Waqas Saleem

A parametric sensitivity study on preforming simulations of woven composites using a hypoelastic computational model

Preforming simulation for structural composite processing can significantly assist in the development of forming tools, prediction of manufacturing issues, optimization of process parameters and structural design analysis. The present study is aimed at investigating the influence of some important parameters in composite forming using a hypoelastic computational model developed for simulating the deformation behaviour of fibrous materials. The process parameters considered within this numerical work investigate the effects of binder force, coefficient of friction and forming speed. The study is conducted using two most commonly used double-curvature geometries for analysis of woven composites: double dome and hemisphere. It has been shown with this comprehensive study that the forming simulations are greatly affected by the choice of process parameters, and models based on finite element approach, such as the proposed hypoelastic model, can only predict its effects.

Turning modeling and simulation of an aerospace grade aluminum alloy using two-dimensional and three-dimensional finite element method

This article presents the development of two-dimensional and three-dimensional finite element–based turning models, for better prediction of chip morphology and machined surface topology. Capabilities of a commercial finite element code Abaqus®/Explicit have been exploited to perform coupled temperature–displacement simulations of an aerospace grade aluminum alloy A2024-T351 machining. The findings show that two-dimensional cutting models predict chip morphologies and machined surface textures on a plane section (with unit thickness) passing through the center of workpiece width, and not at the edges. The contribution highlights the importance of three-dimensional machining models for a close corroboration of experimental and numerical results. Three-dimensional cutting simulations show that a small percentage of material volume flows toward workpiece edges (out of plane deformation), augmenting the contact pressures at the edges of tool rake face–workpiece interface. This enhances the burr formation process. Computational results concerning chip morphologies and cutting forces were found in good correlation with experimental ones. In the final part of the article, numerical simulation results with a modified version of a particular turning tool have been discussed. It has been found that the proposed geometry of the tool is helpful in reducing burr formation as well as cutting force amplitude during initial contact of cutting tool with the workpiece material.

Numerical investigations of optimum turning parameters—AA2024-T351 aluminum alloy

ABSTRACT Aerospace aluminum alloys have gained the prime significance due to their excellent machining characteristics. Numerous experimental and numerical studies have been conducted to establish the optimum cutting parameters of these alloys. In the numerical cutting models, the authenticity of computational results is suspected particularly because of the complex interaction at tool–chip interface, which involves a high material strain rate and thermal processes. The fidelity of cutting simulation results is appraised by a parametric sensitivity analysis and actual experimentation. In this research, the orthogonal turning of AA2024-T351 aluminum is simulated in Abaqus/Explicit by using a thermoviscoplastic damage model and Coulomb friction model for the contact interfaces. A parametric sensitivity analysis is performed to comprehend the chip morphology, tool–chip interface temperature, reaction force, and strain. Different simulations are performed with varied cutting speeds (200, 400, 600, and 800 m/min), rake angles (5°, 10°, 14.8°, 17.5°), feeds (0.3, 0.4 mm), and friction coefficients (0.1, 0.15). It is observed that an increased rake angle decreases the cutting force and increases tool–chip interface temperature. Similarly, the cutting depth has prominent effect on chip–tool interface temperature as compared to the friction. The computational results are found in close approximation with the published experimental data of AA2024-T351.

Finite Element Analysis of Interfacial Debonding in Copper/Diamond Composites for Thermal Management Applications

Copper/diamond (Cu/D) composites are famous in thermal management applications for their high thermal conductivity values. They, however, offer some interface related problems like high thermal boundary resistance and excessive debonding. This paper investigates interfacial debonding in Cu/D composites subjected to steady-state and transient thermal cyclic loading. A micro-scale finite element (FE) model was developed from a SEM image of the Cu/20 vol % D composite sample. Several test cases were assumed with respect to the direction of heat flow and the boundary interactions between Cu/uncoated diamonds and Cu/Cr-coated diamonds. It was observed that the debonding behavior varied as a result of the differences in the coefficients of thermal expansions (CTEs) among Cu, diamond, and Cr. Moreover, the separation of interfaces had a direct influence upon the equivalent stress state of the Cu-matrix, since diamond particles only deformed elastically. It was revealed through a fully coupled thermo-mechanical FE analysis that repeated heating and cooling cycles resulted in an extremely high stress state within the Cu-matrix along the diamond interface. Since these stresses lead to interfacial debonding, their computation through numerical means may help in determining the service life of heat sinks for a given application beforehand.

Prediction of delamination crack growth in carbon/fiber epoxy composite laminates using a non-local cohesive zone modeling

The global behavior of composite materials is strongly influenced by the quality of adhesion between different components. A component can be single phase, like fibers or particles used as reinforcement in a homogenous matrix, or a multiphase material like a layer in long-fiber laminate. In the latter case the degradation of adhesion implies the separation of the layers, known as delamination. Among all different failure mechanisms, Delamination is considered to be the most prominent mode of failure in fiber-reinforced laminates as a result of their relatively weak inter-laminar strength. When laminated structures are subjected to static, dynamic or cyclic loadings, the inter-laminar adhesion strength between individual plies tends to deteriorate significantly and act as the origin of the final failure. Therefore, an efficient and reliable design tool capable of predicting delamination could improve the durability for composite laminates. There exist damage mechanics based formulations capable of simulating the delamination crack growth in carbon/glass fiber epoxy based composite laminates. The present study is focused on taking a step forward in this respect. At first, already existed local interface models effectiveness is tested and results are successfully compared with available experimental data for UD IMS/924 Carbon/fiber epoxy composite laminate. Next, a non-local integral-type regularization scheme is introduced to overcome the spurious localization problem associated to the existing local model. Basic concepts and mathematical modeling of Non-Local damage evolution law are comprehensively studied and presented in this study. Finite Element simulation results based on proposed model are discussed in detail and are compared with experimental results.

Numerical simulation of the effects of elastic anisotropy and grain size upon the machining of AA2024

ABSTRACT Turning modeling and simulation of different metallic materials using the commercially available Finite Element (FE) softwares is getting prime importance because of saving of time and money in comparison to the costly experiments. Mostly, the numerical analysis of machining process considers a purely isotropic behavior of metallic materials; however, the literature shows that the elastic crystal anisotropy is present in most of the ‘so-called’ isotropic materials. In the present work, the elastic anisotropy is incorporated in the FE simulations along with the effect of grain size. A modified Johnson-Cook ductile material model based on coupled plasticity and damage evolution has been proposed to model the cutting process. The simulation results were compared with experimental data on the turning process of Aluminum alloy (AA2024). It was found that the elastic anisotropy influences the average cutting force up to 5% as compared to the isotropic models while the effect of grain size was more pronounced up to 20%.

Fatigue Delamination Crack Growth in GFRP Composite Laminates: Mathematical Modelling and FE Simulation

Glass fibre-reinforced plastic (GFRP) composite laminates are used in many industries due to their excellent mechanical and thermal properties. However, these materials are prone to the initiation and propagation of delamination crack growth between different plies forming the laminate. The crack propagation may ultimately result in the failure of GFRP laminates as structural parts. In this research, a comprehensive mathematical model is presented to study the delamination crack growth in GFRP composite laminates under fatigue loading. A classical static damage model proposed by Allix and Ladeveze is modified as a fatigue damage model. Subsequently, the model is implemented in commercial finite element software via UMAT subroutine. The results obtained by the finite element simulations verify the experimental findings of Kenane and Benzeggagh for the fatigue crack growth in GFRP composite laminates.

Finite Element Analysis of Bend Test of Sandwich Structures Using Strain Energy Based Homogenization Method

The purpose of this article is to present a simplified methodology for analysis of sandwich structures using the homogenization method. This methodology is based upon the strain energy criterion. Normally, sandwich structures are composed of hexagonal core and face sheets and a complete and complex hexagonal core is modeled for finite element (FE) structural analysis. In the present work, the hexagonal core is replaced by a simple equivalent volume for FE analysis. The properties of an equivalent volume were calculated by taking a single representative cell for the entire core structure and the analysis was performed to determine the effective elastic orthotropic modulus of the equivalent volume. Since each elemental cell of the hexagonal core repeats itself within the in-plane direction, periodic boundary conditions were applied to the single cell to obtain the more realistic values of effective modulus. A sandwich beam was then modeled using determined effective properties. 3D FE analysis of Three- and Four-Point Bend Tests (3PBT and 4PBT) for sandwich structures having an equivalent polypropylene honeycomb core and Glass Fiber Reinforced Plastic (GFRP) composite face sheets are performed in the present study. The authenticity of the proposed methodology has been verified by comparing the simulation results with the experimental bend test results on hexagonal core sandwich beams.

Identification of the effective thermal conductivity of a powdered composite using a genetic algorithm

Abstract This work presents a computational method for the identification of the thermal conductivity of a powdered composite. The thermo-physical properties of powdered composites depend not only upon the intrinsic material properties of the filler and the matrix, but also upon several other parameters including the packing density, the particle shape factor and the particle size. In this paper, a genetic algorithm-based model is proposed for the identification of the effective thermal conductivity of a Bakelite–graphite powdered composite. A comparative analysis is also developed between the genetic algorithm and the experimental, theoretical and finite element results. In comparison with the experimental observations, the genetic algorithm model was found to have error values of approximately 5 %, whereas the errors resulting from the theoretical models were up to 12 %.