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fiber-reinforced-composite
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Manufacturing and Mechanical Characterization of Polymeric Composites Reinforced with Natural Fibers
, M.Sc. Thesis Sharif University of Technology ; Rajabzade, Fallah (Supervisor) ; Akbari (Supervisor)
Abstract
With increasing awareness, artificial materials have been replaced by recyclable materials and green materials. In the manufacture of composites, natural and degradable materials are also used. The main object of this research is the fabrication of natural fiber reinforced composites. In this research, fibers are used that are cultivated in the country. Also, the effect of fiber length, fiber mass percentage and fiber correction on composite properties was investigated. The fiber length factor is at two levels of 5 mm and 9 mm, the percentage of fiber mass is in four levels of 5%, 10%, 12.5% and 15%, and the factor for correction of fibers is also in two groups of modified fibers and...
Free Vibration and Buckling Analysis of a Laminated Composite Cylinder Made of Functionally Graded Material with Lengthwise Properties Variation Including Thermal Effects
, M.Sc. Thesis Sharif University of Technology ; Kargarnovin, Mohammad Hossein (Supervisor)
Abstract
In recent decades, employing fiber-reinforced composite has growing field in various industries due to distinct features like high specific stiffness and strength. Studies in case of this type of composite have not been stopped and nowadays, widespread researches are conducted over optimization of them. As a result, the effect of distributing fiber in this composite by taking the concept of functionally graded materials, on vibrations and buckling behaviors including natural frequencies and minimum axial bulking load under different boundary conditions for a multi-layered cylindrical shell in which volume fraction of fiber along its length varies according to power-law model are investigated...
Applying ultrasonic vibration to decrease drilling-induced delamination in GFRP laminates
, Article Procedia CIRP, Leuven ; Volume 6 , April , 2013 , Pages 577-582 ; 22128271 (ISSN) ; Baghlani, V ; Akbari, J ; Bushroa, A. R ; Mardi, N. A ; Sharif University of Technology
2013
Abstract
Delamination is a major problem in drilling of fiber-reinforced composite materials. Thrust force is an important factor leading to propagation of delamination during drilling process. One of effective methods to reduce machining forces is application of ultrasonic vibrations. In this study ultrasonic assisted drilling is applied to reduce thrust force in drilling of GFRP laminates. In order to conduct experiments a setup is designed and fabricated to apply both vibrations and rotation to drill bits. Using Taguchi method, a set of experiments is conducted with feed rate, spindle speed, and ultrasonic vibration amplitude as control factors. The results show that applying ultrasonic vibration...
Aeroelastic instability of aircraft composite wings in an incompressible flow
, Article Composite Structures ; Volume 83, Issue 1 , 2008 , Pages 93-99 ; 02638223 (ISSN) ; Kouchakzadeh, M. A ; Shadmehri, F ; Sharif University of Technology
2008
Abstract
The aeroelastic stability of an aircraft wing modeled as an anisotropic composite thin-walled beam in an incompressible flow is investigated. The wing is built-up as a single-cell box beam whose central point is noncoincident with the mid-chord of the profile. The effects of material anisotropy, transverse shear, warping inhibition, nonuniform torsional model and rotary inertia are considered in the structural model. The unsteady incompressible aerodynamics based on Wagner's function is used to determine the aerodynamic loads. The effects of the offset between reference axis and the mid-chord ("a" parameter), fiber orientation and sweep angle on stability boundary are considered, their...
Performance characterization of composite materials based on recycled high-density polyethylene and ground tire rubber reinforced with short glass fibers for structural applications
, Article Journal of Applied Polymer Science ; Volume 104, Issue 1 , 2007 , Pages 1-8 ; 00218995 (ISSN) ; Yousefian, H ; Saharkhiz, S ; Sharif University of Technology
2007
Abstract
This study addresses the issue of using recycled materials to obtain low-cost structural products for practical applications. Through the use and re-extrusion of virgin high-density polyethylene (HDPE), the effects of the degradation level of HDPE as a matrix phase on its mechanical properties and the mechanical performance of composites produced with the degraded polyethylene have been examined. The degradation level of HDPE caused by reextrusion has been evaluated by the measurement of the melt flow index and mechanical properties of virgin and degraded HDPEs. The results indicate that the modulus and strength of HDPE significantly increase with the addition of polypropylene filled with 30...
Free vibration analysis of multilayered composite cylinder consisting fibers with variable volume fraction
, Article Composite Structures ; Volume 94, Issue 3 , 2012 , Pages 931-944 ; 02638223 (ISSN) ; Hashemi, M ; Sharif University of Technology
Abstract
In this paper, free vibration of a fiber reinforced composite cylinder in which volume fraction of its fibers vary longitudinally, is studied using a semi-analytical method. The distribution of volume fraction of fiber in base matrix is based on power law model. A micromechanical model is employed to represent its mechanical properties including elastic and physical properties of this composite cylinder. In addition, kinematically the first order shear deformation shell theory is employed for strain field. Then, weak form formulation and spatial approximations of variables are utilized to discretize the equations of motion. Different problems are solved in which primarily the validity of the...
Behavior of RC Concrete Column Strengthened with CFRP, Steel Jacketand Reinforced Concrete Jacket
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
Reinforced concrete (RC) column in building often needs strengthening either due to defects in the column themselves, having to support higher loads than those foreseen in the initial design of the structure or as the result of ageing or accidental damage such as earthquake force. The use of FRP wrapping, steel caging or reinforce concrete jacketing for this purpose is now a common practice in many countries throughout the world. Even though a considerable number of researches have been conducted on retrofitting methods during past years, but very limited researches have been done to compare these methods. This research has investigated the effect of jacketing from different views. The...
Interaction of a plane progressive sound wave with anisotropic cylindrical shells
, Article Composite Structures ; Vol. 116, issue. 1 , September–October , 2014 , pp. 747-760 ; ISSN: 02638223 ; Behzad, M ; Sharif University of Technology
Abstract
An exact analysis based on the wave function expansion is carried out to study the scattering of a plane harmonic acoustic wave incident at an arbitrary angle upon an arbitrarily thick helically filament-wound (anisotropic) cylindrical shell submerged in and filled with compressible ideal fluids. Using the laminated approximation method, a modal state equation with variable coefficients is set up in terms of appropriate displacement and stress functions and their cylindrical harmonics to present an analytical solution based on the three-dimensional exact equations of anisotropic elasticity. Taylor's expansion theorem is then employed to obtain the solution to the modal state equation,...
Prediction and optimization of cure cycle of thick fiber-reinforced composite parts using dynamic artificial neural networks
, Article Journal of Reinforced Plastics and Composites ; Volume 31, Issue 18 , September , 2012 , Pages 1201-1215 ; 07316844 (ISSN) ; Shojaei, A ; Reza Pishvaie, S. M ; Sharif University of Technology
2012
Abstract
Curing of thermoset-based composites experience substantial temperature overshoot, especially at the center of thick parts and large temperature gradient exists through the whole part due to large amount of heat released and low conductivity of the composite. This leads to non-uniformity of cure, residual stress and consequently composite cracks and possibly degradation of the polymer. The scope of this work is to optimize the cure cycle in order to improve the properties and gaining a relatively uniform part of composite, using trained recurrent artificial neural networks purposed for speeding up the repetitious model re-calls during the optimization process. Numerical results obtained...
Time-varying structural reliability assessment method: Application to fiber reinforced composites under repeated impact loading
, Article Composite Structures ; 2020 ; Pourtakdoust, S. H ; Crawford, B. J ; Seethalerc, R ; Milani, A. S ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Reliability evaluations play a significant role in engineering applications to ensure the serviceability and safety of advanced structures such as those made of composites. Here, a dynamic reliability evaluation analysis based on the probability density evolution Method (PDEM) has been adapted to assess the reliability of composite structures under uncertainties within the material properties and the external loadings. A Back-Propagation Neural Network approach is employed to identify the system's nonlinear structural response, which is often the case under large deformations. To exemplify, a split Hopkinson pressure bar system was employed to mimic the mechanical behavior of a...
Damage behavior of fiber reinforced composite plates subjected to drop weight impacts
, Article Composites Science and Technology ; Volume 66, Issue 1 , 2006 , Pages 61-68 ; 02663538 (ISSN) ; Shokrieh, M. M ; Lessard, L ; Sharif University of Technology
2006
Abstract
Fiber reinforced materials are widely used in many industrial structures including automotive, aviation, and civil due to their lower weights compared to metal structures. Full-composite body structures, especially in automotive and aviation applications, are becoming a proper replacement for current metal ones. For this reason, damage of such structures subjected to impact is a crucial case study in current research. The typical types of damages are mainly caused during production, repair, maintenance, or by particle crashes during function, and collisions between different structures. In this paper, four different fiber reinforced composite plates are studied after being impacted by a...
Time-varying structural reliability assessment method: Application to fiber reinforced composites under repeated impact loading
, Article Composite Structures ; Volume 261 , 2021 ; 02638223 (ISSN) ; Pourtakdoust, S. H ; Crawford, B. J ; Seethaler, R ; Milani, A. S ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Reliability evaluations play a significant role in engineering applications to ensure the serviceability and safety of advanced structures such as those made of composites. Here, a dynamic reliability evaluation analysis based on the probability density evolution Method (PDEM) has been adapted to assess the reliability of composite structures under uncertainties within the material properties and the external loadings. A Back-Propagation Neural Network approach is employed to identify the system's nonlinear structural response, which is often the case under large deformations. To exemplify, a split Hopkinson pressure bar system was employed to mimic the mechanical behavior of a...
Time-varying structural reliability assessment method: Application to fiber reinforced composites under repeated impact loading
, Article Composite Structures ; Volume 261 , 2021 ; 02638223 (ISSN) ; Pourtakdoust, S. H ; Crawford, B. J ; Seethaler, R ; Milani, A. S ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Reliability evaluations play a significant role in engineering applications to ensure the serviceability and safety of advanced structures such as those made of composites. Here, a dynamic reliability evaluation analysis based on the probability density evolution Method (PDEM) has been adapted to assess the reliability of composite structures under uncertainties within the material properties and the external loadings. A Back-Propagation Neural Network approach is employed to identify the system's nonlinear structural response, which is often the case under large deformations. To exemplify, a split Hopkinson pressure bar system was employed to mimic the mechanical behavior of a...
Panel flutter analysis of general laminated composite plates
, Article Composite Structures ; Volume 92, Issue 12 , November , 2010 , Pages 2906-2915 ; 02638223 (ISSN) ; Rasekh, M ; Haddadpour, H ; Sharif University of Technology
2010
Abstract
The problem of nonlinear aeroelasticity of a general laminated composite plate in supersonic air flow is examined. The classical plate theory along with the von-Karman nonlinear strains is used for structural modeling, and linear piston theory is used for aerodynamic modeling. The coupled partial differential equations of motion are derived by use of Hamilton's principle and Galerkin's method is used to reduce the governing equations to a system of nonlinear ordinary differential equations in time, which are then solved by a direct numerical integration method. Effects of in-plane force, static pressure differential, fiber orientation and aerodynamic damping on the nonlinear aeroelastic...
Dynamic analysis of laminated composite plates traversed by a moving mass based on a first-order theory
, Article Composite Structures ; Volume 92, Issue 8 , 2010 , Pages 1865-1876 ; 02638223 (ISSN) ; Asghari, M ; Sharif University of Technology
2010
Abstract
The dynamic response of angle-ply laminated composite plates traversed by a moving mass or a moving force is investigated. For this purpose, a finite element method based on the first-order shear deformation theory is used. Stationary and adaptive mesh techniques have been applied as two different meshing schemes. The adaptive mesh strategy is then used to avoid off-nodal position of moving mass. In this manner, the finite element mesh is continuously adapted to follow and comply with the path of moving mass. A Newmark direct integration method is employed to solve the equations of motion. Parametric study is directed to find out how different parameters like mass of the moving object as...