Ibrahim Azmi

Magnetorheological Elastomers: A Review

This present paper reviews on the material compositions of Magnetorheological elastomer (MRE) as presented by researchers. As the article review, this paper much focuses on the selection of the material in the MRE ingredients. MRE has been known as a new kind of smart material over past decades. MREs offer innovative solutions for various applications in the engineering field since the rheological properties of MREs can be controlled by an external magnetic field. The characteristic responses of MRE are influenced by many factors such its elastomer matrix, the size, distribution, composition, percentage volume of filler particles and so on.

Effect of Fiber Treatment on the Fiber Strength of Kenaf Bast Fiber as Reinforcing Material in Polymer Composite

The use of natural fibers at high percentages of loading in thermoplastic composites for the production of sustainable and green materials in consumer goods, furniture, automotive industry and construction industry is emerging. Several studies have been conducted by many researchers to improve the mechanical properties of the fibers and the fiber-matrix interface for better bonding and load transfer especially when high fiber loading is used. The natural fiber hydrophilic properties make the poor interface and poor resistance to moisture absorption when used to reinforce hydrophobic matrices. Therefore, this study investigates the effects of different surface treatment namely magnesium chloride (MgCl2) and sodium hydroxide (NaOH) on the properties of kenaf fiber for different molarities. Morphology using scanning electron microscopy (SEM) and fourier transform infrared (FTIR) spectroscopy and tensile properties of kenaf fibers after different surface treatment are evaluated. Results showed that the treatment on kenaf fibers has removed the hydroxyl group in cellulose and increase the surface roughness which resulted in the improvement of the tensile properties of kenaf fibers as compared to untreated kenaf fibers.

Fatigue Crack Inspection and Acoustic Emission Characteristics of Precast RC Beam under Repetition Loading

Fatigue crack of the precast reinforced concrete beam under repetition loading is vital to be examined. Reinforced concrete structures exposed to excessive repetition loading could lead to the failure of the structures. In order to examine the active fatigue crack, the reinforced concrete beams were subjected to three-point repetition maximum loading. Eight phases of maximum fatigue loading with sinusoidal wave, frequency of 1 Hz and 5000 cycles for each phase were performed on the reinforced concrete beams. The inspection was carried out with visual observation of the crack pattern and acoustic emission technique for each load phase. The signal strength of acoustic emission was investigated. It is found that the signal strength of acoustic emission and crack pattern of the reinforced concrete beam subjected to repetition loadings showed promising results for structural health monitoring.

Vulnerability assessment of existing low-rise reinforced concrete school buildings in low seismic region using ambient noise method

Ground movements triggered by the Bukit Tinggi earthquakes in 2007 to 2009 are believed to be the possible cause of several structural damages on a secondary school building of SMK Bukit Tinggi, in the state of Pahang, Malaysia. This paper describes the ambient noise study conducted on the damaged building (a 4-storey reinforced concrete frame laboratory building) and the adjacent buildings using tri-axial 1 Hz seismometer sensors. Fourier amplitude spectra (FAS) analysis was applied to determine the buildings natural frequencies for vulnerability assessment of the damaged structure in both longitudinal and transverse axes. Significant multiple peaks of FAS curves used for natural frequencies determination of the buildings show values between 4.18 to 4.34 Hz, 5.04 to 5.23 Hz, 6.07 to 6.54 Hz and 8.17 to 8.81 Hz, indicating the existence of translational and torsional vibration modes acting on the buildings. Differences in dynamic behaviour between the laboratory and the adjacent buildings may be responsible for the structural damages due to the independent structural response and excessive torsional effect during the Bukit Tinggi earthquake tremors.

Microstructure for Printed Multilayer LTCC Tape of Different Paste Rheology

Screen printing is the most common method of transferring silver thick film paste to a low temperature co-fired ceramic tape. Silver paste with varying rheology will have a varying print quality. The effect of silver paste rheology on the microstructure is investigated. Although there are many parameters to be considered, this parameter is a critical parameter which will control the line width and roughness on the substrate. To study the effect of paste rheology, a test pattern design was printed on the Heraeus CT2000 LTCC tape using silver paste. Then the LTCC tape was stacked and laminated at pressure of 28 MPa and temperature of 65 oC for 10 minutes. The laminated sample then was fired up to 850 oC. The fired silver conductor printed on the LTCC tape then was analyzed. Prints were evaluated by scanning electron microscopy. It was found that silver paste with high viscosity produce a good microstructure.

Defect Observation of Embedded Components of a Low Temperature Co-Fired Ceramic

This paper reports observations of defects in laminated eight layers of a glass-ceramic composite system fabricated by a standard low temperature co-fired ceramic (LTCC) technology. The layers were laminated at 3000 psi and 70 °C for 10 minutes and were fired at 850 °C for 15 minutes. Material characterizations of the green compact and fired substrate were carried out on density, surface roughness and microstructure. The crack and warpage of the substrate were related to the microstructure and densification process of the system. It was found that the presence of these defects could be due to a mismatch of the sintering kinetics of the glass-ceramic composite system and silver conductor materials which lead to the development of stresses which act on both materials. The detailed microscopic observation of the internal and surface defects is explained.

Analysis of acoustic emission cumulative signal strength of steel fibre reinforced concrete (SFRC) beams strengthened with carbon fibre reinforced polymer (CFRP)

In this study, steel fibre reinforced concrete (SFRC) beams strengthened with carbon fibre reinforced polymer (CFRP) were investigated using acoustic emission (AE) technique. Three beams with dimension of 150 mm width, 200 mm depth and 1500 mm length were fabricated. The results generated from AE parameters were analysed as well as signal strength and cumulative signal strength. Three relationships were produced namely load versus deflection, signal strength versus time and cumulative signal strength with respect to time. Each relationship indicates significant physical behaviour as the crack propagated in the beams. It is found that an addition of steel fibre in the concrete mix and strengthening of CFRP increase the ultimate load of the beam and the activity of signal strength. Moreover, the highest signal strength generated can be identified. From the study, the occurrence of crack in the beam can be predicted using AE signal strength.In this study, steel fibre reinforced concrete (SFRC) beams strengthened with carbon fibre reinforced polymer (CFRP) were investigated using acoustic emission (AE) technique. Three beams with dimension of 150 mm width, 200 mm depth and 1500 mm length were fabricated. The results generated from AE parameters were analysed as well as signal strength and cumulative signal strength. Three relationships were produced namely load versus deflection, signal strength versus time and cumulative signal strength with respect to time. Each relationship indicates significant physical behaviour as the crack propagated in the beams. It is found that an addition of steel fibre in the concrete mix and strengthening of CFRP increase the ultimate load of the beam and the activity of signal strength. Moreover, the highest signal strength generated can be identified. From the study, the occurrence of crack in the beam can be predicted using AE signal strength.

Correlation between average frequency and RA value (rise time/amplitude) for crack classification of reinforced concrete beam using acoustic emission technique

Health monitoring of structures during their service life become a vital thing as it provides crucial information regarding the performance and condition of the structures. Acoustic emission (AE) is one of the non-destructive techniques (NDTs) that could be used to monitor the performance of the structures. Reinforced concrete (RC) beam associated with AE monitoring was monotonically loaded to failure under three-point loading. Correlation between average frequency and RA value (rise time / amplitude) was computed. The relationship was established to classify the crack types that propagated in the RC beam. The crack was classified as tensile crack and shear crack. It was found that the relationship is well matched with the actual crack pattern that appeared on the beam surface. Hence, this relationship is useful for prediction of the crack occurrence in the beam and its performance can be determined.Health monitoring of structures during their service life become a vital thing as it provides crucial information regarding the performance and condition of the structures. Acoustic emission (AE) is one of the non-destructive techniques (NDTs) that could be used to monitor the performance of the structures. Reinforced concrete (RC) beam associated with AE monitoring was monotonically loaded to failure under three-point loading. Correlation between average frequency and RA value (rise time / amplitude) was computed. The relationship was established to classify the crack types that propagated in the RC beam. The crack was classified as tensile crack and shear crack. It was found that the relationship is well matched with the actual crack pattern that appeared on the beam surface. Hence, this relationship is useful for prediction of the crack occurrence in the beam and its performance can be determined.

Effect of Heat Treatment on Mechanical Properties of Ternary Blended Eco-friendly UHPFRCC

The rapid expansions in economic development, urbanisation and above all population have been accompanied by an upsurge in the accidental fire hazard. The fire redundancy of buildings can decrease the risk of damage and injury by improving the safety of residents and also by enhancing the reusability of buildings. In the recent decades, investigations on elevated temperature resistant passive fire protection layers have been progressing with the use of several environmental friendly materials. However, there is an inadequate information on the effect of heat treatment on the ultra-high performance fibre-reinforced cementitious composites (UHPFRCC) containing high-alumina cement (HAC), ground granulated blast furnace slag (GGBS) and fly ash (FA) in conjunction with hybrid fibres (basalt and polypropylene fibres), which could be a potential fire resisting UHPFRCC for the structural members. The effect of heat treatment on the compressive strength and flexural strength of UHPFRCC, made of ternary blend and hybrid fibres, was investigated in this study. Besides control sample, five other UHPFRCC samples were prepared. After 28 and 56 days of normal curing, each of the samples was held at room temperature as well as exposed to 400, 700 and 1000 °C, then tested. Examination of results disclosed that the UHPFRCC with the replacement of 25 % of fly ash with GGBS, in conjunction with hybrid fibres, possessed highest residual compressive strength in the temperature range of 28–900 °C with 48 % of RCS value at 900 °C after 56 days of curing. However, in the range of 28–1000 °C, UHPFRCC with PP fibre and hybrid fibre performed almost equally well with the residual flexural strength value of 36 % at 1000 °C after 28 days of curing.

Thermal Conductivity of Akar Bamboo (Dendracalamus pendulus) and Semantan Bamboo (Gigantochloa scortechinii)

Bamboo is known as economically and environmental friendly plant. The most common application of bamboos is furniture and traditional handcrafts. Many studies on mechanical and physical properties of bamboo have been conducted. However the thermal insulation property of these abundance species has never been recognized and commercially utilized which results in the reason why thermal properties of bamboo have never been studied. In this experiment, two species of bamboo which are Akar bamboo (Dendracalamus pendulus) and Semantan bamboo (Gigantochloa scortechinii) has been tested to determine their thermal conductivity. The test samples were prepared to conduct this experiment in parallel and perpendicular grain direction towards the heat source. Wood adhesive was used as the binder for cylindrical laminated bamboo. The result shows that thermal conductivity of bamboo is low in perpendicular direction towards the heat source compared to the parallel direction. Different species of bamboo also give significant result on thermal conductivity hence improved the insulation properties of the bamboo.