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With a view to study the response to impacts, epoxy-fly ash systems, with filler particles treated with silane material to their surface were fabricated. The test coupons made from the cured thermoset cast slabs were subjected to impact in an instrumented test set up, where, provision existed for recording both load and total energy absorbed with respect to time. The investigation shows that the crack path shift was highest for unreinforced ones, which, display river marks.
(Carl Hanser Verlag, Correlating failure features to impact data in epoxy systems without and with silane surface bearing fly ash filler particles in varying amounts; Korrelation von versagensmerkmalen und schlagzähigkeitsdaten in epoxidsystemen mit und ohne silanbeschichtete flugascheteilchen in unterschiedlichen volumenanteilen) Kishore; Ravikumar, N.L.; Kulkarni, S.M.
2004
Neat epoxy (NE) and epoxy system with different volume fractions of fly ash fillers with their surfaces treated by silane bearing material were made and the responses to exposure by immersion in varying aqueous media, such as plain water (PW), seawater (SW) and seawater containing small amount of dilute hydrochloric acid (SWA) maintained at 80°C, established through weight measurements recorded up to 100 h on the test coupons. Further on, the 100 h exposed samples were subjected to compression tests to evaluate the strength. The results showed that both NE and the silane treated ash bearing composites generally exhibited the highest water absorption in SWA case and the lowest in SW media, with the water absorption level for PW case falling in between. When the ash content in the composite is very large, the water absorption levels tend to be lower for both SW and SWA. The data further showed that unexposed samples recorded less strength compared to the exposed ones. In the case of exposed samples, in all the media employed, as the ash content increases the strength also increases. Further, it was noticed that the samples exposed to SW showed higher strength than the corresponding values noticed with SWA case. Lower strength was found in samples immersed in PW case. Attempts to explain these differing trends are made in this effort by analyzing the features observed on the surface of compression failed samples using fractography technique employing scanning electron microscope (SEM).
(Compression strength of aqueous media exposed epoxy system containing silane surface bearing fly ash particles) Kishore; Ravikumar, N.L.; Kulkarni, S.M.
2004
Tensile, impact, and vibration properties of coconut sheath/sisal hybrid composites: Effect of stacking sequence
(SAGE Publications Ltd, 2014) Krishnasamy, K.S.; Siva, I.; Nagarajan, N.; Jeyaraj, P.; Winowlin Jappes, J.W.
This work addresses the tensile, impact, and free vibration properties of sisal/coconut sheath fiber hybrid-reinforced unsaturated polyester composites. The hybrid composites are fabricated using a compression molding technique with varying stacking sequences under as-received or chemically treated conditions. The chemical treatments (alkali and tri-chloro vinyl silane) have shown better performance than untreated composites. Furthermore, the silane-treated composite shows enhanced static mechanical and free vibration properties for all stacking sequences relative to the other two cases. From the experimental results, the silane-treated coconut sheath/sisal/coconut sheath hybrid stack is found to be an optimum stacking sequence for better properties. Further, an encouraging damping factor value is also observed for the optimum stacking sequence. The failure mechanism of interfacial de-bonding between the fibers and the matrix is analyzed with the aid of scanning electron microscopy. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
Failure Analysis of Cast Tubular Specimens of Al–5Zn–1Mg While Processing at Room Temperature by Equal Channel Angular Pressing (ECAP)
(Springer Science and Business Media, LLC, 2014) Valder, J.; Rijesh, M.; Surendranathan, A.O.
The ECAP process is a promising technique for imparting large plastic deformation and breaking down the ingot cast structure without a resultant decrease in cross-sectional area. In the present study, the suitability of this technique for processing cast Al–5Zn–1Mg tubular specimens at room temperature has been investigated. Tubular specimens were extruded through an ECAP die with an angle of 150° between the two intersecting channels without a back pressure. Sand was used as a mandrel during pressing. The tubular specimens failed miserably in the first pass itself. A failure analysis was carried out using SEM, and cause for failure was determined. © 2014, ASM International.
Compressive and flexural properties of functionally graded fly ash cenosphere-epoxy resin syntactic foams
(John Wiley and Sons Inc, 2015) Doddamani, M.; Kishore; Shunmugasamy, V.C.; Gupta, N.; Vijayakumar, H.B.
The present study focuses on developing functionally graded syntactic foams (FGSFs) based on a layered co-curing technique. The FGSFs were characterized for compressive and flexural properties and compared with plain syntactic foams. The results showed that the specific compressive modulus was 3-67% higher in FGSFs compared to plain syntactic foams. FGSF exhibited 5-34% and 34-87% higher specific modulus and strength, respectively in flexural mode. The microscopic examinations of comparative responses of the filler and matrix to deformation suggest that the failure is dominated by the matrix. The gradient in the composition of syntactic foams helps in effectively distributing the stress throughout the microstructure and results in improved mechanical performance of syntactic foams. From the microscopy studies, it is evident that, the failure mechanism in the FGSF under flexural loading is governed by a crack that initiated on the tensile side of the specimen and propagated through the thickness to cause complete fracture. The microscopic observations further clearly demonstrate the existence of seamless interfaces between the layers and a clear difference in the cenosphere concentration across the interface, affirming the gradation in the prepared samples. The results show that appropriate compositions of FGSFs can be selected to develop materials with improved mechanical performance. © 2014 Society of Plastics Engineers.
Seismic behavior of rc framed shear wall buildings as per is 1893 and IBC provisions
(Techno-Press, 2015) Jayalekshmi, B.R.; Chinmayi, H.K.
Usually the analyses of structures are carried out by assuming the base of structures to be fixed. However, the soil beneath foundation alters the earthquake loading and varies the response of structure. Hence, it is not realistic to analyze structures by considering it to be fixed. The importance of soil-structure interaction was realized from the past failures of massive structures by neglecting the effect of soil in seismic analysis. The analysis of massive structures requires soil flexibility to be considered to avoid failure and ensure safety. Present study, considers the seismic behavior of multi-storey reinforced concrete narrow and wide buildings of various heights with and without shear wall supported on raft foundation incorporating the effect of soil flexibility. Analysis of the three dimensional models of six different shear wall positions founded on four different soils has been carried out using finite element software LS DYNA. The study investigates the differences in spectral acceleration coefficient (Sa/g), base shear and storey shear obtained following the seismic provisions of Indian standard code IS: 1893 (2002) (IS) and International building code IBC: 2012 (IBC). The base shear values obtained as per IBC provisions are higher than IS values. © 2015 Techno-Press, Ltd.
Physio-mechanical and wear properties of novel jute reinforced natural rubber based flexible composite
(Institute of Physics Publishing helen.craven@iop.org, 2019) Mahesh, V.; Joladarashi, S.; Kulkarni, S.M.
This paper deals with the design, fabrication, physio-mechanical and wear characterization of the composites prepared from naturally available jute fiber and rubber matrix materials. Jute and natural rubber are cost effective, abundant and environmental friendly materials which can be used as fiber and matrix respectively. The flexible composite with different stacking sequence are manufactured using compression moulding machine and void percentage, water absorption percentage, tensile properties, tear strength, impact strength and shore hardness of the prepared composites are found along with the wear. The void content and water absorption are found to increase with increased number of plies in the composite with fibers contributing more compared to rubber. Tensile, tear, specific wear rate and hardness are found to better with a composite having minimum number of plies, which is JRJ. Charpy impact test revealed that the variation in specific impact strength of the three configuration of composites are negligible and no failure of composites were absorbed owing to their flexibility indicating all the three composites have additional capability to absorb much higher energy and suitable as sacrificial components for structural applications subjected to low velocity impact. The fractography analysis of tensile and tear test shows that the flexible composites are free from matrix cracking, but matrix tearing plays a vital role in failure. The mechanism of wear involved in the proposed composites when different constituents of the composite are exposed to abrasive medium is studied through surface morphology. © 2019 IOP Publishing Ltd.
Study on performance of infilled wall in RC framed structure using basalt fibre in cement mortar
(Structural Engineering Research Centre, 2019) Jagadeesan, P.; Palanisamy, T.
Normally, Reinforced Concrete (RC) framed structure is built by combination of structural and non-structural elements that may satisfy the design and architectural purpose. When RC framed structures are subjected to the static lateral loading, infilled wall and RC frame elements does not react together. At this time, infilled wall is subjected only compressive forces and does not support the tensile force. So, failure is happened due to lacking of ductility and poor interaction between frame elements and infilled wall. Therefore, the objective of this study is to improve the ductility and interaction between RC frame elements and infilled wall through suitable method of strengthening of infilled wall. In this research work, the two types of specimens such as infilled RC framed structure and infilled RC framed structure strengthened by reinforced cement mortar using basalt fibre were cast and tested under experimental and analytical investigation. One-fifth scale model of single-bay, two-storey plane RC framed structure were prepared and tested under cyclic loading with the help of 1000 kN capacity loading frame and foundation block. This study focuses the significant parameters such as load-deflection curve, ductility, energy dissipation capacity, initial stiffness and failure mechanism of infilled RC frame and infilled RC frame with basalt fibre in cement mortar. The result proves that basalt fibre reinforced cement mortar improves the strength, stiffness and ductility of infilled RC framed structure and make infilled wall as integral unit in RC framed structure. © 2019 Structural Engineering Research Centre. All rights reserved.
Assessment of Cohesive Parameters Using High Dimensional Model Representation for Mixed Mode Cohesive Zone Model
(Elsevier Ltd, 2019) Rao, B.; Balu, A.S.
Simulation of the mechanical behavior of bonded joints using a cohesive zone model (CZM) is the most common technique to characterize the delamination process. It is usually dependent on the calculation of cohesive parameters of the traction-separation law, and the parameters are iteratively obtained with the help of simulation and experimental results. The non-availability of standard methods to obtain the parameters necessitates the iterative adjustments of simulation results to the experimental results. However, the calculations based on all individuals for the simulation are not effective as it demands high computational effort. To overcome this issue, this paper proposes a computationally efficient method using high dimensional model representation (HDMR). The cohesive parameters are determined by adopting an efficient sampling scheme within the limits of the parameters. Single leg bending (SLB) joint is tested under the influence of dominant conditions such as mode-I and mode-II to determine the equivalent parameters. The errors resulted from the comparison between the simulation, and experimental values are minimized in order to determine the optimal values. The mixed mode (MM) CZM is then established by pure mode cohesive parameters, and the same is implemented to the SLB joint under various mode mixities for analyzing the fracture process. Comparison between the numerical analysis and the experimental study proves that the proposed HDMR based approach estimates the failure mechanism exactly. © 2019 Institution of Structural Engineers
Role of longitudinal reinforcement on the behavior of under reinforced concrete beams subjected to fatigue loading
(Elsevier Ltd, 2019) Prashanth, M.H.; Singh, P.; Chandra Kishen, J.M.C.
In this work, the role of steel reinforcement in under reinforced concrete beams when subjected to flexural fatigue loading is studied using the acoustic emission (AE) technique. Three-point bend notched beams of three different sizes and with varying reinforcement ratios are subjected to step-wise increasing variable amplitude fatigue loading. The crack mouth opening displacement (CMOD) and AE parameters are analyzed to study the evolution of damage, load carrying and failure mechanisms in under reinforced concrete beams. It is concluded that the presence of reinforcement substantially increases the fatigue life. Further, the CMOD could be used as a criterion for failure in reinforced concrete beams under fatigue loading. © 2019 Elsevier Ltd

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