Effect of Chemical Composition, Anatomy and Cell Wall Structure on Tensile Properties of Bamboo Fiber

Ligno-cellulosic fiber is an effective reinforcement as an alternative for man-made fiber in composite, while keeping the weight of the composite lower. In this paper, the assessment of bamboo fiber for composite was conducted with the determination of strength, Young's modulus and strain to failure using single fiber tensile test. The mean strength and standard deviation were calculated. Furthermore, a correction method assessed the real fiber elongation from the measured clamp displacement. Chemical analysis of bamboo fiber was conducted and the fiber surface and sclerenchyma cell wall in block was anatomically observed under SEM. Chemical analysis and surface analysis results showed that bamboo fiber is a technical fiber with parenchyma and sclerenchyma cell containing high amount of α-cellulose (50.23%) and holocellulose (67.08%). The fibers constitute the sclerenchymatous tissue and occur in the internodes as caps of vascular bundles or isolated strands. The fibers are grouped in bundles and sheaths around the vessels. For that reason bamboo fiber has high tensile strength (882 ± 307 MPa). Young's modulus for 5, 10, 15, 25 and 35 mm span length were found to be 10.41 ± 4.52, 17.90 ± 7.67, 23.67 ± 8.66, 29.49 ± 4.78, 33.52 ± 11.04 GPa respectively. After correction the Young's modulus was found to be 33.86 GPa. Strain to failure of bamboo fiber was found to be 3.90%. Thus it can be concluded that this procedure seems to be useful for strong bamboo fiber to produce more reliable results

Effect of Mimosa Grafting on Anatomy, Chemical Composition and Tensile Properties of Bamboo Fiber

The current study presents systematic and improved methodologies to characterize elementary bamboo fiber grafted with mimosa. For that, control and grafted bamboo culm anatomy was observed under scanning electron microscopy (SEM), chemical analysis was conducted and tensile properties were measured. During surface analysis, smoother surface was found for grafted fiber compared to the control fiber. No significant change in chemical composition was observed after grafting. In this experiment with the increase of span length the value of tensile strength has decreased but the young modulus has increased.  The tensile strength of grafted fiber was higher than the control fiber. This is because fiber of larger span length has much larger surface area having more flaws and surface defects, which make the chance of failure larger .Thus it can be concluded that mimosa grafting seems to be useful for stronger control fiber with more reliable results

Natural fiber reinforced polymer composites

The use of natural fibers as a reinforcement for various materials was recorded already in ancient Egypt; however, their rediscovery can be dated to the beginning of 20th century. Currentspecial issueisdevoted to theroleofnatural fibersas reinforcements for various biodegradable and nonbiodegradable polymer matrices. The application of natural fillers can be seen as an approach to adjust material performance of polymer composites supposing that filler/matrix interactions will be optimized and a hygroscopicity of natural fillers will be hindered. This special issue contains 16 papers that highlight a number of reasons for applications of natural fillers in polymer composites. In recent years the discussion about a balance in carbon footprint increased an attractiveness of natural fibers/fillers derived from agricultural sources predominantly from one-year plants

Introducing ICT into Teacher-Training Programs: Problems in Bangladesh

Information and Communication Technology can offer more adaptable and efficient ways of teacher training for improvement of quality of professional development programs. But the use of ICT into teacher training usually faces certain obstacles. In this paper, we identified different barriers of introducing ICT into teacher training model (this model had been discussed by the authors in a separate paper, titled as “A model for integrating ICT into teacher training programs in Bangladesh based on TPCK) in Bangladesh, a developing country. We then described the strategies to overcome these problems for improving the current status of ICT integration into teacher training. Finally, we concluded with emerging research issues and offered pertinent recommendation with respect to ICT integration into teacher training program for improving quality of teaching in Bangladesh. Keywords: ICT integration, Teacher-training, knowledge and skil

High velocity oxy-fuel (HVOF) thermal spray deposition of functionally graded coatings

The present study investigates an innovative modification of a HVOF (High Velocity Oxy-Fuel) thermal spray process to produce functionally graded thick coatings. In order to deposit thick coatings, certain problems have to be overcome. More specifically these problems include minimizing residual stresses, which cause shape distortion in assprayed components. Residual stresses in coatings also lead to adhesion loss, interlaminar debonding, cracking or buckling and are particularly high where there is a large property difference between the coating and the substrate. Graded coatings enable gradual variation of the coating composition and/or microstructure, which offers the possibility of reducing residual stress build-up in coatings. In order to spray such a coating, modification to a commercial powder feed hopper was required to enable it to deposit two powders simultaneously. This allows deposition of different layers of coating with changing chemical compositions, without interrupting the spraying process. Various concepts for this modification were identified and one design was selected, having been validated through use of a process model, which was developed using ANSYS Finite Element Analysis. The model simulates the flow of nitrogen gas and powder through the system, and verified the supply of mixed composition powders. Based on this information a multi-powder feed unit was manufactured, commissioned and calibrated. Multi-layer coatings of aluminium and tool-steel were sprayed onto aluminium substrates. The chemical composition of different layers of a five layer graded coating was determined using energy dispersive X-ray spectroscopy (EDS) to confirm functionality. Subsequently, various controlled parameters of the HVOF spraying process were studied for this type of coating using 33 factorial design of experiments. Results were analysed in terms of surface stress to deposition thickness ratio. The best combination of spray parameters identified for deposition of the mixed coating resembles those recommended for aluminium powder alone. It is proposed that this arises from the thermal properties of the constituent powders. Different types of aluminium/tool-steel functionally graded coatings were then deposited using the optimised set of spray parameters, and considered using Clyne’s analytical method of stress analysis and Vickers hardness testing method. Coatings composed of thicker layers resulted in much higher residual stress, but also improved hardness compared to thinner samples. It was found that if 5 layers of graded material are sprayed, and the residual stress compared to that of a traditional single layer (of the same thickness), an approximately 48 % reduction can be achieved. However this benefit is mitigated somewhat by the fact that applying these multi-layers reduces the hardness to by approximately 16 % compared to the traditional single layered deposit. Therefore an engineer must compromise between the stress and hardness when designing a functionally graded coating-substrate system

Effect of Chemical Treatment on Thermal Properties of Jute Fiber Used in Polymer Composites

In recent years, natural fibers, such as jute has gained significant research interest in order to fabricate fiber reinforced polymer composites. Chemical treatments are generally carried out on the raw fibers for making composites with improved properties. From a composite manufacturing point of view, it is important to understand how the treatments can affect the thermal properties of the jute fiber. In the present research, the effects of rot-retardant, fire-retardant and water-retardant treatments on thermal properties of the jute fiber were investigated. Fiber samples were collected from the middle portion of whole jute fiber. Thermo-gravimetric analysis (TGA) and differential scanning calorimetric (DSC) analysis were subsequently conducted on the jute fiber for thermal characterization. The results demonstrated a lower thermal decomposition temperature in the case of fire-retardant treated jute fiber but higher residue at above 400 °C, as compared to the raw and other treated fibers. In general, it was found that chemically treated fibers absorbed less heat, in contrast to the raw jute fiber and heat flow became negative in all cases of the treated fibers. This study provides important information about the thermal properties of the treated jute fibers for manufacturing polymer-based composite materials

Chemical Modification Effect on the Mechanical Properties of Coir Fiber

Natural fiber has a vital role as a reinforcing agent due to its renewable, low cost, biodegradable, less abrasive and eco-friendly nature. Whereas synthetic fibers like glass, boron, carbon, metallic, ceramic and inorganic fibers are expensive and not eco-friendly. Coir is one of the natural fibers easily available in Bangladesh and cheap. It is derived from the husk of the coconut (Cocos nucifera). Coir has one of the highest concentrations of lignin, which makes it stronger. In recent years, wide range of research has been carried out on fiber reinforced polymer composites [4-13].The aim of the present research is to characterize brown single coir fiber for manufacturing polymer composites reinforced with characterized fibers. Adhesion between the fiber and polymer is one of factors affecting the strength of manufactured composites. In order to increase the adhesion, the coir fiber was chemically treated separately in single stage (with Cr2(SO4)3•12(H2O)) and double stages (with CrSO4 and NaHCO3). Both the raw and treated fibers were characterized by tensile testing, Fourier transform infrared (FTIR) spectroscopic analysis, scanning electron microscopic analysis. The result showed that the Young's modulus increased, while tensile strength and strain to failure decreased with increase in span length. Tensile properties of chemically treated coir fiber was found higher than raw coir fiber, while the double stage treated coir fiber had better mechanical properties compared to the single stage treated coir fiber. Scanning electron micrographs showed rougher surface in case of the raw coir fiber. The surface was found clean and smooth in case of the treated coir fiber. Thus the performance of coir fiber composites in industrial application can be improved by chemical treatment

Seeking the best practices of assessment in maritime simulator training

publishedVersio

Phosphine resistance status in lesser grain borer Rhyzopertha dominica (Fab.) (Coleoptera: Bostrichidae) strains originating from the tropical countries: Presentation

Stored product beetles that are resistant to the fumigant phosphine (hydrogen phosphide) have been reported for more than 50 years in many places worldwide. The high levels of phosphine resistance in lesser grain borer Rhyzopertha dominica (F.) have been noted from several countries including Bangladesh. This study was designed to evaluate the status of resistance to phosphine in Bangladeshi R. dominica and to verify the possible comparison among other phosphine resistant strains from tropical countries viz. Burkina Faso and Malaysia. The data reported and summarized here showed varied levels of resistance compared to the laboratory phosphine susceptible strain (RDLAB). Rhyzopertha dominica strains originating from Bangladesh (RDBGD) and Burkina Faso (RDBKF) exhibited higher levels of resistance to phosphine compared to the Malaysian strains (RDMAL). Analysis of dose–response data indicated that the RDBGD and RDBKF strains were the most resistant to phosphine under different exposure periods. At LC50, these two strains were more than 80-fold more resistant at all exposures compared to the susceptible strain. Results also revealed that RDBGD and RDBKF strains required a relatively high concentration of 334.94 and 240.081 mg L-1 for 99% mortality. The mean survival time (MST) for the phosphine resistant and susceptible also varied significantly. The maximum MST was recorded for RDBGD and RDBKF strains. The present findings further confirmed that the Bangladeshi originated R. dominica strain contained higher resistance to phosphine compared to strains from other countries. This study could be useful in developing management strategies to prevent stored grain from being infested by resistant strains of R. dominica in tropical countries.Stored product beetles that are resistant to the fumigant phosphine (hydrogen phosphide) have been reported for more than 50 years in many places worldwide. The high levels of phosphine resistance in lesser grain borer Rhyzopertha dominica (F.) have been noted from several countries including Bangladesh. This study was designed to evaluate the status of resistance to phosphine in Bangladeshi R. dominica and to verify the possible comparison among other phosphine resistant strains from tropical countries viz. Burkina Faso and Malaysia. The data reported and summarized here showed varied levels of resistance compared to the laboratory phosphine susceptible strain (RDLAB). Rhyzopertha dominica strains originating from Bangladesh (RDBGD) and Burkina Faso (RDBKF) exhibited higher levels of resistance to phosphine compared to the Malaysian strains (RDMAL). Analysis of dose–response data indicated that the RDBGD and RDBKF strains were the most resistant to phosphine under different exposure periods. At LC50, these two strains were more than 80-fold more resistant at all exposures compared to the susceptible strain. Results also revealed that RDBGD and RDBKF strains required a relatively high concentration of 334.94 and 240.081 mg L-1 for 99% mortality. The mean survival time (MST) for the phosphine resistant and susceptible also varied significantly. The maximum MST was recorded for RDBGD and RDBKF strains. The present findings further confirmed that the Bangladeshi originated R. dominica strain contained higher resistance to phosphine compared to strains from other countries. This study could be useful in developing management strategies to prevent stored grain from being infested by resistant strains of R. dominica in tropical countries