M. Manikandan

Bio: M. Manikandan is an academic researcher. The author has contributed to research in topics: Structural health monitoring & Composite number. The author has an hindex of 4, co-authored 6 publications receiving 89 citations.

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.

The hydroscopic effect on dynamic and thermal properties of woven jute, banana, and intra-ply hybrid natural fiber composites

Abstract: The effect of reinforcing natural fiber in the form of woven fabric on dynamic mechanical and thermogravimetric analysis was investigated. Further the influence of water molecule interaction on dynamic mechanical analysis of natural fiber composite were studied. Results revealed that basket type and intra-ply hybridized composites enhances the dynamic mechanical properties of the composites due to the enhancement in modulus by the reinforcement, whereas herringbone composites enhance the loss factor of the composites. It was noticed that, irrespective of the weaving architecture and intra-ply hybridization, composite samples immersed in the water for 45 days affects the storage and loss modulus of the composite and to enhance the loss factor. Thermogravimetric analysis carried out on composites revealed that, compared to weaving architecture, the presence of cellulose and hemicellulose in the fiber cell wall influences the thermal properties of the composites.

Recent advances and trends in structural health monitoring

Abstract: The implementation of health monitoring in various structures proves to be beneficial in numerous ways like providing enhanced public safety, improving life span of structures, cutting costs, and early detection of risks thus helping in improving the overall performance of the structures. The improved performance of structures is also essential for the nation and its development. Increased usage of various sensors in different bridges like as Tsing Ma Bridge, Confederation Bridge, and Commodore Barry Bridge structures leads to effective structural health monitoring, which further ensures their long life span. Despite using sensors in the structures, there are some factors like environmental factors, misinterpretation of collected data by mixing of various structural health monitoring (SHM) techniques, and on-site construction defects which affects the conclusions related to the nature of damage and its location. In this chapter, a detailed study of benefits of structural health monitoring and thus the need to meet recent requirements by various recent trends is done. With the progress in trends of structural health monitoring techniques challenges which de-toured the final results of SHM techniques are reviewed in detail. This chapter on recent trends in structural health monitoring includes an elaborate study of advanced technology such as optical fiber Bragg grating (OFBG) strain sensors to monitor damages in civil infrastructures, carbon fiber reinforced polymer (CFRP)-OFBG sensing unit to measure the interface strain and fiber optic sensors for measuring small cracks. These recent trends are extremely effective in meeting various requirements for a modern SHM system, but they still encounter various challenges that affect the measurement data and final conclusions. Therefore various research studies are taking place in the SHM field to achieve an absolutely error-proof monitoring system in the near future.

Finite element modeling of natural fiber-based hybrid composites

Abstract: Hybrid composites have distinctive characteristics that can be utilized in various structures and/or structural components without compromising their structural performance and durability. However, use of natural fibers in composites makes the structure more economical as well as eco-friendly. In this chapter, natural fibers and their classifications are discussed, followed by the hybrid composite and its material modeling. Continuous, numerical solutions of natural fiber-based hybrid composites are also demonstrated through appropriate finite element steps. For computational purposes, two different natural fibers, i.e., jute and flax, and epoxy as matrix material are used to different extents. The overall material properties of hybrid composites are evaluated through a simple rule of hybrid mixture and the modified Halpin–Tsai scheme. A higher-order mathematical model is developed in a finite element framework to obtain the flexural responses of hybrid composites. The displacement field is based on higher-order shear deformation theory with nine degrees of freedom. A nine-noded isoparametric Lagrangian element is utilized to discretize the hybrid composite panel. The governing equation of a hybrid composite panel subjected to uniform pressure is achieved through the minimum total potential energy principle. The desired responses of hybrid composites are obtained through customized MATLAB code. Influences of different parameters such as geometrical (side-to-thickness ratio, side-to-length ratio), volume fractions, number of layers, and support conditions on the flexural responses of a natural fiber-based hybrid composite panel are exemplified and discussed in detail through appropriate illustrations. It is found that fully clamped and large side-to-length ratio composite panels exhibit minimum deflection under uniform pressure. However, the addition of flax content enhances the overall stiffness and strength of a hybrid composite.

Deformation characteristics of functionally graded composite panels using finite element approximation

Abstract: Finite element solutions to the static responses of functionally graded plates and shell panels are investigated in this chapter. The overall material properties of metal/ceramic functionally graded material are considered to be temperature independent and modeled via power-law based Voigt's material scheme. The present functionally graded curved panels are modeled and analyzed in the commercially available finite element tool ANSYS APDL via eight-noded serendipity element (SHELL281). The mesh refinement test is executed followed by the validation test by comparing the present results with the reported results. The influences of the volume fractions, boundary conditions, curvature ratios, and thickness ratios on the central deflections and the axial stresses of functionally graded curved shell panels are illustrated and discussed in detail.

RIS-Assisted Coverage Enhancement in Millimeter-Wave Cellular Networks

Abstract: The use of millimeter-wave (mmWave) bandwidth is one key enabler to achieve the high data rates in the fifth-generation (5G) cellular systems. However, mmWave signals suffer from significant path loss due to high directivity and sensitivity to blockages, limiting its adoption within small-scale deployments. To enhance the coverage of mmWave communication in 5G and beyond, it is promising to deploy a large number of reconfigurable intelligent surfaces (RISs) that passively reflect mmWave signals towards desired directions. With this motivation, in this work, we study the coverage of an RIS-assisted large-scale mmWave cellular network using stochastic geometry, and derive the peak reflection power expression of an RIS and the downlink signal-to-interference ratio (SIR) coverage expression in closed forms. These analytic results clarify the effectiveness of deploying RISs in the mmWave SIR coverage enhancement, while unveiling the major role of the density ratio between active base stations (BSs) and passive RISs. Furthermore, the results show that deploying passive reflectors are as effective as equipping BSs with more active antennas in the mmWave coverage enhancement. Simulation results confirm the tightness of the closed-form expressions, corroborating our major findings based on the derived expressions.

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.

Embedded Smart Antenna for Non-Destructive Testing and Evaluation (NDT&E) of Moisture Content and Deterioration in Concrete.

Abstract: Concrete failure will lead to serious safety concerns in the performance of a building structure. It is one of the biggest challenges for engineers to inspect and maintain the quality of concrete throughout the service years in order to prevent structural deterioration. To date, a lot of research is ongoing to develop different instruments to inspect concrete quality. Detection of moisture ingress is important in the structural monitoring of concrete. This paper presents a novel sensing technique using a smart antenna for the non-destructive evaluation of moisture content and deterioration inspection in concrete blocks. Two different standard concrete samples (United Kingdom and Malaysia) were investigated in this research. An electromagnetic (EM) sensor was designed and embedded inside the concrete to detect the moisture content within the structure. In addition, CST microwave studio was used to validate the theoretical model of the EM sensor against the test data. The results demonstrated that the EM sensor at 2.45 GHz is capable of detecting the moisture content in the concrete with linear regression of R2 = 0.9752. Furthermore, identification of different mix ratios of concrete were successfully demonstrated in this paper. In conclusion, the EM sensor is capable of detecting moisture content non-destructively and could be a potential technique for maintenance and quality control of the building performance.