bluuebunny/crossref_metadata_2025_split huggingface dataset:
Resin transfer molding process optimization using numerical simulation and design of experiments approach
Authors: Gou Jihua , Zhang Chuck , Liang Zhiyong , Wang Ben , Simpson James 
Published: April 2004

AbstractThe art of resin transfer molding (RTM) process optimization requires a clear understanding of how the process performance is affected by variations in some important process parameters. In this paper, maximum pressure and mold filling time of the RTM process are considered as characteristics of the process performance to evaluate the process design. The five process parameters taken into consideration are flow rate, fiber volume fraction, number of gates, gate location, and number of vents. An integrated methodology was proposed to investigate the effects of process prameters on maximum pressure and mold filling time and to find the optimum processing conditions. The method combines numerical simulation and design of experiments (DOE) approach and is applied to process design for a cylindrical composite part. Using RTM simulation, a series of numerical experiments were conducted to predict maximum pressure and mold filling time of the RTM process. A half‐fractional factorial design was conducted to identify the significant factors in the RTM process. Furthermore, the empirical models and sensitivity coefficients for maximum pressure and mold filling time were developed. Comparatively close agreements were found among the empirical approximations, numerical simulations, and actual experiments. These results were further utilized to find the optimal processing conditions for the example part.
Ionic polymer‐metal composites as multifunctional materials
Authors: Shahinpoor Mohsen , Kim Kwang J. , Leo Don J. 
Published: April 2004

AbstractThis paper presents a description and a set of experimental results on Ionic Polymer‐Metal Composites (IPMC's) as dynamic sensors, transducers, and actuators. Strips of IPMC can exhibit large dynamic deformation if placed in a time‐varying electric field of the order of 10's of volts/mm. Conversely, dynamic deformation and flexing of such ionic polymers produces dynamic electric fields that closely follow the form of the electric signal. The underlying principle of such a mechanoelectric effect in IPMC's can be explained by the linear irreversible thermodynamics in which ion and solvent transport are the fluxes and electric field and solvent pressure gradient are the forces. Important parameters include the material conductance and the solvent permeability. The dynamic sensing, transduction, and actuation responses of a strip of IPMC under an impact‐type loading is also discussed. When a cantilever strip of IPMC is flipped, a damped oscillatory electric response is produced across a pair of electrodes placed at the cantilever of the strip, which is highly repeatable with a broad frequency range above 104 Hz. Such direct mechanoelectric responses of IMPC's are related to the endo‐ionic mobility due to stresses imposed. Imposition of a finite solvent flux without allowing a current flux causes the material to create a certain conjugate electric field that can be dynamically monitored and measured. IPMC's are shown to be highly capacitive at low frequencies while they are highly resistive under high frequency excitations. IN a sending mode, IPMC strips can also sense chemical environments and humidity. These types of sensors/transducers/actuators conceivably can replace piezoresistive and piezoelectric sensors with just one sensor for broad ranges of frequencies.
Cure temperature effects on cryogenic microcracking of polymeric composite materials
Authors: Timmerman John F. , Hayes Brian S. , Seferis James C. 
Published: April 2004

AbstractA model prepreg system was used to evaluate the effect of cure temperature on microcracking in polymeric composite materials exposed to cryogenic cycling. Symmetic and unsymmetric carbon fiber/epoxy laminates were fabricated to examine the development of thermal stresses and microcracks at cryogenic temperatures. The residual strains and theoretical curvatures of the laminates were calculated from the composite properties and correlated with the microcrack density and experimentally observed curvatures. Higher cure temperatures resulted in higher stress free temperatures and residual strains in the laminates, which corresponded directly to increased levels of microcracking.
Investigation of convective heating in a polymer fiber drawing process
Authors: Reeve Hayden M. , Mescher Ann M. , Emery Ashley F. 
Published: April 2004

AbstractPolymer optical fibers are drawn from a preform rod in a manufacturing process that requires heating. A polymer preform in a tubular furnace enclosure receives energy from the furnace wall via natural convection and thermal radiation. Natural convection, in comparison to radiation, contributes a smaller fraction of the total energy required during the transient heating of the preform and also during the fiber drawing. Based on numerical predictions, natural convection and radiation contribute approximately equal heating to the preform when it is initially introduced at room temperature into a preheated furnace. As the preform temperature rises, the fraction of convective heating decreases as a result of weakening of gas‐phase circulation cell(s) between the furnace wall and preform. These findings are supported by the measured temperature histories in the interior of the preforms that, for all of the cases studied, differed by less than 1.3°C from numerical predictions. Although radiation contributes a larger fraction of the total required energy, natural convection can nevertheless have a strong and detrimental effect on the fiber quality. Specifically, convective instabilities caused air temperature oscillations of 0.3 to 2°C with frequencies from 0.01 to 0.30 Hz. Experimental observations show that these gas phase temperature oscillations promote unwanted diameter variations during fiber drawing.
Wetting of a fiber bundle in fibrous structures
Authors: Lukas David , Pan Ning 
Published: April 2004

AbstractIn this paper we dealt with the problem of wetting and ascending of a liquid along a fiber bundle. Two issues are first addressed including the criterion for complete wetting of the fiber bundle and the ascension liquid profile on a partially dipped vertical fiber bundle. Both topics are studied theoretically by deriving a mathematical theory by which predictions are generated and important parametric analyses are carried out. Further, a 3D Ising model is used for computer modeling to simulate the fiber wetting and liquid ascending processes on a partially dipped single fiber. The significance and potential applications of the study are also summarized.
All‐plant fiber composites. II: Water absorption behavior and biodegradability of unidirectional sisal fiber reinforced benzylated wood
Authors: Lu Xun , Zhang Ming Qiu , Rong Min Zhi , Shi Guang , Yang Gui Cheng 
Published: April 2004

AbstractSisal fiber reinforced benzylated fir sawdust composites belong to a new category of composite materials, in which both the reinforcement and matrix are based on plant fibers, i.e. renewable resources. The present paper discusses the water absorption behavior of the composites and its influence on the mechanical properties of the composites. In addition, biodegradability of the composites is assessed by using enzyme and fungi tests, respectively. The experimental results indicate that water absorption behavior of the composites is mainly controlled by the reinforcing fiber and the fiber/matrix interfacial characteristics. The inherent biodegradability of the raw materials of the all‐plant fiber composites proves to be retained. During the tests of enzymolysis and biodeterioration in soil, damage of the composites was initiated either inside the sisal fiber or at the surface of the composites.
Application of digital speckle photography to measure thickness variations in the vacuum infusion process
Authors: Andersson H. M. , Lundström T. S. , Gebart B. R. , Synnergren P. 
Published: April 2004

AbstractA new method to measure the movement of the flexible bag used in vacuum infusion is presented. The method is based on an in‐house developed stereoscopic digital speckle photography system (DSP). The advantage with this optical method, which is based on cross‐correlation, is that the deflection of a large area can be continuously measured with a great accuracy (down to 10 μm). The method is at this stage most suited for research but can in the long run also be adopted in production control and optimization. By use of the method it was confirmed that a ditch is formed at the resin flow front and that there can be a considerable and seemingly perpetual compaction after complete filling. The existence of the ditch demonstrates that the stiffness of the reinforcement can be considerably reduced when it is wetted. Hence, the maximum fiber volume fraction can be larger than predicted from dry measurements of preform elasticity. It is likely that the overall thickness reduction after complete filling emanates from lubrication of the fibers combined with an outflow of the resin. Besides, the cross‐linking starts and the polymer shrinks. Hence, the alteration in height will continue until complete cross‐linking is reached.
Effect of high‐energy vibro‐milling of filler on the mechanical properties of filled high‐density polyethylene
Authors: Guo Shaoyun , Wu Hong , Chen Guangshun , Chen Xiangrong 
Published: April 2004

AbstractThe effect of high‐energy mechanical milling of CaCO3 (calcium carbonate) and STC (a mixture of sericite, tridymite and cristobalite) on mechanical properties, rheological and dynamical mechanical behavior of high‐density polyethylene (HDPE)/CaCO3 and HDPE/STC was studied through SEM (scanning electron microscope), DMTA (dynastic mechanical test analysis), mechanical and melt rheological properties tests. The experimental results show that addition of fillers treated by coupling agent and vibromilling to HDPE makes the impact strength of HDPE greatly increased. The impact strength of HDPE/treated CaCO3 (60/40) and HDPE/treated STC (60/40) is ca. 4 and 3 times respectively as high as that of HDPE. The SEM micrographs of impact fractured surfaces of treated fillers filled HDPE show extensive plastic deformation of HDPE matrix, indicating that the plastic deformation of matrix induced by the treated fillers is the main contribution for absorbing a great amount of impact energy. This is the reason why the impact strength of HDPE greatly increases with addition of coupling agent and vibromilling treated fillers. The intensity of γ relaxation peak of HDPE in HDPE/treated CaCO3 on tanδ vs. temperature curve increases and the peak shifts to higher temperature due to its stronger interface interaction as compared with that of HDPE/untreated CaCO3.
Low‐velocity impacts in continuous glass fiber/polypropylene composites
Authors: Trudel‐Boucher David , Bureau Martin N. , Denault Johanne , Fisa Bo 
Published: April 2004

AbstractThe low‐velocity impact behavior of a continuous glass fiber/polypropylene composite was investigated. Optical microscopy and ultrasonic scanning were used to determine the impact‐induced damage. At low impact energy, the predominant damage mechanism observed was matrix cracking, while at high energy the damage mechanisms observed were delamination, plastic deformation, which produced a residual specimen curvature, and a small amount of fiber breakage at the edge of the indentation on the impacted face of the specimens. The impact load vs. time signals were recorded during impact and showed that the load corresponding to the onset of delamination was independent of the impact energy in the range tested. The load at which the onset of delamination occurred corresponded to the values obtained by performing a linear regression of the delaminated area, obtained by ultrasonic scanning, as a function of the impact force. Tensile and flexural tests performed on impacted specimens showed that the tensile and flexural residual strengths and the flexural modulus decreased with increasing incident impact energy, while the post‐impact residual tensile modulus remained constant. The dynamic interlaminar fracture toughness was evaluated from the critical dynamic (impact) strain energy release rate of specimens with a delamination simulated by an embedded insert. The results are compared with the interlaminar fracture toughness values obtained during subcritical steady crack growth.
Structure and properties of amorphous polyamide/liquid crystalline polyester blends
Authors: García M. , Eguizábal J. I. , Nazábal J. 
Published: April 2004

AbstractAmorphous polyamide (AP)/liquid crystalline polyester (VA) blends were obtained by extrusion‐injection molding (EI) throughout the whole composition range. The phase behavior, chemical nature and morphology of the blends were studied, and the mechanical properties discussed and compared with those of the 10 and 30% VA blends obtained by direct injection molding (DI). The blends showed two almost pure slightly reacted amorphous phases. The apparently higher reaction level of the EI blends, although small, led to a more homogeneous, fine and fibrillated morphology, attributed to a lower interfacial tension. Significant synergisms in the modulus of elasticity (up to 25%) and in the tensile strength (up to 40%) were seen in EI blends. The similar values of both specific volume and orientation in the blends and in the pure components suggest that the contribution to the modulus of the dispersed VA rigid particles is greater than that due to the proportion of VA in the blend. The 10% VA DI blend showed a similar behavior in these two properties, indicating that the DI procedure is preferred, provided that only stress‐related properties are sought. At 30% VA content, the moduli of elasticity were similar by the two molding processes, but the clearly lower tensile strength and lower ductility of the easier DI procedure, means that the more complex, but more effective, EI procedure is the one of choice for high performance materials.
Mechanical property improvement of carbon fiber reinforced polybenzoxazine by rubber interlayer
Authors: Ishida Hatsuo , Chaisuwan Thanyalak 
Published: April 2004

AbstractThe rubber interlayer method was chosen in order to improve the properties of carbon fiber‐reinforced polybenzoxazine composites. The resin used is benzoxazine based on bisphenol‐A, formaldehyde and 3,5‐xylidine. The effect of rubber concentration on the flexural properties of the composites is investigated. Sized and desized carbon fiber woven fabrics are used to study the effect of the sizing materials on the mechanical properties. The delamination toughness of the composites is increased by the ATBN rubber interlayer with increasing ATBN concentration. The strength of the composite also increased, but an anomalous concentration effect has been observed.
Predicting molding forces during sheet molding compounds (SMC) compression molding. II: Effect of SMC composition
Authors: Boylan Sarah , Abrams Lisa M. , Castro Jose M. 
Published: April 2004

AbstractOne of the fastest‐growing applications of SMC compression molding is the manufacture of truck body panels. Because of their large size, the molding forces required are substantial and have a major influence on the molding cycle. Also, as SMC moves towards parts requiring higher strength, the fiber length and percentage by weight of fibers must increase. This will also contribute to larger molding forces. In this paper, a procedure is presented to evaluate the SMC rheological parameters needed to predict molding forces. In addition, the effect of SMC composition on the molding forces is investigated. In particular, we evaluate the effect of reinforcement type (glass versus carbon) and level, filler level and thickener level. It was found that the factors most affecting molding forces are the reinforcement length and level; and the filler level. In addition, it was discovered that for SMC thickened with magnesium oxide, the level of thickener does not affect the molding force.
Injection molding of glass fiber reinforced phenolic composites. 2: Study of the injection molding process
Authors: Singh R. , Chen F. , Jones F. R. 
Published: April 2004

AbstractThis study of injection molding of glass fiber reinforced phenolic molding compounds examines fiber breakage and fiber orientation with key material and processing variables, such as injection speed, fiber volume fraction, and the extent of resin pre‐cure. The fiber orientation, forming discrete skin‐core arrangements, is related to the divergent gate to mold geometrical transition, the extent of pre‐cure and injection speed functions of the melt viscosity. Transient modifications to the melt viscosity during mold filling produce variations in skin/core structure along the flow path, which are correlated to the mechanical properties of injection moldings. The melting characteristics of the phenolic resin during plasticization impose a severe environment of mechanical attrition on the glass fibers, which is sequentially monitored along the screw, and during subsequent flow through runners and gates of various sizes. Differences found between the processing characteristics of thermosets and thermoplastics raise questions concerning the applicability of thermoplastic injection molding concepts for thermosets.
Effect of CaCO3 on the mechanical and rheological properties of a ring‐opening phenolic resin: Polybenzoxazine
Authors: Suprapakorn Nimolrat , Dhamrongvaraporn Sujitra , Ishida Hatsuo 
Published: April 2004

AbstractTensile, flexural, and impact behaviors of CaCO3‐filled polybenzoxazine are studied in the 0–30 wt% filler content range. This work also investigates the role of the particle size of the filler and the effect of the interface on these properties. Dynamic mechanical measurement has been carried out to support the static mechanical testing. Moreover, the viscosity of neat benzoxazine monomer and the monomer with 18% oligomer has been measured to compare against the viscosity of a novolac resin.
Ionic interphase of glass fiber/polyamide 6,6 composites
Authors: Salehi‐Mobarakeh Hamid , Brisson Josée , Ait‐Kadi Abdellatif 
Published: April 2004

AbstractInterfacial polymerization to polyamide 6, 6 followed by introduction of ionic groups was performed on the surface of short glass fibers. The ionic interphase‐modified fibers were used with poly(ethylene‐co‐methacrylic acid) (DuPont Surlyn) to prepare composites with specific fiber‐matrix interactions. Fiber treatment increased composite tensile and bending properties. An increase in the average fiber length was observed, which was attributed to a decrease in the fiber attrition during mixing. The effect of increasing temperature on the composite mechanical properties was studied. Different behavior was observed before and after the glass transition temperature, Tg, of the matrix. The dynamic mechanical measurements showed an increase in the Tg of the matrix after the treatments, which is attributed to a decrease in chain mobility at the interface resulting from increased interactions of the treated fiber surface with the polymer. Scanning electron microscopy of fractured composites after tensile tests revealed a smooth fiber surface with no polymer at the surface for the untreated composites. Adhered polymer was clearly observed on the surface of treated fibers, indicating better fiber wetting by the matrix. This improved adhesion was attributed to the grafted nylon molecules at the glass fiber surface.
Manufacturing of all‐thermoplastic sandwich systems by a one‐step forming technique
Authors: Breuer U. , Ostgathe M. , Neitzel M. 
Published: April 2004

AbstractThermoplastic sandwich composite systems offer great potential for future automotive applications. High specific bending stiffness, good insulation properties, high specific energy absorption and impact resistance can be achieved by the use of fabric reinforced sheets as sandwich faces and thermoplastic foam as core material. Recycling is possible by chopping and injection molding. Fabric‐reinforced thermoplastic sheets consisting of 10 layers glass fabric were impregnated continuously with a polyamide‐12 matrix using isobaric double belt press technique to 2‐mm‐thick faces with a fiber content of 50 vol%. Sandwich angles and hemispheres were manufactured by heating the faces and the 13‐mm‐thick foam core above the melting temperature and high‐speed stamp forming with matched metal tools. Cycle times for forming and cooling were below 40 s/part. Different heating methods were matter of investigation. Best results could be achieved by conductive heating. This new material system and its processing technology are promising methods to reduce structural car weight and enhance passenger safety.
Modeling of heat transfer and crystallization kinetics in thermoplastic composites manufacturing: Pultrusion
Authors: Carlsson Andreas , Åström B. Tomas 
Published: April 2004

AbstractWhereas pultrusion with thermoset resins has been widely analyzed, there is a scarcity of knowledge about pultrusion with thermoplastic resins. The aims of this work were to strive towards deeper knowledge of temperature distribution and degree of crystallinity in the composite during processing, to develop a tool for process simulations with a variety of processing parameters, and to provide input data to models for pressure and matrix flow. The heat transfer model presented herein describes the temperature distribution within the composite throughout the thermoplastic pultrusion process. The transient heat transfer situation is modeled one‐dimensionally through a transverse cross section far from the edges of a high aspect ratio composite. Temperature‐dependent thermal properties, partly non‐infinite contact conductance, and heat contribution from crystallization were taken into consideration. The degree of crystallinity within the composite was determined as well. The analysis also includes an experimental verification of the heat transfer model. Results show good agreement with experimental data.
The effect of long‐term ultraviolet light irradiation on polymer matrix composites
Authors: Liau W. B. , Tseng F. P. 
Published: April 2004

AbstractThis study reports the individual and combined effects of ultraviolet light and thermal shock on the physical properties of polymer matrix composites in air and in a “near‐vacuum system.” The longest exposure time was 180 days. It was found that the weight loss of composites increased with irradiation time. In the graphite/epoxy system, the weight loss in air was 2–3 times that in a “near‐vacuum system.” Similarly, the weight loss of the glass/epoxy system in air was 3–6 times that in a “near‐vacuum system.” The weight loss of the glass/epoxy system was always larger than that of the graphite/epoxy system. In all cases, the UV irradiation and 1000 times thermal shock did not change the fracture mechanism—it was always brittle fracture in addition to fiber pullout. Surface erosion was observed in the irradiated surfaces by scanning electron microscopy. For both graphite/epoxy and glass/epoxy composites, the tensile strength decreased with increasing irradiation time irrespective of the irradiation environment. However, the decrease was not significant. By SEM, cracks could be observed in the up‐surface and side‐surface of the glass/epoxy system that was irradiated more than 1 month in air and through 1000 times thermal shock. Obviously, UV light cannot deeply penetrate the sample, and only the surface of the sample will be influenced. The UV radiation initiated microcracks, which propagated through the thermal shock.