A. Arockiarajan

Bio: A. Arockiarajan is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Materials science & Piezoelectricity. The author has an hindex of 18, co-authored 163 publications receiving 1421 citations. Previous affiliations of A. Arockiarajan include Kaiserslautern University of Technology & University of Nottingham.

Parameters influencing the impact response of fiber-reinforced polymer matrix composite materials: a critical review

Abstract: The damage of fiber reinforced polymer matrix composite materials induced by impact load is one of the most critical factors that restrict extensive use of these materials. The behavior of composite structures under transient impact loading and the ways to enhance their characteristics to withstand this type of dynamic loading might be of specific significance in the aerospace sector and other applications. This paper critically reviews the important parameters from the published literature influencing the impact resistance and the damage mechanics of fiber-reinforced composite materials. Firstly, the paper reviews the influence of impact velocity on various failure modes. Following this, a comprehensive review on the four key parameters specifically material, geometry, event and the environmental-related conditions that affect the structural behavior of fiber reinforced polymer matrix composites to impact loading is discussed. The review further outlines areas to improve the impact damage characteristics of composites and then conclude with a summary of the discussion on the future work relating to the most influencing parameters.

Defects in composite structures: Its effects and prediction methods – A comprehensive review

Abstract: The principal aim of this paper is to present a comprehensive literature survey on the defects, like debonds/delamination in composite joints/structures, focusing on the effect of defects, its growth initiation and prediction methods in fibre reinforced plastics. The effects of delaminations, its size, shape and position have been extensively studied over the past few decades. Very little attention has been paid in the area of adhesively bonded joints with closed debonds. The phenomena associated with debond in adhesively bonded composite joints require additional studies in order to allow a better understanding of the behaviour of this category when subjected to uni-axial compression. Recently virtual crack closure technique (VCCT) and cohesive zone modelling (CZM) are used as promising tools for the prediction of defects onset and its growth initiation. In this paper a comprehensive review on the prediction methods and experimental techniques are carried out and presented for the application in this field of study.

A multiplicative approach for nonlinear electro-elasticity

Abstract: The recent interest in dielectric elastomers has given rise to a pressing need for predictive non-linear electromechanical coupling models. Since elastomers behave elastically and can sustain large deformations, the constitutive laws are naturally based on the formulation of adequate free energy functions. Due to the coupling, such functions include terms which combine the strain tensor and the electric field. In contrast to existing frameworks, this paper proposes to establish the electromechanical coupling by the multiplicative split of the deformation gradient into a part related to the elastic behavior of the material and further one which describes the deformation induced by the electric field. Already available and well tested functions of elastic free energy functions can be immediately deployed without any modifications provided the argument of the function is the strain tensor alone which in turn is defined by the elastic part of the deformation gradient only. An appropriate constitutive relation is formulated for the electrically induced part of the deformation gradient. The paper discusses in depth such a formulation. The approach is elegant, straightforward and above all, provides clear physical insight. The paper presents also a numerical formulation of the theoretical framework based on a meshfree method. Various numerical examples of highly non-linear coupled deformations demonstrate the potential and strength of the theory.

Influence of patch lay-up configuration and hybridization on low velocity impact and post-impact tensile response of repaired glass fiber reinforced plastic composites:

Abstract: This paper aims to investigate the effect of homogenous and hybrid external patches based on plain weave woven glass and Kevlar fabric on low velocity impact and quasi-static tensile after impact r...

Magneto-elastic oscillator: Modeling and analysis with nonlinear magnetic interaction

Abstract: The magneto-elastically buckled beam is a classic example of a nonlinear oscillator that exhibits chaotic motions. This system serves as a model to analyze the motion of elastic structures in magnetic fields. The system follows a sixth order magneto-elastic potential and may have up to five static equilibrium positions. However, often the non-dimensional Duffing equation is used to approximate the system, with the coefficients being derived from experiments. In few other instances, numerical methods are used to evaluate the magnetic field values. These field values are then used to approximate the nonlinear magnetic restoring force. In this manuscript, we derive analytical closed form expressions for the magneto-elastic potential and the nonlinear restoring forces in the system. Such an analytical formulation would facilitate tracing the effect of change in a parameter, such as the magnet dimension, on the dynamics of the system. The model is derived assuming a single mode approximation, taking into account the effect of linear elastic and nonlinear magnetic forces. The developed model is then numerically simulated to show that it is accurate in capturing the system dynamics and bifurcation of equilibrium positions. The model is validated through experiments based on forced vibrations of the magneto-elastic oscillator. To gather further insights about the magneto-elastic oscillator, a parametric study has been conducted based on the field strength of the magnets and the distance between the magnets and the results are reported.

Determining Beta Sheet Crystallinity in Fibrous Proteins by Thermal Analysis and Infrared Spectroscopy

Abstract: We report a study of self-assembled beta-pleated sheets in B. mori silk fibroin films using thermal analysis and infrared spectroscopy. B. mori silk fibroin may stand as an exemplar of fibrous proteins containing crystalline beta-sheets. Materials were prepared from concentrated solutions (2−5 wt % fibroin in water) and then dried to achieve a less ordered state without beta-sheets. Crystallization of beta-pleated sheets was effected either by heating the films above the glass transition temperature (Tg) and holding isothermally or by exposure to methanol. The fractions of secondary structural components including random coils, alpha-helices, beta-pleated sheets, turns, and side chains were evaluated using Fourier self-deconvolution (FSD) of the infrared absorbance spectra. The silk fibroin films were studied thermally using temperature-modulated differential scanning calorimetry (TMDSC) to obtain the reversing heat capacity. The increment of the reversing heat capacity ΔCp0(Tg) at the glass transition fo...

Stochastic Processes And Filtering Theory

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Variational Principles in Mechanics

Abstract: The recognition that minimizing an integral function through variational methods (as in the last chapters) leads to the second-order differential equations of Euler-Lagrange for the minimizing function made it natural for mathematicians of the eighteenth century to ask for an integral quantity whose minimization would result in Newton’s equations of motion. With such a quantity, a new principle through which the universe acts would be obtained. The belief that “something” should be minimized was in fact a long-standing conviction of natural philosophers who felt that God had constructed the universe to operate in the most efficient manner—but how that efficiency was to be assessed was subject to interpretation. However, Fermat (1657) had already invoked such a principle successfully in declaring that light travels through a medium along the path of least time of transit. Indeed, it was by recognizing that the brachistochrone should give the least time of transit for light in an appropriate medium that Johann Bernoulli “proved” that it should be a cycloid in 1697. (See Problem 1.1.) And it was Johann Bernoulli who in 1717 suggested that static equilibrium might be characterized through requiring that the work done by the external forces during a small displacement from equilibrium should vanish. This “principle of virtual work” marked a departure from other minimizing principles in that it incorporated stationarity—even local stationarity—(tacitly) in its formulation. Efforts were made by Leibniz, by Euler, and most notably, by Lagrange to define a principle of least action (kinetic energy), but it was not until the last century that a truly satisfactory principle emerged, namely, Hamilton’s principle of stationary action (c. 1835) which was foreshadowed by Poisson (1809) and polished by Jacobi (1848) and his successors into an enduring landmark of human intellect, one, moreover, which has survived transition to both relativity and quantum mechanics. (See [L], [Fu] and Problems 8.11 8.12.)

Energy harvesting technologies in roadway and bridge for different applications – A comprehensive review

Abstract: Energy harvesting is a promising technique that can help produce renewable and clean energy and improve sustainability of infrastructure. The objective of this paper is to review available energy harvesting techniques that are used for roadway and bridge for different applications, including photovoltaic cell, solar collector, geothermal, thermoelectric, electromagnetic, and piezoelectric systems. The energy harvested can produce electric energy, provide heating or cooling, ice melting, power wireless sensors, and monitor structure conditions. Each energy harvesting technology is examined in depth including working principles, application examples, prototype developments, and major findings reported in the literature. The review summarized previous study efforts on energy harvesting system in the areas of material design, system optimization, theoretical analysis, laboratory testing, field experiment, and numerical modeling. Different energy-harvesting technologies were compared in terms of power output, cost-effectiveness, technology readiness level, advantages and disadvantages, support from government and industry. Finally, future research recommendations of energy harvesting in roadway and bridge were proposed.