M. Rajesh

Bio: M. Rajesh is an academic researcher from VIT University. The author has contributed to research in topic(s): Natural fiber & Composite number. The author has an hindex of 11, co-authored 34 publication(s) receiving 450 citation(s). Previous affiliations of M. Rajesh include National Institute of Technology, Karnataka.

Structural health monitoring of aerospace composites

Abstract: The health monitoring of aerostructures assists performance enhancement of existing structures. Continuous monitoring and different techniques involved in the structural monitoring help to increase the efficiency of structures, postpone the failures, and provide the prototype for future aerospace structures with better durability. Structural performance of aerospace composites depends on strength, stiffness, yield capacity, bending capacity, resistance against corrosion, impact and lightning, and fatigue due to cyclic loading. In structural monitoring, the four different stages followed to monitor any damage in aerospace composite structure are operation evaluation, data accession, feature extraction, followed by statistical modeling. This chapter on structural health monitoring for aerostructures elaborates the methods to detect and prevent the failures in the structures, as observed through a series of literature available based on the type of damages and techniques to detect them like cracking, fiber pullout, delamination and shearography, eddy current method, transient thermographic method, etc, respectively. In this chapter structural health monitoring of composite aerostructures is reviewed in detail. Different techniques used to monitor the various failures occurring in the composite structures in aerospace industry are explained in detail. Structures made of composite material used in aerospace fail due to fiber-matrix damage. Hence, it is important to analyze such damage like fiber buckling, fiber splitting, fiber cracking, fiber fracture, and fiber bending, and cracks in the matrix etc. to prevent catastrophic results.

Dynamic mechanical analysis and free vibration behavior of intra-ply woven natural fiber hybrid polymer composite:

Abstract: Influence of nature of weaving pattern and intra-ply hybridization of natural fibers on dynamic mechanical and free vibration characteristics of woven banana/jute polyester composite has been inves...

Free Vibration Characteristics of Banana/Sisal Natural Fibers Reinforced Hybrid Polymer Composite Beam

Abstract: Natural fibers having more advantage compared to man-made fiber, such as glass, carbon, Kevlar fiber. But due to the hydrophilic nature of natural fiber gives poor adhesion between fiber-matrix. This will decrease the properties of polymer composite. In this study influence of surface pre-treatment with sodium hydroxide and hybridization effect of natural fiber are investigated on flexural test and free vibration behavior. In this work sisal and banana natural fibers are used in short and random orientations to prepare the polymer composites using compression moulding method. From the experimentation, it is found that chemical treatment improves the mechanical and free vibration properties of polymer composites due to the enhancement of interfacial bond between fiber and matrix as the result of chemical treatment.

Experimental investigation on physical and mechanical properties of lime mortar: Effect of organic addition

Abstract: Influence of organic addition in the lime matrix on its mechanical and physical properties has been investigated. Results revealed that addition of organics in the lime matrix enhances the mechanical properties of the mortar significantly as it improves the binding strength between two consecutive lime particle in the mortar. Physical property results reveal loading of organics in the lime mortar decreases the pore size due to formation of weddellite element in the lime mortar, which fills the gap between two consecutive lime particle in the mortar. Results also reveal that the addition of organics does not reducing total porosity due to formation of large numbers of smaller size pores in the lime mortar. However, addition of organics enhances the strength of mortar. Curing studies reveal that mortar with higher curing days enhances the compressive strength of composites while lower curing reduces the performance of mortar due to lower carbonation rate. X-ray diffraction and FT-IR analysis has been used to confirm the new element formation in the organically modified lime mortar due to interaction of protein and carbohydrate with lime particle.

Mechanical Properties of Natural Fiber Braided Yarn Woven Composite: Comparison with Conventional Yarn Woven Composite

Abstract: The effect of reinforcing natural fiber in the form of braided yarn woven fabric on mechanical properties of polymer composite was investigated. The results of braided yarn fabric composites were compared with the conventional yarn fabric composite and random oriented intimately mixed short fiber composites for the same percentage of fiber weight. The effect of intra-ply hybridization, by keeping two different natural fiber yarns along two different directions of a woven fabric, on mechanical properties of the woven fabric composite was also analyzed. Natural fiber braided yarn fabric reinforcement significantly increased the mechanical properties of the composites compared with that of the conventional woven fabric and short fiber reinforcements. Intra-ply hybridization of two different natural fibers improved the mechanical properties of the conventional woven fabric composite while it could not enhance the properties of the braided fabric composite. The improvement in impact property is very high compared to tensile and flexural properties due to the braided yarn fabric reinforcement.

Mechanical properties evaluation of sisal fibre reinforced polymer composites: A review

Abstract: Recently, growing environmental impact associated with production, disposal and recycling of synthetic fibre based polymer composites triggers the development of ecofriendly composite for various applications such as automotive, marine, chemical, Infrastructure, sporting goods etc. Among many natural fibres like kenaf, jute, oil palm, cotton, flax, banana and hemp, sisal are gaining attention as they are abundantly available, cheaper, eco-friendly and possess remarkable and satisfactory mechanical properties to hemp, banana and jute. Sisal fibre will play a key role to fabricate a varied range of structural and non-structural industrial products with different polymer matrix. This review article deals the mechanical properties of sisal fibre and the several factors influencing the mechanical properties of its polymer composites, such as fibre loadings, fibre length, fibre architecture, chemical treatments and hybridization by incorporating different natural/synthetic fibre/fillers or additive, according to the application and strength requirements. Attempt also been made to investigate the effect of water absorption, chemical concentration, exposure time, filler weight% and individual fibre loading % in the hybrid configuration on the mechanical properties. Overall present review article was designed to explore, highlights and gathered the previous reported studies directing the mechanical properties of sisal fibre and its polymer composites to provide a perfect source of data and literature for doing future research to reveal it as construction and building materials like synthetic fibres.

Recent progress on natural fiber hybrid composites for advanced applications: A review

Abstract: Natural fibers, as replacement of engineered fibers, have been one of the most researched topics over the past years. This is due to their inherent properties, such as biodegradability, renewability and their abundant availability when compared to synthetic fibers. Synthetic fibers derived from finite resources (fossil fuels) and are thus, affected mainly by volatility oil prices and their accumulation in the environment and/or landfill sites as main drawbacks their mechanical properties and thermal properties surpass that of natural fibers. A combination of these fibers/fillers, as reinforcement of various polymeric materials, offers new opportunities to produce multifunctional materials and structures for advanced applications. This article intends to cover recent developments from 2013-up to date on hybrid composites, based on natural fibers with other fillers. Hybrid composites preparation and characterization towards their applicability in advanced applications and the current challenges are also presented.

Detection of Spatially Distributed Damage in Fiber-Reinforced Polymer Composites.

Abstract: This work describes a novel method of embedded damage detection within glass fiber–reinforced polymer composites. Damage detection is achieved by monitoring the spatially distributed electrical conductivity of a strain-sensitive multiwalled carbon nanotube thin film. First, thin films were spray-deposited directly upon glass fiber mats. Second, using electrical impedance tomography, the spatial conductivity distribution of the thin film was determined before and after damage-inducing events. The resolution of the sensor was determined by drilling progressively larger holes in the center of the composite specimens, and the corresponding electrical impedance tomography response was measured by recording the current–voltage data at the periphery of the monitored composite sample. In addition, the sensitivity to damage occurring at different locations in the composite was also investigated by comparing electrical impedance tomography spatial conductivity maps obtained for specimens with sets of holes drilled at different locations in the sensing area. Finally, the location and severity of damage from low-velocity impact events were detected using the electrical impedance tomography method. The work presented in this study indicates a paradigm shift in the available possibilities for structural health monitoring of fiber-reinforced polymer composites.

Effects of Fibre Configuration on Mechanical Properties of Banana Fibre/PP/MAPP Natural Fibre Reinforced Polymer Composite ☆

Abstract: Natural fibre reinforced polymer matrix composite (PMC) is one of the advanced technologies developed in the materials engineering industry. Amongst the advantages of natural fibre reinforced PMC are biodegradable, recyclable, lightweight, low production cost, and readily available. Therefore, natural fibre reinforced polymer composites have been used for many applications such as automotive components, aerospace parts, sporting goods and building industry. In this research, high performance polypropylene (PP) composites, using continuous banana fibre as reinforcement with polymer to fibre by weight percent ratio of 70:30, were developed. This research aims to investigate the effects of different configurations of continuous banana fibre reinforcement on mechanical properties of the composite materials. Coupling agent, which is maleic anhydride grafted polypropylene (MAPP) is added to the composites to improve bonding between the polymer matrix and the natural fibre. To further improve the PMC's mechanical properties, banana fibre's configurations are varied, in which their performance are tested. The banana fibre is varied by three different configurations; raw banana fibre, banana fibre yarn, and banana fibre mat. Mechanical properties of the composite samples were assessed using tensile and flexural testing in accordance to ASTM D638 and ASTM D790, respectively. Microstructural analysis was performed by using scanning electron microscope to explain the failure mechanisms and behavior of the composites. This study has enabled ranking of different banana fibre configurations towards mechanical properties of the natural fibre reinforced thermoplastic-based composites. Morphology examination of the fracture surfaces confirmed failure mechanisms and explained why one fibre configuration is superior to the others.

Mechanical properties of a polyurethane hybrid composite with natural lignocellulosic fibers

Abstract: Several low-cost hybrid composites composed of polyurethane and renewable natural fibers were developed and analyzed for their mechanical and physical properties. Composites were fabricated by replacing up to 20% w/w of the polyethylene glycol present in conventional polyurethane foams with one and the mixture of three natural fibers: sugarcane bagasse, sisal or rice husk. Prior to composite production, fibers were mercerized with sodium hydroxide and hydrogen peroxide to remove lignin and hemicellulose. A simplex-centroid mixture design model was used to evaluate the effects of the added fibers on composite properties such as resilience, elastic modulus and deformation under permanent compression. Obtained hybrid composites demonstrated up to 32% of resilience, 0.1 GPa of elastic modulus, and 7.32% of permanent deformation. In order to optimize these properties, fiber amounts were adjusted using a quadratic mathematical model, indicating that formulations containing only the rice husk or an 82/18 (% w/w) rice husk/sugarcane bagasse mixture will perform best. The obtained composite is a unique low cost material because is environmentally friendly and has a high potential for applications in shock absorption and padding materials, due its proven good resilience and elastic modulus.