Mahmood Shokrieh

Iran University of Science and Technology · School of Mechanical Engineering

In the past two decades, various research works have been conducted in the field of flexible electronic devices (FEDs). Researchers have focused their efforts on solving the existing challenges in the electronic, electrochemical and mechanical behaviors of FEDs. The importance of flexible lithium-ion batteries (FLIBs) in the area of FEDs is evident...

The current research presents a semi-numerical (SN) method to obtain the critical J-integral (JC) of an Al 2024-T3 plate under plane-stress conditions. In the present method, estimation of the JC is performed by the finite element simulating a simple tensile test of a dumbbell specimen, using the true experimental stress–strain curve. To this end,...

Many studies have been performed on composite patches as reinforcement of cracked metal sheets. However, in most previous research, composite patches without prestressing have been used to repair cracks. In the present study, a novel method for repairing cracked aluminum sheets is proposed by using polymer composite patches with embedded prestresse...

In the present research, the optimum paths and orientations for curvilinear and straight fibers of variable-and constant-stiffness composite cylindrical shells subjected to an external hydrostatic pressure and bending were found. For this purpose, a linear variation in the fiber orientation was considered for the curvilinear fibers. A genetic algor...

Thermography has been used in some research works to evaluate the residual life of laminated composites under fatigue loading. In this method, the temperature-rise distribution at the outer surface of the composite specimen is monitored. However, thermography may not be able to provide detailed information on temperature rise and the fatigue damage...

For incorporating thermally reversible covalent bonds into polymers, Diels–Alder (DA) cycloaddition reaction has been widely used. The thermally reversible DA reaction is a [4 + 2] cycloaddition between an electron-poor dienophile and an electron-rich diene. Furan and maleimide are the most popular pair that has been used as diene and dienophile. T...

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Many studies have been conducted on the simultaneous measurement of temperature and strain of different structures by fiber bragg grating (FBG) sensors for structural health monitoring purposes. However, most of them have used more than one FBG sensor to discriminate between temperature and strain. The present paper utilized the capability of one u...

The present paper aims to study the effect of crack-tip geometrical constraints and welding residual stresses (WRS), as well as their interaction on fracture behavior of IN939 superalloy, which is widely used in gas turbine hot section components, such as turbine vanes. For the thermal–mechanical simulation of welding processes, a finite element (F...

The purpose of the present study was to assess the capability of finite element (FE) simulations of guided Lamb wave propagation for the characterization of the modulus of fiber‐metal laminates (FMLs) and detection of the matrix cracking in them. An FE model of an FML specimen with a [Al/ 902$$ {90}_2 $$/Al/ 902$$ {90}_2 $$/Al] layup was developed....

Embedding pre-strained shape memory alloy (SMA) wires within laminated composites can enhance their fatigue performance due to pseudoelastic and shape memory effects. In the present research, an experimental program was conducted to investigate the fatigue behavior of carbon/epoxy laminated composites with/without embedded SMA wires. Moreover, a no...

The impact behavior of sandwich structures was studied using experimental and numerical methods. Polypropylene with 0.5 wt% of graphene (PP/0.5% G) or pure polypropylene (PP) was sandwiched between aluminum face sheets for experimental tests. Impact tests revealed that the nanoreinforced structures had a higher contact force and a shorter contact d...

The harness and the weave style are among the most important properties of woven fabrics. Most of the previous studies utilized woven fabrics with specific harnesses to explore the effects of nanoparticles on woven composites. Therefore, an experimental study was conducted to examine the impact of three weave patterns, namely plain, 5-harness satin...

The low-velocity impact response of sandwich structures with aluminum face sheets and neat or nano-reinforced polypropylene core was studied. A strain-rate dependent micromechanics model (SRDM) was presented in the literature for predicting the dynamic behavior of nano-reinforced polymers. In the present study, the dynamic behavior of nano-reinforc...

The idea of using glass nanofibers was proposed to overcome the weakness of out-of-plane properties of glass/epoxy composites. Glass nanofibers were produced by electrospinning solution of tetraethyl orthosilicate and polyvinylpyrrolidone as carrying polymer and dispersing the nanofibers in resin using an ultrasonic mixer. Various percentages of gl...

The accurate determination of residual stresses has a crucial role in understanding the complex interactions between microstructure, mechanical state, mode(s) of failure, and structural integrity. Moreover, the residual stress management concept contributes to industrial applications aiming to improve the product’s service performance and life cycl...

The previous experimental studies have demonstrated that fiber-reinforced laminated composites exhibit lower interlaminar fracture resistance at high loading rates. This global behavior has been physically attributed to the rate dependency of the fiber bridging extent. The first aim of the present paper is to assess the influence of the local separ...

In the present paper, the destructive behavior of distilled water, salty water, sulfuric acid, and heat on glass/vinyl ester composites was investigated by experimental methods. Hetron 922 vinyl ester resin and two types of mat and woven glass fibers as the reinforcements were used to fabricate composite test samples. All samples were immersed in d...

In the present research, the self-heating phenomenon in laminated composites under fatigue loading was studied. The generated-dissipated energy (GDE) model was developed to calculate the generated energy due to the viscoelastic nature of the matrix, and the dissipated energy through the convection and conduction mechanisms. To consider the effects...

The estimation of the damping coefficient may help to improve the damage detection in composite materials. The purpose of this study was to develop the simulated Lamb wave propagation method for nondestructive monitoring of matrix cracking in laminated composites via the accurate estimation of their damping coefficient. Cross-ply composite specimen...

This research is devoted to studying the capability of the damage-entropy model for fatigue life prediction of the off-axis unidirectional composites. The damage process in composites was characterized by the micro-continuum damage mechanics (MCDM) and an available reformulated form of the Mori-Tanaka model was used. In the present study, the fract...

Microelectronic packages are typically composed of different layers of materials with un-similar thermo-mechanical properties. Fabrication-induced residual stresses, resulting from the mismatch of layers’ thermo-mechanical properties, may lead to adverse effects such as warpage and delamination at the interface of layers. In this study, the fabrica...

One of the problems in type-IV pressure vessels (composite pressure vessels with a thermoplastic inner liner) is the quality of bonding between the liner to the outer reinforcement layer. In the present research, the effect of the ultraviolet (UV) irradiation on the surface of the high-density polyethylene (HDPE) for the co-bonding process of E-gla...

The applications of polymeric composites are growing fast in many industries. Composite structures, however, suffer from different unknown damage mechanisms [1]. Andersons et al. proposed a semi-analytical model based on the shear lag method, in which a relation between the matrix cracking in cross-ply laminated composite and stress in 90-degree la...

This work aims at studying the loading rate dependency of mode I delamination growth in CFRPs, using typical fracture toughness analysis through both the R-curve and the crack tip opening rate. The average SERR is a method of data reduction based on energy balance which has been previously introduced to characterize delamination growth under differ...

Microelectronics components used to package integrated circuits (ICs) are composite structures and typically consist of several layers of polymer, silicon, and fiber-reinforced laminates, which are bonded together under heat and pressure. The mismatch in thermo-mechanical properties between different layers can induce significant residual stresses...

The analytical models on the evaluation of the ply scale or macroresidual stresses in polymeric composite materials are reviewed. It is shown that the models’ ability to describe the behavior of the polymer matrix during the cure is crucial for the accuracy of the analysis. Due to the complex thermo-chemo-rheological viscoelastic behavior of the re...

This chapter discusses categories of residual stress in composite materials, their effects, and the importance of their measurement. It also summarizes issues in measuring residual stresses and introduces the range of techniques available.

This chapter discusses the theoretical and experimental aspects of the residual stress measurement through-the-thickness of laminated composites using the slitting method (or the crack compliance method). First, the common methods of approximation of residual stress distribution when using the slitting method were discussed. Then, a finite element...

The nonuniform residual stresses are determined by consecutive drilling of a laminated composite at the center of an installed rosette strain gauge and recording the strains after drilling each layer of the laminated composite. The calibration factors convert the released strains of the incremental drilling method to the residual stresses in the la...

Nondestructive testing (NDT) includes a wide group of techniques utilized in science and industry to evaluate the properties of a material (such as residual stresses) without causing any major damage. Since NDT does not cause any permanent changes in the material being inspected, it is a valuable technique that can save both money and time in evalu...

Using the incremental hole-drilling technique and eigenstrain concept, a new method is introduced to calculate the calibration coefficients of laminated composites. Based on the Saint-Venant principle, strain responses on the surface of the specimen rapidly become nonsensitive to the stresses in the depth of the sample. To overcome these limitation...

In this study, the residual stresses in the laminated polymer-matrix composite sample with a configuration of [04/904]s were measured and investigated using the incremental hole-drilling and slitting methods combined with the digital image correlation (DIC) technique. By averaging the values of strain obtained by the DIC technique in the location o...

Existing methods of measuring residual stresses in composite materials are often categorized into two broad groups: destructive and nondestructive. Destructive testing implies damaging or removing a section of material so that the specimen may no longer be usefully employed. This chapter aims to introduce the main methods that fall into the categor...

The application of low thermal expansivity nano-additives as matrix fillers to reduce thermal residual stresses in polymer composites is relatively a new area of research. Considering high Young’s modulus and low coefficient thermal expansion (CTE) of nano-additives, they can reduce the natural mismatch between the fiber and matrix (make matrix the...

This chapter presents a complete literature review of thermal residual stresses from different points of view such as their formation and effects as well as methods of measurement and prediction of them. In order to understand the effects of residual stresses, the main factors for the residual stress build-up must be understood. Consequently, the f...

Delamination is known as the most important damage in fiber-metal laminates (FMLs). The purpose of this study was to assess the ability of guided Lamb waves for the detection of delamination in FMLs through numerical models developed using the finite element method (FEM). The developed FEM models consisted of an FML sample with [Al / 90 / Al / 90 /...

The effect of NiTi alloy long wires on the viscoelastic behavior of epoxy resin was investigated by utilizing the dynamic mechanical analysis (DMA) and a novel micromechanical model. The present model is capable of predicting the viscoelastic properties of the shape-memory-alloy (SMA) reinforced polymer as a function of the SMA volume fraction, ini...

In the current paper, the effects of interface fiber angles on the characteristics of R-curve and the cohesive law shape of end-notch-flexure specimens are investigated using numerical and empirical methods. To this aim, laminated composites manufactured by E-glass/epoxy with 0//θ interface where θ = 0, 15, 45, 60, and 90 were fabricated and tested...

The main purpose of the present study is to investigate the effect of adding carbon nanofibers (CNFs) in fibrous polymeric composites on the reduction of matrix cracking. A tensile testing machine was used to apply five loading steps and induce different crack densities in [02/906]s composite specimens with and without CNF fillers. After each loadi...

A comprehensive review is conducted on the very high cycle (VHC) and gigacycle (GC) fatigue of fiber-reinforced composite materials. The main objective was to conduct a benchmarking survey of high-frequency fatigue test methods that have been introduced by different research groups for testing beyond 107 loading cycles. Therefore, test methods are...

he various factors affecting the firm’s innovation performance are strongly influenced by the contextual factors. Considering the economic and strategic importance of the Advanced Materials Sector in Iran, this paper attempts to model the factors influencing the innovation performance of the firms in this sector. For this purpose, a survey was carr...

In this study, a finite element model was introduced to study the low-velocity impact behavior of sandwich structures with a nano-reinforced polypropylene core and aluminum face sheets. Most previous studies on low-velocity impact behavior of nano-reinforced sandwich structures used experimental and analytical methods. A finite element model was de...

The fiber-reinforced polymer (FRP) composites under different dynamic loads experienced various strain rates. Since mechanical behaviors of fiber-reinforced polymer composites vary with the strain rate, the transient response of most of the composite structures will be dependent on the strain rate. In the present research, a comprehensive review of...

Background The slitting method is a widely used destructive technique for the determination of residual stresses. Because of the rich data content of the full-field methods, optical techniques such as digital image correlation (DIC) are replacing strain gages for surface measurements.Objective The objective of the current paper is to overcome the d...

In the present study, a new model was developed that considers the amount of the environmental fluid absorption by different constituents of polymeric laminated composites including fibers, resin, fiber-matrix interphase region, ply interface region, and voids. By knowing the fluid absorption behavior of the composite constituents, the present mode...

In the present research, a novel dynamic constitutive micromechanical (DCM) model was developed to predict the strain rate dependent mechanical behavior of laminated glass/epoxy composites. The present model is an integration of the generalized strain rate dependent constitutive model as a constitutive model for the neat polymer, the plasticity mod...

In the present research, effects of applying strain rate on the mechanical behavior of single-lap glass/CNF/epoxy composite bolted joints including, damage initiation bearing stress, 2% offset bearing strength, ultimate bearing strength, bearing chord stiffness, ultimate bearing strain, and energy absorption were studied. To this end, a comprehensi...

The residual stresses (RSs) generated from partial penetration repair welding of a specimen extracted from the 4th stage vane of a gas turbine replace studied. The RSs are maximum in the heat-affected zone, beneath the weld along the weld center at the specimen mid-section. The RS field tends to exhibit over a large volume beneath the weld bead whe...

Mechanical properties of woven fabric composites are influenced by fabric geometry and harness. In the present research, woven fabric composites made of ML-506 epoxy resin and E-glass woven fabrics with three different fabric geometries (harnesses of 2, 5, and 8) were studied experimentally. The new concepts of warp and fill-fiber volume fractions...

The present paper deals with the effects of repair welding residual stresses on the fracture behavior of IN939. A finite element (FE) model was developed using SYSWELD for the thermal-mechanical simulation of the welding process. The predicted residual stresses were verified through experiments. The results were then mapped to the fracture FE model...

Guided waves have shown a great potential in monitoring large structures. The purpose of this study was to assess the ability of guided Lamb waves for the characterization of fiber-metal laminates (FMLs) through finite element method (FEM) simulations. The developed FEM model consisted of an FML sample with [Al/90/Al/90/Al] layup, an actuator and s...

In the present research, a novel rate-dependent micromechanical model was presented to predict the stiffness and strength of unidirectional glass/epoxy composites. To predict the strain-rate dependent stress–strain behavior of glass fibers, using the Maxwell model with the aid of semi-empirical relations, a new viscoelastic constitutive model was p...

Electrospinning of glass nanofibers, as one of the most important techniques for producing nanofibers, was the focus of the present research. This process was done using a carrying polymer in order to modify all important parameters of the process including the solution parameters, the electrospinning voltage, the electrospinning distance and feedi...

This paper is concerned with the effect of core pile yarn hybridization on the low-velocity impact response of 3D integrated-woven sandwich composite panels. For this purpose, at first, hybrid yarn was produced by a co-wrapped technique that is composed of polyester and glass fibres as shell and core structure, respectively. Then, 3D-woven samples...

The purpose of the present study is to develop a nondestructive evaluation method and propose a model-independent viscoelastic characterization approach for the identification and classification of the matrix cracking in polymeric composites using the Lamb wave propagation method. To this end, cross-ply laminated composite specimens were fabricated...

In the present paper, the effect of loading rate on the interfacial properties of shape memory alloy (SMA) reinforced polymer composites is investigated using experiments and theoretical methods. First, experimental pull-out tests were performed at three different loading rates with the crosshead speeds of 0.3, 25 and 400 mm/min. The effect of load...

The formation and healing of cracks in fiber-reinforced composites made of a thermally remendable polymeric matrix were studied. A new thermally remendable polymer, using furan and maleimide moieties based on the Diels–Alder reaction was synthesized and employed for the fabrication of fiber-reinforced composites. To find the healing efficiency of c...

In this paper, the effect of the cross‐links' conversion degree on the healing efficiency of a thermally remendable polymer based on the Diels‐Alder (DA) reaction was studied quantitatively. By using the differential scanning calorimetry (DSC) results along with the Kissinger method, the conversion degree of the thermally reversible cross‐links was...

In this chapter, new models, Nano-NSDM and Nano-EFAT based on the micromechanical theory, normalized stiffness degradation approach and energy method were established to predict the fatigue life of nanoparticle-filled fibrous composites based on the experimental data of fibrous composites without nano-fillers and they were evaluated under different cas...

The major concern in using the shape memory alloy (SMA) wires embedded in a polymer matrix is the possibility of debonding between SMA and the surrounding polymer due to the SMA phase transition recovery stress. Hence, it is important to examine the distribution of stresses in the SMA wire and the surrounding matrix. In the present study, using the...

This paper demonstrates how the critical strain energy density in the delamination tip vicinity may be used to explain the physics of delamination growth under mixed mode I/II. A theory previously proposed to physically relate mode I and mode II delamination growth is further extended towards describing the onset of mixed mode I/II delamination. Su...

The slitting method is a destructive procedure whereby the residual stresses are determined throughout the thickness of the specimen. One should repeat this experiment to ascertain the uncertainties of the obtained results. However, performing the slitting experiment relieves the residual stresses around the cut which influences the results of the...

A novel self-healing polymer composite made of the thermally reversible polymer matrix and shape memory alloy reinforcement is introduced. The healing system is designed in such a way that by heating the structure, activation of shape recovery in shape memory alloy and chemical reversible reactions in polymer occur simultaneously. In the present he...

In Table 1 on page 769, the second and third columns’ title should be: “Lay-up corresponding to the maximum buckling pressure”

One of the challenges of measuring the residual stresses in metals and composites is the adverse effect of the noise and error on final results. The least squares and the Tikhonov regularization methods are the two available techniques for the noise reduction of the residual stress measurement in materials. In the present paper, the least squares m...

In the present research, the creep behavior of graphene/epoxy nanocomposites with a random distribution of nanographene was simulated. Recently, the present authors modified two micromechanical models to simulate the creep modulus and the total strain of graphene/epoxy nanocomposites. The modified micromechanical models showed good accuracy in the...

In order to understand the physics of the delamination onset in laminated composites, an experimental investigation of delamination growth is presented. The main objective of this paper is to demonstrate that delamination onset occurs at lower values than G c defined by the ASTM standards, and that the strain energy release rate level at which the...

In the present research, the stiffness and the damage initiation load of single-lap composite bolted joints (SLJs) reinforced with carbon nanofibers (CNFs) were studied. To this end, an analytical approach was developed and in the first step, the spring-mass model was modified. By having the elastic properties of the fiber, matrix and nano reinforc...

The optimum paths and orientations for curvilinear and straight fibers in composite cylindrical shells of variable and constant stiffness under external hydrostatic pressure are obtained and compared. The optimization was performed for several length-to-diameter ratios of the shells. Results showed that the buckling pressure of the variable-stiffne...

The effect of the conversion degree on the healing efficiency of a remendable polymer which consists of reversible and irreversible bonds was experimentally studied. Using the results of DSC test, an autocatalytic model was fitted to the conversion degree of the reversible part of the polymer cross-links. Then, monomers with the capability of rever...

Mechanical properties of composite materials are a function of fiber volume fraction. Based on the existing micromechanical models, the in-plane shear strength of these materials is decreased as their fiber volume fraction is increased. However, their compressive strength is initially increased and then it is dropped as the fiber content increases....

Tensile fatigue behaviour of glass fiber/polyamide composites, including unidirectional ([0]8, [90]8) and cross-ply ([02/902]s, [04/904]s and [904/04]s) laminates, was studied and compared to that of similar glass fiber/epoxy composites. The fatigue resistance of cross-ply glass/polyamide was greater than that of glass/epoxy while also exhibiting l...

Impact failure of newly-designed textile composites from three-dimensional integrated weft-knitted spacer fabrics (3D-IWK-SF) was aimed to be investigated under drop weight loading. Using a computerized flat knitting machine, three different 3D-IWK-SF as the composite reinforcements varied in their cross-sectional shapes, were produced from E-glass...

In the present research, a durable vulcanized silicone-based nanocomposite coating was synthesized which can retain its hydrophobic properties when exposed to heat, sulfuric acidic, and the ultraviolet (UV) radiation. Polydimethylsiloxane (PDMS) was used as the base silicone for the manufacturing of the coating. In order to improve the hydrophobici...

In this research, a new model was presented to estimate the strength of graphene/polymer nanocomposites. This model, called “the laminate analogy progressive damage (LA-PD) model” is a combination of the laminate analogy (LA) approach and a progressive damage model. A nanocomposite was replaced by an equivalent laminated composite (ELC) which conta...

In the present study, the effect of the fiber angle orientation of the delamination interface on the initiation and the propagation fracture toughness of plain woven composites with stacking sequences of [012//012], [011/30//0/011], [011/45//0/011] and [011/30//−30/011], where “//” stands for the location of starter delamination in DCB specimens, u...

In this paper, by considering the absorbed energy in the fracture process zone and extension of the minimum strain energy density theory for orthotropic materials, a new mixed mode I/II failure criterion was proposed. The applicability of the new criterion, to predict the crack growth in both laminated composites and wood species, was investigated....

In this study the behavior of a novel 3D integrated weft knitted sandwich composite (3DIWKSCs) were investigated. The weft knitted spacer fabrics produced by E-glass fibers on a flat knitted machine with tow cross-sectional shapes (rectangular and triangular). The 3DIWKSCs manufactured by use of the vacuum assisted resin transfer molding (VARTM). T...

Despite the advantages of incremental hole-drilling and slitting methods for measurement of residual stresses, there are also some limitations in their utilization. For example, decreasing of the measurement accuracy of strain gauges by increasing the hole depth in the incremental hole-drilling method, and necessity of having an assumption for dist...

The viscoelastic properties of carbon nanotube (CNT) reinforced epoxy resin were researched experimentally, in this study. To this end, single walled CNT with CY 219 epoxy resin and HY 5161 hardener were utilized and dynamic mechanical thermal analysis (DMTA) and creep tests were carried out. The DMTA were performed in several frequencies and the e...

The advanced materials sector is one of the high-tech and knowledge-based areas which is recently becoming an independent industrial sector in Iran. Being innovative in this sector, in addition to its economic importance, is of strategic importance to the country. As a result, identifying the set of innovation determinants of the firms in this sect...

The quality of bonding between the liner and composite shell of a type IV pressure vessel is a crucial point to prevent the leakage of this vessel subjected to fill and refill cycles. In the present research, acid etching was used for surface treatment of a plastic liner to increase the bonding strength. The numerical and experimental study was con...

Axisymmetric equilibrium of an elastic solid circular finite cylinder is one of the oldest problems in the theory of linear elasticity. Crosswise superposition is a well-known method that is used to solve this boundary value problem (BVP); however, technical realization of its underlying ideas still seems to be vague and the solution obtained by th...

In unidirectional laminated composites, fiber bridging as a toughening mechanism has a significant effect on the behavior of mixed mode I/II delamination. In the present paper, effects of fiber bridging and related micro-mechanisms were investigated quantitatively. To this end, a novel micromechanical model called “mixed mode I/II micromechanical b...

The mechanical behavior of epoxy-based nanocomposite in the presence of pristine single wall carbon nanotube (SWCNT) and the SWCNTs including Thrower-Stone-Wales and vacancy defects has been studied using non-equilibrium molecular dynamics simulation and the density functional theory calculations. The continuous SWCNT as a long nanofiber has been c...

This paper is concerned with a theoretical and experimental verification of a micromechanical model of newly developed sandwich panels denoted as 3D integrated woven sandwich composite panels. The integrated hollow core was made of a pile of 3D bars with a special configuration. Integrated woven sandwich composite panels consist of two fabric faces...

The surface treatment is a method to increase the bond strength of two different materials. In this research, the acid etching is used for the surface treatment of Polyethylene in order to improve the bonding strength of Polyethylene and E-glass/Epoxy composites. An experimental study is conducted to present the effect of the surface treatment dura...

In the present research, a combined molecular structural/micromechanics multiscale model was developed to predict the viscoelastic properties of carbon nanotube (CNT) reinforced polymer composites. At the nanoscale, transversely isotropic time-dependent properties of an embedded CNT in the matrix were obtained using a finite element (FE) based mole...

In the classical micro-mechanical method, the moduli of the reinforcement and the matrix are used to predict the stiffness of composites. However, using the classical micro-mechanical method to predict the stiffness of CNT/epoxy nanocomposites leads to overestimated results. One of the main reasons for this overestimation is using the stiffness of...

The effects of temperature on the static tensile behavior of continuous E-glass/polyamide laminates were studied in order to assess the feasibility of using the material system for structural applications. Uniaxial tensile tests were conducted on [0]8, [90]8, [02/902]s and [04/904]s laminates at multiple temperatures above and below the glass trans...