Dr. Paul Praveen A

The present study aims to fabricate a novel design of composite structure i.e. a multi-layered sandwich structure with corrugated cores with different levels of CNT nanoparticles reinforcement. This study also analyses and compares the fundamental natural frequencies by performing modal analysis under different boundary conditions using impact hammer testing. The values of natural frequencies will help us understand the influence of CNT reinforcement on the structure as well as the properties of this structural design. Depending on this, the structures can be further applied in the aerospace industry like aircraft floors and wings. This is as a result owing to its high strength-to-weight ratio and stiffness.

This study reports the optimal frequencies and damping factor of the honeycomb sandwich composite plates. The sandwich panel face sheets have been considered as layered composite and honeycomb core. The higher-order shear deformation theory has been adopted to formulate the structural model and solve the governing equations of motion of sandwich structures to compute the frequencies. An optimal layout of the honeycomb composite laminated sandwich structure is being utilized to improvise both the fundamental natural frequencies and damping factors using a teaching–learning-centered artificial bee colony (TLABC). An experimental investigation is performed to demonstrate the effectiveness of the current TLABC algorithm to identify the optimal values by comparing them with numerically obtained results. Additionally, for the optimal layer sequences and the fiber orientations of the composite laminated plates, several optimization problems are developed with the objective functions of fre...

This study investigates the progressive failure analysis of a tapered thick composite plate. The governing differential equation of motion of the various tapered configurations of a thickness tapered reinforced composite plate are presented in the finite element method using first order shear deformation theory. The failure analysis is carried out by considering the fact that the crack exits parallel to the fibers when the ply fails and the cracked ply is being replaced by a hypothetical ply that has no transverse stiffness, transverse tensile strength and shear strength. However, the longitudinal modulus and strength is considered to remain unchanged. First the local stress and strains in each ply is found out under various loading conditions. Then by employing the ply-by-ply stresses and strains in failure theories, the strength ratio is calculated. Multiplying the strength ratio to the applied load yields the load level of the failure of the first ply. Once the first ply failure ...

In this study, numerically and experimentally the dynamic characteristics of graphene-reinforced glass fiber–reinforced polymer hybrid uniform and thickness tapered laminated composite beams were investigated. First, the graphene-epoxy nanocomposite solution without and with 0.25, 0.50, and 0.75 wt.% of graphene reinforcement is prepared by the heat shearing technique and then used for the fabrication of glass fiber–reinforced polymer hybrid uniform and thickness tapered composite beams using the hand lay-up method. The elastic properties of the hybrid beams were evaluated using the impulse excitation of vibration technique (ASTM E1876-15) under elevated temperature. Further, the numerical and experimental modal analysis of the hybrid beams with uniform and tapered configurations were conducted with variation in wt.% of graphene particles under fixed-fixed and fixed–free end supports. The results reveal that the natural frequencies of the glass fiber–reinforced polymer hybrid unifor...

In this paper, the shear properties of the functionally graded (FG) honeycomb composite (HC) material are investigated using the experimental dynamic approach. Fabrication of the FG-HC material was carried out without and with multi walled carbon nanotube (MWCNT) strip reinforcement at odd, even and every locations of the interfacing layer of the GFRP corrugated strips of a conventional honeycomb material. The transverse shear properties were identified using vibration analysis along lateral and longitudinal directions of the FG-HC material with and without MWCNT strip reinforcement. The results revealed that the addition of MWCNT strip reinforcement in the every location of hexagonal geometry of FG-HC material increases the shear rigidity and damping capabilities, significantly than those of the strip reinforcement without and with MWCNT at the odd and even locations. Result outcomes provide the guidelines for the engineering designer which could help increasing the transverse shear characteristics and structural life through the incorporation of MWCNT strip in the FG-HC materials.

In the present study, the shear properties of a functionally graded (FG) honeycomb core (HCC) material without and with CNT reinforcement are investigated. The multi walled carbon nanotubes (MWCNTs) functionalized with carboxylic acid (COOH) were randomly added in an organic solvent to disintegrate and disperse homogenously into the viscous less epoxy resin matrix (LY556) using the ultrasonic liquid processor. The FG-HCC composite test materials were made-up without and with CNT reinforcement using high carbon-high chromium honeycomb die using the vacuum assisted hand-layup method. The dynamic analysis of HCC composite materials reinforced with CNT in the ribbon located along the transverse direction was carried out experimentally to identify the shear modulus along the corrugated (Gxz) and joined (Gyz) direction using the alternative dynamic approach method. The materials were functionally tailored in such a way that CNTs were reinforced in ribbon located in between the two honeycomb patters viz, continuou ly and alternatively, It was shown that the reinforcement of CNT continuous ribbon in the FG honeycomb core materials would increase the shear modulus considerably without any changes in the mass of the composite structure. The strong bonding and random dispersion of CNTs in the FG-HCC composite enhances the shear properties significantly than that of odd and even ribbon sheets reinforced composite structures. This study gives the guidelines for the designer on improving the shear properties of FG-HCC composite structures through CNT reinforcement in the ribbon reinforced core materials.

In the present study, the free and forced vibration responses of the composite sandwich plate with carbon nanotube reinforced honeycomb as the core material and laminated composite plates as the top and bottom face sheets are investigated. The governing equations of motion of hybrid composite honeycomb sandwich plates are derived using higher order shear deformation theory and solved numerically using a four-noded rectangular finite element with nine degrees of freedom at each node. Further, various elastic properties of honeycomb core materials with and without reinforcement of carbon nanotube and face materials are evaluated experimentally using the alternative dynamic approach. The effectiveness of the finite element formulation is demonstrated by performing the results evaluated experimentally on a prototype composite sandwich plate with and without carbon nanotube reinforcement in core material. Various parametric studies are performed numerically to study the effects of carbon...

This paper presents the state of art in the field of composite shells with focus on stress analysis, buckling and post‐buckling responses under mechanical and thermal loading. Many researchers have investigated the buckling and post‐buckling responses of cylindrical, conical, spherical, thin and thick composite shells with single and doubly curved shells under mechanical and thermal loading. From the literature it can be inferred that hydrostatic pressure, axial compression and thermal environment influence the buckling behavior of laminated composite shell significantly. An effort is taken to review the research on buckling and post‐buckling responses of cylindrical and conical shaped shells under mechanical and thermal loading and their behavior during buckling and post‐buckling conditions. POLYM. COMPOS., 39:4231–4242, 2018. © 2017 Society of Plastics Engineers

In boring process due to larger overhanging length of tool holder, tool vibration is considered as a significant factor which results in poor surface finish, noise generation, accelerated tool wear and reduced life period of machine tool. This tool vibration is a result of interaction between metal cutting process and the dynamics of machine tool. In order to reduce tool vibration it is necessary to develop suitable mechanisms which will in-turn increase the productivity in manufacturing industries. This investigation aims at analyzing the tool holder with impact damper on tool vibration during boring of hardened AISI4340 steel using hard metal insert with sculptured rake face. Impact damper used in this study consists of a concentrated mass of predetermined size and shape mounted on the tool shank at a specific location by means of springs. Material of impact damper and the location of the damper on the tool shank for achieving effective damping was determined by using computational analysis. When the damper was mounted on the tool shank, its vibration characteristics got altered and provided an inherent damping capability to the tool holder by suppressing tool vibration. Experimental work was carried out to study the influence of impact damper on tool vibration and cutting performance. From both computational and experimental results, it was observed that tool vibration was reduced effectively when impact damper was embedded with tool holder.

In this study, the elastic properties of the various honeycomb core configurations tailored with MWCNT filled glass fiber reinforced polymer composite materials (GFRP) were investigated numerically using vibration based techniques and verified with experimental works. The shear properties of GFRP and CNT-GFRP strips corrugated hybrid honeycomb core structures with the influence of Armchair and Zigzag arrangement in CNTs using the vibration analysis have been carried out along the out of plane with respect to Gxz and Gyz directions. The fabrication of honeycomb core using MWCNT filled glass fiber reinforced polymer composite materials (GFRP) were prepared with corrugation method after preparing the lamina using vacuum bagging assisted hand layup technique and tested using vibration based techniques for verifying the developed numerical formulation. Finally, the parametric study was carried out to identify the effects of the addition of various different types of CNT; weight percentages of MWCNT, different ply orientations of the fibers, various honeycomb configurations and honeycomb cell size. It was observed that significant difference is noticed in the shear characteristics of the honeycomb with respect to the variations in the parameters considered. Further, it was noticed from the analysis that the honeycomb structures made by the insertion of strips in various locations of the hexagonal honeycomb cells could yield higher shear moduli than that of the conventional honeycomb structure. It can be concluded that the vibration based techniques implemented for evaluation the elastic properties of the various honeycomb core configurations tailored with MWCNT filled GFRP composite materials and results extracted could support the designers for developing various cell core with the addition of MWCNT for the light weight applications such robots, aircraft and automobile applications.

In this study, the material and free vibration characterizations of Multi-Walled Carbon Nano Tube (MWCNT) reinforced hybrid composite material are investigated. The MWCNT Nano material is genuinely prepared by using the Chemical Vapour Deposition (CVD) method with 97% purity. The thermogravimetric analysis (TGA), Raman Spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) are used before and after Ultra sonication. The results obtained from the above analyses for with and without sonication process of MWCNT and the mixture of MWCNT and ly556 epoxy resin is presented.

In the present study, the shear properties of a functionally graded (FG) honeycomb core (HCC) material without and with CNT reinforcement are investigated. The multi walled carbon nanotubes (MWCNTs) functionalized with carboxylic acid (COOH) were randomly added in an organic solvent to disintegrate and disperse homogenously into the viscous less epoxy resin matrix (LY556) using the ultrasonic liquid processor. The FG-HCC composite test materials were made-up without and with CNT reinforcement using high carbon-high chromium honeycomb die using the vacuum assisted hand-layup method.  The dynamic analysis of HCC composite materials reinforced with CNT in the ribbon located along the transverse direction was carried out experimentally to identify the shear modulus along the corrugated (Gxz) and joined (Gyz) direction using the alternative dynamic approach method. The materials were functionally tailored in such a way that CNTs were reinforced in ribbon located in between the two honeycomb patters viz, continuou ly and alternatively, It was shown that the reinforcement of CNT continuous ribbon in the FG honeycomb core materials would increase the shear modulus considerably without any changes in the mass of the composite structure. The strong bonding and random dispersion of CNTs in the FG-HCC composite enhances the shear properties significantly than that of odd and even ribbon sheets reinforced composite structures. This study gives the guidelines for the designer on improving the shear properties of FG-HCC composite structures through CNT reinforcement in the ribbon reinforced core materials.

In the present study, the free and forced vibration responses of the composite sandwich plate with carbon nanotube reinforced honeycomb as the core material and laminated composite plates as the top and bottom face sheets are investigated. The governing equations of motion of hybrid composite honeycomb sandwich plates are derived using higher order shear deformation theory and solved numerically using a four-noded rectangular finite element with nine degrees of freedom at each node. Further, various elastic properties of honeycomb core materials with and without reinforcement of carbon nanotube and face materials are evaluated experimentally using the alternative dynamic approach. The effectiveness of the finite element formulation is demonstrated by performing the results evaluated experimentally on a prototype composite sandwich plate with and without carbon nanotube reinforcement in core material. Various parametric studies are performed numerically to study the effects of carbon nanotube wt% in core material, core thickness, ply orientations, and various boundary conditions on the dynamic properties of composite honeycomb sandwich plate. Further, the transverse vibration responses of hybrid composite sandwich plates under harmonic force excitation are analyzed at various wt% of carbon nanotubes and the results are compared with those obtained without addition of carbon nanotubes to demonstrate the effectiveness of carbon nanotube reinforcement in enhancing the stiffness and damping characteristics of the structures. The study provides the guidelines for the designer on enhancing both the stiffness and damping properties of sandwich structures through carbon nanotube reinforcement in core materials.

This paper presents the state of art in the field of composite shells with focus on stress analysis, buckling and post-buckling responses under mechanical and thermal loading. Many researchers have investigated the buckling and post-buckling responses of cylindrical, conical, spherical, thin and thick composite shells with single and doubly curved shells under mechanical and thermal loading. From the literature it can be inferred that hydrostatic pressure, axial compression and thermal environment influence the buckling behavior of laminated composite shell significantly. An effort is taken to review the research on buckling and postbuckling responses of cylindrical and conical shaped shells under mechanical and thermal loading and their behavior during buckling and post-buckling conditions.

In boring process due to larger overhanging length of tool holder, tool vibration is considered as a significant factor which results in poor surface finish, noise generation, accelerated tool wear and reduced life period of machine tool. This tool vibration is a result of interaction between metal cutting process and the dynamics of machine tool. In order to reduce tool vibration it is necessary to develop suitable mechanisms which will in-turn increase the productivity in manufacturing industries. This investigation aims at analyzing the tool holder with impact damper on tool vibration during boring of hardened AISI4340 steel using hard metal insert with sculptured rake face. Impact damper used in this study consists of a concentrated mass of predetermined size and shape mounted on the tool shank at a specific location by means of springs. Material of impact damper and the location of the damper on the tool shank for achieving effective damping was determined by using computational analysis. When the damper was mounted on the tool shank, its vibration characteristics got altered and provided an inherent damping capability to the tool holder by suppressing tool vibration. Experimental work was carried out to study the influence of impact damper on tool vibration and cutting performance. From both computational and experimental results, it was observed that tool vibration was reduced effectively when impact damper was embedded with tool holder.