Showing papers in "Journal of Reinforced Plastics and Composites in 1995"
TL;DR: In this article, the effects of environmental exposure of a chemical and a thermal nature on fiber-reinforced polymer (FRP) composites are considered, such exposures include temperature, moisture and chemicals in liquid solutions or in gaseous mixtures.
Abstract: Technical literature on the subject of environmental exposure effects related to determining accelerated test methods for the prediction of long-term performance of FRP composite materials for highway structural applications is reviewed in this paper. Effects of environmental exposure of a chemical and a thermal nature on fiber-reinforced polymer (FRP) composites are considered. Such exposures include temperature, moisture and chemicals in liquid solutions or in gaseous mixtures. The effects include the changes in the physical and mechanical properties of the composite materials. Such changes are typically related to the degradation or deterioration of the composite material. Synergistic effects of mechanical load and exposure are also reviewed. The review is divided in topics entitled Materials, Exposure Conditions, Experimental Techniques, Failure Mechanisms and Theoretical Modeling. 81 refs.
222 citations
TL;DR: A review of the technical literature related to the creep behavior of fiber reinforced polymer (FRP) composites can be found in this paper, where the review is directed toward those papers that...
Abstract: This report provides a review of the technical literature related to the creep behavior of fiber reinforced polymer (FRP) composites. The review presented here was directed toward those papers that...
149 citations
TL;DR: In this article, a three-dimensional examination of the temperature and thermochemical properties of pultruded advanced composites is presented, which is useful for understanding the manufacturing process.
Abstract: Computer simulation is helpful for understanding the manufacturing of pultruded advanced composites. This research involves a three-dimensional examination of the temperature and thermochemical asp...
72 citations
TL;DR: A review of the existing literature on what has been done and what needs to be done for the development of accelerated test methods, with emphasis on mechanical loads, is presented in this article, where the focus of the report is on new, bonded FRP reinforcement for concrete bridge structures.
Abstract: This report addresses the methodology for determining the long-term behavior of bridge structures reinforced with fiber reinforced plastic (FRP) rods. In particular, a review of the existing literature on what has been done and what needs to be done for the development of accelerated test methods, with emphasis on mechanical loads, is presented. The focus of the report is on new, bonded FRP reinforcement for concrete bridge structures. Companion reports address stand-alone FRP systems subjected to mechanical loads, and stand-alone FRP and FRP-concrete systems subjected to environmental loads. 98 refs.
68 citations
TL;DR: In this article, the effects of fiber content, fiber orientation and testing speed on the crush zone morphology and specific energy absorption capability are discussed, and an energy absorption behavior of knitted glass fiber fabric/epoxy and knitted carbon fiber fabric and composite tubes is described.
Abstract: This paper describes the energy absorption behaviors of knitted glass fiber fabric/epoxy and knitted carbon fiber fabric/epoxy composite tubes. The effects of fiber content, fiber orientation and testing speed on the crush zone morphology and specific energy absorption capability are discussed. Attempts have been made to relate the energy absorption capability to the crush zone morphology.
61 citations
TL;DR: In this paper, a need for the renewal of infrastructure because of age, deterioration, misuse, lack of timely repair and maintenance, use of improper materials and/or techniques in the original...
Abstract: Worldwide there is a need for the renewal of infrastructure because of age, deterioration, misuse, lack of timely repair and maintenance, use of improper materials and/or techniques in the original...
40 citations
TL;DR: In this article, an indirect measuring method was proposed to obtain the fiber permeabilities of the fiber reinforcements, which can avoid the edge effect and greatly simplify the procedures in the permeability measurements.
Abstract: In the composites manufacturing processes such as resin transfer molding (RTM), pultrusion, autoclave, and compression molding, the mechanism and resistance of resin flow through fiber reinforcements have an important effect on the final part quality. Because of the anisotropic characteristics of the fiber reinforcements, the flow resistance is different in various directions. To study the mechanisms of resin impregnation during the fabrication of the fiber reinforced composites, it is important to investigate the permeabilities of the fiber reinforcements first. This study proposes an indirect measuring method to obtain the fiber permeabilities. The proposed method can avoid the edge effect and greatly simplify the procedures in the permeability measurements. Reliable and repeatable permeability data can be obtained using this technique.
34 citations
TL;DR: In this paper, a degenerated finite shell element was implemented for the analysis of the burst failure of the filament wound wound pressure vessel composed of T-800 graphite/epoxy.
Abstract: An investigation was conducted to study the burst failure of the filament wound pressure vessel composed of T-800 graphite/epoxy. Of particular concern was to predict the propagation of damage after initial failure and the burst pressure of the filament wound pressure vessel as a function of applied load. In the present study a degenerated finite shell element was implemented for the analysis. This element takes into account the variations of the winding angle and the thickness along the meridional line of the vessel. This model can also represent geometrical nonlinear behavior by considering large displacements/large rotations. In order to predict the burst pressure, a progressive failure analysis was performed by using a failure criteria with a property degradation model. Experiments were also conducted to measure the strains and the burst pressure of the filament wound pressure vessel. A fairly good agreement was obtained between the analysis and the test results.
31 citations
TL;DR: In this paper, the mixed-mode bending (MMB) test was employed in an investigation of delamination fracture behavior in static and fatigue loading for carbon/epoxy composites 1300/M10 and HTA/6376.
Abstract: The mixed-mode bending (MMB) test was employed in an investigation of delamination fracture behavior in static and fatigue loading for carbon/epoxy composites 1300/M10 and HTA/6376. As specimens were loaded at different ratios of alL for different mixed-mode ratios, both investigated composites exhibited brittle unstable or brittle stable behavior of crack growth. Mixed-mode delamination fracture toughness was determined at a IL = 0.5. Fracture surfaces of MMB specimens were examined using scanning electron microscopy to distinguish fracture features. Stable crack growth was observed over the entire range of crack lengths investigated in the cyclic tests. A consistent relation of crack growth per cycle to the cyclic strain energy release rate was obtained. The trend of reduction in crack growth rate data with diminution in cyclic strain energy release rate suggests the presence of a threshold strain energy release rate.
29 citations
TL;DR: In this paper, a non-isothermal simulation model was developed to simulate the thermal behaviors of the resin and mold during the resin transfer molding process based on the control volume finite element method.
Abstract: The manufacture of polymer composites through the process of the resin transfer molding (RTM) involves the impregnation of the reactive polymer resin into a mold with preplaced fibrous reinforcements. Determination of RTM processing conditions requires the understanding of various parameters, such as material properties, mold geometry, and mold filling conditions. Modeling of the entire RTM process provides a tool for analyzing the relationship of the important parameters. This study developed a non-isothermal simulation model to simulate the thermal behaviors of the resin and mold during the resin transfer molding process based on the control volume finite element method. The model will be able to simulate the thermal and chemical changes of the resin and the thermal variations of the mold during the filling and curing stages. Thermal effect of the epoxy mold was shown to have large influence on the temperature distribution and curing process of the resin. Results of some numerical studies in RTM show the applications of the proposed model
28 citations
TL;DR: In this paper, upper and lower bounds for the stiffness of laminated beam elements under flexure were defined and correlated with experimental effective beam moduli with analytica, and the results were shown to correlate well with the performance of beam modulus analysis.
Abstract: The objectives of this study are: (1) to define upper and lower bounds for the stiffness of laminated beam elements under flexure, (2) to correlate experimental effective beam moduli with analytica...
TL;DR: In this article, the effects of fiber volume fraction and incident energy on the impact damage tolerance of composite laminates subjected to low13; velocity impacts at constant strike velocities were studied.
Abstract: An effort made to study the effects of fiber volume fraction and incident13; energy on the impact damage tolerance of composite laminates subjected to low13; velocity impacts at constant strike velocities. Repeated drop tests were conducted using an13; inhouse built drop weight impact-tester: Delamination-area was used as parameter for13; quantifying damage while the number of drops (impacts) to failure use to assess the13; damage tolerance limits. The delamination area was found to increase and then saturate13; after a certain number of drops. Impact fatigue studies showed the existence of a critical13; Incident energy (Ec) around which design of opmposite structures can be based. Also the13; minimum incident energy required to fracture the sample in a single impact (ESDT)was13; evaluated from the data. One of the interesting observations made was that for any given13; incident energy, the delamination area was found to be minimum at a certain fiber volume13; fraction (0.5 in this case) of the laminate. This was explained on lines of failure13; mechanisms reported earlier.13;
TL;DR: In this paper, a two-dimensional finite element analysis is performed in order to analyze and improve the performance of the three-rail shear test specimen as prescribed by the ASTM Standard Guide for testing of in-plane shear properties of composite laminates.
Abstract: A two-dimensional finite element analysis is performed in order to analyze and improve the performance of the three-rail shear test specimen as prescribed by the ASTM Standard Guide for testing of in-plane shear properties of composite laminates [1]. Of main interest is the location of high-magnitude stresses in the matrix direction that affect the fatigue life of the specimen. Through finite element analysis, the optimal specimen configuration is determined by inserting slots in the positions at which there are stress concentrations. This has the effect of transferring the location of high stress away from critical areas, thus increasing the fatigue life of the specimen. The results are verified by three-rail shear tests performed for both standard un-notched and new notched specimens. The notched specimens show great improvement in both static strength and fatigue life.
TL;DR: In this article, the suggested design detail recommendations for connections and stiffeners for pultruded fiber reinforced plastics (PFRP) structural shapes are introduced, which serve as a prac...
Abstract: This paper aims at introducing some suggested design detail recommendations for connections and stiffeners for pultruded fiber reinforced plastics (PFRP) structural shapes. It also serves as a prac...
TL;DR: In this article, the stochastic finite element method based on second moment method is developed for the probabilistic analysis of laminated composite structures in which physical properties have uncertainties and variability.
Abstract: The stochastic finite element method based on second moment method is developed for the probabilistic analysis of laminated composite structures in which physical properties have uncertainties and variability. The material properties, fiber angles, laminate thickness, and curvatures are modeled as random parameters. The first order shear deformable shell element is employed in application. Numerical results are presented for three example problems. The validity and accuracy of the method are verified through comparison of the present results with those obtained by the Monte Carlo simulation. Statistics of strains and stresses are derived very accurately by considering the randomness of the strain-displacement relation and principal material directions. The probability distribution of structural responses of composite structures can be assumed to be normal distribution, and therefore, can be evaluated quantitatively.
TL;DR: In this article, the authors describe the full-scale tests conducted to study the behavior and recommend design criteria for deep I-shape reinforced plastic (RP) pultruded beams subjected to transverse loads in the plane of the web.
Abstract: The paper describes the full-scale tests conducted to study the behavior and recommend design criteria for deep I-shape reinforced plastic (RP) pultruded beams subjected to transverse loads in the plane of the web. The beam utilized in these experiments was made of a vinylester matrix reinforced with E-glass, and their cross sections consisted of a 610 mm × 9.5 mm (24 in. × 3/8 in.) web and 190 mm × 19 mm (71/2 in. × 3/4 in.) flanges. Beams were instrumented at various locations using strain gages, LVDTs and potentiometers. Both finite element analysis and approximate beam theory for composite sections predicted deflections within 5 percent of those observed. Engineering beam theory may be used for design of such RP beams
TL;DR: In this article, the moisture diffusion characteristics of autoclave moulded T300-914C unidirectional composite specimens hygrothermally conditioned at 85% RH and 70'C till saturation to 1.5% moisture content were presented.
Abstract: This paper presents the moisture diffusion characteristics of autoclave moulded T300-914C unidirectional composite specimens hygrothermally conditioned at 85% RH and 70'C till saturation to 1.5% moisture content. In all, pin bearing strength test specimens of three different layup sequences viz. [45/03/ A 45/03/90/0],, [0/ 4 45/9012s and [45/02/45/03/45/0], were studied. All the test specimens exhibited Fickian Diffusion behaviour. It was further found that the Diffusion coefficient (D,) value of the composites increased with increase in the cut edge surface area and the values obtained compared well with those reported in literature. The difference in D, values obtained for different layup sequences was attributed to tortuousity caused by fibre orientations.
TL;DR: A comparison of the isothermal and adiabatic based models for both cure and viscosity data is presented in this paper for fiberite 977 2 and 977 3 thermosetting resins.
Abstract: Heat of reaction, degree of cure, and viscosity of ICI Fiberite 977-2 and 977-3 thermosetting resins were measured. Degree of cure and viscosity for Fiberite 977-2 and 977-3 resins was determined under isothermal and adiabatic conditions. Expressions relating the degree of cure and viscosity to the time temperature profile during processing were found for each resin. Typically, these relationships are determined by conducting isothermal tests at several temperatures. A new approach which employs adiabatic data is proposed. A comparison of the isothermal and adiabatic based models is presented for both cure and viscosity data. The adiabatic based models require fewer test runs to develop the model parameters, yet accurately predict resin cure and viscosity characteristics.
TL;DR: In this article, the porosity and the permeability of a TGFM-300 P/E random fiber mat were investigated and the edge effect was simulated by the creeping motion of the resin with permeable boundary condition along the edge of the fiber mat.
Abstract: The correlation of the porosity and the permeability, based on the experimental data, for the TGFM-300 P/E random fiber mat is proposed in the present work. The edge effect is simulated by the creeping motion of the resin with permeable boundary condition along the edge of the fiber mats. Results show that the edge effect is very sensitive to the shape of the fiber mat. Numerical predictions agree with experimental results, when the fiber mat is well shaped. The edge effect is negligible as the dimension of the fiber mat is slightly larger than that of the mold cavity. The present paper combines the body-fitted FDM and the FEM to deduce an auto-meshed and auto-node-element relating numerical scheme. This scheme is convenient and effective in solving the moving boundary problems with irregularly geometric boundaries, such as the filling process of RTM. The difference between the elliptic type body-fitted FDM and the FEM are compared and discussed in detail.
TL;DR: In this paper, the effects of levels of kenaf fiber and modified polyethylenes, as the coupling agents, on the performance of the composites have been discussed, and good correlations of the experimental data for the physico-mechanical properties were obtained.
Abstract: The mechanical properties and dimensional stability of kenaf fiber-filled recycled polyethylene (PE) composites have been evaluated at room temperature and after immersion in boiling water. The effects of levels of kenaf fiber and modified polyethylenes, as the coupling agents, on the performance of the composites have been discussed. Maleated PE offered best balance in mechanical properties and dimensional stability compared to those of chlorinated PE and chlorosulphonated PE. The variations in properties with change in concentrations of fiber and a coupling agent (i.e., chlorinated PE) have been statistically analyzed based on an empirical quadratic model. Good correlations of the experimental data for the physico-mechanical properties were obtained.
TL;DR: In this paper, the structural durability of a composite panel with a discontinuous stiffener is investigated under compressive loading induced by the gradual displacement of an end support, and it is shown that damage initiation and progression have significant effects on structural behavior under loading.
Abstract: The design of composite structures requires an evaluation of their safety and durability under service loads and possible overload conditions. This paper presents a computational tool that has been developed to examine the response of stiffened composite panels via the simulation of damage initiation, growth, accumulation, progression, and propagation to structural fracture or collapse. The structural durability of a composite panel with a discontinuous stiffener is investigated under compressive loading induced by the gradual displacement of an end support. Results indicate damage initiation and progression to have significant effects on structural behavior under loading. Utilization of an integrated computer code for structural durability assessment is demonstrated.
TL;DR: In this paper, a complete understanding of the behavior of a structural system comprising RP components necessitates the determination of material properties for these components, and material properties of interest include t...
Abstract: A complete understanding of the behavior of a structural system comprising RP components necessitates the determination of material properties for these components. Properties of interest include t...
TL;DR: A numerical analysis based on polynomial interpolation was done to fit the experimental results of the mechanical characterization of a composite made of polyester resin and short natural fiber (palma samandoca-zacate).
Abstract: A numerical analysis based on polynomial interpolation was done to fit the experimental results of the mechanical characterization of a composite made of polyester resin and short natural fiber (palma samandoca-zacate) The experimental tensile strength of the composite was compared to the one obtained from a theoretical model A correction factor, attributed to the empty spaces (voids) formed between the resin and the fibers, was necessary for fitting the experimental data The behavior of this factor as a function of the fiber volume fraction showed that a polynomial interpolation could be used to approximate this function and then predict any point over the appropriate range
TL;DR: In this article, the structural advantages offered by composites due to their inherent tailorability await realization for lack of a clear understanding of their response under transient loading, and one tool currentl...
Abstract: Many structural advantages offered by composites due to their inherent tailorability await realization for lack of a clear understanding of their response under transient loading. One tool currentl...
TL;DR: In this paper, a general strength theory based on dual kriging is proposed to model the failure behavior of composite materials, which can be used as a general and systematic tool to model effectively a great variety of failure behaviours.
Abstract: Failure behaviour of composite materials presents several characteristics which depend on the materials selected, the manufacturing process used and the state of stress or strain. An important number of strength criteria have been applied to model failure in the last two decades. Each criterion is different and can be used to fit particular experimental results. Up to now, there is no general and systematic approach to describe the failure of composite materials. In this study, a general strength theory based on dual kriging is proposed to model the failure behaviour of composite materials. The theoretical background of the method is first presented, then its application to model failure of composite materials is demonstrated on two examples: a graphite-epoxy composite and paperboard. The mathematical expression of the criterion can be obtained either through a parametric or an implicit formulation. The parametric formulation is used to predict three-dimensional failure envelopes of graphite-epoxy fabrics and paperboard. The method shows an excellent agreement with available experimental data. Different types of interpolating functions, can be used such as polynomials or trigonometric functions. The results obtained are compared with the tensor quadratic, tensor cubic and parametric criteria. The model can be improved when a nugget effect is added in the kriging equations: the interpolating function does no longer fit the data points. This approach permits incorporating the effect of measurements errors in the interpolation procedure. The intensity of the nugget effect is usually chosen to be proportional to the variance error. The uncertainty of the measurements is thus reflected on the shape of the failure envelope. Note that general tensor polynomial criteria can be derived as a limit case of this approach, and additional experimental data incorporated in the model to refine its accuracy. The proposed methodology can be used as a general and systematic tool to model effectively a great variety of failure behaviours
TL;DR: In this paper, the authors used the conventional 9-noded Lagrangian element for studying geometrically non-linear elastic transient response analysis of composite stiffened shell, and an improved version of the stiffener modelling has been used in which a stiffener can be placed anywhere inside the element.
Abstract: The paper uses the conventional 9-noded Lagrangian element for studying geometrically non-linear elastic transient response analysis of composite stiffened shell. An improved version of the stiffener modelling has been used in which a stiffener can be placed anywhere inside the element. For the first time in the literature, concentric or eccentric stiffeners has been used for composite stiffened shells for solving the problem of the paper which is not available in any existing commercial packages. Large deflection transient response analysis of composite stiffened shells has also been presented for the first time. The results of stiffened composite cylindrical shells and doubly curved shells with different boundary conditions and varius laminae orientations have been presented for eccentric stiffeners. Parametric studies considering different variables have also been carried out
TL;DR: In this article, the postbuckling behavior of stiffened composite cylindrical panels was studied analytically and experimentally, and a progressive failure analysis was implemented for the prediction of failure characteristics and post-buckling ultimate load.
Abstract: The postbuckling behavior of stiffened composite cylindrical panels was studied analytically and experimentally. Progressive failure analysis was implemented for the prediction of failure characteristics and postbuckling ultimate load. For the progressive failure analysis, the maximum stress criterion is applied to the average stress in each layer of all the finite elements. Using the same degenerated three dimensional isoparametric solid element in order to model stiffeners and the skin, the global and the local buckling of the stiffened panel can be depicted exactly. The results show the effects of stiffener location, and various stiffener heights and thickness on the postbuckling behavior of stiffened composite cylindrical panels. The postbuckling ultimate load of stringer-stiffened composite cylindrical panel is not dependent of the initial buckling load, but becomes higher as the stiffener thickness and height increase.
TL;DR: In this paper, the deformed state of knitted fabrics as the reinforcement in knitted structural composites was investigated. But the authors focused on the design of parameters that influence the mechanical properties of the knitted structures.
Abstract: The authors focused on designing the mechanical properties of knitted fabrics as reinforcement and knitted structural composites, including warp knit and weft knit. Two parts are described in this paper: one is the design of the deformed state of knitted fabric as the reinforcement in knitted structural composites; the other is the concept of design of parameters which influence the mechanical properties of knitted structural composites.
TL;DR: In this paper, a finite element code was developed which allowed an effective investigation of the transient thermoelastic analysis of composite brake disks, and coupled heat and elastic analysis was done using the finite element method differently from other previous researches.
Abstract: This paper presents a modeling analysis of transient thermoelastic behavior occurring in composite brake disks. A finite element code was developed which allowed an effective investigation of the transient thermoelastic analysis. The coupled heat and elastic analysis was done using the finite element method differently from other previous researches. The result of the finite element analysis presented the pressure distributions and the temperature distributions along the friction surfaces, and heat flux vectors for the present model. The thermoelastic state on any friction surface affected the other friction surfaces each other. Thus, the whole modeling of brake disks was necessary for accurate results. The orthotropic brake disks showed better characteristics as a brake friction material than the isotropic ones. Since the composite multiple brake disk system showed the larger contact region of the friction surfaces, the smoother heat flow through the contact interfaces took place. Therefore, the more uniform and lower temperatures and the milder pressure distributions along the friction surfaces than the isotropic multiple brake disk system was caused.
TL;DR: Inelastic Energy Curves (IEC) as discussed by the authors are introduced as a tool to facilitate interpretation of data generated by instrumented drop weight impact towers, which can map the progressive degradation of energy transfer capability between the local impact zone and the global structure.
Abstract: The elegance and paramount value of composites manifests in the ability to tailor a structure for a given task such as maximizing energy absorption in a cost and weight efficient manner. A combination of factors, including recent developments in commercially available fabric architectures and resin transfer molding techniques, have led to a resurgence of interest in several classes of low-cost fiber reinforced composites for resistance to low velocity impact. Inelastic Energy Curves (IEC) are introduced as a tool to facilitate interpretation of data generated by instrumented drop weight impact towers. A general form of IEC is presented which describes distinct regions of failure. Results are presented for four representative E-glass fabric architectures in resin transfer molded composites with impact energies varying over the range to complete puncture. Since IEC's map the progressive degradation of energy transfer capability between the local impact zone and the global structure they may have applicability in interrogating generic failure processes which are prevalent in other layered composite systems. It is generally understood that matrtix properties govern the damage initiation threshold and that fiber properties control penetration resistance ; IEC provide a means of identifying and quantifying what happens in between these two extremes.