Papers by Vaibhav Phadnis
Journal of Physics: Conference Series, 2015
ABSTRACT Ballistic damage of hybrid woven-fabric composites made of plain-weave E-glass- fabric/e... more ABSTRACT Ballistic damage of hybrid woven-fabric composites made of plain-weave E-glass- fabric/epoxy and 8H satin-weave T300 carbon-fabric/epoxy is studied using a combination of experimental tests, microstructural studies and finite-element (FE) analysis. Ballistic tests were conducted with a single-stage gas gun. Fibre damage and delamination were observed to be dominating failure modes. A ply-level FE model was developed, with a fabric-reinforced ply modelled as a homogeneous orthotropic material with capacity to sustain progressive stiffness degradation due to fibre/matrix cracking, fibre breaking and plastic deformation under shear loading. Simulated damage patterns on the front and back faces of fabric-reinforced composite plates provided an insight into their damage mechanisms under ballistic loading.
Procedia CIRP, 2013
ABSTRACT Ultrasonically assisted drilling (UAD) is a novel machining technique suitable for drill... more ABSTRACT Ultrasonically assisted drilling (UAD) is a novel machining technique suitable for drilling difficult-to-machine materials such as carbon/epoxy composites, where ultrasonic vibrations are superimposed on the tip of the revolving drill bit. Recently, UAD has been shown to possess several advantages in comparison to conventional drilling, including a reduced thrust force and torque, reduced drilling-induced damage and overall improvement in roundness and surface finish of the drilled hole. Here, a finite element model of UAD in carbon/epoxy composite is presented. This model accounts for volumetric and thermal softening phenomena in the workpiece material under the influence of localized vibro-impacts, which is a characteristic feature of UAD. The model was implemented in Abaqus/Explicit and validated with results from experiments, demonstrating a reasonable correlation between them. A parametric study was also carried out to examine the effect of variation in intensity of ultrasonic energy on the extent of softening in the carbon/epoxy composite for UAD.
Journal of Sound and Vibration, 2014
ABSTRACT This research focuses on the effect of ultrasonically-assisted drilling (UAD) on carbon ... more ABSTRACT This research focuses on the effect of ultrasonically-assisted drilling (UAD) on carbon fibre-reinforced plastics. High-frequency vibration was used to excite a drill bit during its standard operation. An extensive experimental study of drilling forces, temperature, chip formation, surface finish, circularity, delamination and tool wear was conducted using empty set3 mm drill and presented here. UAD showed a significant improvement in drill quality when compared to conventional drilling processes. A finite-element study was also conducted to understand the nature of drilling-force reduction in UAD.
Key Engineering Materials, 2013
ABSTRACT Conventional-drilling (CD) methods often initiate discrete damage phenomena such as micr... more ABSTRACT Conventional-drilling (CD) methods often initiate discrete damage phenomena such as micro-cracking, matrix burning; delamination and fibre pull-out in difficult-to-machine heterogeneous materials such as carbon fibre-reinforced polymer (CFRP) composites. Ultrasonically assisted drilling (UAD) is a promising machining technique suitable for drilling holes in CFRP composites. UAD has been shown to possess several advantages over CD, including reduction in a thrust force and torque, diminished burr formation at drill exit in ductile materials and an overall improvement in roundness and surface finish of the drilled hole. Recently, our in-house experiments of UAD in CFRP composites demonstrated remarkable reductions in levels of thrust force and torque (average force reductions in excess of 60%) when compared to CD with the same machining parameters. 3D Finite Element (FE) models of CD and UAD techniques for a CFRP laminate were developed using a general-purpose FE software ABAQUS/Explicit and validated using experimental results. The magnitudes of thrust force and torque obtained with FE analysis of UAD are compared with those for CD. The numerical results obtained with the developed FE model were found to be in a good agreement with the experimental data.
Materials & Design, 2014
ABSTRACT Numerical studies were conducted to investigate the optimum curvature of a carbon fibre-... more ABSTRACT Numerical studies were conducted to investigate the optimum curvature of a carbon fibre-reinforced polymer (CFRP) panel that would provide an improved blast resistance. A dynamic finite-element (FE) model that incorporates fluid–structure interaction was developed to evaluate the response of these panels to blast in commercial finite-element software ABAQUS/Explicit. Previously reported experimental data by authors were utilised to validate a FE model, where a shock-tube apparatus was utilised to apply a controlled shock loading to quasi-isotropic composite panels with different radii of curvature. A three-dimensional digital image correlation (DIC) technique coupled with high-speed photography was employed to measure out-of-plane deflections and velocities, as well as in-plane strains at the back face of panels. Macroscopic post-mortem analysis was performed to compare the deformation in these panels. The numerical results were compared to the experimental data and demonstrated a good agreement. The validated FE model was further used to predict the optimal curvature of CFRP panel with the aim to improve its blast-mitigation characteristics.
Solid State Phenomena, 2012
Abstract The use of composite materials such as carbon fiber-reinforced plastic (CFRP) has grown ... more Abstract The use of composite materials such as carbon fiber-reinforced plastic (CFRP) has grown considerably in recent years, especially in aerospace, automotive, sports and construction industries. The properties such as high strength and stiffness, low weight, excellent fatigue and corrosion resistance have made them a useful material for light-weight applications. Though parts made from CFRP are often manufactured to a near-net shape, various machining processes such as drilling, can be used to facilitate assembly of ...
Journal of Physics: Conference Series, 2012
Carbon fiber reinforced polymer composite (CFRP) laminates are attractive for many applications i... more Carbon fiber reinforced polymer composite (CFRP) laminates are attractive for many applications in the aerospace industry especially as aircraft structural components due to their superior properties. Usually drilling is an important final machining process for components made of composite laminates. In drilling of CFRP, it is an imperative task to determine the maximum critical thrust forces that trigger inter-laminar and intra-laminar damage modes owing to highly anisotropic fibrous media; and negotiate integrity of composite structures. In this paper, a 3D finite element (FE) model of drilling in CFRP composite laminate is developed, which accurately takes into account the dynamic characteristics involved in the process along with the accurate geometrical considerations. A user defined material model is developed to account for accurate though thickness response of composite laminates. The average critical thrust forces and torques obtained using FE analysis, for a set of machining parameters are found to be in good agreement with the experimental results from literature.
Journal of Physics: Conference Series, 2013
ABSTRACT Ultrasonically assisted drilling (UAD) is a novel machining technique suitable for drill... more ABSTRACT Ultrasonically assisted drilling (UAD) is a novel machining technique suitable for drilling in hard-to-machine quasi-brittle materials such as carbon fibre reinforced polymer composites (CFRP). UAD has been shown to possess several advantages compared to conventional drilling (CD), including reduced thrust forces, diminished burr formation at drill exit and an overall improvement in roundness and surface finish of the drilled hole. Recently, our in-house experiments of UAD in CFRP composites demonstrated remarkable reductions in thrust-force and torque measurements (average force reductions in excess of 80%) when compared to CD with the same machining parameters. In this study, a 3D finite-element model of drilling in CFRP is developed. In order to model acoustic (ultrasonic) softening effects, a phenomenological model, which accounts for ultrasonically induced plastic strain, was implemented in ABAQUS/Explicit. The model also accounts for dynamic frictional effects, which also contribute to the overall improved machining characteristics in UAD. The model is validated with experimental findings, where an excellent correlation between the reduced thrust force and torque magnitude was achieved.
Journal of Physics: Conference Series, 2013
ABSTRACT Experimental and numerical studies were conducted to understand the effect of plate curv... more ABSTRACT Experimental and numerical studies were conducted to understand the effect of plate curvature on blast response of carbon/epoxy composite panels. A shock-tube system was utilized to impart controlled shock loading to quasi-isotropic composite panels with differing range of radii of curvatures. A 3D Digital Image Correlation (DIC) technique coupled with high-speed photography was used to obtain out-of-plane deflection and velocity, as well as in-plane strain on the back face of the panels. Macroscopic post-mortem analysis was performed to compare yielding and deformation in these panels. A dynamic computational simulation that integrates fluid-structure interaction was conducted to evaluate the panel response in general purpose finite-element software ABAQUS/Explicit. The obtained numerical results were compared to the experimental data and showed a good correlation.
International Journal of Impact Engineering, 2006
Resistance to high velocity impact is an important requirement for high performance structural ma... more Resistance to high velocity impact is an important requirement for high performance structural materials. Even though, polymer matrix composites are characterized by high specific stiffness and high specific strength, they are susceptible to impact loading. For the effective use of such materials in structural applications, their behaviour under high velocity impact should be clearly understood. In the present study, investigations on the ballistic impact behaviour of two-dimensional woven fabric composites have been presented. Ballistic impact is generally a low-mass high velocity impact caused by a propelling source. The analytical method presented is based on wave theory. Different damage and energy absorbing mechanisms during ballistic impact have been identified. These are: cone formation on the back face of the target, tension in primary yarns, deformation of secondary yarns, delamination, matrix cracking, shear plugging and friction during penetration. Analytical formulation has been presented for each energy absorbing mechanism. Energy absorbed during each time interval and the corresponding reduction in velocity of the projectile has been determined. The solution is based on the target material properties at high strain rate and the geometry and the projectile parameters. Using the analytical formulation, ballistic limit, contact duration at ballistic limit, surface radius of the cone formed and the radius of the damaged zone have been predicted for typical woven fabric composites. The analytical predictions have been compared with the experimental results. A good correlation has been observed. r
Composites Part A: Applied Science and Manufacturing, 2013
Drilling carbon fibre reinforced plastics (CFRPs) is typically cumbersome due to high structural ... more Drilling carbon fibre reinforced plastics (CFRPs) is typically cumbersome due to high structural stiffness of the composite and low thermal conductivity of plastics. Resin-rich areas between neighbouring plies in a laminate are prone to drilling-induced delamination that compromises structural integrity. Appropriate selection of drilling parameters is believed to mitigate damage in CFRPs. In this context, we study the effect of cutting parameters on drilling thrust force and torque during the machining process both experimentally and numerically. A unique three-dimensional (3D) finite element model of drilling in a composite laminate, accounting for complex kinematics at the drill-workpiece interface is developed. Cohesive zone elements are used to simulate interply delamination in a composite. Experimental quantification of drilling-induced damage is performed by means of X-ray micro computed tomography. The developed numerical model is shown to agree reasonably well with the experiments. The model is used to predict optimal drilling parameters in carbon/epoxy composites.
Composite Structures, 2013
ABSTRACT Experimental and numerical studies wereconducted to understand the effect of plate curva... more ABSTRACT Experimental and numerical studies wereconducted to understand the effect of plate curvature on the blast response ofcarbon/epoxy composite panels. A shock-tube system was utilized to impartcontrolled shock loading to quasi-isotropic composite panels with varying radiiof curvature. A 3D digital image correlation (DIC) technique coupled withhigh-speed photography was used to assess the out-of-plane deflection ofcomposite panels. A finite element (FE) model integrating fluid-structureinteraction to represent coupling between the air surrounding composite panels,shock wave and panels, was developed using a general-purpose FE softwareABAQUS/Explicit. The numerical results were compared to the experimental dataand showed a good correlation.
The surface machining of carbon fiber reinforced plastics materials is a challenging process, giv... more The surface machining of carbon fiber reinforced plastics materials is a challenging process, given the heterogeneity and anisotropic nature of composites, which, combined with the abrasiveness of the fibers, can produce some surface damage and extensive tool wear. The cutting temperature is one of the most important factors associated with the tool wear rate and machinability of these materials, which are also affected by the mechanical and thermal properties of the workpiece material and the cutting conditions. In this work, the cutting temperature, cutting forces, and composite surface roughness were measured under different cutting conditions for the end milling of unidirectional carbon fiber reinforced plastics. Cutting speeds ranging from 200 to 350 m/min; a feed rate of 0.063 mm/rev; fiber orientations of 0, 45, 90, and 135 ; and a 0.5 mm depth of cut were considered. The results show that the cutting speed and fiber orientation have a significant influence on the cutting temperature and cutting forces. The maximum and minimum cutting forces and temperatures were achieved for fiber orientations of 90 and 0 , respectively.
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Papers by Vaibhav Phadnis