Amen Agbossou - Academia.edu (original) (raw)

Papers by Amen Agbossou

Research paper thumbnail of Modelling and Experimental Analysis of Multi-Coating Effect on Thermal Expansion and Thermal Stresses of Polymer Fiber-Reinforced Composites

Journal of Composite Materials, 1999

Due to Thermal Expansion Coefficient (TEC) mismatch between the fiber and matrix, thermal stresse... more Due to Thermal Expansion Coefficient (TEC) mismatch between the fiber and matrix, thermal stresses can appear during cooling from the processing temperature to room temperature. In this paper, we (1) analyze experimentally the effect of coating on the TEC of fiber composite and (2) present a thermal self-consistent model to predict thermal stresses and TEC in multi-coated fiber. Over a

Research paper thumbnail of Passive and Active Vibration Control With Piezoelectric Fiber Composites

The possibility of dissipating mechanical energy with piezoelectric fiber composites (PFC) is inv... more The possibility of dissipating mechanical energy with piezoelectric fiber composites (PFC) is investigated. The techniques for manufacturing an active beam with integrated (PFC) are presented and applied to a cantilevered beam experiment. We evaluated experimentally the performances of the active beam in passive energy dissipation. Three vibration cases were analysed: electrodes of the PFCs are (i) in open circuit, (ii)

Research paper thumbnail of Solar micro-energy harvesting based on thermoelectric and latent heat effects. Part I: Theoretical analysis

Sensors and Actuators A: Physical, 2010

This article presents a new method of harvesting ambient renewable micro-energy by using both the... more This article presents a new method of harvesting ambient renewable micro-energy by using both thermoelectric and latent heat effects. We designed a prototype work unit made of phase change material (PCM) and a thermoelectric generator (TEG) and used a numerical method to inspect system performance. Special attention was paid to the implementation of ambient loading (including solar radiation, temperature variation and wind speed) in the numerical simulation process. The calculated results show that the proposed work unit (TEG & PCM) can harvest micro-energy day and night, thanks to the heat storage function of the PCM which is placed behind the TEG.

Research paper thumbnail of Phase Change Material and the Thermoelectric Effect for Solar Energy Harvesting and Storage

ASME/JSME 2011 8th Thermal Engineering Joint Conference, 2011

A new method of harvesting solar and ambient energy is presented. The method is based on thermoel... more A new method of harvesting solar and ambient energy is presented. The method is based on thermoelectric and latent heat effects and is put into practice in a prototype work unit composed of a thermoelectric generator (TEG) and phase change material (PCM). Numerical and experimental analyses of the work unit are developed. The numerical analysis deals with finite elements modeling on solar radiation, temperature variation and wind-speed effects. The results demonstrate the utility of sensible and latent heat storage in the phase change material and confirm the capacity to generate continuous voltage by day and by night. Subsequently, with an optimized thermodynamic design and with several work units linked together, the proposed energy harvesting system could be utilized as both sensor and actuator in low power applications in buildings. It could replace dry batteries for wireless applications, LED lighting and autonomous systems.

Research paper thumbnail of Interfacial stresses in vibration of multilayer composite materials: experimental and theoretical analysis

Smart Materials & Structures, 2005

In laminated composites, interfaces are the transfer spots of mechanical charges, mechanical over... more In laminated composites, interfaces are the transfer spots of mechanical charges, mechanical over-stress adaptations and energy dissipations. In order to examine the dynamic effects of interface stresses, we have inserted a thin layer of piezoelectric material at the interface of composite plies of a multilayer cantilever beam excited in bending. The voltage signals generated by the piezoelectric elements are seen

Research paper thumbnail of On thermoelectric and pyroelectric energy harvesting

Smart Materials and Structures, 2009

This paper deals with small-power energy harvesting from heat. It can be achieved using both ther... more This paper deals with small-power energy harvesting from heat. It can be achieved using both thermoelectric and pyroelectric effects. In the first case, temperature gradients are necessary. The main difficulty of thermoelectric energy harvesting is imposing a large temperature gradient. This requires huge heat flows because of the limited surface heat exchanges and the large heat conductivity of thermoelectric materials. This results in a drastic decrease of power and the efficiency of conversion. In case of pyroelectric energy harvesting, a time varying temperature is necessary. Although such a temperature time profile is hard to find, the overall optimization is easier than the thermoelectric strategy. Indeed, it depends much less on heat exchange between the sample and the outer medium, than on heat capacity that dimensions optimization may easily compensate. As a consequence, it is shown that the efficiency and output power may be much larger using pyroelectric energy harvesting than thermoelectric methods. For instance, using a limited temperature gradient due to the limited heat exchange, a maximum efficiency of 1.7% of Carnot efficiency can be expected using a thermoelectric module. On the contrary, a pyroelectric device may reach an efficiency up to 50% of Carnot efficiency. Finally, an illustration shows an estimation of the output power that could be expected from natural time variations of temperature of a wearable device. Power peaks up to 0.2 mW cm −3 were found and a mean power of 1 μW cm −3 on average was determined within 24 h testing.

Research paper thumbnail of Solar micro-energy harvesting with pyroelectric effect and wind flow

Sensors and Actuators A: Physical, 2011

This article proposes to harvest solar micro-energy using the pyroelectric effect and low wind fl... more This article proposes to harvest solar micro-energy using the pyroelectric effect and low wind flow. The basic concept was presented and validated by laboratory experiments with controlled airflow. The measured temperature variation, subject to the intensity of radiation and wind speed in the environment was demonstrated to reach 16 • C. The time variation of temperature was 0.53 • C s −1 with the speed of airflow at 2 ms −1 . The power density with PZT as the pyroelectric material was 4.2 W cm −3 in laboratory conditions. Both the thermodynamic model and electric model of the pyroelectric generator were established, and a numerical procedure was developed to predict the system performance which was proven to be reliable. The characteristics of such an energy harvesting system were analyzed in detail by simulation, and the results indicated that the proposed idea is promising.

Research paper thumbnail of Fiber distribution effects in linear viscoelastic behavior of polymer matrix composites: Computation modelling and experimental comparison

Mechanics Research Communications, 1998

properties of composites with polymeric constituents am strongly temperature dependent. This beha... more properties of composites with polymeric constituents am strongly temperature dependent. This behavior manifests itself in different ways : creep under constant load, stress relaxation under constant deformation, damping of dynamic response, etc. Recently it has been pointed out that the tune-dependent properties may be used to explain and chamcte& the interphase in polymer composite. The efficient design and utilisation of such composites in structurally related applications requites a good understanding of viscoelasticity.

Research paper thumbnail of Two self-powered energy harvesting interfaces based on the optimized synchronous electric charge extraction technique

Journal of Physics: Conference Series, 2013

ABSTRACT Optimized synchronous electric charge extraction (OSECE) interface is a load weakly-depe... more ABSTRACT Optimized synchronous electric charge extraction (OSECE) interface is a load weakly-dependant circuit, which is a favorable characteristic for piezoelectric wideband vibration energy harvesting. However, it introduces synchronous switches that need to be self-powered in a stand-alone system. This paper presents the design and experimental testing of two self-powered approaches for the OSECE technique. One is made of electronic switches driven by analog peak detector circuits; the other uses mechanical switches directly controlled by the ambient vibrations. Finally, advantages and drawbacks of the two approaches will be compared and discussed.

Research paper thumbnail of Dynamic Analysis of Piezoelectric Fiber Composite in an Active Beam Using Homogenization and Finite Element Methods

Journal of Intelligent Material …, Jan 1, 1998

Abstract The purpose of this work is to point out the improvement, which could be achieved throug... more Abstract The purpose of this work is to point out the improvement, which could be achieved through use of piezoelectric fiber composite elements in place of piezoelectric patch elements, in structural vibration systems. Therefore, we review the homogenization ...

Research paper thumbnail of Piezoelectric vibration energy harvesting by optimized synchronous electric charge extraction

Journal of Intelligent Material Systems and Structures, 2013

ABSTRACT This article presents a novel nonlinear energy extraction technique for piezoelectric vi... more ABSTRACT This article presents a novel nonlinear energy extraction technique for piezoelectric vibration energy harvesting. The proposed approach is an improvement of the previous technique, “synchronous electric charge extraction,” which is the first that optimizes the harvested power whatever the connected load. The new approach is then named as “optimized synchronous electric charge extraction.” Compared with synchronous electric charge extraction, the conversion effectiveness is enhanced while simplifying the electronic circuitry and the switch control strategy. The analytical expression of the harvested powers is derived for a classical electromechanical structure. Finally, theoretical predictions confirmed by experimental results show that optimized synchronous electric charge extraction increases the harvested power for a very large range of load resistance, which is a favorable characteristic for wideband vibration energy harvesting.

Research paper thumbnail of Piezoelectric tube with helical electrodes: Numerical analysis of actuator and energy harvesting devices

Journal of Intelligent Material Systems and Structures, 2013

This article presents a finite element analysis of a polarized piezoelectric tube driven by helic... more This article presents a finite element analysis of a polarized piezoelectric tube driven by helical electrodes. It is thanks to a helical coordinate meshing and local coordinate system association with each element that the problem of piezoelectric coupling has been studied. The numerical results agree well with the experimental data without the need of compensation factors as in previous works. The developed model was used to determine the electromechanical coupling coefficients of the tubes in axial and torsional modes. The electromechanical coupling coefficient depends on the helical angle of the electrode. In the axial mode, electromechanical coupling coefficient goes through a maximum value of 25% when the helical angle of the electrode is close to 30°, while in the torsional mode, the maximum value of electromechanical coupling coefficient was reached at a helical angle near 60°. The analysis investigates the tube size effects and shows the potential uses of piezoelectric tubes as an actuator or energy harvesting device. The presented model could be used to analyze the electric fields in the tube during the polarization process or to analyze the mechanical stress (without any limitation due to Saint-Venant's principle) imposed by the simplified analytical approaches available in the literature. The developed approach can also be used for theoretical analysis of the helical/spiral piezoelectric element.

Research paper thumbnail of Strain Rate and Coupling Agent Effects in Discontinuous Glass Fiber Reinforced Polypropylene Matrix

Journal of Composite Materials, 1994

ABSTRACT Mechanical tensile behaviour studies are reported for discontinuous glassfibers reinforc... more ABSTRACT Mechanical tensile behaviour studies are reported for discontinuous glassfibers reinforced polypropylene matrix. Samples were prepared by varying fiber/matrix coupling agents. The influence of strain rate on mechanical properties was analyzed in low and moderate (10-sec-1 to 10 sec-1) strain rate ranges. It was found that (1) in the moderate strain rate range, optical extensometry is invaluable in determining the actual specimen strain, (2) a drastic transition of mechanical tensile behaviour occurs with increasing strain rates, and (3) fiber/matrix coupling agents affect particularly stress-strain behaviour in the moderate strain rate range. A strong interfacial bond seems to improve the ability of the fibers to take up load in regions of matrix cracking; this leads to higher tensile strength.

Research paper thumbnail of A layered approach to the non-linear static and dynamic analysis of rectangular reinforced concrete slabs

International Journal of Mechanical Sciences, 2006

A simplified model for the static and dynamic behaviour of reinforced concrete slab has been deve... more A simplified model for the static and dynamic behaviour of reinforced concrete slab has been developed, based on laminated theory. The proposed model considers the slab as a layered structure and leads to explicit relations, which account for the macroscopic linear and non-linear behaviour of slabs on lines of simple supports. The presented models aim to analyse and design slab

Research paper thumbnail of Rock fall impact on reinforced concrete slab: an experimental approach

International Journal of Impact Engineering, 2005

This paper concerns the protective structures against rock fall. We propose a new concept of rock... more This paper concerns the protective structures against rock fall. We propose a new concept of rock-shed protection. The proposed rock-shed protection is made of reinforced concrete slabs held up by specially designed supports that act as a type of expendable fuse to absorb high rock-fall energy especially when shock occurs on the side of the slab. Thus, by a simple change of damaged supports and local restoration of concrete in the impact area, the structure can continue to be used. We present also an experimental method to characterize and analyze shock absorption effected by this type of reinforced concrete slab. The analyzed slab is a 1/3 scale reproduction of an actual structure. r

Research paper thumbnail of Thermal stresses and thermal expansion coefficients ofn-layered fiber-reinforced composites

Composites Science and Technology, 1997

In this work we develop a thermal self-consistent (TSC) model for n-layered fiber-reinforced comp... more In this work we develop a thermal self-consistent (TSC) model for n-layered fiber-reinforced composites. The fundamental representative volume element is an inclusion made up of a fiber coated by (n −1) layers encapsulated in an infinite equivalent homogeneous medium. On the basis of the energy equivalence principle we show that the thermal problem under conditions of no external loading can

Research paper thumbnail of Segmented piezoelectric fiber composite for vibration control: fabricating and modeling of electromechanical properties

Composites Science and Technology, 2003

This work presents an available prototyping technique and numerical model for development and opt... more This work presents an available prototyping technique and numerical model for development and optimization of piezoelectric fiber composites (PFC). The proposed technique, named “segmented piezoelectric fiber composite” (S-PFC) technique, consists of forming and polarizing PFC directly in the structure. To do this, we make molds directly in the structure, stack PZT fiber layers in the molds and develop specific segmentation

Research paper thumbnail of Strengthening slabs using externally-bonded strip composites: Analysis of concrete covers on the strengthening

Composites Part B: Engineering, 2008

... CFRP increases the initial cracking load of slabs (Table 3). In addition, it decreases the ma... more ... CFRP increases the initial cracking load of slabs (Table 3). In addition, it decreases the maximalbending displacement, while ... 3. Theoretical analysis. ... The William–Warnke model shows the failure criterion of concrete with five experimental constants [6]. The uniaxial stress–strain ...

Research paper thumbnail of Flexural stiffness modelling of RC slab strengthened by externally bonded FRP

Composites Part B: Engineering, 2009

This paper describes the behaviour of strengthened and unstrengthened reinforced concrete slabs, ... more This paper describes the behaviour of strengthened and unstrengthened reinforced concrete slabs, subjected to a single, specific, local, load at their centres. In the experimental stage, the influence of the reinforcement on the various slabs tested was analysed by studying their behaviour at failure and by making a bending stiffness analysis. In order to predict the mechanical behaviour of the

Research paper thumbnail of Strengthening RC beams with composite fiber cement plate reinforced by prestressed FRP rods: Experimental and numerical analysis

Composite Structures, 2012

This paper deals with the development of a new strengthening system for reinforced concrete beams... more This paper deals with the development of a new strengthening system for reinforced concrete beams with externally-bonded plate made of composite fiber cement reinforced by rebars made of fiber-reinforced plastic (FRP) [1]. The proposed strengthening material involves the preloading of FRP rod before mortar casting. The paper presents experimental and numerical analysis carried out on many large-scale beams strengthened by

Research paper thumbnail of Modelling and Experimental Analysis of Multi-Coating Effect on Thermal Expansion and Thermal Stresses of Polymer Fiber-Reinforced Composites

Journal of Composite Materials, 1999

Due to Thermal Expansion Coefficient (TEC) mismatch between the fiber and matrix, thermal stresse... more Due to Thermal Expansion Coefficient (TEC) mismatch between the fiber and matrix, thermal stresses can appear during cooling from the processing temperature to room temperature. In this paper, we (1) analyze experimentally the effect of coating on the TEC of fiber composite and (2) present a thermal self-consistent model to predict thermal stresses and TEC in multi-coated fiber. Over a

Research paper thumbnail of Passive and Active Vibration Control With Piezoelectric Fiber Composites

The possibility of dissipating mechanical energy with piezoelectric fiber composites (PFC) is inv... more The possibility of dissipating mechanical energy with piezoelectric fiber composites (PFC) is investigated. The techniques for manufacturing an active beam with integrated (PFC) are presented and applied to a cantilevered beam experiment. We evaluated experimentally the performances of the active beam in passive energy dissipation. Three vibration cases were analysed: electrodes of the PFCs are (i) in open circuit, (ii)

Research paper thumbnail of Solar micro-energy harvesting based on thermoelectric and latent heat effects. Part I: Theoretical analysis

Sensors and Actuators A: Physical, 2010

This article presents a new method of harvesting ambient renewable micro-energy by using both the... more This article presents a new method of harvesting ambient renewable micro-energy by using both thermoelectric and latent heat effects. We designed a prototype work unit made of phase change material (PCM) and a thermoelectric generator (TEG) and used a numerical method to inspect system performance. Special attention was paid to the implementation of ambient loading (including solar radiation, temperature variation and wind speed) in the numerical simulation process. The calculated results show that the proposed work unit (TEG & PCM) can harvest micro-energy day and night, thanks to the heat storage function of the PCM which is placed behind the TEG.

Research paper thumbnail of Phase Change Material and the Thermoelectric Effect for Solar Energy Harvesting and Storage

ASME/JSME 2011 8th Thermal Engineering Joint Conference, 2011

A new method of harvesting solar and ambient energy is presented. The method is based on thermoel... more A new method of harvesting solar and ambient energy is presented. The method is based on thermoelectric and latent heat effects and is put into practice in a prototype work unit composed of a thermoelectric generator (TEG) and phase change material (PCM). Numerical and experimental analyses of the work unit are developed. The numerical analysis deals with finite elements modeling on solar radiation, temperature variation and wind-speed effects. The results demonstrate the utility of sensible and latent heat storage in the phase change material and confirm the capacity to generate continuous voltage by day and by night. Subsequently, with an optimized thermodynamic design and with several work units linked together, the proposed energy harvesting system could be utilized as both sensor and actuator in low power applications in buildings. It could replace dry batteries for wireless applications, LED lighting and autonomous systems.

Research paper thumbnail of Interfacial stresses in vibration of multilayer composite materials: experimental and theoretical analysis

Smart Materials & Structures, 2005

In laminated composites, interfaces are the transfer spots of mechanical charges, mechanical over... more In laminated composites, interfaces are the transfer spots of mechanical charges, mechanical over-stress adaptations and energy dissipations. In order to examine the dynamic effects of interface stresses, we have inserted a thin layer of piezoelectric material at the interface of composite plies of a multilayer cantilever beam excited in bending. The voltage signals generated by the piezoelectric elements are seen

Research paper thumbnail of On thermoelectric and pyroelectric energy harvesting

Smart Materials and Structures, 2009

This paper deals with small-power energy harvesting from heat. It can be achieved using both ther... more This paper deals with small-power energy harvesting from heat. It can be achieved using both thermoelectric and pyroelectric effects. In the first case, temperature gradients are necessary. The main difficulty of thermoelectric energy harvesting is imposing a large temperature gradient. This requires huge heat flows because of the limited surface heat exchanges and the large heat conductivity of thermoelectric materials. This results in a drastic decrease of power and the efficiency of conversion. In case of pyroelectric energy harvesting, a time varying temperature is necessary. Although such a temperature time profile is hard to find, the overall optimization is easier than the thermoelectric strategy. Indeed, it depends much less on heat exchange between the sample and the outer medium, than on heat capacity that dimensions optimization may easily compensate. As a consequence, it is shown that the efficiency and output power may be much larger using pyroelectric energy harvesting than thermoelectric methods. For instance, using a limited temperature gradient due to the limited heat exchange, a maximum efficiency of 1.7% of Carnot efficiency can be expected using a thermoelectric module. On the contrary, a pyroelectric device may reach an efficiency up to 50% of Carnot efficiency. Finally, an illustration shows an estimation of the output power that could be expected from natural time variations of temperature of a wearable device. Power peaks up to 0.2 mW cm −3 were found and a mean power of 1 μW cm −3 on average was determined within 24 h testing.

Research paper thumbnail of Solar micro-energy harvesting with pyroelectric effect and wind flow

Sensors and Actuators A: Physical, 2011

This article proposes to harvest solar micro-energy using the pyroelectric effect and low wind fl... more This article proposes to harvest solar micro-energy using the pyroelectric effect and low wind flow. The basic concept was presented and validated by laboratory experiments with controlled airflow. The measured temperature variation, subject to the intensity of radiation and wind speed in the environment was demonstrated to reach 16 • C. The time variation of temperature was 0.53 • C s −1 with the speed of airflow at 2 ms −1 . The power density with PZT as the pyroelectric material was 4.2 W cm −3 in laboratory conditions. Both the thermodynamic model and electric model of the pyroelectric generator were established, and a numerical procedure was developed to predict the system performance which was proven to be reliable. The characteristics of such an energy harvesting system were analyzed in detail by simulation, and the results indicated that the proposed idea is promising.

Research paper thumbnail of Fiber distribution effects in linear viscoelastic behavior of polymer matrix composites: Computation modelling and experimental comparison

Mechanics Research Communications, 1998

properties of composites with polymeric constituents am strongly temperature dependent. This beha... more properties of composites with polymeric constituents am strongly temperature dependent. This behavior manifests itself in different ways : creep under constant load, stress relaxation under constant deformation, damping of dynamic response, etc. Recently it has been pointed out that the tune-dependent properties may be used to explain and chamcte& the interphase in polymer composite. The efficient design and utilisation of such composites in structurally related applications requites a good understanding of viscoelasticity.

Research paper thumbnail of Two self-powered energy harvesting interfaces based on the optimized synchronous electric charge extraction technique

Journal of Physics: Conference Series, 2013

ABSTRACT Optimized synchronous electric charge extraction (OSECE) interface is a load weakly-depe... more ABSTRACT Optimized synchronous electric charge extraction (OSECE) interface is a load weakly-dependant circuit, which is a favorable characteristic for piezoelectric wideband vibration energy harvesting. However, it introduces synchronous switches that need to be self-powered in a stand-alone system. This paper presents the design and experimental testing of two self-powered approaches for the OSECE technique. One is made of electronic switches driven by analog peak detector circuits; the other uses mechanical switches directly controlled by the ambient vibrations. Finally, advantages and drawbacks of the two approaches will be compared and discussed.

Research paper thumbnail of Dynamic Analysis of Piezoelectric Fiber Composite in an Active Beam Using Homogenization and Finite Element Methods

Journal of Intelligent Material …, Jan 1, 1998

Abstract The purpose of this work is to point out the improvement, which could be achieved throug... more Abstract The purpose of this work is to point out the improvement, which could be achieved through use of piezoelectric fiber composite elements in place of piezoelectric patch elements, in structural vibration systems. Therefore, we review the homogenization ...

Research paper thumbnail of Piezoelectric vibration energy harvesting by optimized synchronous electric charge extraction

Journal of Intelligent Material Systems and Structures, 2013

ABSTRACT This article presents a novel nonlinear energy extraction technique for piezoelectric vi... more ABSTRACT This article presents a novel nonlinear energy extraction technique for piezoelectric vibration energy harvesting. The proposed approach is an improvement of the previous technique, “synchronous electric charge extraction,” which is the first that optimizes the harvested power whatever the connected load. The new approach is then named as “optimized synchronous electric charge extraction.” Compared with synchronous electric charge extraction, the conversion effectiveness is enhanced while simplifying the electronic circuitry and the switch control strategy. The analytical expression of the harvested powers is derived for a classical electromechanical structure. Finally, theoretical predictions confirmed by experimental results show that optimized synchronous electric charge extraction increases the harvested power for a very large range of load resistance, which is a favorable characteristic for wideband vibration energy harvesting.

Research paper thumbnail of Piezoelectric tube with helical electrodes: Numerical analysis of actuator and energy harvesting devices

Journal of Intelligent Material Systems and Structures, 2013

This article presents a finite element analysis of a polarized piezoelectric tube driven by helic... more This article presents a finite element analysis of a polarized piezoelectric tube driven by helical electrodes. It is thanks to a helical coordinate meshing and local coordinate system association with each element that the problem of piezoelectric coupling has been studied. The numerical results agree well with the experimental data without the need of compensation factors as in previous works. The developed model was used to determine the electromechanical coupling coefficients of the tubes in axial and torsional modes. The electromechanical coupling coefficient depends on the helical angle of the electrode. In the axial mode, electromechanical coupling coefficient goes through a maximum value of 25% when the helical angle of the electrode is close to 30°, while in the torsional mode, the maximum value of electromechanical coupling coefficient was reached at a helical angle near 60°. The analysis investigates the tube size effects and shows the potential uses of piezoelectric tubes as an actuator or energy harvesting device. The presented model could be used to analyze the electric fields in the tube during the polarization process or to analyze the mechanical stress (without any limitation due to Saint-Venant's principle) imposed by the simplified analytical approaches available in the literature. The developed approach can also be used for theoretical analysis of the helical/spiral piezoelectric element.

Research paper thumbnail of Strain Rate and Coupling Agent Effects in Discontinuous Glass Fiber Reinforced Polypropylene Matrix

Journal of Composite Materials, 1994

ABSTRACT Mechanical tensile behaviour studies are reported for discontinuous glassfibers reinforc... more ABSTRACT Mechanical tensile behaviour studies are reported for discontinuous glassfibers reinforced polypropylene matrix. Samples were prepared by varying fiber/matrix coupling agents. The influence of strain rate on mechanical properties was analyzed in low and moderate (10-sec-1 to 10 sec-1) strain rate ranges. It was found that (1) in the moderate strain rate range, optical extensometry is invaluable in determining the actual specimen strain, (2) a drastic transition of mechanical tensile behaviour occurs with increasing strain rates, and (3) fiber/matrix coupling agents affect particularly stress-strain behaviour in the moderate strain rate range. A strong interfacial bond seems to improve the ability of the fibers to take up load in regions of matrix cracking; this leads to higher tensile strength.

Research paper thumbnail of A layered approach to the non-linear static and dynamic analysis of rectangular reinforced concrete slabs

International Journal of Mechanical Sciences, 2006

A simplified model for the static and dynamic behaviour of reinforced concrete slab has been deve... more A simplified model for the static and dynamic behaviour of reinforced concrete slab has been developed, based on laminated theory. The proposed model considers the slab as a layered structure and leads to explicit relations, which account for the macroscopic linear and non-linear behaviour of slabs on lines of simple supports. The presented models aim to analyse and design slab

Research paper thumbnail of Rock fall impact on reinforced concrete slab: an experimental approach

International Journal of Impact Engineering, 2005

This paper concerns the protective structures against rock fall. We propose a new concept of rock... more This paper concerns the protective structures against rock fall. We propose a new concept of rock-shed protection. The proposed rock-shed protection is made of reinforced concrete slabs held up by specially designed supports that act as a type of expendable fuse to absorb high rock-fall energy especially when shock occurs on the side of the slab. Thus, by a simple change of damaged supports and local restoration of concrete in the impact area, the structure can continue to be used. We present also an experimental method to characterize and analyze shock absorption effected by this type of reinforced concrete slab. The analyzed slab is a 1/3 scale reproduction of an actual structure. r

Research paper thumbnail of Thermal stresses and thermal expansion coefficients ofn-layered fiber-reinforced composites

Composites Science and Technology, 1997

In this work we develop a thermal self-consistent (TSC) model for n-layered fiber-reinforced comp... more In this work we develop a thermal self-consistent (TSC) model for n-layered fiber-reinforced composites. The fundamental representative volume element is an inclusion made up of a fiber coated by (n −1) layers encapsulated in an infinite equivalent homogeneous medium. On the basis of the energy equivalence principle we show that the thermal problem under conditions of no external loading can

Research paper thumbnail of Segmented piezoelectric fiber composite for vibration control: fabricating and modeling of electromechanical properties

Composites Science and Technology, 2003

This work presents an available prototyping technique and numerical model for development and opt... more This work presents an available prototyping technique and numerical model for development and optimization of piezoelectric fiber composites (PFC). The proposed technique, named “segmented piezoelectric fiber composite” (S-PFC) technique, consists of forming and polarizing PFC directly in the structure. To do this, we make molds directly in the structure, stack PZT fiber layers in the molds and develop specific segmentation

Research paper thumbnail of Strengthening slabs using externally-bonded strip composites: Analysis of concrete covers on the strengthening

Composites Part B: Engineering, 2008

... CFRP increases the initial cracking load of slabs (Table 3). In addition, it decreases the ma... more ... CFRP increases the initial cracking load of slabs (Table 3). In addition, it decreases the maximalbending displacement, while ... 3. Theoretical analysis. ... The William–Warnke model shows the failure criterion of concrete with five experimental constants [6]. The uniaxial stress–strain ...

Research paper thumbnail of Flexural stiffness modelling of RC slab strengthened by externally bonded FRP

Composites Part B: Engineering, 2009

This paper describes the behaviour of strengthened and unstrengthened reinforced concrete slabs, ... more This paper describes the behaviour of strengthened and unstrengthened reinforced concrete slabs, subjected to a single, specific, local, load at their centres. In the experimental stage, the influence of the reinforcement on the various slabs tested was analysed by studying their behaviour at failure and by making a bending stiffness analysis. In order to predict the mechanical behaviour of the

Research paper thumbnail of Strengthening RC beams with composite fiber cement plate reinforced by prestressed FRP rods: Experimental and numerical analysis

Composite Structures, 2012

This paper deals with the development of a new strengthening system for reinforced concrete beams... more This paper deals with the development of a new strengthening system for reinforced concrete beams with externally-bonded plate made of composite fiber cement reinforced by rebars made of fiber-reinforced plastic (FRP) [1]. The proposed strengthening material involves the preloading of FRP rod before mortar casting. The paper presents experimental and numerical analysis carried out on many large-scale beams strengthened by