development of interwoven fabric for composite production is a novel approach that can be adopted to address the challenges of balanced mechanical properties and water absorption behaviour of polymer composites. In this paper, kenaf and PET (polyethylene terephthalate) fibre were selected as reinforcing materials to develop the woven fabric, and low viscosity epoxy resin was chosen as the matrix. Vacuum infusion process was adopted to produce the hybrid composite due to its superior advantages over hand lay-up technique. The weight percentage composition of the Epoxy/kenaf/PET hybrid composite was maintained at 70/15/15 and 60/20/20, respectively. A significant increase in tensile strength and elastic modulus of approximately 73% and 53% was recorded in relation to neat epoxy. Similarly, a substantial increase in flexural, impact, and interlaminar properties was also realized in relation to neat epoxy. This enhancement in mechanical properties may be attributed to the interlocking structure of the interwoven fabric, individual properties of kenaf and PET fibres, strong interfacial bonding, and resistance of the fibres to impact loading. The water absorption of the composites was studied by prolonged exposure in distilled water, and the moisture absorption pattern was found to follow Fickian behaviour.

2 5

Publication

Perturbation parameters tuning of multi-objective optimization differential evolution and its application to dynamic system modeling

(Penerbit UTM Press, 2015)

Mohd Zakimi Zakaria

;

Hishamuddin Jamaluddin

;

Robiah Ahmad

;

Azmi Harun

;

Radhwan Hussin

;

Ahmad Nabil Mohd Khalil

;

Muhammad Khairy Md Naim

;

Ahmad Faizal Annuar

This paper presents perturbation parameters for tuning of multi-objective optimization differential evolution and its application to dynamic system modeling. The perturbation of the proposed algorithm was composed of crossover and mutation operators. Initially, a set of parameter values was tuned vigorously by executing multiple runs of algorithm for each proposed parameter variation. A set of values for crossover and mutation rates were proposed in executing the algorithm for model structure selection in dynamic system modeling. The model structure selection was one of the procedures in the system identification technique. Most researchers focused on the problem in selecting the parsimony model as the best represented the dynamic systems. Therefore, this problem needed two objective functions to overcome it, i.e. minimum predictive error and model complexity. One of the main problems in identification of dynamic systems is to select the minimal model from the huge possible models that need to be considered. Hence, the important concepts in selecting good and adequate model used in the proposed algorithm were elaborated, including the implementation of the algorithm for modeling dynamic systems. Besides, the results showed that multi-objective optimization differential evolution performed better with tuned perturbation parameters.

4 18

Publication

Experimental and theoretical study of the electronic structure and optical spectral features of PbIn6Te10

( 2016)

A. H. Reshak

;

Oleg. V. Parasyuk

;

Kamarudin Hussin

;

I. V. Kityk

;

Zeyad A. Alahmed

;

Nasser S. AlZayed

;

Sushil Auluck

;

Anatolii O. Fedorchuk

;

J. Chyský

Laying of InTe4 tetrahedra in the structure of the compound PbIn6Te10

4 6

Publication

Finite element modelling of thin intermetallic compound layer fractures

( 2017)

Ooi Eang Pang

;

Ruslizam Daud

;

Nasrul Amri Mohd Amin

;

Mohd Afendi Rojan

;

Mohd Shukry Abdul Majid

A thin intermetallic compound (IMC) of solder ball joint induces strong stress concentration between the pad and solder where a crack propagated near the IMC layer. The fracture mechanism of the IMC layer is complex due to the effect of IMC thickness, crack length, solder thickness and Young’s Modulus. At present, there is still an undefined exact geometrical model correlation for numerical simulations of IMC layer fracture. Thus, this paper aims to determine the accuracy of IMC layer models subjected to crack-to-width length ratio (a/W) in correlation with the ASTM E399-83 Srawley compact specimen model using finite element (FE) analysis. Several FE models with different geometrical configurations have been proposed under 10 MPa tensile loading. In this study, the two dimensional linear elastic displacement extrapolation method (DEM) is formulated to calculate the stress intensity factor (SIF) at the crack tip. The study showed that with an error of 0.58% to 0.59%, a width of 2.1 mm and a height of 1.47 mm can be recommended as the best geometrical model for IMC layer fracture modelling which provides a wider range for a/W from 0.45 to 0.85 instead of from 0.45 to 0.55. This result is significant as it presents a method for determining fracture parameters at thin IMC layers with a combination of singular elements with meshes at different densities which is tailored to the Srawley model.

Publication

Finite element modelling of thin intermetallic compound layer fractures

( 2017)

Ooi Eang Pang

;

Ruslizam Daud

;

Nasrul Amri Mohd Amin

;

Mohd Afendi Rojan

;

Mohd Shukry Abd Majid

A thin intermetallic compound (IMC) of solder ball joint induces strong stress concentration between the pad and solder where a crack propagated near the IMC layer. The fracture mechanism of the IMC layer is complex due to the effect of IMC thickness, crack length, solder thickness and Young’s Modulus. At present, there is still an undefined exact geometrical model correlation for numerical simulations of IMC layer fracture. Thus, this paper aims to determine the accuracy of IMC layer models subjected to crack-to-width length ratio (a/W) in correlation with the ASTM E399-83 Srawley compact specimen model using finite element (FE) analysis. Several FE models with different geometrical configurations have been proposed under 10 MPa tensile loading. In this study, the two dimensional linear elastic displacement extrapolation method (DEM) is formulated to calculate the stress intensity factor (SIF) at the crack tip. The study showed that with an error of 0.58% to 0.59%, a width of 2.1 mm and a height of 1.47 mm can be recommended as the best geometrical model for IMC layer fracture modelling which provides a wider range for a/W from 0.45 to 0.85 instead of from 0.45 to 0.55. This result is significant as it presents a method for determining fracture parameters at thin IMC layers with a combination of singular elements with meshes at different densities which is tailored to the Srawley model.

Publication

Parametric optimization of the processing of all-cellulose composite laminae

( 2017)

M. Mat Salleh

;

K. Magniez

;

S. Pang

;

J. W. Dormanns

;

M. P. Staiger

Single-polymer composites based on cellulose I and/or II (aka all-cellulose composites) are emerging as a class of high-performance bio-based composite materials with mechanical properties suited to structural applications. There are various synthesis routes for the preparation of all-cellulose composites. However, little has been reported on the optimization of the processing variables affecting the properties of all-cellulose composites. In the present work, a range of all-cellulose composites were produced as single laminae via solvent infusion processing using a precursor of cellulose II fibers that were assembled as a woven 2D textile. The effects of dissolution time, dissolution temperature, and compaction pressure during hot pressing on the properties of the laminae were then systematically examined using a Taguchi design of experiment approach in order to identify the critical control factors. The tensile properties, fiber volume fraction, and crystallinity of the laminae were determined. Statistical analysis of variance and the signal-to-noise ratio were used to rank the importance of key control factors.

Publication

Properties and behavior of geopolymer concrete subjected to explosive air blast loading: a review

( 2017)

Nurul Aida Mohd Mortar

;

Kamarudin Hussin

;

Andrei Victor Sandu

;

Mohd. Mustafa Al Bakri Abdullah

;

Ahmad Humaizi Hilmi

;

Rafiza Abdul Razak

The severe damage to civilian buildings, public area, jet aircraft impact and defense target under explosive blast loading can cause a huge property loss. Most of researcher discusses the topics on design the concrete material model to sustain againts the explosive detonation. The implementation of modern reinforcement steels and fibres in ordinary Portland cement (OPC) concrete matrix can reduce the extreme loading effects. However, most researchers have proved that geopolymer concrete (GPC) has better mechanical properties towards high performance concrete, compared to OPC. GPC has the high early compressive strength and high ability to resist the thermal energy from explosive detonation. In addition, OPC production is less environmental friendly than geopolymer cement. Geopolymer used can lead to environmental protection besides being improved in mechanical properties. Thus, this paper highlighted on an experimental, numerical and the analytical studies cause of the explosive detonation impact to concrete structures.

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Publication

Influence of material properties on the fluid-structure interaction aspects during molded underfill process

( 2017)

C.Y. Khor

;

Muhammad Ikman Ishak

;

M.U. Rosli

;

Mohd Riduan Jamalludin

;

M.S Zakaria

;

A.F.M. Yamin

;

M.S. Abdul Aziz

;

M.Z. Abdullah

This paper presents the investigation of the effects of epoxy moulding compound’ (EMC) viscosity on the FSI aspects during moulded underfill process (MUF). Finite volume (FV) code and finite element (FE) code were connected online through the Mesh-based Parallel Code Coupling Interface (MpCCI) method for fluid and structural analysis. The EMC flow behaviour was modelled by Castro-Macosko model, which was written in C language and incorporated into the FV analysis. Real-time predictions on the flow front, chip deformation and stress concentration were solved by FV- and FE-solver. Increase in EMC viscosity raises the deformation and stress imposed on IC and solder bump, which may induce unintended features on the IC structure. The current simulation is expected to provide the better understandings and clear visualization of FSI in the moulded underfill process.

1 13

Publication

Antioxidant capacity and total phenolic content of fresh, oven-dried and stir-fried tamarind leaves

( 2017)

Lee Yit Leng

;

Mohd Nadzrin Mohammad Radzi

;

Abd Razak Shaari

;

Norawanis Abdul Razak

;

Khor Chu Yee

The aim of this study was to compare the antioxidant capacity and total phenolic content as well as the chemical groups of fresh, oven-dried and stir-fried tamarind (Tamarindus indica L.) leaves. Methanol was used for extraction of fresh, oven-dried and stir-fried tamarind leaves. The stir-fried leaves were prepared using medium heat for 10 minutes prior to extraction and chemical analysis while dried leaves were obtained by oven drying at 60°C for 3 hours. The stir-fried leaves had significantly highest total phenolic content (TPC) (139.87 mg/g) and percentage DPPH radical-scavenging inhibition (69.92%) while the fresh leaves had the lowest TPC (39.31 mg/g) and antioxidant capacity (16.46%). The FTIR spectral data suggest that the heat treatment increased the amine groups as well as the antioxidant capacity of the tamarind leaves. To increase the antioxidant capacity, the tamarind leaves should be prepared in a stir-frying process.

1 15

Publication

Preliminary studies on antimicrobial activity of extracts from aloe vera leaf, citrus hystrix leaf, zingiber officinale and Sabah snake grass against bacillus subtilis

( 2018)

M.N.A. Uda

;

Subash Chandra Bose Gopinath

;

Nur Hulwani Ibrahim

;

Mohd Khairul Rabani Hashim

;

Nuradibah Mohd Amer

;

Midhat Nabil Ahmad Salimi

;

Tan Ewe Shen

;

Ong Yee Fen

;

Maisara A. M. Akhir

;

Uda Hashim

Herbal plants have several potential antimicrobial activities either as antifungal or antibacterial to fight against the disease and pathogen that attack the plants. The extractions of the Aloe vera leaf, Citrus hystrix leaf, Zingiber officinale rhizome and Sabah snake grass were selected in this study to fight against Bacillus subtilis. B. subtilis is a Gram-positive bacterium, rodshaped and catalase-positive that lives on decayed organic material. It is known as Gram-positive bacteria because of its thick peptidoglycan and would appear purple when subjected to Gram test. This species is commonly found in the upper layers of the soil, in meat or vegetables, in pastry, cooked meat, in bread or poultry products. The extracts of Sabah Snake Grass found to be most effective than A.vera leaf, Z. officinale, and C. hystrix against the B. subtilis.

1 17

Publication

Synthesis and characterization of natural fiber reinforced polymer composites as core for honeycomb core structure: a review

(SAGE Publications, 2018)

ES Zaini

;

Mohd Azaman Md Deros

;

Jamali Md Sah

;

Khairul Azwan Ismail

Researchers have worked on variety of natural fibers reinforced with polymer composites using different parameters to come up with various recommendations. The investigation involved aspects of composition materials and mechanical properties of natural fiber composites. The satisfactory results of natural fiber composites have encouraged researchers to delve deeper into the abilities of natural fiber composite in the form of a core structure. The potentiality of utilizing natural fiber composite in core design has wide potential in modern industries. This paper presents a review on natural fibers and polymer matrices commonly used in core fabrication, core design, fabricating processes of cores, and mechanical properties of cores. Ongoing research of rice husk composites to be fabricated in the form of honeycomb core structures is also discussed.

8 1

Publication

Gait classification using Mahalanobis–Taguchi system for health monitoring systems following anterior cruciate ligament reconstruction

( 2019)

Hamzah Sakeran

;

Noor Azuan Abu Osman

;

Mohd Shukry Abdul Majid

In this paper, a gait patterns classification system is proposed, which is based on Mahalanobis–Taguchi System (MTS). The classification of gait patterns is necessary in order to ascertain the rehab outcome among anterior cruciate ligament reconstruction (ACLR) patients. (1) Background: One of the most critical discussion about when ACLR patients should return to work (RTW). The objective was to use Mahalanobis distance (MD) to classify between the gait patterns of the control and ACLR groups, while the Taguchi Method (TM) was employed to choose the useful features. Moreover, MD was also utilised to ascertain whether the ACLR group approaching RTW. The combination of these two methods is called as Mahalanobis-Taguchi System (MTS). (2) Methods: This study compared the gait of 15 control subjects to a group of 10 subjects with laboratory. Later, the data were analysed using MTS. The analysis was based on 11 spatiotemporal parameters. (3) Results: The results showed that gait deviations can be identified successfully, while the ACLR can be classified with higher precision by MTS. The MDs of the healthy group ranged from 0.560 to 1.180, while the MDs of the ACLR group ranged from 2.308 to 1509.811. Out of the 11 spatiotemporal parameters analysed, only eight parameters were considered as useful features. (4) Conclusions: These results indicate that MTS can effectively detect the ACLR recovery progress with reduced number of useful features. MTS enabled doctors or physiotherapists to provide a clinical assessment of their patients with more objec

1 20

Publication

Conceptual design and simulation validation based finite element optimisation for tubercle leading edge composite wing of an unmanned aerial vehicle

( 2019)

Ernnie Illyani Basri

;

Faizal Mustapha

;

Mohamed Thariq Hameed Sultan

;

Adi Azriff Basri

;

Mohd Firdaus Abas

;

Mohd Shukry Abdul Majid

A finite element model is developed to determine deformation and stresses on a composite wing of unmanned aerial vehicle (UAV) with a tubercle design at the leading edge of the wing. Tubercles, commonly known as protuberances found on the leading edge of a whale pectoral flipper, offering great performance from an aerodynamic perspective. This paper deals with a first order shear deformation theory (FSDT) approach to discover the UAV laminates composite wing model of tubercle leading edge (TLE) with rib-reinforced so that the equivalent stiffness and material properties are obtained from the simulation of finite element analysis using ANSYS. Another structural configuration of design replicating the idea of monocoque concept, whereby foam is used at the leading and trailing edges of the wing. Styrene acrylonitrile (SAN) core foam is used representing high strength-to-weight ratio with its superiority in the mechanical properties of polymeric sandwich composites. The updated static structural analysis from rib-reinforced can be applied to update the wing stiffness distribution of monocoque-foam. The optimum design is concluded from the tabulated deformation and stresses of both wings, where monocoque-foam showed better performance with a reduction in 50.72% of deformation and 35.88% of stress, compared to rib-reinforced design.

1 23

Publication

Effect of pineapple leaf (PALF), napier, and hemp fibres as filler on the scratch resistance of epoxy composites

( 2019)

Mohd Ridzuan Mohd Jamir

;

Mohd Shukry Abdul Majid

;

Azduwin Khasri

;

E.H.D. Gan

;

Zuradzman Mohamad Razlan

;

S. Syahrullail

This article presents the effects of pineapple leaf (PALF), napier, and hemp fibres as filler on the scratch resistance of epoxy composites. In particular, it explores the effect of these natural fillers on the horizontal load, coefficient of friction (COF), penetration depth, fracture toughness, scratch hardness, brittleness index and scratch observation. The mixing method using magnetic stirrer was used to produce the natural fibre-filled epoxy composites with different wt%, namely, 5, 7.5, and 10 wt%. The test was performed using a CSM Revetest Xpress, which consisted of a cone of the half-apex angle of 60° ending with a sphere having a tip radius of 200 μm. The indenter scratch distance and speed were 7 mm and 1.5 mm/min, respectively. The results show that the napier fibre-filled epoxy composites have the highest peak load and COF. It was also noted that the napier fibre-filled epoxy composites have the lowest penetration depth for each wt% of filler. Lastly, the fracture toughness (Kc) for the napier fibre-filled epoxy composites with 10 wt% of filler yielded the highest value of 4.33 MPa.m1/2. It can also be seen that using a scanning electron microscope (SEM), the amount of debris increased with higher of wt% of the natural fibre fillers in the composites. Hence it was demonstrated that the napier fibre-filled epoxy composites have higher scratch resistance compared to the PALF and hemp fibre-filled epoxy composites. Keywords: Surface analysis, Fracture toughness, Scratch resistance, PALF, Napier, Hemp fibres.

12 16

Publication

Mechanical properties and microstructural behaviour of microwave sintered WC–Co

(Springer, 2019)

Raihan Rumman

;

Lee Chang Chuan

;

Jamie S. Quinton

;

Reza Ghomashchi

Abstract: Cemented carbides have been of great interest within industrially manufacturable hard materials for their mechanical properties. Microwave sintering is known for its application on a range of hard materials. Although it has been widely used, its effect on grain growth of materials still requires clear understanding. Three different types of particle size, ranging from 1–3 µm to 100 nm were used for microwave sintering where temperature was used in this study within the range of 1000–1400 °C, while pressure during initial compaction of powder particles was kept constant. The maximum hardness was observed in the order of nearly 1800 Hv for submicron samples, sintered at 1250 °C. Fracture toughness on the samples reached a maximum of 16 MPa √m for micron samples sintered at 1400 °C. Grain growth in all samples was not more than 1–3 µm, even without the presence of any commercial grain growth inhibitors as part of the composition. Line scanning between grains demonstrates the presence of homogenous Co, confirming good mechanical behaviour. The microstructural features associated to the sintering process have also been focused as part of the study, highlighting some challenges in the research. Graphic Abstract: Line scanning of WC (1–3 μm)–7.5 wt% Co (1–3 μm) sample, microwave sintered at 1400 °C[Figure not available: see fulltext.].

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