bluuebunny/crossref_metadata_2025_split huggingface dataset:
Toughening of carbon fiber/thermoset composite by the morphology spectrum concept
Authors: Kim Yu‐Seung , Kim Sung‐Chul 
Published: April 2004

AbstractMorphology spectrum toughening, a novel technique for toughening brittle carbon fiber/thermoset composites, was applied to a polyetherimide‐modified carbon fiber/dicyanate composite. Composites were prepared by inserting a polyetherimide film between the prepregs of carbon fabric impregnated by dicyanate alone, and by controlling both the relative rates of dissolution of the polyetherimide and the polymerization of the dicyanate by adding zinc stearate catalyst. A composite with 13 wt% polyetherimide afforded a mode I interlaminar fracture toughness of 1.4 kJ/m2, almost 1.8 times higher than that of a control composite containing same composition of polyetherimide. Two effects were observed. First, a thermoplastic continuous morphology formed in the center interply zone, where the concentration of polyetherimide was high, provided good fracture toughness. Second, a thermosetting continuous morphology formed in the fiber‐rich zone, where the concentration of polyetherimide was low, maintained good interfacial shear strength between the fiber and the matrix.
Investigation of the role of transverse flow in co‐injection resin transfer molding
Authors: Gillio Emanuele F. , Advani Suresh G. , Gillespie John W. , Fink Bruce K. 
Published: April 2004

AbstractA co‐injection resin transfer molding (CIRTM) process has been developed at the University of Delaware's Center for Composite Materials in collaboration with the U.S. Army Research Laboratory. It enables two or more resins to be simultaneously injected into a mold filled with a stationary fiber preform. This process allows for the manufacturing of co‐cured multi‐layer, multi‐resin structures in a single processing step. A separation layer is used to provide resin compatibility during cure and to control resin mixing. Scaling issues relating the role of transverse permeability in resin mixing are investigated. This study presents two different approaches taken to understand the causes of transverse flow and to quantify the amount of transverse flow that occurs during processing. The first approach, a one‐dimensional model, explains the important parameters that govern resin flow in CIRTM. The second approach is based on an existing finite element code that is modified to allow for the injection of multiple resins. The total amount of transverse flow was quantified using the finite element code. This research shows that the CIRTM process requires a totally impermeable separation layer if CIRTM is used to manufacture large parts and/or if the resins injected have significantly different viscosities.
An a priori grid permutation for isothermal flow models
Authors: Freese Colin E. , Walsh Shawn M. 
Published: April 2004

AbstractMesh permutations are used to enhance the computational efficiency of an implicit finite element based scheme for modeling isothermal incompressible viscous flow through a permeable medium. A new software implementation of the implicit algorithm permits a realization of these potential savings and is discussed in some detail. The efficiency of the modeling application is shown to be particularly sensitive to the ordering of the grid nodes. An a priori arrangement of nodes approximating the order of their activation (fill) during the actual simulation is indicated. A new ordering procedure is proposed to achieve this task. The algorithm utilizes both geometric relationships and modeling parameters and demonstrates predictive capabilities analogous to the actual flow simulation while requiring a fraction of the computational resources. Examples are used to verify and quantify the efficiency projections and to investigate the apparent contradictory objectives of the proposed grid permutation with those of the more familiar profile or bandwith minimization procedures.
Product design with glass fiber reinforced polymer blends, with potential applications in recycling
Authors: Xanthos M. , Narh K. A. 
Published: April 2004

AbstractThis paper addresses the issue of compositional variation in multiphase, multi‐component polymer mixtures equivalent to those found in commingled waste streams, such as those obtained from reclamation/recycling operations of post‐consumer containers. By using virgin resins, the effects of variations in the composition of matrices containing high density polyethylene (HDPE) as the major phase on the properties of composites containing varying amounts of glass fiber and different adhesion promoters are studied. The results obtained on injection molded thin‐section parts indicate that it is possible, through the addition of glass fibers and in the presence of suitable adhesion promoters, to obtain enhanced and reproducible properties with relatively little dependence on matrix composition. Preliminary structural and flow analyses were performed with commercial software on different types of plastic parts that could be eventually molded from actual mixed waste plastics suitably modified through glass reinforcement. Experimentally generated rheological and mechanical property data on HDPE based blends containing 20 wt% glass fibers and different adhesion promoters were used for the simulation. Issues concerned with injection molding and product performance of glass‐fiber reinforced blends are discussed.
Effects of rate and temperature on fracture behavior of TPX (poly‐4‐methyl‐1‐pentene) polymer
Authors: Ye Lin , Yuan Chao‐Ting , Mai Yiu‐Wing 
Published: April 2004

AbstractThe fracture behavior of TPX (poly‐4‐methyl‐1‐pentene) polymer was studied using compact tension (CT) and single‐edge‐notch bending (SENB) specimens. Effects of crosshead rate and environmental temperature (−40°C to 160°C) on fracture behavior were investigated. Fractographic analyses were conducted after fracture tests using scanning electron microscopy (SEM). The results showed that the fracture behavior of the TPX polymer was highly dependent on crosshead rate and temperature. Unstable‐stable transition of crack growth and stiky‐slip behavior were observed for both low and high crosshead rates when the environmental temperature was increased.
Injectin molding of short fiber reinforced thermoplastics in a center‐gated mold
Authors: Larsen Å. 
Published: April 2004

AbstractWe have studied injection molding of a rectangular box using short fiber reinforced polypropylene. The fiber orientation distribution and the local stiffness properties in radial and transverse directions have been measured in the bottom plane. The deduced orientation tensors are compared with predictions of a commercial computer code. Discrepancies are related to approximations made in the calculations and effects not accounted for by the present modeling approach. In the calculations the fiber interaction coefficient was varied seeking to fit experiments. We comment on the out‐of‐plane components of the orientation tensor, the relative thickness of skin and core layers, and the radial dependence of the fiber orientation in each layer. Values of the components of the 4th‐order orientation tensor calculated from the measured orientation distribution are used to compare different closure approximations referred in the literature. Anisotropy in the stiffness properties, calculated form the measured fiber orientation, agree well with measurements.
Structure and mechanical properties of fast cooled and annealed poly(phenylene sulfide)/Vectra A blends
Authors: Ruiz De Gauna B. E. , Gaztelumendi M. , Nazábal J. 
Published: April 2004

AbstractPoly(phenylene sulfide) (PPS)/Vectra A blends were directly injection molded and obtained throughout the composition range both as molded, low crystallinity, and annealed highly crystalline materials. The blends were immiscible, but, contrary to an earlier work on PPS/Vectra A blends, they showed a clear fibrous morphology that was a consequence of the higher viscosity of the matrix compared with that of the Vectra A at the shear strain rate used. The mechanical properties of the annealed blends showed that when highly crystalline materials are sought, annealing post‐cold molding is a valid alternative to molding at high mold temperatures. The fracture properties of the as‐molded blends, such as ductility and tensile strength, were higher than in annealed blends, as a consequence of the higher deformability of the less crystalline structure. The presence of the LCP in the as‐molded low‐crystallinity PPS blends counteracts their intrinsic lower stiffness by means of a faster stiffness increase when Vectra A was added, compared with that which took place in annealed blends. These facts rendered the as‐molded PPS/Vectra A blends alternative materials to the usual highly crystalline ones.
Processing conditions and compatibilizing effects on reinforcement of polypropylene‐liquid crystalline polymer blends
Authors: Farasoglou P. , Kontou E. , Spathis G. , Gomez Ribelles J. L. , Gallego Ferrer G. 
Published: April 2004

AbstractThe effect of the processing conditions in respect to the presence of maleic anhydride‐grafted polypropylene on the thermomechanical properties of two series of polyropylene‐liquid crystalline polymer blends has been studied. Two types of Liquid Crystalline Polymers (LCPs) which were copolyesters, namely Vectra A and Vectra B have been used. A systematic study of processing conditions such as die temperature, speed of mixing, and speed of elongation, as well as the presence of compatibilizer, has been made. The blends were tested in terms of tensile experiments and dynamic mechanical analysis. The experimental data were connected with interesting remarks about the morphology of the materials, and this analysis has been supported with Scanning Electron Microscopy (SEM) micrographs.
Pulling tension monitoring during the melt impregnation of glass roving
Authors: Bates P. J. , Charrier J. M. 
Published: April 2004

AbstractThe force required to pull a 2400 tex glass roving through a melt impregnation compounding process was studied. Pulling force was continuously measured by suspending the double belt puller in a sling held stationary by a force transducer. Process variables such as roving pulling speed, number of cylindrical pins, pin diameter, and melt temperature were studied using polymide 66 and polypropylene polymers. The results suggest that the tension build‐up in the roving is caused by a combination of two effects: viscous shear stresses in a thin polymer‐rich layer between the roving and the pin, as well as frictional forces caused by roving contact with the pin. A simple mathematical model is developed and used to adequately describe the experimental results.
A machine system for the rapid production of composite structures
Authors: Brown Jessica H. , Colton Jonathan S. 
Published: April 2004

AbstractA rapid manufacturing process for thermosetting materials was developed to produce composite structures in a manner similar to rapid prototyping. The machine system builds the part layer by layer with continuous curing and consolidation, making traditional curing methods unnecessary. Each part layer, which has been prestaged to provide a desired degree of cure, moves under a heat gun and a roller for curing and consolidation. The heat gun initiates the cure in the part layer, partially curing it and making it tacky enough for the next layer to stick to it when it goes through the consolidation process. The cure continues to advance as each layer is placed. Testing was performed by fabricating three‐layer parts and performing tests on single strips of towpreg to determine how temperature and time affect the degree of cure. The material was IM7 carbon fiber/977‐3 epoxy towpreg, prestaged in a tunnel oven to an approximate 30% degree of cure. Hot air temperatures of 150 – 380°C (302 – 716°F), roller forces of 236 – 472 N (53 – 106 Ibf), table speeds of 13 – 38 mm/sec (0.5 – 1.5 in/sec), and times of exposure to hot air of 5, 10, and 20 seconds were used. The results showed that the machine system can continuously cure and consolidate parts. The cure was advanced to any level up to 100% degree of cure with an air temperature of 380°C. Parts were produced with layers well stuck together. Within the limitations of the experiments, temperature was determined to be the most significant factor affecting degree of cure. With the correct processing conditions, the machine system has the capability to produce well‐consolidated, high quality parts without using traditional curing methods. The design of the machine system allows for the addition of components for the fabrication of arbitrarily shaped parts and for different curing methods.
Experimental analysis and numerical modeling of flow channel effects in resin transfer molding
Authors: Bickerton S. , Advani S. G. , Mohan R. V. , Shires D. R. 
Published: April 2004

AbstractComposite manufacturing by Liquid Composite Molding (LCM) processes such as Resin Transfer Molding involve the impregnation of a net‐shape fiber reinforcing perform a mold cavity by a polymeric resin. The success of the process and part manufacture depends on the complete impregnation of the dry fiber preform. Race tracking refers to the common phenomenon occurring near corners, bends, airgaps and other geometrical complexities involving sharp curvatures within a mold cavity creating fiber free and highly porous regions. These regions provide paths of low flow resistance to the resin filling the mold, and may drastically affect flow front advancement, injection and mold pressures. While racetracking has traditionally been viewed as an unwanted effect, pre‐determined racetracking due to flow channels can be used to enhance the mold filling process. Advantages obtained through controlled use of racetracking include, reduction of injection and mold pressures required to fill a mold, for constant flow rate injection, or shorter mold filling times for constant pressure injection. Flow channels may also allow for the resin to be channeled to areas of the mold that need to be filled early in the process. Modeling and integration of the flow channel effects in the available LCM flow simulations based on Darcian flow equations require the determination of equivalent permeabilities to define the resistance to flow through well‐defined flow channels. These permeabilities can then be applied directly within existing LCM flow simulations. The present work experimentally investigates mold filling during resin transfer molding in the presence of flow channels within a simple mold configuration. Experimental flow frot and pressure data measurements are employed to experimentally validate and demonstrate the positive effect of flow channels. Transient flow progression and pressure data obtained during the experiments are employed to investigate and validate the analytical predictions of equivalent permeability for a rectangular flow channel. Both experimental data and numerical simulations are presented to validate and characterize the equivalent permeability model and approach, while demonstrating the role of flow channels in reducing the injection and mold pressures and redistributing the flow.
Effect of stacking sequence on the compressive performance of impacted aramid fiber/glass fiber hybrid composite
Authors: Park Rohchoon , Jang Jyongsik 
Published: April 2004

AbstractAramid fiber/glass fiber hybrid composites were prepared to examine the compressive performance of impacted composites. The effect of stacking sequence and surface treatment on compression after impact (CAI) performance of three‐layer hybrid composites was investigated with respect to delamination area. As the impact velocity increased, the laminates exhibited a significant reduction of compressive strength owing to larger delamination area within laminate. The surface treatment aramid fiber reduced the delamination area and enhanced the resistance to buckling. The strength reduction of laminate AAA was considerable because of wide delaminated region, whereas the residual strength of laminate GGG was not affected by impact energy because the laminate absorbed most of impact energy through formation of fiber cracks rather than delamination. Considering stacking sequence, the laminate GAG and GAA exhibited an energy threshold due to insensitivity to impact damage. As a result, the residual performance of composite was primarily dominated by delamination extent rather than fiber cracks.
Modeling compression molding of all‐thermoplastic honeycomb core sandwich components. Part A: Model development
Authors: åkermo Malin , Tomas åström B. 
Published: April 2004

AbstractThe compression molding process is studied with the aim of modeling the instantaneous degree of face‐core bonding in all‐thermoplastic sandwich components during molding. The theory of bonding is briefly discussed and it is concluded that for most thermoplastic materials, processing is performed at temperatures where full bond strength is seemingly immmediately established at positions in full face core contact. A two‐dimensional model is developed to predict increase in contact area due to flow of melted core material during molding. Further, heat transfer during processing is modeled in order to determine the extent of melted core material. The two models are coupled into one process model and a numerical example is presented illustrating the predicted behavior of polypropylene‐based sandwich components in compresion molding. The process model suggests that the face‐core bond strength may be significantly increased through flow of the melted core wall.
Compression after impact (CAI) strength of concrete cylinders reinforced by non‐adhesive filament wound composites
Authors: Tai Nyan‐Hwa , Liu Hsien‐Kuang , Chen Zhi‐Cheng 
Published: April 2004

AbstractConcrete cylinders reinforced by filament wound composites were fabricated, and the compressive strength of the composite/concrete cylinders was tested after low‐energy impact. In this study, a glass fiber woven cloth wrapping method and a filament winding technique were adopted to wrap the concrete cylinder. In order to investigate the influence of composite/concrete interfacial bonding on the compression after impact (CAI) strength, aluminum foil was introduced into the composite/concrete interface; thus, the compressive behavior of the composite/concrete system with or without inserting the aluminum foil was compared. The effects of aluminum foil in the curing process were also revealed. Based upon the results of this study, the placement of aluminum foil can significantly enhance the compressive strength of the composite/concrete cylinder. The CAI strength depicts that the winding angle used in the filament winding process can significantly influence the reinforcing effects. Among the tested cylinders, the FWIC (defined in the text) [902/±60/902] cylinder shows the highest CAI strength—129.4 MPa—which is 4.5 times higher than the impacted concrete cylinder and 4.1 times higher than the pure concrete cylinder. Fracture mode was also investigated on the cylinder reinforced by the composites wound with different winding angles. The placement of aluminum foil reduces shear stress transfer across the composite/concrete interface, which affects not only the impact response but also the compressive strength.
Carbon fiber reinforced phenolic Resin/Silica ceramer composites—processing, mechanical and thermal properties
Authors: Lin Jia‐Min , Ma Chen‐Chi M. , Tai Nyan‐Hwa , Chang Wen‐Chi , Tsai Chuan‐Chung 
Published: April 2004

AbstractPhenolic/silica ceramers were prepared by the sol‐gel method. Carbon fiber reinforced phenolic/silica ceramer composites with high thermal resistance were fabricated. Tetraethyl orthosilicate (TEOS) was used as a monomer for sol‐gel system. Different ratios of the sol‐gel solutoins and phenolic resins were adopted and the resulting ceramers were used as matrices for carbon fiber reinforced composites. The mechanical and thermal properties of the fabricated composites were studied. The results show that the incorporation of inorganic ingredients into the phenolic resins will increase the thermal resistance of the fabricated composites but not affect the flexural strength of the carbon fiber reinforced phenolic/silica ceramer composites up to 60 wt%. The morphologies of the ceramer matrices were examined by SEM. SiO2 particles from at the gaps between fibers for higher inorganic contents.
Impact behavior of a short glass fiber reinforced thermoplastic polyurethane
Authors: Jancar J. 
Published: April 2004

AbstractThe temperature dependence of critical strain energy release rate (Gc′) and standardized Charpy notched impact strength (CNIS) were measured for a thermoplastic polyurethane (TPUR) reinforced with 30 wt% of short glass fibers (SGF) over a temperature interval ranging from −150°C 23°C (RT) at two strain rates, 70 and 150 s−1, respectively. Fractographic observation of fracture planes was used to qualitatively assess the fracture modes and mechanisms. Adhesion between the reinforcement and the matrix was excellent and the integrity of the fiber‐matrix interfacial contact was relatively insensitive to exposure to hydrolysis during the immersion in boiling water for 100 hours. At temperatures above −30°C, there was a large extent of plastic deformation in the vicinity of crack planes while at temperatures below −50°C, the extent of plastic deformation was substantially reduced. This resulted in a change in the major energy dissipation mechanism and led to a decrease of both CNIS and Gc′ values for SGF/TPUR composites. It was suggested that the plastic deformation of TPUR matrix in the immediate vicinity of glass fibers was the primary source of energy dissipation at temperatures above −30°C, while the friction and fiber pull‐out was the main dissipative process below −50°C. Over the whole temperature interval investigated, greater Gc′ values were obtained at higher strain rate of 150 s−1, without any significant change in the fractographic patterns observed on the fracture planes. The CNIS/Gc′ ratio, used to assess suitability of CNIS for comparison of materials, changed with temperature substantially suggesting that the functional dependences of CNIS and Gc′ on temperature differ substantially. Hence, CNIS data do not provide a reliable base for material selection and for design purposes in this case.
Interfacial stress transfer in nylon‐6/E‐Glass microcomposites: Effect of temperature and strain rate
Authors: Pegoretti Alessandro , Fambri Luca , Migliaresi Claudio 
Published: April 2004

AbstractIn this study, the interfacial properties between E‐glass fibers with different commercial sizings have been investigated on model composites with a nylon‐6 matrix. In particular, the fiber critical length was measured by means of the single‐fiber fragmentation test over a wide range of temperatures (from 25 to 175°C) and strain rates (from 0.0008 to 4 min−1). The general trend observed is that the fiber critical aspect ratio increases as the temperature increases and it decreases as strain rate is increased. The fiber critical aspect ratio for unsized fibers resulted to be reasonably well linearly related to the square root of the fiber to matrix modulus ratio. This results is in accordance with the Cox's shear‐lag theoretical model and the Termonia's numerical simulations. Sized fibers display an higher deviation from the theoretical prevision probably because of the presence of interphases whose properties are different from the bulk matrix. As a consequence, the interfacial shear strength values resulted to be dependent on the fiber sizing. In particular, the fibers coated with an epoxy sizing showed a superior thermal stability of the fiber matrix‐interface with respect to the unsized or nylon compatible sized fibers.