• Advances in aircraft and spacecraft science
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• v.4 no.6
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• pp.679-699
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• 2017

The aim of this study is to perform a finite element analysis of the Von Mises stresses distribution in the adhesive layer and of the J-Integral for a damaged plate repaired by a composite patch. Firstly, we study the effect of the fiber orientation, especially the position of the layers that have orientation angle different of $0^{\circ}$ from the first layer which is in all cases of our study oriented at ($0^{\circ}$) on the J-Integral. Secondly, we evaluate the effects of the mechanical properties of the patch and the use of a hybrid patch on the reduction of stresses distribution and J-Integral. The results show clearly that the stacking sequence for the composite patch must be selected to absorb optimally the stresses from the damaged area and to position the various layers of the composite under the first layer whose fibers orientation will remain in all cases equal to $0^{\circ}$. The use of a hybrid composite reduces significantly the J-Integral and the stresses in both damaged plate and the adhesive layer.

• Computers and Concrete
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• v.25 no.4
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• pp.303-310
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• 2020

In this research, a hybrid mathematical model is derived using the higher-order polynomial kinematic model in association with soft computing technique for the prediction of best fiber volume fractions and the minimal mass of the layered composite structure. The optimal values are predicted further by taking the frequency parameter as the constraint and the projected values utilized for the computation of the eigenvalue and deflections. The optimal mass of the total layered composite and the corresponding optimal volume fractions are evaluated using the particle swarm optimization by constraining the arbitrary frequency value as mass/volume minimization functions. The degree of accuracy of the optimal model has been proven through the comparison study with published well-known research data. Further, the predicted values of volume fractions are incurred for the evaluation of the eigenvalue and the deflection data of the composite structure. To obtain the structural responses i.e. vibrational frequency and the central deflections the proposed higher-order polynomial FE model adopted. Finally, a series of numerical experimentations are carried out using the optimal fibre volume fraction for the prediction of the optimal frequencies and deflections including associated structural parameter.

• Steel and Composite Structures
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• v.34 no.1
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• pp.91-105
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• 2020

Steel-concrete composite beam with profiled steel sheet has gained its popularity in the last two decades. Due to the ageing of these structures, retrofitting in terms of flexural strength is necessary to ensure that the aged structures can carry the increased traffic load throughout their design life. The steel ribs, which presented in the profiled steel deck, limit the use of shear connectors. This leads to a poor degree of composite action between the concrete slab and steel beam compared to the solid slab situation. As a result, the shear connectors that connects the slab and beam will be subjected to higher shear stress which may also require strengthening to increase the load carrying capacity of an existing composite structure. While most of the available studies focus on the strengthening of longitudinal shear and flexural strength separately, the present work investigates the effect of both flexural and longitudinal shear strengthening of steel-concrete composite beam with composite slab in terms of failure modes, ultimate load carrying capacity, ductility, end-slip, strain profile and interface differential strain. The flexural strengthening was conducted using carbon fibre reinforced polymer (CFRP) or steel plate on the soffit of the steel I-beam, while longitudinal shear capacity was enhanced using post-installed high strength bolts. Moreover, a combination of both the longitudinal shear and flexural strengthening techniques was also implemented (hybrid strengthening). It is concluded that hybrid strengthening improved the ultimate load carrying capacity and reduce slip and interface differential strain that lead to improved composite action. However, hybrid strengthening resulted in brittle failure mode that decreased ductility of the beam.

• Steel and Composite Structures
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• v.34 no.5
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• pp.743-767
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• 2020

Due to the impressive flexural performance, enhanced compressive strength and more constrained crack propagation, Fibre-reinforced concrete (FRC) have been widely employed in the construction application. Majority of experimental studies have focused on the seismic behavior of FRC columns. Based on the valid experimental data obtained from the previous studies, the current study has evaluated the seismic response and compressive strength of FRC rectangular columns while following hybrid metaheuristic techniques. Due to the non-linearity of seismic data, Adaptive neuro-fuzzy inference system (ANFIS) has been incorporated with metaheuristic algorithms. 317 different datasets from FRC column tests has been applied as one database in order to determine the most influential factor on the ultimate strengths of FRC rectangular columns subjected to the simulated seismic loading. ANFIS has been used with the incorporation of Particle Swarm Optimization (PSO) and Genetic algorithm (GA). For the analysis of the attained results, Extreme learning machine (ELM) as an authentic prediction method has been concurrently used. The variable selection procedure is to choose the most dominant parameters affecting the ultimate strengths of FRC rectangular columns subjected to simulated seismic loading. Accordingly, the results have shown that ANFIS-PSO has successfully predicted the seismic lateral load with R² = 0.857 and 0.902 for the test and train phase, respectively, nominated as the lateral load prediction estimator. On the other hand, in case of compressive strength prediction, ELM is to predict the compressive strength with R² = 0.657 and 0.862 for test and train phase, respectively. The results have shown that the seismic lateral force trend is more predictable than the compressive strength of FRC rectangular columns, in which the best results belong to the lateral force prediction. Compressive strength prediction has illustrated a significant deviation above 40 Mpa which could be related to the considerable non-linearity and possible empirical shortcomings. Finally, employing ANFIS-GA and ANFIS-PSO techniques to evaluate the seismic response of FRC are a promising reliable approach to be replaced for high cost and time-consuming experimental tests.

• 전자공학회논문지 IE
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• v.44 no.3
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• pp.6-11
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• 2007

In this study, which was performed to identify a degradation mechanism in macromolecular insulating material, the contact angle, surface potential decay, surface resistance rate and XPS analysis were compared after exposure of fibre-glass-reinforced polymer laminate to plasma discharge. In the case of chemical changes arising from plasma treatment, carboxyl radicals were generated mainly in the plasma-treated surface, which was rapidly changed to a hydrophilic surface. In the corona potential decay study to determine the electrical changes, leading to a negative surface for the untreated specimen. However, in the case of the hydrophilic surface, a lot of carboxy radicals(-COO) acting as positive polarity were generated, resulting in a positive surface. Owing to such a positive surface, the charges of applied negative polarity were decreased rapidly.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.7
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• pp.996-1002
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• 2003

A 6 (accession)${\times}$5 (cutting interval) factorial experiment was conducted over two years to investigate the effect of stage of growth on herbage production, nutritive value and water soluble carbohydrate (WSC) content of Napier grass and Napier grass${\times}$Pearl millet hybrids (hybrid Pennisetum). The purpose of the experiment was to determine the optimum stage of growth to harvest the Pennisetums for ensilage. Two Napier accessions (SDPP 8 and SDPP 19) and four hybrid Pennisetum (SDPN 3, SDPN 29, SDPN 38 and Bana grass) were compared at five harvest intervals (viz. 2, 4, 6, 8, and 10 weeks). Basal fertilizers were similar in all treatment plots, although nitrogen (N) top-dressing fertilizer was varied proportionately, depending on the harvesting interval. The application was based on a standard rate of 60 kg N/ha every six weeks. Stage of growth had significant effects on forage yield, WSC content and nutritive value of the Pennisetums. Herbage yields increased in a progressively linear manner, with age. Nutritive value declined as the harvesting interval increased. In particular, crude protein content declined rapidly (p<0.001) from $204g\;kg^{-1}$ DM at 2 weeks to $92g\;kg^{-1}$ DM at 8 weeks of growth. In vitro dry matter digestibility decreased from 728 to $636g\;kg^{-1}$ DM, whilst acid and neutral detergent fibre contents increased from 360 and 704 to 398 and $785g\;kg^{-1}$ DM, respectively. Rapid changes in nutritive value occurred after 6 weeks of growth. The concentration of WSC increased in a quadratic manner, with peaks ($136-182g\;kg^{-1}$ DM) at about 6 weeks. However, the DM content of the forage was low ($150-200g\;DM\;kg^{-1}$) at 6 weeks. Therefore, it was concluded that Pennisetums should be harvested between 6 and 7 weeks, to increase DM content and optimize herbage production without seriously affecting nutritive value and WSC content. Accessions SDPN 29 and SDPP 19 appeared to be most suited for ensilage. It was suggested that WSC content should be incorporated as a criterion in the agronomic evaluation and screening of Pennisetum varieties.

• Composites Research
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• v.32 no.4
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• pp.171-176
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• 2019

In this paper, the strength of the composite securement device was characterised by FE analysis. Preliminary frontal crash analysis for the vehicle, equipped with the conventional steel securement device, was carried out according to the ISO 10542 for special transportation to obtain loading data, which were applied to securement device during crash. The securement device consists of block, guide and rail and the weight fraction of rail was the highest among them, therefore, it is desirable to reduce weight of rail by applying carbon/epoxy composite. Also, it was found that 27% of lightweight effect was obtained by hybrid rail that bottom part was replaced by a composite compared to the conventional rail, i.e., made of SAPH 440, without sacrificing the structural strength.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.3
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• pp.145-155
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• 2002

The results of the present feasibility study are summarized as follows, 1. The three unit bridge of knitted material and UD fibre reinforcement has both the rigidity and the strength against a vertical occlusal load of 75N. 2. Stress concentration at the junctional area between the bridge and the abutments, i.e. between the pontic and the knitted caps was observed. In the case of the bridge with reinforcement straps, it was partly shown that the concentration problem could be improved by simply increasing the fillet size at the area. Further refining in the surface of the junctional area will be needed to ensure a further improvement in the stress distribution. This will require some trade off in the level of the stress and the available space. A parametric study will help to decide the appropriate size of the fillet. 3. Design refinement is a must to improve the stress distribution and realize the most favourable shape in terms of fabrication. The current straight bar with a constant cross section area can be redesigned to a tapered shape. The curve from the dental arch should also be placed on the pontic design. In accordance with design refinement, the resistance of the bridge frame to other load cases should be evaluated. 4. Although not included in the present feasibility study, it is estimated that bridges of the anterior teeth can be made strong enough with the knitted material without further reinforcement using unidirectional materials. In this regard, a feasibility study on design concepts and stress analysis for 3, 4, 5 unit bridge is suggested. 5. Two types of bridge were analysed in terms of fatigue. The safe life design concept, i.e. fatigue design concept, looks reasonable for the bridge where if cracks should form and propagate there is virtually nothing a dentist to do. The bridge must be designed so that no crack will be initiated during the life span. In the case of crowns, however, if constructed with composite resin with knitted materials, it might be possible to repair them, which in general is impossible for crowns of PFM or of metal. Therefore for composite resin crowns, a damage tolerance design concept can be applied and reasonably higher operational stresses can be allowed. In this case, of course, a periodic inspection program should be established in parallel. 6. Parts of future works in terms of structural viewpoint which need to be addressed are summarized as the following: 1) To develop processing technology to accommodate design concepts; 2) More realistic modelling of the bridge and analysis-geometry and loading condition. Thickness variation in the knitted material, taper in the pontic, design for anterior tooth bridge, the effect of combined loads, etc, will need to be included; 3) To develop appropriate design concepts and design goals for the fibre composite FPD aiming at taking the best advantage of knitted materials, including the damage tolerance design concept; 4) To develop testing method and perform test such as static ultimate load test, fatigue test, repair test, etc, as necessary.