Resume

• 2007

  PhD

  GPA: 4.25/4.5\nThesis title: 'Model for time-dependent damage evolution and its \n influence on creep of multidirectional polymer composite laminates'\n Advisor: Dr. R. Jayaraman

  Composites

  Aerospace

  Mechanical Engineering

  Expected graduate date: Dec. 2011

  University of Manitoba

• 2004

  Master of Science

  GPA: 18.5/20

  Ranked 2nd \n Thesis title: 'Design and manufacturing of modified tabs to test \n composite axisymmetric components'\nAdvisor: Dr M. M. Shokrieh

  Composites

  Applied Design

  Mechanical Engineering

  Iran University of Science and Technology

  Pneumatic and Hydraulic diplomas from FESTO

• 1999

  Turkish

  French

  English

  Persian

  Georgia Institute of Technology

  Postdoctoral researcher

  Bachelor of Science

  Thesis title: 'Design

  manufacturing and assembling of the release \n mechanisms of the satellite solar arrays'

  Mechanical Engineering

  Iran University of Science and Technology

• Composites

  CFD

  Finite Element Analysis

  Simulations

  languages (Persian

  English

  French)

  Materials Science

  Labview

  Deign of Pneumatic

  Hydraulic

  Electro-Pneumatic and Electro-Hydraulic Circuits

  Fracture Mechanics

  Mechanical Engineering

  Computer analysis (ANSYS

  ABAQUS

  NASTRAN

  PATRAN

  ADAMS)

  Experimentation

  Aerospace

  Catia

  Differential Scanning Calorimetry

  Computer programming (Matlab

  pascal)

  Matlab

  Polymers

  Structural Analysis

  ANSYS

  3D Microstructural and Damage Analysis of Polymer Matrix Composites Using X-Ray Computed Tomography with High Contrast and Submicron Voxel Resolution

  Conventional optical and electron microscopy requires elaborate sample preparation and physical sectioning / chemical etching to expose sub-surface features. Furthermore

  accurate modeling of 3D information from 2D images is difficult. X-ray computed tomography is a rapidly emerging 3-D imaging technique for non-destructive evaluation of biological and non-biological materials [1-5]. Microstructural features of interest at various size scales

  in a polymer composite

  are fiber and void volume fraction

  fiber orientation and architecture

  fiber-matrix interface

  and various damage modes. Low atomic number of

  and minimal difference in density between

  the constituents of the polymer composite as well as variation in X-ray path length with orientation of the samples present significant challenges in imaging the various microstructural features within a thin polymer composite lamina layer of a composite laminate

  because conventional X-ray detectors of CT equipment lack the contrast. While the contrast may be acceptable for low resolution features (> 5 m) focused in many publications on textiles and textile composites

  higher contrast is required for sub-micron resolution. In this study

  a CT equipment

  capable of submicron pixel resolution and improved contrast resolution

  is used to study the multi-scale microstructure of

  and damage in

  non-woven and woven continuous fiber and random fiber composites. Few representative images are presented in Figures 1-5; Issues related to non-destructive microstructural and damage analysis of the polymer composites will be highlighted and discussed during presentation.

  3D Microstructural and Damage Analysis of Polymer Matrix Composites Using X-Ray Computed Tomography with High Contrast and Submicron Voxel Resolution

  J. Raghavan

  An experimental study (Birur et al.

  2006 [1]) on time-dependent evolution of various damage modes under constant load was extended; specifically

  time-dependent evolution and influence of transverse cracks

  in ±45° and 90° plies

  on the creep of [±45/902]S multidirectional laminate of a polymer composite (Hexcel F263-7/Toho G30-500) was studied and modeled. The damage evolved with time in both ply groups sequentially and/or simultaneously depending on the test conditions. For the latter case

  the two ply groups influenced each other’s damage evolution. The creep of the laminate was due to both the viscoelasticity of the plies and the time-dependent damage. A damaged ply was modeled using an equivalent undamaged ply with an apparent compliance

  which was determined as a function of time-dependent transverse crack density. This was used along with a model frame work

  based on lamination theory

  to predict the creep compliance of the [±45/902]S laminate. The model predictions compared well with experimental results.

  Influence of Time-Dependent Damage on Creep of Multidirectional Polymer Composite Laminates

  Kyriaki Kalaitzidou

  Robert J Moon

  Mark Miller

  the interfacial and mechanical properties of cellulose nanocrystals (CNC) coated glass fiber/epoxy\ncomposites were investigated as a function of the CNC content on the surface of glass fibers (GF). Chopped GF rovings were coated with CNC by immersing the GF in CNC (0–5 wt%) aqueous suspensions. Single fiber fragmentation (SFF) tests showed that the interfacial shear strength (IFSS) increased by ~69% in composites produced with CNC coated GF as compared to uncoated GF

  suggesting an enhancement of stress transfer across the GF/matrix interface. The role of CNC\ncoatings on the tensile

  flexural

  and thermo-mechanical properties of the CNC-coated GF/epoxy composites was investigated. Incorporation of 0.17 wt% CNC in the composite resulted in increases of ~10% in both elastic modulus and tensile strength

  and 40 and 43 % in flexural modulus and strength respectively.In conclusion

  CNC coatings on GF alter the GF/matrix interface resulting in improvement of the mechanical performance of the corresponding composites.

  Improving the interfacial and mechanical properties of short glass fiber/epoxy composites by coating the glass fibers with cellulose nanocrystals

  Kyriaki Kalaitzidou

  Robert J Moon

  Sanzida Sultana

  Mark Miller

  The mechanical properties of short glass fiber/epoxy SMC composites containing cellulose nanocrystals (CNC) made using sheet molding compound (SMC) manufacturing method as well as the rheological and thermomechanical properties of the CNC-epoxy systems were investigated as a function of the CNC content. CNC up to 1.4 wt% were dispersed in the epoxy to produce the resin for SMC production. The addition of CNC in the resin increased its viscosity and slightly reduced the heat of reaction during the polymerization without altering the curing time and temperature; and the effective pot life of the resin. The incorporation of 0.9 wt% CNC in the SMC composite resulted in increases in elastic modulus

  tensile strength and elongation at break by ∼25%

  30% and 22%

  respectively and 44% and 33% in flexural modulus and strength respectively. Concentrations of CNC up to 0.9 wt% in the SMC composite did not alter the impact energy.

  Introducing cellulose nanocrystals in sheet molding compounds (SMC)

  A scalable technique was introduced to produce high volume lightweight composites using sheet molding compound (SMC) manufacturing method by replacing 10 wt% glass fibers (GF) with a small amount of cellulose nanocrystals (CNC). The incorporation of 1 and 1.5 wt% CNC by dispersing in the epoxy matrix of short GF/epoxy SMC composites with 25 wt% GF content (25GF/CNC-epoxy) produced 7.5% lighter composites with the same tensile and flexural properties of 35GF/epoxy composites with no CNC.

  Lightweight sheet molding compound (SMC) composites containing cellulose nanocrystals

  A. R. Gowhari-Anaraki

  M. H. Yazdi

  This paper presents equations for estimating the elastic stress intensity factor (SIF) for hollow tubes with internal projections subjected to axial loading. The cracks with different angles have been considered in the fillet region

  where cracks are usually emanated. A wide range of geometries

  suggested by Engineering Science Data Unit (ESDU)

  have been considered for hollow tubes with different crack shapes and dimensions. The extensive range of crack configuration factors resulted from finite element analyses are used to obtain predictive equations using statistical multiple nonlinear regression model. The accuracy of this model is measured using a multiple coefficient of determination

  R2

  where 0 ≤ R2 ≤ 1. This coefficient is found to be greater than or equal to 0.98 for all cases considered in this study

  demonstrating the quality of the model fit to the data. Designers are able to determine the SIF of these components easily using proposed predictive equations.

  Fracture parameter in hollow tubes with internal projections subjected to axial loading

  Various damage modes that evolve with time in polymer composite laminates

  such as transverse cracking

  vertical cracking

  delamination

  and fiber fracture

  as well as the interaction among them

  influence the time-dependent degradation in modulus (creep) and strength (creep rupture) of polymer composite laminates. This study is focused on modeling the time-dependent evolution of transverse cracking in [90] plies of a multidirectional polymer composite laminate [θm/90n]. This model uses a two-dimensional variational analysis to determine the stress state at any given creep time. The elastic stored energy

  determined using this stress state

  is compared with a critical energy for fracture to determine the crack evolution with creep time. Model predictions are compared with experimental results to validate the model.

  Modeling of Time-Dependent Progressive Damage in [90] Plies of Multidirectional Polymer Composite Laminates

  Quasi-static damage in multidirectional polymer composite (PMC) laminates developing during manufacturing and quasi-static loading degrades the modulus and strength. A model to predict simultaneous evolution of quasi-static transverse cracking in multiple plies and its effect on modulus of multidirectional PMCs is presented. A 3-D variational analysis formulating the in-plane and out-of-plane stresses of the plies in occurrence of multiple cracking has been developed to work within a lamination theory-based model framework. The stress state in the plies is determined using the lamination theory during an incremental change in loading. The strain energy

  determined using this stress state

  is compared to strain energy-based failure criteria to determine if a ply cracks after the increment. If crack is predicted

  crack density of the ply is updated and the variational analysis is used to determine the perturbation in ply stresses due to cracking. The new stress state is used to determine the laminate modulus after cracking and the ply stresses for the next increment. This procedure is repeated to determine the crack evolution and modulus until reaching the desired load. Model predictions compare very well with experimental results for a [±θm/90n]s laminate at two elevated test temperatures of 80 ˚C and 180 ˚C.

  Model for evolution of quasi-static transverse cracking in multiple plies of multidirectional polymer composite laminates

  M. M. Shokrieh

  This paper is mainly concerned with designing modified tabbing systems for testing of composite thin-walled tubes with symmetric layup. The modified tabs are presented based on the concept of iso-displacement points—the points of the specimen that move together and behave similarly during a test. Numerical solutions are carried out for tubular specimens in order to find the displacement field and hence the iso-displacement points. The analyses are carried out for two loading cases: pure torsion and pure tension. Finite element analyses are conducted for both cases

  to estimate the displacement fields of thin-walled tubular specimens and then predictive equation were determined using multiple nonlinear regression models. The accuracy of these models is evaluated using a multiple coefficient of determination

  R 2

  where 0 ≤ R 2 ≤ 1

  coupled with predicted squared error (PSE) and mean squared error (MSE). R 2 is found to be greater than or equal to 0.98 for all cases considered in this study while PSE and MSE values are minimized

  demonstrating the reliability of the model. Comparison between the modified tabs

  based on the iso-displacement points determined by predictive equations

  with conventional tabs indicates an improvement in the uniformity of stress and strain distribution (which is an important factor in order to have a successful test) within the specimen for both load cases. It is also demonstrated that due to the elimination of the stress and strain non-uniformities

  the measured permissible maximum load of the specimens is significantly increased during the test.

  Design of Modified Tabs for Testing of Symmetric Composite Thin Walled Tubes under Pure Torsional and Tensile Loadings

  A model to predict time-dependent evolution of simultaneous transverse cracking developed in multiple plies during creep loading and its effects on creep of multidirectional polymer matrix composite laminates is presented. The stress states in the intact regions of the plies are determined using the lamination theory during an incremental change in time. The stored elastic energy

  determined using this stress state

  is compared with a critical stored elastic energy value for damage to determine if a ply would fracture after the increment. If fracture is predicted

  variational analysis is used to determine the perturbation in ply stresses due to cracking. This procedure is repeated to determine the crack evolution and creep strain. Model predictions compared well with experimental results for a [±θm/90n]s laminate.

  Model for prediction of simultaneous time-dependent damage evolution in multiple plies of multidirectional polymer composite laminates and its influence on creep

  Amir

  Asadi

  University of Manitoba

  UC Irvine

  Iran composites institute

  Texas A&M University

  Iran Khodro Industrial Dies (IKID)

  Winnipeg

  Georgia Institute of Technology

  University of Manitoba

  Canada

  Analytical modeling

  simulation and experimental study of damage in multidirectional polymer composites and its influence on creep\n • Developed a model based on 3-D variational analysis combined with a viscoelastic energy-based failure criterion integrated in a lamination theory framework to predict process-induced

  quasi-static and time-dependent damage evolution and their effect on mechanical properties and creep behavior of multidirectional carbon fiber-reinforced polymer (CFRP) composite laminates. \n•\tDeveloped a model based on continuum damage mechanics (CDM) to predict the influence of time-dependent damage on creep of multidirectional CFRP composite laminates. \n•\tExperimental characterization of various damage modes in multidirectional carbon fiber/epoxy composite laminates developed under various loading and temperature conditions using microscopy and X-ray tomography.\n

  Ph.D.

  University of Manitoba

  Bryan/College Station

  Texas Area

  Assistant Professor

  Texas A&M University

  Irvine

  California

  Damage diagnostics in preform composites\n • Worked on damage diagnostics emanated from starved and rich resin regions in preform composites using non-destructive in-situ quantitative percussion diagnostics (QPD).\n

  Postdoctoral Researcher

  UC Irvine

  Atlanta

  Georgia

  1) Manufacturing of lightweight hybrid composites by bridging nanotechnology and industrial \n manufacturing \n • Set up a sheet molding compound (SMC) manufacturing line from scratch.\n • Introduced two novel scalable techniques to incorporate cellulose nanomaterials (CNC) in glass \n fiber/epoxy composites in an SMC line (mixed in the resin and as coating on fibers) to produce \n lighter composites for better fuel efficiency and lower CO2 emission in auto/marine composite \n components.\n2) Nanotechnology\n • Cellulose nanomaterials (CNC

  CNF) and graphite nanoplatelets synthesis and their \n nanocomposites characterization and utilization. \n • Investigated the effect of manufacturing method

  e.g. melt compounding/injection molding

  \n selective laser sintering on nanocomposites properties\n • Explored interfacial interactions (micro/nano scale) and synergy of CNC

  i.e. 1) as a coating on \n fiber surface and 2) as dispersion in polymer matrix

  with other components and its effect on \n macroscopic properties of polymer composites.\n3) Manufacturing of novel composites in industrial scale\n • Introduced new technology to use uncured prepreg trim waste (remained from aerospace \n industries) in SMC manufacturing to produce high value carbon fiber/epoxy composites targeted \n for new markets. \n • Introduced new technology to use ecofriendly basalt fibers in SMC manufacturing to produce \n lighter composites in comparison with glass fiber composites.\n • Working on improving the mechanical performance of carbon fiber/epoxy adhesive joints of wind \n turbines using a two-step VARTM manufacturing process.\n4) Modeling\n • Working on microstructure property linkage to understand the effect of geometry and interfacial \n interactions of composite components on macroscopic behavior.\n

  Postdoctoral Research Fellow

  Georgia Institute of Technology

  Die design and manufacturing

  Iran Khodro Industrial Dies (IKID)

  Winnipeg

  University of Manitoba

  2011: Teaching Assistant

  Mechanics of Materials II

  \n University of Manitoba

  Winnipeg

  Canada\n2008-2010: Teaching Assistant

  Dynamics

  \n University of Manitoba

  Winnipeg

  Canada \n2008-2010: Teaching Assistant

  Thermal Science

  \n University of Manitoba

  Winnipeg

  Canada

  Teaching Assistant

  Modeling of composite testing using analytical and numerical approaches

  Failure of pressure vessels and tubes

  Iran composites institute