World Academy of Science, Engineering and Technology, International Journal of Materials and Metallurgical Engineering, 2016
Authors : Navid Zarif Karimi, Giangiacomo Minak, Parnian Kianfar Abstract : Drilling is one of th... more Authors : Navid Zarif Karimi, Giangiacomo Minak, Parnian Kianfar Abstract : Drilling is one of the most frequently used machining process for glass fiber reinforced polymer composites due to the need for structural joining. In drilling of composite laminates, interlaminar cracking, or delamination, has a detrimental effect on the compressive strength of these materials. The delamination can be controlled by adopting proper drilling condition. In this paper, the effect of feed rate, cutting speed and drill point angle on delamination and residual compressive strength of drilled GFRPs is studied. The objective is to find optimal conditions for maximum residual compressive strength.
Authors : Parnian Kianfar, Navid Zarif Karimi, Giangiacomo Minak Abstract : Drilling is one of th... more Authors : Parnian Kianfar, Navid Zarif Karimi, Giangiacomo Minak Abstract : Drilling is one of the most important machining operations as numerous holes must be drilled in order to install mechanical fasteners for assembly in composite structures. Delamination is a major problem associated with the drilling of fiber reinforced composite materials, which degrades the mechanical properties of these materials. In drilling, delamination is initiated when the drilling force exceeds a threshold value, particularly at the critical entry and exit locations of the drill bit. The chisel edge of twist drill is a major contributor to the thrust force which is the primary cause of delamination. The main objective of this paper is to study the effect of chisel edge and pilot hole on thrust force and delamination during drilling of glass fiber reinforced composites. For this purpose, two sets of experiments, with and without pilot hole, were conducted with different drilling conditions. The result...
In this study, modified fibrous mats of poly(ethylene oxide) (PEO) were fabricated through the ve... more In this study, modified fibrous mats of poly(ethylene oxide) (PEO) were fabricated through the versatile technique of electrospinning. Acrylic monomers were added to PEO with different composition ratios, and the mats were irradiated. The kinetics of photo-cross-linking reaction in the presence of the acrylic cross-linkers, as well as the structural, thermal and mechanical properties of the nanofibers, were studied. The morphology of the fibrous membranes before and after water treatment was monitored, and the insoluble fraction of the fibers was measured. As a result, by tuning the photo-cross-linking reaction, the control over fibers properties was feasible. The photo-cured PEO-based nanofibrous mats showed the solubility resistance needed to use them as membranes and to apply them in aqueous environments, as in water treatment processes and biomedical applications. Graphical Abstract
This paper investigates the photo-grafting of a halochromic molecule on cotton fabric surfaces. N... more This paper investigates the photo-grafting of a halochromic molecule on cotton fabric surfaces. Nitrazine yellow (NY) dye was modified with a methacrylate moiety (GMA) obtaining a photo-reactive dye (GMA-NY), which was covalently grafted onto the cellulosic substrate by means of UV irradiation. The photo-grafting reaction was studied by FT-IR spectroscopy, while the pH response of the functionalized fabric was evaluated at different pH conditions (i.e., acidic and alkaline conditions) both in wet and vapor environments by spectrophotometric analyses. The results showed that the photografting of the modified dye onto the fabric was successful: treated cotton clearly changed color when subjected to different pH. It was thus demonstrated that the GMA-NY dye, photo-grafted on cotton, can successfully impart pH sensing properties to the fabric, which can therefore find numerous applications in the area of smart textiles.
This study investigated the adhesion behavior of Contactin4 (CNTN4), a member of Immunoglobulin S... more This study investigated the adhesion behavior of Contactin4 (CNTN4), a member of Immunoglobulin Super Family (Ig-SF) of cell adhesion molecules. Contactin4 plays a crucial role in the formation, maintenance, and plasticity of neuronal networks. Contactin in its complex configuration with protein tyrosine phosphatase gamma (PTPRG) was selected for simulation. By utilizing Steered Molecular Dynamics (SMD), the uniaxial force was applied to induce unbinding of the complex, and the force-induced detachment of complex components was probed. Three sets of simulations with three values of transducer stiffness and five pulling speeds were designed. Our results showed the dependence of unbinding force on both accessible parameters of pulling speed and spring stiffness. By increasing the stiffness value and pulling speed the rupture force increased. Accordingly, the dissociation rates due to the Bell's theory based on rupture forces and loading rates were calculated.
Volume 3: Advanced Composite Materials and Processing; Robotics; Information Management and PLM; Design Engineering, 2012
ABSTRACT Drilling composite materials is one of the primary processes of manufacturing industrial... more ABSTRACT Drilling composite materials is one of the primary processes of manufacturing industrial structures. The ultimate goal towards on-line monitoring of composites drilling is in order to produce damage free high quality drilled holes. In the present investigation, the acoustic emission (AE) technique was applied for monitoring the drilling-induced delamination. Delamination is major damage mechanisms in glass fiber reinforced plastic (GFRP) laminates correlated with the thrust force during drilling process. By feature extraction of AE time domain, root mean square (RMS) is selected as the best parameter to monitor thrust force variations. The experimental results show that AE is very sensitive to the response of the drilling conditions. Keywords : composite, drilling, feature extraction, acoustic emission, delamination. INTRODUCTION Glass fiber reinforced composites are broadly recognized for their great mechanical properties such as weight saving, high specific stiffness and resistance to fatigue loads. The mechanisms involved when machining composite materials have been regarded as considerably distinct from those observed when machining metallic materials which is mainly because composite materials are not homogeneous and have anisotropic characteristics [1]. Conventional drilling in composites materials is a very common process in the assembly of composites structures. A major concern that has received considerable attention in drilling holes in GFRP laminates is the interlaminar crack propagation or delamination [2]. Peel-up at the drill entrance and push-out at the drill exit are two main mechanisms of delamination. The thrust force developed during the drilling process affects the extent of the delamination area. It has been shown that there is a critical thrust force below which delamination is negligible [3]. F. Lachaud et.al proposed a method which links the axial penetration of the drill bit to the conditions of delamination (crack opening mode I) of the last few plies [4]. R.Q.Sardinas et.al studied Multi-objective optimization of cutting parameters for drilling laminate composite materials by using genetic algorithms [5]. The main purpose of on-line monitoring of composite drilling is to produce damage free high quality drilled holes. F.A. Al-Sulaiman used electrical power for online monitoring of tool wear in drilling [6]. Among numerous types of monitoring tools, acoustic emission is considered as one of the powerful methods in the drilling process. Acoustic emission is defined as the transient energy wave generated by the rapid release from a localized sources within a material when subjected to a state of stress. The acoustic waves generated during drilling of composite laminates mostly emanate from sources like matrix cracking, fiber breakage, debonding, friction mechanisms and delamination [7]. These AE signals have remarkable real-time information about the state of the material health. S.R. Ravishankar monitored drilling of composite laminates by employing acoustic emission technique. The experimental results show that AE-RMS signal level increases with an increase in the applied thrust and further reveal that it is feasible to estimate the drill induced damages in composites by AE signal characterization [8]. An experimental study has been performed to analyze the influence of drilling parameters and drill point angle on the extension of the damage. The design of experiment based on Taguchi method is used.
Highlights Chitosan/poly(eyhylene oxide) nanofibers are obtained by electrospinning Successfu... more Highlights Chitosan/poly(eyhylene oxide) nanofibers are obtained by electrospinning Successful photo-crosslinking of the nanofiber mats is performed Morphological and thermal properties are preserved after the irradiation process Photo-crosslinking increases the solvent resistance of the nanofiber mats
Phase change materials (PCMs) in the form of fibers or fibrous mats with exceptional thermal ener... more Phase change materials (PCMs) in the form of fibers or fibrous mats with exceptional thermal energy storage ability and tunable working temperature are of high interest to produce smart thermoregulating textiles, useful for increasing human thermal comfort while avoiding energy waste. Common organic PCMs suffer from instability in their molten state, which limits their applicability as highly performing fibrous systems. In this work, electrospun fibrous mats made of polyethylene oxide (PEO), a PCM with excellent thermal properties and biocompatibility, were fabricated and their shape instability in the molten state was improved through UV photo-crosslinking. The characterization aimed to assess the performance of these shape-stable electrospun mats as nanofibrous PCMs for thermal management applications. In addition to an enhanced resistance to water-based solvents, UV-cured electrospun PEO mats demonstrated a remarkable latent heat (≈112 J/g), maintained over 80 heating/cooling cyc...
World Academy of Science, Engineering and Technology, International Journal of Materials and Metallurgical Engineering, 2016
Authors : Navid Zarif Karimi, Giangiacomo Minak, Parnian Kianfar Abstract : Drilling is one of th... more Authors : Navid Zarif Karimi, Giangiacomo Minak, Parnian Kianfar Abstract : Drilling is one of the most frequently used machining process for glass fiber reinforced polymer composites due to the need for structural joining. In drilling of composite laminates, interlaminar cracking, or delamination, has a detrimental effect on the compressive strength of these materials. The delamination can be controlled by adopting proper drilling condition. In this paper, the effect of feed rate, cutting speed and drill point angle on delamination and residual compressive strength of drilled GFRPs is studied. The objective is to find optimal conditions for maximum residual compressive strength.
Authors : Parnian Kianfar, Navid Zarif Karimi, Giangiacomo Minak Abstract : Drilling is one of th... more Authors : Parnian Kianfar, Navid Zarif Karimi, Giangiacomo Minak Abstract : Drilling is one of the most important machining operations as numerous holes must be drilled in order to install mechanical fasteners for assembly in composite structures. Delamination is a major problem associated with the drilling of fiber reinforced composite materials, which degrades the mechanical properties of these materials. In drilling, delamination is initiated when the drilling force exceeds a threshold value, particularly at the critical entry and exit locations of the drill bit. The chisel edge of twist drill is a major contributor to the thrust force which is the primary cause of delamination. The main objective of this paper is to study the effect of chisel edge and pilot hole on thrust force and delamination during drilling of glass fiber reinforced composites. For this purpose, two sets of experiments, with and without pilot hole, were conducted with different drilling conditions. The result...
In this study, modified fibrous mats of poly(ethylene oxide) (PEO) were fabricated through the ve... more In this study, modified fibrous mats of poly(ethylene oxide) (PEO) were fabricated through the versatile technique of electrospinning. Acrylic monomers were added to PEO with different composition ratios, and the mats were irradiated. The kinetics of photo-cross-linking reaction in the presence of the acrylic cross-linkers, as well as the structural, thermal and mechanical properties of the nanofibers, were studied. The morphology of the fibrous membranes before and after water treatment was monitored, and the insoluble fraction of the fibers was measured. As a result, by tuning the photo-cross-linking reaction, the control over fibers properties was feasible. The photo-cured PEO-based nanofibrous mats showed the solubility resistance needed to use them as membranes and to apply them in aqueous environments, as in water treatment processes and biomedical applications. Graphical Abstract
This paper investigates the photo-grafting of a halochromic molecule on cotton fabric surfaces. N... more This paper investigates the photo-grafting of a halochromic molecule on cotton fabric surfaces. Nitrazine yellow (NY) dye was modified with a methacrylate moiety (GMA) obtaining a photo-reactive dye (GMA-NY), which was covalently grafted onto the cellulosic substrate by means of UV irradiation. The photo-grafting reaction was studied by FT-IR spectroscopy, while the pH response of the functionalized fabric was evaluated at different pH conditions (i.e., acidic and alkaline conditions) both in wet and vapor environments by spectrophotometric analyses. The results showed that the photografting of the modified dye onto the fabric was successful: treated cotton clearly changed color when subjected to different pH. It was thus demonstrated that the GMA-NY dye, photo-grafted on cotton, can successfully impart pH sensing properties to the fabric, which can therefore find numerous applications in the area of smart textiles.
This study investigated the adhesion behavior of Contactin4 (CNTN4), a member of Immunoglobulin S... more This study investigated the adhesion behavior of Contactin4 (CNTN4), a member of Immunoglobulin Super Family (Ig-SF) of cell adhesion molecules. Contactin4 plays a crucial role in the formation, maintenance, and plasticity of neuronal networks. Contactin in its complex configuration with protein tyrosine phosphatase gamma (PTPRG) was selected for simulation. By utilizing Steered Molecular Dynamics (SMD), the uniaxial force was applied to induce unbinding of the complex, and the force-induced detachment of complex components was probed. Three sets of simulations with three values of transducer stiffness and five pulling speeds were designed. Our results showed the dependence of unbinding force on both accessible parameters of pulling speed and spring stiffness. By increasing the stiffness value and pulling speed the rupture force increased. Accordingly, the dissociation rates due to the Bell's theory based on rupture forces and loading rates were calculated.
Volume 3: Advanced Composite Materials and Processing; Robotics; Information Management and PLM; Design Engineering, 2012
ABSTRACT Drilling composite materials is one of the primary processes of manufacturing industrial... more ABSTRACT Drilling composite materials is one of the primary processes of manufacturing industrial structures. The ultimate goal towards on-line monitoring of composites drilling is in order to produce damage free high quality drilled holes. In the present investigation, the acoustic emission (AE) technique was applied for monitoring the drilling-induced delamination. Delamination is major damage mechanisms in glass fiber reinforced plastic (GFRP) laminates correlated with the thrust force during drilling process. By feature extraction of AE time domain, root mean square (RMS) is selected as the best parameter to monitor thrust force variations. The experimental results show that AE is very sensitive to the response of the drilling conditions. Keywords : composite, drilling, feature extraction, acoustic emission, delamination. INTRODUCTION Glass fiber reinforced composites are broadly recognized for their great mechanical properties such as weight saving, high specific stiffness and resistance to fatigue loads. The mechanisms involved when machining composite materials have been regarded as considerably distinct from those observed when machining metallic materials which is mainly because composite materials are not homogeneous and have anisotropic characteristics [1]. Conventional drilling in composites materials is a very common process in the assembly of composites structures. A major concern that has received considerable attention in drilling holes in GFRP laminates is the interlaminar crack propagation or delamination [2]. Peel-up at the drill entrance and push-out at the drill exit are two main mechanisms of delamination. The thrust force developed during the drilling process affects the extent of the delamination area. It has been shown that there is a critical thrust force below which delamination is negligible [3]. F. Lachaud et.al proposed a method which links the axial penetration of the drill bit to the conditions of delamination (crack opening mode I) of the last few plies [4]. R.Q.Sardinas et.al studied Multi-objective optimization of cutting parameters for drilling laminate composite materials by using genetic algorithms [5]. The main purpose of on-line monitoring of composite drilling is to produce damage free high quality drilled holes. F.A. Al-Sulaiman used electrical power for online monitoring of tool wear in drilling [6]. Among numerous types of monitoring tools, acoustic emission is considered as one of the powerful methods in the drilling process. Acoustic emission is defined as the transient energy wave generated by the rapid release from a localized sources within a material when subjected to a state of stress. The acoustic waves generated during drilling of composite laminates mostly emanate from sources like matrix cracking, fiber breakage, debonding, friction mechanisms and delamination [7]. These AE signals have remarkable real-time information about the state of the material health. S.R. Ravishankar monitored drilling of composite laminates by employing acoustic emission technique. The experimental results show that AE-RMS signal level increases with an increase in the applied thrust and further reveal that it is feasible to estimate the drill induced damages in composites by AE signal characterization [8]. An experimental study has been performed to analyze the influence of drilling parameters and drill point angle on the extension of the damage. The design of experiment based on Taguchi method is used.
Highlights Chitosan/poly(eyhylene oxide) nanofibers are obtained by electrospinning Successfu... more Highlights Chitosan/poly(eyhylene oxide) nanofibers are obtained by electrospinning Successful photo-crosslinking of the nanofiber mats is performed Morphological and thermal properties are preserved after the irradiation process Photo-crosslinking increases the solvent resistance of the nanofiber mats
Phase change materials (PCMs) in the form of fibers or fibrous mats with exceptional thermal ener... more Phase change materials (PCMs) in the form of fibers or fibrous mats with exceptional thermal energy storage ability and tunable working temperature are of high interest to produce smart thermoregulating textiles, useful for increasing human thermal comfort while avoiding energy waste. Common organic PCMs suffer from instability in their molten state, which limits their applicability as highly performing fibrous systems. In this work, electrospun fibrous mats made of polyethylene oxide (PEO), a PCM with excellent thermal properties and biocompatibility, were fabricated and their shape instability in the molten state was improved through UV photo-crosslinking. The characterization aimed to assess the performance of these shape-stable electrospun mats as nanofibrous PCMs for thermal management applications. In addition to an enhanced resistance to water-based solvents, UV-cured electrospun PEO mats demonstrated a remarkable latent heat (≈112 J/g), maintained over 80 heating/cooling cyc...
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