Fiber Reinforced Plastic Research Papers (original) (raw)

A new popular method for retrofitting reinforced concrete beams is to bond fiber reinforced plastic (FRP) plates to the soffit. An important failure mode for such strengthened members is the debonding of the FRP plate from the member due to high interfacial stresses near the plate ends. As a result, previous researchers have developed several analytical methods to predict the interface performance of bonded repairs. In this paper, a theoretical interfacial stress analysis is presented, including creep and shrinkage effect for simply supported RC beams with a thin FRP composite plate. It explicitly considers the interface slip effect on the structural performance. The results agree reasonably well with those from the existing solutions. The influence of creep and shrinkage effect relative to the time of the casting and the time of the loading of the beams is taken into account. A parametric study has been conducted to investigate the sensitivity of interface behaviours to parameters such as the interface layer stiffness.

Fiber reinforced plastics (FRP) have been widely used as a high strength material. However, it is well known that the FRP is one of the most difficult materials to fractionate into elemental components, namely fiber, filler, and polymers in the waste recycling process. Therefore, the wastes are treated in the incineration or landfilling without any recycling approaches. We have developed a new recycling method using subcritical fluids where unsaturated polyester (UP) resin in FRP can be efficiently depolymerized to separate glass fiber from filler and polymer. Reactions were carried out with or without a catalyst (K 3 PO 4 ) in diethyleneglycol monomethylethter (DGMM) and benzyl alcohol under their subcritical state at temperatures 463-623 K for 1-8 h in a batch reactor. The conversion of UP became fast as the catalyst/solvent molar ratio increased and it was enhanced in the presence of K 3 PO 4 catalyst in subcritical BZA. The glass fiber recovered after the FRP treatment in subcritical BZA was relatively long, while it became short and somewhat damaged at temperature higher than 573 K. The similar trend was observed when DGMM was used as a solvent.

- by Mitsuru Sasaki
- •
- Engineering, Materials Science, Fiber Reinforced Plastic, CHEMICAL SCIENCES

The design of GFRP beams is often governed by deflection limits in service, hence it becomes crucial to evaluate accurately their flexural stiffness. In this work, the flexural stiffness of GFRP pultruded profiles is evaluated experimentally, numerically and analytically. A procedure that simultaneously yields the flexural and the shear modulus of GFRP pultruded profiles directly from 3-point bending tests is applied. Direct tension and 3-point bending tests on coupons extracted from these profiles were also conducted. The TBT and the FEM were applied to analyze the profiles under bending, using material properties estimated by CLT. Comparisons of numerical, analytical and experimental results are presented and discussed at the end.

- by Henriette La Rovere
- •
- Engineering, Modeling, Finite element method, Fiber Reinforced Plastic

This paper describes the various analysis and design aspects of a fiber reinforced plastic (FRP) bridge. The design methodology is illustrated by describing the steps taken in the design of the first US FRP cable-stayed pedestrian bridge to be constructed in Lincoln, Nebraska. The analysis is made using three dimensional (3-D) macro models of the bridge to describe its overall behavior under static and dynamic loads. Separate analysis is done to study the local stability of the different structural elements. The orthotropy of the material is taken into account during this analysis. The short term and long term stiffnesses and strengths are evaluated and accounted for in the design process.

- by osama Hodhod
- •
- Engineering, Fiber Reinforced Plastic, Design process, Design Methodology

A continuum damage model for the prediction of the onset and evolution of intralaminar failure mechanisms and the collapse of structures manufactured in fiber-reinforced plastic laminates is proposed. The failure mechanisms occurring in the longitudinal and transverse directions of a ply are represented by a set of scalar damage variables. Crack closure effects under load reversal are taken into account by using damage variables that are established as a function of the sign of the components of the stress tensor. Damage activation functions based on the LaRC04 failure criteria are used to predict the different failure mechanisms occurring at the ply level.

Electric scooters are considered a new technical green product and a potential industry for many countries. With the highest scooter per capita density and the major producer of motor scooters around the world, Taiwan possesses sufficient conditions for developing electric scooters. In this article, work concerning product design and prototype making of an electric scooter is described, which was the outcome of a collaborative project for new product development. The final product was satisfactory, and was designed according to the aesthetic principle of golden section proportion, and subsequently outer housings were produced with fiber reinforced plastics (FRP) by hand lay-up process. Not only the product appearance was created, but a prototype of an electric scooter was also built using various traditional modeling and engineering techniques.

An experimental investigation was conducted to study the behavior of unreinforced masonry (URM) walls retrofitted with composite laminates. The first testing phase included testing 24 URM assemblages under different stress conditions present in masonry walls. Tests included prisms loaded in compression normal and parallel to bed joints, diagonal tension specimens, and specimens loaded under joint shear. In the second testing phase, five masonry-infilled steel frames were tested with and without retrofit. The composite laminates increased the stiffness and strength and enhanced the post-peak behavior by stabilizing the masonry walls and preventing their out-of-plane spalling. Tests reported in this paper demonstrate the efficiency of composite laminates in improving the deformation capacity of URM, containing the hazardous URM damage, preventing catastrophic failure and maintaining the wall integrity even after significant structural damage.

- by Wael El-dakhakhni
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- Engineering, Seismic Hazard, Fiber Reinforced Plastic, Composite structures

In the past two decades, the use of fiber-reinforced polymer (FRP) for strengthening structural members has shown to be an effective method, with respect to both structural performance and economic features. This paper presents the results of a study conducted to investigate the feasibility of glue-laminated (glulam) timber columns strengthened with fiber-reinforced polymer (FRP) sheets. Experimental and computational investigations were conducted on axially loaded glulam timber columns strengthened with FRP. Several parameters such as slenderness ratio, boundary conditions, FRP reinforcement length, and relative cost were considered in this study. The principal aim of this study was to produce data and information for practicing engineers and architects. The main objective was to justify promotion of the use of cost-effective glulam timber components as a viable alternative in structural applications.

- by Mahavir Nagaraj
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- Engineering, Fiber Reinforced Plastic, Cost effectiveness, Composite structures

The upgrading of existing structures that are not adequate to withstand seismic demand is a widely adopted and effective approach aimed at risk reduction. Nowadays, many are feasible retrofit strategies, employing traditional and/or innovative materials, and several options are available to professionals. Each one has different performances in respect to some criteria, i.e., technical and/or economical, by which each alternative can be evaluated. The selection of the most suitable retrofit strategy for a particular structure may be not straightforward since, in many applications, there is no alternative which clearly emerges among others as the best one according to the whole of the criteria considered.

The paper provides an overview of the conceptual design of the Lunar Rover conceived by Team Italia for the AMALIA Mission, candidate for the Google Lunar X Prize Challenge. The name of the mission is an acronym of the Latin language sentence ''Ascensio Machinae Ad Lunam Italica Arte''. With the Lunar Challenge initiative, the X Prize Foundation intends to promote the involvement of private actors in the access to space, by endowing a prize to the first privately funded lunar mission covering a certain minimum distance on the Moon surface. Additional prizes are available in case of achievement of more challenging goals, like surviving lunar night, travelling for a longer distance, visiting areas of the first Apollo Missions. Although the AMALIA Rover Subsystems are the typical ones of an Exploration Rover, their design is highly influenced by the above depicted mission context. The followed design approach is closer to the one of a commercial mission than to an Institutional Space Exploration Mission one. It has to be noted that, for being compliant with GLXP rules, at least 90% of funds required for competing in the Prize has to come from private or non-governmental sources. The achievement of such challenging goals requires adopting suitable technical and programmatic solutions, having the need to optimize costs and schedule while still maximizing the probability of success.

Drilling in woven fiber-reinforced plastics is a well-known practice in modern-day manufacturing. The high fracture toughness of woven fiber-based composites over unidirectional counterparts is increasing demand in aviation and electronics industries. Hence, failure of these materials at harsh environments is a matter of concern. Very few numerical studies on drilling of these composites have been carried out; hence, the present scope may be considered as a trial de novo. Delamination was studied in the present work at different feed–speed combinations. Drilling responses were estimated using finite element as a numerical simulation tool. An equivalent elastic macromechanical model was assumed for the woven composite workpiece. A 3D drill bit was modeled using commercial CAD package Pro-Engineer and Ansys Autodyn was used as the solver environment. The simulation and validation experiments were carried out at planned feed–speed combinations. The effect of process parameters on exit and entry delamination is also documented. The thrust determined by finite element techniques showed good prediction with the experimental results.

To develop an effective repair technique for rapid bridge restoration after an earthquake, four hollow bridge columns were cyclically loaded to failure, repaired and retested. The repair process includes using dog-bone shape bars to replace the fractured longitudinal bars in plastic hinges and using FRP (Fiber Reinforced Plastic) wraps to enhance the deformation capacity of columns. The repair aims to restore seismic capacity in terms of strength and ductility. Test results indicate that the fractured longitudinal bars can be completely repaired and the deformation capacities of the columns were enhanced by FRP wraps. However, due to concrete deterioration and the buckling of the longitudinal bars in the inner layer of the hollow sections, the test results also indicate the repaired column strengths are less than anticipated. ᮊ

- by Shen-En Chen
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- Civil Engineering, Fiber Reinforced Plastic, FRP, Building
- by Madhusoodana Kurup
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- Zoology, Aquaculture, Fiber Reinforced Plastic, Profitability

A finite element model was developed to simulate chip formation in the edge trimming of unidirectional Fiber Reinforced Plastics (FRPs) with orthogonal cutting tools. Fiber orientations () within the range of 0 degрр90 deg were considered and the cutting tool was modeled as both a rigid and deformable body in independent simulations. The principal and thrust force history resulting from numerical simulations for orthogonal cutting were compared to those obtained from edge trimming of unidirectional Graphite/Epoxy (Gr/Ep) using polycrystalline diamond tools. It was found that principal cutting forces obtained from the finite element model with both rigid and deformable body tools compared well with experimental results. Although the cutting forces increased with increasing fiber orientation, the tool rake angle had limited influence on cutting forces for all orientations other than ϭ0 deg and 90 deg. However, the tool geometry did affect the degree of subsurface damage resulting from interlaminar shear failure as well as the cutting tool stress distribution. The finite element model for chip formation provides a means for optimizing tool geometry over the total range in fiber orientations in terms of the cutting forces, degree of subsurface trimming damage, and the cutting tool stresses.

Machining of fiber reinforced plastic (FRP) components is often needed in spite of the fact that most FRP structures can be made to near net shape. The material removal mechanism of FRP is very difficult as compared with metals due to their inherent inhomogeneity and anisotropy. This results in frequent fiber pullout, delamination, matrix burning, and other damages leading to poor cut surface quality. A finite element model is proposed to quantify the material damage, which has been experimentally validated by means of nondestructive dyepenetrant testing. Good agreement is observed for laminates with fiber orientations up to 60 . Divergence is noticed for higher fiber orientations, and the discrepancies increase with increasing fiber orientation. Proper interfacial properties vis-a`-vis machining of FRP materials are considered to be the main reasons for the divergence.

Fibre reinforced plastics are increasing their importance as one of the most interesting groups of material on account of their low weight, high strength and stiffness. To obtain good quality holes, it is important to identify the type of material, ply stacking sequence and fibre orientation. In this paper, the drilling of quasi-isotropic hybrid carbon+glass/epoxy plates is analyzed. Two commercial drills and a special step drill are compared considering the thrust force and delamination extension. Results suggest that the proposed step drill can be a suitable option in laminate drilling.

- by João Manuel R. S. Tavares and +2
- •
- Materials Engineering, Materials, Image Processing and Analysis, Fiber Reinforced Plastic

Current regulations mainly consider maximum head form acceleration as the criterion to evaluate crash helmet effectiveness in terms of shock absorption. From more basic research, however, five general phenomena have been identified to be associated with head protection: the kinetic energy involved in the impact, the maximum load on the head, the load distribution, the rate of onset of loading and the time duration of the impact. Considering the high importance of head injury prevention as a whole and the ongoing discussions on the mechanisms of head injury, it seems worthwhile to address helmet optimization on the basis of these five phenomena. An experimental study has been performed to address helmet optimization, mainly considering the characteristics of the outer and inner shell.

- by Riender Happee
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- Fiber Reinforced Plastic, Experimental Study, Head injury, Kinetic Energy

Seismic retrofitting of under-designed structures is a consolidated approach to risk management. Several options are available for the achievement of the vulnerability reduction goals, each of those having peculiar performances in respect of different technical and non-structural criteria. Selection of the best solution is a non-trivial task, because criteria may conflict each other. Multi-Criteria Decision Making (MCDM) methods may be useful in the matter, allowing to rank the overall performances for the set of alternatives and, therefore, to identify the optimal one. In the study presented herein, such approach was applied to the seismic upgrade of an old type RC building, hypothesizing an update of the seismic hazard at the site where the structure is supposed to be located. Four different strategies were designed to get the required seismic performance. Non-linear structural modeling, seismic risk analysis, criteria selection and MCDM results are also discussed.

The drilling of fiber reinforced plastics (FRP) often results in damage around the drilled hole. The drilling induced damage often serves to impair the long-term performance of the composite products with drilled holes. The present research investigation focuses on developing a predictive model for the residual tensile strength of uni-directional glass fiber reinforced plastic (UD-GFRP) laminates with drilled hole which has not been developed worldwide till now. Artificial neural network (ANN) predictive approach has been used. The drill point geometry, the feed rate and the spindle speed have been used as the input variables and the residual tensile strength as the output. The results of the predictive model are in close agreement with the training and the testing data.

- by Roshan Mishra
- •
- Neural Network, Fiber Reinforced Plastic, Materials Design, Prediction Model

A combined experimental/analytical approach for effective evaluation of in-plane and out-of-plane shear moduli of structural composite laminates from torsion is presented. The test samples are produced by pultrusion and consist of E-glass fiber systems and vinylester resin. Three types of rectangular samples are used: unidirectional samples cut from plates; angle-ply and angle/cross ply samples cut from wide-flange beams. The shear moduli are obtained from the experimental torsional stiffnesses (T/) and data reduction techniques based on torsion solutions by Lekhnitskii and Whitney. The classical approach of using paired samples of different widths but same material orientation can grossly underestimate out-ofplane shear moduli. Thus, to overcome this problem, samples with material orientations normal to each other are used, and to obtain samples of larger dimensions than the available thicknesses of the material, the pultruded laminates are bonded flat-wise, from which transverse strips of different widths are cut. Consistent results are obtained by the two data reduction techniques, and the experimental values are compared to predictions by micro/macro-mechanics models.

- by Tinh Nguyen
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- Fiber Reinforced Plastic, Environmental Exposure

- by osama Hodhod
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- Engineering, Fiber Reinforced Plastic, Design process, Design Methodology

Drilling of fiber reinforced plastic (FRP) composite materials is a field open to a plethora of questions. Drillinginduced damage is a research area that has not been explored exhaustively. The present research endeavor is an effort to correlate drilling-induced damage with drilling parameters. Tool point geometry is considered a major factor that influences drillinginduced damage. Experiments were conducted and drillinginduced damage was quantified using the digital image processing technique. The results also reestablished the cutting speed to feed ratio as an important variable that influences drillinginduced damage. Mathematical models for thrust, torque, and damage are proposed that agree well with the experiments.

- by Naresh Bhatnagar
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- Engineering, Finite Element, Digital Image Processing, Fiber Reinforced Plastic

This article describes a study of the application of solar energy in a Fiber Reinforced Plastic (FRP) house designed for a brown rice drying system. The theoretical heat collection characteristics of an FRP solar drying house when empty are presented and compared to experimental results. The purpose of the study was to evaluate: (1) the temperature variation inside the house; (2) the effect of solar radiation and airflow rate on the temperature difference between the air inside and outside the FRP house (temperature rise); and (3) the heat collection efficiency of an FRP house when using and not using a solar collector. It was observed both theoretically and experimentally that the temperature of the air inside the house is higher than that of the outside air, and in the mathematical model, the solar collector shows a higher temperature than the roof cover. As the airflow rate from the dryer fan inside the house increases, temperature rise decreases. For global solar radiation in the range of 100 to 800W/m 2 , the temperature rise shows an exponential relationship with global solar radiation, and the values of temperature rise are higher when using a collector (5-16°C) than when not using one (4-11°C). Thus, collector installation inside an FRP solar house has a clear effect on increasing the air temperature inside the house, which leads to an increase in the heat collection efficiency of the house of around 27.23%. In this work, some relationships predicting the optimal house floor size required, the airflow rate per unit mass of product to be dried, and the energy collection are discussed. Then, from the house floor size, airflow rate and collected energy requirements to dry a given amount of product optimally could be calculated.

- by Ridwan Rachmat
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- Engineering, Materials Science, Material Science, Fiber Reinforced Plastic

A new hand lay-up technique for fabrication of fiber reinforced plastic (FRP) laminated plates, using glass fibers in the form of continuous rovings, is presented. The advantages of this method over its existing counterparts are discussed. This broad approach can further be categorized into three different sub-methods or techniques. Various difficulties encountered in this process and remedial measures to overcome them are described in detail. In addition, some of the important mechanical properties of such plates have been investigated and reported. All of the three techniques offer the ability to lay the continuous rovings with certain amounts of tension manually. In this sense, these fabrication techniques retain the advantages of both hand lay-up and filament winding techniques, while avoiding their disadvantages to a great extent. These techniques permit fabrication of any laminated anisotropic plate consisting of arbitrary number of layers oriented at desired fiber directions without employing complicated and expensive tooling required by other methods. Equally important, an inverse method is presented wherein the elastic stiffnesses/moduli of the corresponding 0°lamina are computed from the experimentally determined fundamental resonant frequencies of any three of the same series of simply supported symmetric rotated cross-ply anisotropic [

- by Reaz Chaudhuri
- •
- Engineering, Fiber Reinforced Plastic, Quality assessment, Composite structures

Steel needle gates which are being used in Kolhapur Type Weirs (K.T. weirs) need to be replaced to overcome their disadvantages like heavy weight, corrosive nature, maintenance cost etc. Fiber Reinforced Plastic (F.R.P.) having advantages like light weight, low maintenance cost, corrosion resistance, longer service life etc. can be thought of as a replacement to steel in K.T. Weirs. In the present investigation an attempt is made to analyze the FRP Needle gates using finite element method. A generalized software tool is developed using FORTRAN which gives structural responses (deflections, stresses) as a result by input of material properties

The literature published on single mechanically fastened joints in ®ber-reinforced plastics is reviewed. A ®nite-element model is developed to predict the response of pin-loaded composite plates. The model takes into account contact at the pin±hole interface, progressive damage, large deformation theory, and a non-linear shear stress±strain relationship. To predict the progressive ply failure, the analysis combines Hashin and the maximum stress failure criteria. The objectives of the study are to determine the in¯uence of the failure criteria, the inclusion of a non-linear shear behavior on the strength prediction and the load±pin displacement curve. The proposed model is used to predict the bearing response of composite plates with dierent stacking sequences. Good agreement between experimental results and numerical predictions is observed. Ó

- by Guy Gendron
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- Engineering, Fiber Reinforced Plastic, Failure Analysis, Finite Element Analysis

A ®nite element analysis of reinforced concrete beams with ®ber-reinforced plastic re-bars is performed. Corrosion of steel rebars is a common problem encountered in the civil construction sector, due to the porosity of concrete. The use of ®ber-reinforced polymers (FRP) instead of steel re-bars can lead to a better corrosion-resistant reinforced concrete with applications in many construction ®elds. The need for non-linear geometrical and material models implies the use of numerical methods such as the ®nite element method. In this paper the use of a ®rst-order shear-deformation theory in the analysis of concrete shells reinforced with internal composite unidirectional re-bars is proposed. The theory is implemented in a shell element that allows for a layered discretization of the laminate materials. A perfect plastic and a strain-hardening plasticity approach are used to model the compressive behavior of the concrete. A dual criterion for yielding and crushing in terms of stresses and strains is considered, which is complemented by a tension cut-o representation. The material law for the unidirectional re-bars is linear elastic/brittle, whereas the concrete allows for elasto-plastic±brittle behavior. A simply-supported concrete beam, reinforced with composite re-bars is analysed. The eects of the reinforcement and the comparison of composite and steel re-bars on concrete are discussed. Comparison between numerical and experimental results is made for a RC beam reinforced with pultrusion rods. Ó

- by A.T. Marques
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- Engineering, Linear Elasticity, Finite element method, Composite Materials
- by V. Cech and +1
- •
- Engineering, Materials Science, Fiber Reinforced Plastic, Thin Film

The automotive sector, given the need to reduce energy demand and environmental impact of vehicles, needs to reduce the weight of vehicles. Lightweighting strategy to implement is based on the massive use of plastics and composites, which are lighter than steel and alloys. Use of plastics and composites will significantly reduce emissions during the use stage In that phase energy demand is about 85% of the total energy required during the life cycle of the vehicle. However, it should be assessed whether the improvements are not offset in other stages of the life of the product, in which steels and alloys may have less environmental impact than plastics and composites. In order to work out the fuel savings achieved during the use stage of the vehicle due to the weight reduction, several mathematical models can be used during the design phase. The study of those models will let us know the design parameters that must be considered in order to successfully apply the lightweighting strategy.

- by Daniel Cordero
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- Engineering, Fiber Reinforced Plastic, Fuel Consumption, Reinforced Plastic

Nanomaterials and nanotechnologies play a significant role in many fields of modern science, such as material science, chemistry, molecular biology and medicine. They exhibit novel, better physical and chemical properties than the bulk materials. This is a result of the change in the electronic structure, which is responsible for electroconductivity, optical absorption, chemical reactivity, catalytically activity and mechanical properties. In the past few decades there has been a great expansion in research related to the polymer nanocomposites, due to development of advanced materials for many engineering applications.

- by marina-eirini mitrousi
- •
- Composites, Carbon Nanotubes, Graphene, Polymer Nanocomposites

Flexible composite marine propellers, made of fiber-reinforced plastic (FRP) composites, have a number of advantages over conventional rigid metallic propellers. In particular, composite propellers have great potential for performance improvement. In the current work, fluid-structure interaction effects are utilized to improve the performance of composite marine propellers under a wide range of operating conditions. Two important mechanisms, namely, the bending-twisting coupling effects of anisotropic composites and load-dependent self-adaptation behavior of composite blades are the primary sources for performance improvement of composite marine propellers. Systematically designed self-twisting composite propellers are evaluated under both steady and unsteady operating conditions. Response and performance curves are compared between the rigid and self-twisting propellers. Governing mechanisms and fluid-structure interaction effects are identified and analyzed. It is shown that the self-twisting propeller leads to significant improvement in energy efficiency over its rigid counterpart.

- by Y. Young
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- Engineering, Fluid structure interaction, Vibration, Energy efficiency

- by Jyh-Rong Chou
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- Product Design, New Product Development, Fiber Reinforced Plastic, Materials Design

BibliatMque nationale du Canada Acquisitions and Acquisitions et Bibliographie Services senrices bibliographiques 395 W e l l i Street 395, rue Wellington OriawaON K I A W û(tawa0N K1A ON4 Canada Canada The author has granted a nonexclusive licence allowing the National Library of Canada to reproduce, loan, distribute or seil copies of this thesis in microform, paper or electronic formats. The author retains ownership of the copyright in this thesis. Neither the thesis nor substantial extracts fiom it may be printed or othewise reproduced without the author's permission. L'auteur a accordé une licence non exclusive permettant à la Bibliothèque nationale du Canada de reproduire, prêter, distribuer ou vendre des copies de cette thèse sous la forme de microfiche/nlm, de reproduction sur papier ou sur format électronique. L'auteur conserve la propriété du droit d'auteur qui protège cette thèse. Ni la thèse ni des extraits substantiels de celle-ci ne doivent être imprimés ou autrement reproduits sans son autorisation.

Coupon tests are investigated and used to calibrate three-dimensional (3D) micromechanical models and to verify their prediction for the nonlinear elastic behavior of pultruded ®ber reinforced plastic composites. The tested composite material system is made from E-glass/ vinylester pultruded composite plate with both glass roving and continuous ®lament mat (CFM) layers. Tension, compression, and shear tests were performed, using off-axis coupons cut with different roving reinforcement orientations. The overall linear elastic properties are identi®ed along with the nonlinear stress±strain behavior under in-plane multi-axial tension and compression loading. The tests were carried out for coupons with off-axis angles: 0, 15, 30,45, 60, and 908, where each test was repeated three to ®ve times. Finite element analyses are used to simulate the off-axis tests and examine the effects of coupon geometry, end-clamping condition, and off-axis orientation, on the spatial distribution of the axial strains at the center of the coupons. Lower initial elastic modulus and a softer nonlinear stress±strain responses were consistently observed in the tension tests compared to those in compression, for all off-axis (roving) orientations. The nonlinear behavior can be attributed to the relatively low overall ®ber volume fractions (FVFs) in pultruded composites and the existence of manufacturing defects, such as voids and microcracks. It is also shown that the end-clamping effects for the tested geometry are relatively small at the center and allow extracting the nonlinear stress±strain response of the anisotropic material. The analytical part of this study includes two (3D) micromechanical models for the roving and CFM layers. Shear tests are used to calibrate the in situ nonlinear elastic properties of the matrix. Good prediction ability is shown by the proposed micromodels in capturing the stress±strain behavior in the off-axis tests. q

- by Hakan Kilic
- •
- Engineering, Nonlinear Elasticity, Linear Elasticity, Finite element method

The use of fiber reinforced plastics has increased in the last decades due to their unique properties. Advantages of their use are related with low weight, high strength and stiffness. Drilling of composite plates can be carried out in conventional machinery with some adaptations. However, the presence of typical defects like delamination can affect mechanical properties of produced parts. In this paper delamination influence in bearing stress of drilled hybrid carbon+glass/epoxy quasi-isotropic plates is studied by using image processing and analysis techniques. Results from bearing test show that damage minimization is an important mean to improve mechanical properties of the joint area of the plate. The appropriateness of the image processing and analysis techniques used in the measurement of the damaged area is demonstrated. Table 3: Drill geometry comparison results (Avg -average; Max -higher value; min -lowest value)

- by João Manuel R. S. Tavares and +1
- •
- Image Processing and Analysis, Fiber Reinforced Plastic, Carrying Capacity

- by Jyh-Rong Chou
- •
- Product Design, New Product Development, Fiber Reinforced Plastic, Materials Design

- by anant gupta
- •
- Multidisciplinary, Fiber Reinforced Plastic, Dimensional Analysis, Wind Tunnel test

An effective integration of a three-dimensional (3D) micromechanical and finite element (FE) modeling framework is proposed for the analysis of thick-section fiber reinforced plastic (FRP) composite materials and structures. The proposed modeling framework is applied to a pultruded composite system. It consists of two alternating layers with unidirectional fiber (roving) and continuous filaments mat (CFM) reinforcements. Nonlinear 3D micromechanical models representing the different composite layers are used to generate through-thickness composite's effective responses. Approximate traction continuity and strain compatibility relations in the micromechanical models are expressed in terms of the average stresses and strains of the sub-cells that recognize the fiber and matrix responses. The nonlinear elastic behavior is attributed only to the matrix sub-cells. The nested nonlinear micromechanical models are implemented at each integration (Gaussian) point in the FE structural analyses. A linearized structural response will produce a trial strain increment for each Gaussian integration point and an iterative solution is performed until a structural-level convergence criterion is met. At every iteration, the micromechanical models are called to provide effective material responses. An efficient numerical implementation of the micromodels is required in order to achieve accurate solutions and accelerate the structural-level convergence. Thus, stress correction algorithm is performed in each level of the nested micromodels. Axial tension and compression tests on off-axis E-glass/vinylester coupons and notched specimens are used to calibrate the in situ material properties of the fiber and matrix and verify the prediction ability of the nested micromodels. The nonlinear calibration of the matrix is done by using the overall axial shear stress-strain response generated from Iosipescu (V-notched) specimens. Good agreement is shown for all off-axis angles when comparing the experimental stress-strain curves with those predicted by the analyses with the proposed micromodels.

- by Hakan Kilic and +1
- •
- Engineering, Nonlinear Elasticity, Finite Element, Finite Element Analysis (FEA)

The present paper is aimed at providing a better understanding of the effect of interference and influence of strakes for wind load on Thermal Power Station (TPS) chimneys. Measurements of across and along vibration have been made on scale model of Panipat power station chimney, India. The aeroelastic model of the chimney has been tested in a simulated atmospheric boundary layer of height 1.0 m in the Boundary Layer Wind Tunnel at IIT Roorkee, India. The chimney model has been fabricated with FRP (fiber-reinforced plastic) at a geometric scale of 1:150 representing a chimney with height of 100 m in prototype. The wind tunnel tests for the present study have been carried out with the objective of obtaining the maximum along-wind and across-wind response of the chimney and this has been expressed in terms of bending moments. In particular, the interference effect between other nearby structures of the TPS has been investigated. Based on dimensional analysis measured values of chimney model have been converted into prototype values.

- by Alok John
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- Multidisciplinary, Fiber Reinforced Plastic, Dimensional Analysis, Wind Tunnel test

This paper presents some of the research done during the last 8 years at the Technical University of Denmark developing improved low-energy window solutions. The focus has been on maximizing the net energy gain of windows for residential buildings. The net energy gain of windows is the solar gain minus the heat loss integrated over the heating season. It is

- by Svend Svendsen
- •
- Fiber Reinforced Plastic, Seasonality, Low Energy Buildngs, Composite Material