Key Engineering Materials Vols. 471-472

Abstract: Composites are becoming essential part of today’s material because they offer advantages such as low weight, corrosion resistance, high fatigue strength; faster assembly etc. composites are generating curiosity and interest all over the worlds. The attempts can be found in literature for composite materials high strength fiber and also natural fiber like jute, flax and sisal natural fibers provides data but there is need of experimental data availability for unidirectional natural fiber composite with seldom natural fiber like cotton, palm leaf etc., it can provide a feasible range of alternative materials to suitable conventional material. It was decided to carry out the systematic experimental study for the effect of volume fraction of reinforcement on longitudinal strength as well as Modulus of Elasticity (MOE) using developed mould-punch set up and testing aids. The testing is carried out as per ASTM D3039/3039M-08. The comparative assessment of obtained experimental results with literature is also carried out, which forms an important constituent of present work. It is also observed through SEM images and theoretical investigations that interface/interphase plays and important role in natural fiber composite.

Abstract: In this study, composite of Themoplastic polyurethane (TPU) reinforced with short fiber (Hibiscus Cannabinus) kenaf (KF) were prepared via melt blending method using Haake Polydrive R600 internal mixer. Effect of various processing temperatures, times and speeds on tensile strength was studied, together with effect of various fiber sizes on tensile, flexural properties and impact strength. Optimum blending parameters were 190°C, 11 min, and 40 rpm for temperature, time and speed, respectively. Using the optimum processing parameters TPU-KF composites with different fiber sizes were prepared. Composite sheets were prepared by hot press machine at 190 °C for 10 min. Five samples were cut from the composite sheet. Mean value was taken for each composite according to ASTM standards. Tensile and flexural strength were best for fibers between 125-300 micron. Impact strength showed an increasing trend with increasing fiber size.

Abstract: The biomaterial composites consisting of a polymer with a matrix addition of particulate bioactive phase that analogous to the bone microstructure had been extensively studied as a substitute for human’s hard and soft tissues. In this work, HA reinforced HDPE composite (HDPE/HA) was made, with HA contents being up to 50 phr using single screw extruder nanomixer for the compounding process, and later followed by the injection moulding. These characteristics of the HDPE/HA composites were examined using various techniques including differential scanning calorimetry (DSC), scanning electron microscopy (SEM), tensile testing. Mechanical and thermal properties of the composite are differed when the amount of HA incorporated into the composite were varied. It is shown that HA particles were well dispersed and homogeneously distributed within the HDPE matrix. The elastic modulus and tensile strength were increased when the HA volume percentage increased from 10 phr to 50 phr with corresponding decreases in elongation at break. However no significant influence on thermal stability was found with increasing HA loadings. The enhancement of bioactivity has been proved while incorporation of HA into HDPE composite. SEM-EDX image showed the bulk formation of apatite layers on the composite surface with 30 wt% HA after 7 days immersed in simulated body fluid (SBF) solution. These results suggest the great potential of the composites for a range of temporary application in which bone bonding ability is a desired property.

Abstract: Prepreg resin systems are typically of complex composition and require very specific manufacturing conditions. These characteristics restrict the use of some commonly used micro analysis techniques. This paper investigates the use of low acceleration voltage scanning electron microscopy and energy dispersive x-ray analysis for the characterization of diffused polymer interfaces. It is shown that, by operating at the dynamic charge balance, high resolution secondary electron images of polymer interfaces can be obtained and that conductive coating is not required. In addition, the effect of acceleration voltage on the interaction volume in EDX analysis is discussed using Monte Carlo simulation. X-ray intensity measurements in combination with afore mentioned Monte Carlo simulation is used to define practically obtainable spatial resolution limits. It is shown that by reducing the acceleration voltage below 5kV spatial resolution higher the 500nm can be obtained.

Abstract: The blister test is a promising test method to determine the interface fracture toughness of thin films adhering to rigid fibre reinforced plastics. In this paper nonlinear finite element analysis is used to determine a suitable layout for both the shaft loaded and the pressurised blister test. On the example of a PET film adhering to a quasi-isotropic fibre reinforced plastic, it is shown that energy release rates in a range of 0-1500N/m can be obtained for a 0.5mm thick film if test parameters are carefully selected. The two main causes for deviations of the analytic solution from the FEA results is attributed to infringement of the membrane limit condition and plastic deformation in the film.

Abstract: Interfacial interaction in zeolite filled polymer composites was investigated in this study. Two types of polymer which are polypropylene (PP) and ethylene vinyl acetate (EVA) were used as matrix in the preparation of the composites. Moreover, different modifications of zeolite filled polymer composites such as zeolite surface treatment with vinyl silane and alkylammonium and also chemical crosslinking were done to improve the interfacial adhesion between zeolite and polymer matrix. The zeolite filled polymer composites were homogenized using Thermo Haake Polydrive internal mixer and then compression molded into sheets according to standard test specimen. Uniaxial tensile test was performed in order to evaluate the mechanical behavior of the composites. The obtained experimental data for ultimate stress was correlated with Pukanszky theoretical model. The experimental results for all systems of zeolite filled polymer composites showed a good fit to the Pukanszky model. Interfacial interaction for each system of zeolite filled polymer composites was theoretically evaluated by determining the parameter B through this model. The value of parameter B for all zeolite filled polymer composite systems differs significantly from one another thus suggesting the applicability of this Pukanszky model in characterizing the filler-matrix interfacial adhesion.

Abstract: Nanostructured titania/hydroxyapatite (HA) composite layer was developed on commercially pure titanium (Cp Ti) implant material by plasma electrolytic processing (PEP) technique in order to improve its bioactivity and corrosion resistance under physiological conditions. The phases present in the developed composite layer were studied by X-ray diffraction (XRD) technique. The surface morphology and thickness of the composite layers were observed by scanning electron microscopy (SEM). The corrosion characteristics of the developed layer were studied by potentiodynamic polarization scan under simulated body fluid (7.4 pH Hanks solution) and simulated osteoclast (4.5 pH) conditions. The in-vitro bioactivity of the composite layers was studied by using Kokubu’s simulated body fluid (SBF) solution. The X-ray diffractograms reveal the presence of anatase TiO2 and HA phases in the developed layer. The SEM results confirm the pore-free morphology of the implant material surface and the thickness of the developed composite layer was observed to be 110 ± 5 µm for 12 min of PEP. The potentiodynamic polarization study shows an improved corrosion resistance and the in-vitro bioactivity test results indicate enhanced apatite forming ability of PEP treated Cp Ti surfaces compared to that of the untreated Cp Ti, under simulated body fluid conditions.

Abstract: In this paper, fundamental frequency optimization of fiber metal laminated plates is studied using the combination of Elitist-Genetic algorithm (E-GA) and finite strip method (FSM). The design variables are the number of layers, the fiber orientation angles of inner composite layers, edge conditions and plate length/width ratios. The classical laminated plate theory (CLPT) is used to calculate the natural frequencies and the fitness function is computed with a semi-analytical finite strip method which has been developed on the basis of full energy methods. To check the validity, the obtained results are also compared with some other stacking sequences.

Abstract: In this paper, fundamental frequency optimization of symmetrically laminated cylindrical panels is investigated by the Elitist-Genetic algorithm (E-GA). The number of layers, the fiber orientation angles, edge conditions, length/width (a/b) and length/R (a/R) ratios are considered as design variables. The classical shallow shell theory (Donnell’s formulation) is applied to calculate the natural frequencies of laminated cylindrical curved panels. To improve the speed of the optimization process, the elitist strategy is used in the Genetic algorithm and the fitness function is computed with a semi-analytical finite strip method (FSM). A program based on Maple is used for this purpose. To check the validity, the obtained results are also compared with some other stacking sequences.

Abstract: Glass fibre composite reinforcement bars have been used in the reinforced concrete structures as a powerful solution of the steel corrosion problem. This research work aims to use a 3D finite element method and EURO – code models to simulate a concrete beam reinforced with fibre composite bars under the effects of high temperature. The behaviour of the structure is very complex due to load combination and different material response. The applied load was an external mechanical load and a thermal load. The material response was considered as thermal expansion, cracking, crushing, yielding and changing of material properties with the temperature increase. The FE element was modified to allow temperature distribution and material properties changing to throw thickness of the concrete beam. In addition, the geometrical non – linearity is considered in the analysis due to the large deflection of the structure. The prediction results were compared with the available experimental results, and it gives a well correspond.