Zakiah Ahmad

Preparation and characterization of potato starch nanocrystal reinforced natural rubber nanocomposites

Potato starch nanocrystals were found to serve as an effective reinforcing agent for natural rubber (NR). Starch nanocrystals were obtained by the sulfuric acid hydrolysis of potato starch granules. After mixing the latex and the starch nanocrystals, the resulting aqueous suspension was cast into film by solvent evaporation method. The composite samples were successfully prepared by varying filler loadings, using a colloidal suspension of starch nanocrystals and NR latex. The morphology of the nanocomposite prepared was analyzed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). FESEM analysis revealed the size and shape of the crystal and their homogeneous dispersion in the composites. The crystallinity of the nanocomposites was studied using XRD analysis which indicated an overall increase in crystallinity with filler content. The mechanical properties of the nanocomposites such as stress-strain behavior, tensile strength, tensile modulus and elongation at break were measured according to ASTM standards. The tensile strength and modulus of the composites were found to improve tremendously with increasing nanocrystal content. This dramatic increase observed can be attributed to the formation of starch nanocrystal network. This network immobilizes the polymer chains leading to an increase in the modulus and other mechanical properties.

Moisture Absorption Characteristics of Epoxy Based Adhesive Reinforced with CTBN and Ceramic Particles for Bonded-in Timber Connection: Fickian or Non-Fickian Behaviour

For in-situ bonding of pultruded rod into timber structural members, such as in the construction of bonded-in timber connection, strengthening and repair of timber structures, the adhesive used must be thixotropic, room temperature cure, environmentally stable and friendly and applied at without pressure. This study investigates the moisture absorption characteristics of three adhesives specially formulated for bonded-in timber connections where the adhesives are reinforced with nano- and micro-particles denoted as CB10TSS (standard adhesive), Albipox (CB10TSS/CTBN) and Timberset (ceramics filled adhesive) with the aim to improve mechanical properties and raise glass transition temperature. The effect of high temperatures and high humidity on the properties of adhesives were determined following conditioning at different temperatures (20°C, 30°C and 50°C) and relative humidities (65%, 75% and 95%) and soaking in water at 20°C In all cases the properties of Albipox were least affected by environment but Timberset exhibited the lowest moisture uptake. Exposure to humid environments at temperatures 20°C and 30°C for CB10TSS and Albipox and 50°C for Timberset resulted in water uptake characterized as Fickian which had only a modest effect on properties. However, exposure to humid environments at temperature (50°C) which is higher than Tg resulted in non-Fickian uptake of water for CB10TSS and Albipox and a more adverse effect on properties.

Ultimate Strength of Kekatong Glued Laminated Timber Railway Sleepers

Pre-stressed concrete (PSC) sleepers are the main components of railway track systems in Malaysia. However, there are sections in the track system which PSC sleepers cannot be utilized, where timber sleepers are still needed. Due to limited supply of large sections timber logs and high cost in high grade timber, an alternative for this timber product is needed. Thus, this study is conducted to determine the ultimate strength of the alternative timber product which is glued laminated (glulam) timber railway sleepers from selected Malaysian tropical heavy hardwood timber species namely Kekatong. The static bending test at rail seats was carried out in order to achieve the objective and the test is accordance to AREMA Manual. The values of modulus of rupture (MOR) and modulus of elasticity (MOE) for two numbers of glulam timber sleepers were evaluated and compared with the MOR and MOE values of two numbers of solid timber sleeper. Then the properties are verified with the minimum performance requirement in AREMA Manual. The results showed the glulam Kekatong timber railway sleepers met the requirement set by AREMA with the static yield load surpassed the Keretapi Tanah Melayu Berhad (KTMB) specific design load.

Dowel-Bearing Strength Properties of Two Tropical Hardwoods

Bearing strength of wood is one of the properties that are use to estimate the lateral connection of wood design strength based on the European Yield Model (EYM), National Design Specification [NDS 2005 in National design specification for wood construction american forest and paper association (AFPA), Washington D.C, 2005] theory. This study investigated the characterisation of load to grain directions and two dowel sizes in two high-density Malaysian hardwood species; Kempas (koompassia Malaccensis) and Kapur (Dryobalanop spp.). Experimental work as stipulated in ASTM 5764-9a [American Standard Testing Method (ASTM) D 5764-95a in ), Standard test method for evaluating dowel-bearing strength of wood and wood-based products, 2007] was adopted. Result shows that according to the species, the lower strength group of species attributes to higher bearing strength of wood. It was also found that the bearing strength of parallel to the grain is higher than the perpendicular to the grain. In terms of dowel diameter, the bearing strength perpendicular and parallel to the grain decreased slightly as the dowel diameter increased regardless of the timber species. The EYM equations were found viable and sufficient in predicting the dowel-bearing strength of bigger dowel diameter for Kempas but not for the smaller dowel diameter. Contradict to Kempas species; the EYM equations were viable for the smaller dowel diameter and not for the bigger dowel diameter for Kapur. Thus, in the case of the insufficient predictions, three modified equations based on EYM, were proposed according to the specific gravity, density, species, dowel diameter and loading directions respectively.

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.

The Effect of Long Term Loading on Epoxy-Based Adhesive Reinforced with Nano-Particles for In Situ Timber Bonding

The mechanical properties of adhesive materials change over time, especially when they are subjected to long-term loading regimes. The significance of this is often overlooked at the design stage. When adhesives are subjected to a constant load, they may deform continuously, depending on temperature, humidity and cross-link density. This progressive deformation is called creep and will continue until rupture or yielding causes failure. It is imperative that reliable accelerated tests be developed to determine the long-term time-dependent performance of adhesives under different environmental conditions. The long-term creep behaviors of thixotropic and room temperature cure epoxy based adhesives reinforced with nano-particles specially formulated for in-situ bonding of pultruded rod into timber for repair and strengthening of timber structures were investigated. In this study two epoxy-based adhesives with nano-particles (silica fume and rubber) addition were subjected to bending creep tests, in accelerated environments. Experimental data showed that the adhesives reinforced with nano-rubber particles showed less creep deformation than the unreinforced adhesives.

Shear capacity of dowelled mortise and tenon in tropical timber

The European Yield Models (EYM) concept has been applied to observe an experimental study of single-dowelled mortise and tenon. Specimens consisting of structural size mortise and tenon dowelled with 20.6 mm diameter were axially loaded in shear. Test variables are the material for the dowels namely steel; glass fibre reinforced plastic (GFRP) and wood. Connections were tested until failure to observe the ultimate capacities and possible modes of failure as the variables were changed. Results show that the shear strength capacity of the mortise and tenon connection single-dowelled with steel, GFRP and wood is not directly reflected the capacity of the dowel. The proportional limit, 5% diameter offset and maximum strength of the connection are in the order of steel, wood and GFRP but the dowel yield modes are in the order of steel, GFRP and wood. Failure modes of GFRP were found as stiff as steel (mode Im) compared to wood (mode IIIs).

Bending strength of glulam from selected malaysian hardwood timber

Malaysian government has already built the first glulam structure in Malaysia with the aim of demonstrating the potentialities of using indigenous hardwood timber for glulam. Since Malaysia possesses a vast variety of timber species, hence there is a need to identify suitable species for glulam manufacturing. This paper presents the bending performance of Malaysian hardwood glulam beams, manufactured from different categories namely heavy, medium and light hardwood timbers. A series of tests were carried out on the glulam beam that includes bending test, delamination test and shear test of glue line. Results in this study will be useful to manufacturers interested in using Malaysian hardwood for glulam beams.

Experimental performance of mortice and tenon joint strengthened with glass fibre reinforced polymer under tensile load

This paper reported on the experimental performance of mortise and tenon joint for beam-to-column structural member made of Kempas species. The joints were dowelled with glass fibre reinforced polymer (GFRP) and compared to the joints strengthened with steel dowel and wood dowel. The failure modes performance analyses were observed based on European Yield Model (EYM) theory according to National Design Specification (NDS) 2008. Results show that the experimental performance of the mortise and tenon joints dowelled with GFRP under tensile load may provide comparable strength to the joints dowelled with steel. The sequence of having the higher capacity to hold the mortise and tenon joints is by strengthening it using GFRP, followed by steel and wood dowel. The failure behavior of both joints dowelled with steel or GFRP were almost similar. Nevertheless, different behavior was shown in wood dowelled joints, the flexibility of wood dowels extended the displacement longer made the yield load and load at rapture extended compared to the other types of joints.

Compressive Strength and Water Absorption Characteristics of Brick Using Quarry Dust

This paper reports the investigation made on the suitability and the optimum ratio of quarry dust in replacing river sand for brick production. A series of mix proportions for different ratio of cement:sand:quarry dust were prepared. Five types of mix proportions were practiced in the production of brick specimens were 1:10:0, 1:7.5:2.5, 1:5:5, 1:2.5:7.5 and 1:0:10 (Cement:Sand:Quarry Dust) and denoted as B1, B2, B3, B4 and B5 respectively. The curing method applied in this study was air dry as this type of curing was widely used in the manufacturing of bricks. The compressive strength of the samples was determined at 7, 28 and 45 days. Compressive strength tests were conducted in accordance with BS 3921:1985. Water absorptions of the samples were determined by using 24 h cold immersion test and 5 h boiling test. Bricks with mix ratio 1:0:10 (B5) containing 100 % quarry dust in replacing the sand gave the highest strength and the lowest water absorption compared to other ratios. All the quarry dust-sand-cement bricks exhibited a compressive strength much higher than the minimum requirement for standard bricks (5 N/mm2) according to British Standard (BS 3921:1985). Bricks B5 can be considered to be in ‘severe weathering’ grade and the other bricks are in ‘moderate weathering’ grade in accordance with ASTM C62.