Ahmad B H Kueh

Universiti Malaysia Sarawak (UNIMAS), Faculty of Engineering, Faculty Member

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Dr. Kueh is Assoc. Prof. in structural engineering at the Department of Civil Engineering, Faculty of Engineering, Universiti Malaysia Sarawak (UNIMAS). His research curiosity falls within but not restricted to the thermo-mechanics of structures, natural or man-made, specializing in fiber reinforced composite materials, and gaining great engineering inspiration from the mechanics of biological bodies. He received his B. Eng in Civil Engineering from UTM. His Ph.D. was conducted under the supervision of Professor Pellegrino at the Engineering Department of the University of Cambridge. One of his missions is to treat natural beings as working template for motivation for betterment and optimized performance of structures.

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Papers by Ahmad B H Kueh

Aqueous-phase reforming of glycerol using Cu-Ni bimetal catalyst supported over coconut shell activated carbon

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 115(1), 193-205, 2024

The increasing generation of glycerol as a waste from biodiesel production calls for its various ... more The increasing generation of glycerol as a waste from biodiesel production calls for its various consumptions, especially in producing industrial chemicals. However, the focus of popular studies in this process is on using noble metals as the catalyst. It should be shifted to a low cost and abundant element to ensure sustainability. Therefore, this study uses activated carbon from coconut shells to support a bimetal catalyst copper-nickel in converting glycerol into value-added products. The catalyst was synthesized via the wet impregnation method and was characterized using scanning electron microscopy-energy dispersive X-ray spectroscopy, Fourier-Transform infra-red spectroscopy, and a surface area analyser. It was revealed that the BET surface area (582 m2 /g) is smaller than the pristine carbon because of the exposure to high temperature during calcination. The average pore size (1.7 nm) is also smaller than the coconut shell carbon due to the same effect. The surface functional groups mainly consist of carboxylic acids that is known to contribute to the hydrogenolysis of glycerol. At 20 wt% initial glycerol concentration, 20 bar and 200 °C, acetic acid, propylene oxide, carbon monoxide and acetaldehyde were detected as the products. A possible mechanism was proposed considering the aqueous-phase reforming of glycerol and the dehydration process. The optimum operating conditions in this case are 20 wt% initial glycerol concentration, 25 bar and 200 °C. More studies are needed to evaluate the reactions involved in aqueous-phase reforming of glycerol using the Cu-Ni doped on coconut shell activated carbon. In conclusion, glycerol can be converted to valuable chemicals under mild conditions by using the cost-effective catalyst.

Mechanical characteristics of silica aerogel mortar and sandwiched mortar with silica aerogel mat core

Journal of Materials in Civil Engineering, 36(1), 04023516, 2024

Due to increasing awareness of the indoor environmental quality, efforts to maintain human indoor... more Due to increasing awareness of the indoor environmental quality, efforts to maintain human indoor thermal comfort have been intensely carried out worldwide in recent decades. Particularly, thermal insulating materials with good mechanical performance are of great interest to suit this functionality. In this respect, construction materials should be able to impede heat transfer while achieving the required mechanical strength. Silica aerogel (SA) is attractive to fit these criteria due to its favorable characteristics such as low thermal conductivity, lightweight, and sustainability. Therefore, the present work studies the mechanical properties of both mortar with sand replaced by silica aerogel and sandwiched mortar with silica aerogel mat core. First, the optimal mix design was determined for the mortars with 0%, 15%, 20%, and 25% sand replaced by volume with silica aerogel through compressive strength on Days 7 and 28. Flexural strength and modulus of elasticity were also assessed. In terms of sandwiched mortar with silica aerogel mat core, both edgewise and flatwise compressive characteristics were examined for 9-, 12-, and 15-mm core thicknesses. Additionally, the optimal parameters of both specimen types were linked to their microstructures and failure modes. According to the result, 15% by volume of silica aerogel (by replacing sand) was determined as the optimum ratio for the SA powder mortar. Meanwhile, for silica aerogel sandwiched mortar, samples with 15- and 12-mm core thicknesses achieved the highest flatwise and edgewise compressive strengths, respectively.

Packing optimization and design of the deployable parabolic rigid antenna based on origami

Advances in Space Research, 73(12), 6226-6240, 2024

This paper introduces a novel approach for optimizing the packing and design of deployable parabo... more This paper introduces a novel approach for optimizing the packing and design of deployable parabolic rigid antenna structures based on origami, tailored to meet specific requirements related to the number of solid-surface blocks and the size of the folded antenna. The study begins by selecting a single-vertex four-crease configuration with one degree of freedom from the origami pattern, guided by mobility analysis, to optimize block arrangement. Subsequently, a planar model is employed to qualitatively examine the impact of geometric parameters on the stowage efficiency of the antenna. Building upon the insights gained from the planar model, an optimization framework for the parabolic rigid deployable antenna structure is established. The objective function of the optimization is the stowage volume, while simultaneously adhering to stiffness, collision, and mobility constraints. The design parameters of the antenna structure are thoroughly analyzed. To mitigate collision risks during folding, design considerations are applied to placement of support nodes, location of rotating axes, and block division, leveraging the optimized parameters. The practicality of the proposed method is successfully demonstrated through the folding of a simulated 3D model and of a physical 3D printed model. These tangible representations show the feasibility of the presented approach, affirming its potential applicability in the optimization and design of deployable parabolic rigid antenna structures.

An analysis of the environmental effects of three types of concrete: Ready-mixed, reactive powder, and geopolymer

Ain Shams Engineering Journal, 15(9), 102926, 2024

This study assesses the effects of three forms of concrete: geopolymer concrete, reactive powder ... more This study assesses the effects of three forms of concrete: geopolymer concrete, reactive powder concrete (RPC), and ready-mix concrete (RMC) on the environment, the economy, and sustainability. Evaluating their cost-effectiveness for construction, embodied energy (EE), and embodied carbon (EC) is the aim. The research method employed involves calculating the EE, EC, and cost of materials used during the production stage only. The results show that although RMC gives ease at a high carbon emission cost, RPC delivers great strength at a high cost and emissions. Utilizing waste resources, geopolymer concrete lowers emissions while providing sustainability. Reusing waste materials improves the performance of concrete and lowers pollution. The study emphasizes that, especially when waste is used well, strength need frequently translate into expense. RMC has a major negative influence on the environment while guarantees consistent quality. Despite its strength, RPC has issues with cost and material availability. The strength and emission reduction of geopolymer concrete are excellent. In geopolymers, alkali activators and steel fibers are the source of EE and EC, whereas cement and steel fibers are the reason for their high levels in RMC and RPC. Overall, the research indicates that favorable, ecologically friendly results are feasible obtained by improving the composition of concrete. To provide cost-effective and sustainable concrete compositions and enable well-informed decision-making in building projects, ongoing research and innovation are crucial.

Compressive characteristics of interleaved origami tube metamaterials based on the “flip-flop” fold pattern

International Journal of Applied Mechanics 16 (8), 2450093, 2024

This study investigates the compressive characteristics of rigidly folded interleaved origami tub... more This study investigates the compressive characteristics of rigidly folded interleaved origami tube metamaterials, following the" Flip-Flop" pattern, across principal directions. The geometry of the metamaterial's fundamental unit is outlined, establishing theoretical models for compressive stresses in the [Formula: see text]/[Formula: see text]-directions and mean compressive stress in the [Formula: see text]-direction, which show strong agreement with numerical simulations. These simulations assess the effects of thickness-to-length ratio and angular parameters on compressive performance. When compared to hexagonal honeycomb structures, the findings indicate that, with carefully selected structural parameters, origami tube metamaterials exhibit superior energy absorption efficiency and compressive energy absorption characteristics, surpassing the constraints of relative density.

Blasting resistance of curved sandwich composite concrete bunkers

Structural Engineering and Mechanics 91 (1), 63-73, 2024

Improving the blast resistance of structural establishments has become an imperative engineering ... more Improving the blast resistance of structural establishments has become an imperative engineering commitment to prevent property damage and fatalities in terrorist incidents. This study investigates the effects of blast mass and stand-off distance on CFRP skin concrete core sandwich bunkers of varying thicknesses using ABAQUS/Explicit software with CONWEP functionality. The considered parameters include TNT masses of 1, 10, and 25 kg and stand-off distances of 0.1, 1, 2, and 2.5 meters on structures with 200, 250, and 500 mm core thicknesses. The study finds that there exists a declining response corresponding to the blasting mass reduction coupled with increases in the stand-off distance and core thickness. The 500 mm thick bunker sustains less damage compared to those with 200 mm and 250 mm core thicknesses. The sandwich configuration remains structurally advantageous vs. those without skins. The sandwich bunker with a 500 mm thick concrete core gives the best performance against the 10 kg TNT blast load with a 1 m standoff distance exhibiting a 22.8% reduction in damage vs. that without skins. Mathematical expressions are then formulated for predicting maximum von Mises stress, principal stress, and displacement of sandwich bunkers as functions of TNT masses, stand-off distances, and core thicknesses.

Tensegrity prediction of E. coli deactivation by sonication strategy

Journal of Advanced Research Design 122 (1), 71-84, 2024

Bacterial infections continue to pose a significant challenge to public health especially in clea... more Bacterial infections continue to pose a significant challenge to public health especially in clean drinking water production. Hence, it is crucial to have effective methods for their elimination. The successful deactivation of bacteria like E. coli through emerging sonic means depends on the identification of their resonant frequencies. However, the conventional approach of determining these frequencies through labor-intensive physical experimentation can be both time-consuming and expensive. This article introduces an innovative approach to determining the resonant frequency of E. coli using a specifically designed tensegrity model that incorporates spectral element formulation. This model, which conforms to the shape of E. coli, enables the calculation of resonant frequencies without the need for time-consuming simulations of element sensitivity. To address the challenges associated with rigid body motion, a small incremental operation is employed to compute the system determinant. The resonant frequencies obtained from the model are shown to align excellently with existing experimental findings. Furthermore, the model reveals that alterations in the geometry of E. coli have a substantial impact on the frequency of deactivation, while other parameters such as density have less influence. The proposed tensegrity model is a potent technique that can rapidly and accurately identify resonant frequencies, thereby enabling instantaneous and more efficient bacterial deactivation, especially during periods of health emergencies.

Simplified surface wettability determination defined by new interfacial interaction compatibility expressions for composites

Journal of Adhesion Science and Technology, Aug 2, 2024

To date, the compatibility of two different materials of composites has been determined solely by... more To date, the compatibility of two different materials of composites has been determined solely by the empirical surface wettability approach, using methods such as contact angle measurement. However, this method can be quite cumbersome, requiring specific equipment and different liquid probes. Therefore, this paper aims to develop a simplified approach to determining surface wettability, incorporating novel generalized expressions that account for the interfacial interaction compatibility of various constituents within composites. First, an economical, simplistic, and verified water probe method is employed to measure apparent contact angles. The determined apparent contact angles are shown to fit well within the thresholds established from the available findings. Then, new mathematical expressions incorporating the adhesion concept are derived to describe the constitutive relationship between the ratios of apparent contact angles of two materials for composites formation and their liquid-solid interfacial tension by fitting data gathered from existing studies. The newly developed constitutive equations offer a convenient and reliable means to determine the compatibility relationships of numerous composite constituent mixes for varying contact angle ratios. This approach enables a simple and cost-effective estimation of surface interaction via the apparent contact angle between water and the composite constituents.

Monotonic behaviour of beam-to-column connections with double channel cold-formed steel sections

Cold-formed steel is a lightweight construction material generally in C or Z shaped produced by c... more Cold-formed steel is a lightweight construction material generally in C or Z shaped produced by cold rolling from strip steel. It can be applied in the Industrialized Building System (IBS) in order to reduce the time and cost in construction project. Partial strength connection is a connection whereby the moment resistance of the connection is less than that of the moment capacity of the connected beam. In this paper, Numerical simulation is conducted by using ANSYS Workbench 14.0 in order to predict the structural behaviors of cold formed steel partial strength connection. The objective of this study is to develop moment rotation curve for flange-web-cleat connection using double channel cold formed steel section under monotonic loading. Experiment test results are then used to compare and validate the results from the finite element modeling. This study aims to understand the behaviour of cold-formed steel connections under monotonic loading. The beam section of 1.5-meter length and column of 3-meter length is modeled in this study. Three different beam depth have been selected in this study, which is 150mm, and the depth of column section is fix to 250mm. Brackets connections were chosen and all connections were formed using bolts. The monotonic load is applied at 1000mm from the column surface. The stiffness and moment capacity is obtained from the moment rotation curve which plotted from the modeling results. As a conclusion, The FEM initial results showed good agreement with experimental results.

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Thermal behaviour of single ply triaxial woven fabric composites

This paper studies the complex thermal deformation of single-ply triaxial weave composites. This ... more This paper studies the complex thermal deformation of single-ply triaxial weave composites. This behaviour is studied experimentally, by testing ?at plates and narrow strips of TWF, and numerically, by carrying out ?nite-element simulations that capture the e?ects of the thermo-mechanical anisotropy of the individual tows that make up the composite. It is shown that the dominating e?ect is the development of a thermally-induced twist..

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Physical, thermal, and mechanical properties of polypropylene composites filled with rattan nanoparticles

Journal of Applied Research and Technology, Aug 1, 2017

Natural fillers are recognized as the materials that feature a poor fiber/matrix interaction. As ... more Natural fillers are recognized as the materials that feature a poor fiber/matrix interaction. As a result, their composites behaviors are directly compromised. Existing evidence has exhibited that nanoparticle fillers can be employed as an alternative size to overcome this problem. We thus examined in this study the effects of rattan filler of nanoparticle size on the physical, thermal, and mechanical properties of the composite. Neat polypropylene (PP), PP with 5% rattan nanoparticle (PP/R5), and PP with 5% glass fiber (PP/FG5) were considered. For performance assessment, particle size analysis, morphology, X-ray diffraction, thermal inspection, and mechanical tests were carried out. The highest degree of crystallinity was discovered in PP/R5. Tensile properties of both PP/FG5 and PP/R5 were comparable although the former demonstrated higher moduli of elasticity and rupture. Well-distributed constituents were displayed in PP/R5 by means of morphological study, which offered insight into its highest average hardness, maximum strain, and therefore its advantageous ductile behavior compared to the other considered materials.

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Proportionally Damped Finite Element State-Space Model of Composite Laminated Plate with Localized Interface Degeneration

Zenodo (CERN European Organization for Nuclear Research), Nov 1, 2014

In the present work, the finite element formulation for the investigation of the effects of a loc... more In the present work, the finite element formulation for the investigation of the effects of a localized interfacial degeneration on the dynamic behavior of the [90˚/0˚] laminated composite plate employing the state-space technique is performed. The stiffness of the laminate is determined by assembling the stiffnesses of subelements. This includes an introduction of an interface layer adopting the virtually zero-thickness formulation to model the interfacial degeneration. Also, the kinematically consistent mass matrix and proportional damping have been formulated to complete the free vibration governing expression. To simulate the interfacial degeneration of the laminate, the degenerated areas are defined from the center propagating outwards in a localized manner. It is found that the natural frequency, damped frequency and damping ratio of the plate decreases as the degenerated area of the interface increases. On the contrary, the loss factor increases correspondingly.

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Rigidity analysis and mechanical properties of programmable origami tubes

Mechanics Research Communications

The article presents the rigidity analysis and mechanical properties evaluation of ‘Flip-Flop’ ty... more The article presents the rigidity analysis and mechanical properties evaluation of ‘Flip-Flop’ typed interleaved origami tubes. This origami configuration is composed of two tubes arranged in an orthogonal manner. The rigidity of the basic unit is judged by using the loop-closure equation and dual quaternion methods while the corresponding compression performance is studied with the numerical simulation. A parametric analysis is performed to assess the effects of geometrical parameters on their compression performance. The parameters are thickness-to-length ratio (t/l) and angles (α, β) of the basic unit. The parametric analysis outcomes reveal that the interleaved origami tube has good programmability. Generally, when |α-β| is larger, the compression energy absorption characteristics in the X/Y-direction of the basic unit are greatly improved, while the decrease of angles α and β is conducive to improving the structural bearing capacity and compression energy absorption characteristics in the Z-direction. Fixing α while changing β has a greater effect on reducing the normalized mean stress ratio although, for a fixed β, a variation in α has no obvious contribution. Thus, highlighting the importance of the variation of β in influencing the compressive performance of the interleaved origami tubes as reference for future research.

Quantification, characteristics, and distribution of microplastics released from waste burning furnaces and their associated health impacts

Environmental Quality Management

Although investigation of microplastics (MPs) present in air environment has been intensively car... more Although investigation of microplastics (MPs) present in air environment has been intensively carried out, quantification, characteristics, and distribution of MPs released from the waste burning furnace (WBF) has been missing in literature. The aim of this study was to characterize the presence of MPs released from WBFs and analyze their associated health impacts. The examined locations were at two WBFs (nominated as TPS1 and TPS2) in Sidoarjo, Indonesia. MPs were collected using a 9 cm diameter glass beaker for a period of 8 h at two different sampling points, which are 3 and 15 m from each WBF. Several characteristics of MPs in terms of the number of particles, size, shape, color, and polymer type were comprehensively characterized. This study found that the obtained MPs were of fiber type and in the range of 46–77 and 41–59 particles at TPS1 and TPS2, respectively. In general, the polymer types of MPs were, respectively, cellophane and polytetrafluoroethylene at TPS1 and TPS2. Moreover, it was estimated that about 1.9–2.3 MPs can enter the human body via inhalation. This study offers a pilot examination of MPs released from WBF and findings from this study are crucial to provide new knowledge as a basis to carefully regulate the use of WBF particularly that are located closely to local community.

Thermally-induced responses of triaxially woven fabric composites

Heliyon

The article examines the thermal responses of one-ply triaxially woven fabric composites (TWFCs).... more The article examines the thermal responses of one-ply triaxially woven fabric composites (TWFCs). A temperature change experimental observation is first conducted on plate and slender strip specimens of TWFCs. Computational simulations are then performed with analytical and simple, geometrically-similar model configurations to capture thereby offering insights into the anisotropic thermal effects of the experimentally observed deformation. It is revealed that the leading cause of the observed thermal responses is the advancement of a locally formed twisting deformation mode. Therefore, a newly defined thermal deformation description called the coefficient of thermal twist is then characterized for TWFCs for different loading cases.

Acoustical and mechanical characteristics of mortars with pineapple leaf fiber and silica aerogel infills – Measurement and modeling

Materials Today Communications

While offering good thermal insulation, silica aerogels inclusion in cementitious matrices compro... more While offering good thermal insulation, silica aerogels inclusion in cementitious matrices compromises hugely the products’ compressive strength. Enhancement of the mechanical performance of concrete reinforced by fibers, on the other hand, has been well evident in existing scholarly works. Even so, natural fibers are under-exploited compared to their synthetic counterpart. Therefore, this study examines the acoustical and mechanical characteristics of mortars mixed with silica aerogel and pineapple leaf fiber for various mixture designs in determining the optimal blends that exhibit good performance in both compressive strength, σu, and sound absorption coefficient, Sa. Due to the widely reported mixing issue of silica aerogel in cement matrix, the examined samples have been fabricated through a carefully planned dry mixing method with a slow introduction of water in stages. The investigated silica aerogels are in powder form whereas pineapple leaf fibers are prepared in 10 mm length, from which their examined proportions are 0 %, 10 %, 20 %, 30 %, and 40 % as well as 0 %, 1 %, and 2 %, respectively. Scanning electron microscopy and Fourier transform infrared spectroscopy are additionally conducted to offer insight into the variation observed in σu and Sa for different mixes. The commonly reported drop in mechanical strength attributed to silica aerogel inclusion is witnessed but offset by the added pineapple leaf fiber. To circumvent laborious laboratory effort, statistical and machine learning explicit expressions are derived to generalize σu and Sa as functions of silica aerogel and pineapple leaf fiber contents. Also, the optimal constituents’ contents that exhibit good soundproofing while low in mechanical strength degradation are determined from the models for future design convenience.

ABD Matrix of Single-Ply Triaxial Weave Fabric Composites

48th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Apr 23, 2007

The linear-elastic response of single-ply triaxial weave fabric composites is modelled in terms o... more The linear-elastic response of single-ply triaxial weave fabric composites is modelled in terms of a homogenized Kirchhoff plate. The ABD matrix for this plate is computed from an assembly of transversely isotropic three-dimensional beams whose unit cell is analysed using standard finite-element analysis, assuming periodic boundary conditions. A subset of the analytical results is validated by means of careful experiments. It is shown that this simple unit cell beam model captures accurately the experimentally observed behaviour.

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Resonant frequency of coronavirus: The tensegrity approach

Alexandria Engineering Journal

COVID-19 is a worldwide health hazard. In discovering a fully efficient vaccination for continual... more COVID-19 is a worldwide health hazard. In discovering a fully efficient vaccination for continually evolving viruses, alternatives such as the sonication treatment methods, which have seen encouraging outcomes in disinfection and medical therapies, are worth exploring. Such treatments incapacitate microbes or diseased cells by selectively invoking large deformation at the resonant frequency that initiates structural failure. Nevertheless, due to biodiversity, the precise range of resonant frequencies for different biological bodies can be widely varying, its determination of which is best achieved with the cost-effective computational simulation approach. The paper proposes, therefore, the numerical determination of the resonant frequency of the coronavirus employing the tensegrity method, due to its efficacy in modeling various biomechanical behaviors of different biological bodies and systems. Initiating from successfully verifying the resonant frequency with existing findings, the model then determines the operative sonication frequencies range for the resonant state of the virus. At these sonication frequencies, the modal analysis exhibits a large structurally destructive deformation of the coronavirus. For practical convenience, the operative range of sonication resonant frequencies of the coronavirus has been mapped alongside healthy human cells. These findings offer an alternative technological avenue in combating the COVID-19 progressive threat.

Methylene blue adsorption mechanism onto palm kernel shell-derived activated carbon: From particle diffusion to site adsorption

BioResources

The mechanism of methylene blue adsorption was investigated for palm kernel shell-derived activat... more The mechanism of methylene blue adsorption was investigated for palm kernel shell-derived activated carbon from the bulk solution to active sites. For different initial dye concentrations, 100 ppm methylene blue led to approximately 10 mg/g adsorption capacity while experiencing a decreasing trend at lower initial dye concentrations as follows: 50 ppm (approximately 5 mg/g) > 20 ppm (approximately 2 mg/g) > 5 ppm (approximately 0.5 mg/g). Based on the Boyd external diffusion model, the mechanism of methylene blue adsorption started with its diffusion from the bulk solution via the bounding film encapsulating the activated carbon. The adsorbed species occupied more than one class of active site with an adsorption rate of 0.54 mg/g.min, while the adsorption capacity accounted for 14.7 mg/g. The information about methylene blue offers useful insights into describing the steps of dye adsorption onto palm kernel shell-activated carbon.

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Editorial Scope – Waste Management and Recycling

Journal of Civil Engineering, Science and Technology

The present editorial scope of the Journal of Civil Engineering, Science, and Technology (JCEST) ... more The present editorial scope of the Journal of Civil Engineering, Science, and Technology (JCEST) emphasizes one of the main disciplines of civil engineering: waste management and recycling. Waste management studies provide insights into new waste management techniques, such as recycling, composting, and waste-to-energy technologies, all of which are essential in reducing the volume of waste in landfills. In this brief editorial paper, information is gathered from the freely-accessible Scopus database to identify common keywords found in published papers related to waste management and recycling in the past decade. Based on the analysis, “waste” is found to be the top keyword in articles published on this topic in JCEST. The primary aim of this exercise is to provide researchers with a brief guide to explore the latest knowledge and advancements in waste management and recycling, in safeguarding the cleanliness and safety of our environment.

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Aqueous-phase reforming of glycerol using Cu-Ni bimetal catalyst supported over coconut shell activated carbon

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 115(1), 193-205, 2024