bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of initiation value of mode I interlaminar fracture toughness of unidirectional polymer composites
Authors: He Tianbai , Zhou Jiang , Liu Weilian 
Published: May 2005

AbstractThe use of interlaminar fracture tests to measure the delamination resistance of unidirectional composite laminates is now widespread. However, because of the frequent occurrence of fiber bridging and multiple cracking during the tests, it leads to artificially high values of delamination resistance, which will not represent the behavior of the laminates. Initiation fracture from the crack starter, on the other hand, does not involve bridging, and should be more representative of the delamination resistance of the composite laminates. Since there is some uncertainty involved in determining the initiation value of delamination resistance in mode I tests in the literature, a power law of the formGIC=A· Δab(whereGICis mode I interlaminar fracture toughness and Δais delamination growth) is presented in this paper to determine initiation value of mode I interlaminar fracture toughness. It is found that initiation values of the mode I interlaminar fracture toughness.GICini, can be defined as theGICvalue at which 1 mm of delamination from the crack starter has occurred. Examples of initiation values determined by this method are given for both carbon fiber reinforced thermoplastic and thermosetting polymers.
Mechnical properties of thermoplastic film/metallic glass composites with improved interfacial strength
Authors: Sidhu A. S. , Varin R. A. 
Published: May 2005

AbstractThe mechanical properties of the uniaxial and continuous composite with high strain to fracture PP matrix reinforced with the Fe40Ni40B20 (at%) and Metglas 2605SC metallic glass ribbons have been determined and compared with the rule of mixtures. The reinforcing ribbons were coated with PVA (polyvinlyl alcohol) to improve interfacial bonding. The experimental fracture strength results for both types of reinforcement deviate from the values predicted. The strength of composite at the fracture strain of ribbon determined experimentally obeys a modified rule of mixture (isostrain condition) for both types of reinforcement over the entire volume fraction range of reinforcement (up to 16%). The experimental composite eleastic modulus results for composite reinforced with relatively narrow Fe40Ni40B20 ribbons are found to be generally near the values predicted by the rule of mixtures, but for the Metglas 2605SC wide the modified rule of mixtures, which takes into account the thermally induced tensile stresses at the interface resulting from the mismatch of the coefficients of thermal expansion.
Microstructure‐based processing parameters of thermoplastic composite materials. Part I: Theoretical models
Authors: Yang Heechun , Colton Jonathan S. 
Published: May 2005

AbstractProcessing parameters for composites are predicted by new models which are based on the microstructure of the composite. Three types of termoplastic prepregs are considered, ICI tape, BASE commingled two, and CCMI powder coated tow. The permeability of the composites depends on their fiber distribution. The elastic behavior of the fiber network compression depends on the fiber oreientation. These two are integrated to predict the processing parameters.
Prediction of mechanical properties of short kevlar fiber‐nylon‐6,6 composites
Authors: Yu Z. , Brisson J. , Ait‐Kadi A. 
Published: May 2005

AbstractInjection molded short Kevlar (DuPont) fiber/nylon‐6,6 composites have been studied. Fiber length and length distribution were measured as a function of processing variables. Critical fiber length was measured by an embedded single‐fiber method. Tensile modulus of the molded composites was predicted by an adapted classical lamination analogy. Fiber and matrix orientation factors, derived from X‐ray diffraction, were introduced to modify Kelly Tyson equation to estimate the composite tensile strength. It has been found that fiber length is dramatically shortened by the injection molding process, and is affected by processing conditions. Predictions gave reasonable agreement with data for tensile modulus and strength.
Simulation of the fracture behavior of elastomeric composites: Mechanical interactions at material interfaces
Authors: Khan M. B. , Briscoe B. J. 
Published: May 2005

AbstractThe fracture mechanics of multilayered elastomeric composites was simulated by the Blister Test using a polyurethane (PU)/A1 base plate interfacial assembly. In the various systems studies, and hard or soft intrposed layer (∼50 μm) separated the bulk matrix (∼ 1000 μm) from the metal counterface, with a hard‐to‐soft modules ratio of 1.70. Debonding was performed at a constant pressurization rate 1 × 10−8 m3/s corresponding to an average delamination rate of 0.25 m/s. Lateral hardening of the composite modules (negative transversal gradient of modulus) improved the fracture resistance (by 35%) at the material interface, in conformance with analytical predictions. Particle‐dispersed and liquid‐doped systems exhibited a sharp attenuation (40 to 90%) in the debond pressure. The latter results were substantiated by subjective assessement using optical microscopy, and were found consistent with stress concentration and weak conhesive fracture at the resin‐substrate interface, respectively.
Effect of two stage pressure molding on surface quality of sheet molding compounds
Authors: Dziewatkoski Nicholas A. , Xu Jingyi , James Lee L. , Castro Jose 
Published: May 2005

AbstractThe goal of this work was to investigate the effect of two stage pressure molding on the compression molding of a sheet molding compound (SMC). It has been shown in previous studies that a rapid drop in pressure during SMC curing significantly reduced severity of sink marks. This study concentrated on a method of predicting the optimum time during curing to release pressure by examining material behavior through process data from in‐mold sersors. A simple control scheme was them applied for automatic pressure release at the optimum time corresponding with the peak of the material expansion and the onset of the reaction exotherm.
Studies on a fiber reinforced plastics honeycomb structure
Authors: Mukherjee G. S. , Saraf M. N. 
Published: May 2005

AbstractBased on an adhesive and fabric screening program, a rubber‐modified resole adhesive and a flexible grade plain weave glass fabric were found appropriate for the fabrication of a glass‐reinforced plastics honeycomb core material. Sandwich structures of different densities were fabricated. A linear regression analysis was performed to correlate the mechanical properties (S) with the density (p) for a wide range of sandwich structures based on honeycomb and cellular plastic core materials. An analytical model of the formS=Kρnwas derived, with two empirical constantsKandn. The density exponentnwas between 1 ≤n≤ 2 in all cases. An equation was also derived to relate density with thermal conductivity. The dynamic mechanical analysis (DMA) results revealed that the glass transition temperature of the resin matrix associated with the sandwich structure was higher than that of the corresponding facing laminate or near resin casting.
Deformation studies of polystyrene/poly(vinyl methyl ether) blends by mechanical‐vibrational spectroscopy
Authors: Lu F. J. , Burchell D. J. , Li X. , Hsu S. L. 
Published: May 2005

AbstractWe have analyzed the deformation behavior of compatible and incompatible polystyrene (PS) and poly(vinyl methyl ether) (PVME) blends by a combination of mechanical and vibrational spectroscopy. Macroscopic properties and segmental orientation were found to be sensitive to molecular weight, strain rate, and temperature of measurement above the glass‐transition temperature. Considerably different orientation functions were found for the PS and PVME components. For the experiments carried out above the Tg of the blends, the deformation behavior measured was consistent with expectations of a rubbery network.
Predicting conversion using temperature as the measured variable in the reaction injection molding process. Part II: Implementation of the on‐line corrective algorithm
Authors: Pino Oscar Del , Romagnoli José A. , Castro José M. 
Published: May 2005

AbstractIn the reaction injection molding process, we need to know the evolution of the conversion field with a high level of confidence in order to minimize the mold opening time. Thus, the mold can be opened as soon as there is conversion everywhere in the mold above the value needed for the part to become dimensionally stable. Since conversion can not be determined readily by experimental measurements, and since a thermocouple can provide reliable dynamic temperature data, it is best to predict the conversion field from the solution of a state estimation problem using temperature as the measured variable. Here, we develop an on‐line corrective system which uses temperature to correct the model predictions. It is shown that by measuring at the center and at the mold wall, both of which are physically possible, the performance of the corrective algorithm is fairly good.
Rebound test to measure the strength of polymeric materials
Authors: Casiraghi T. 
Published: May 2005

AbstractIn this work it is shown that rebound experiments, carried out at low blow impact and by means of instrumented pendula, can be described in terms of the equation for a freely oscillating linear viscoelastic body with added mass. The experimental and calculated load‐time curves are in very good agreement when the behavior of the material is linear viscoelastic; the assumptions made (transitory time shorter than rebound time, and negligible mechanical friction) are thus proved to be reasonable. The rebound test, which can be carried out on unnotched or notched specimens, allows one to obtain quickly and easily relevant material properties such as Young modulus or compliance, stored and dissipated energies, and the upper linear elastic limit at a testing speed not too far from that of impact testing.
Profile modification of resist patterns in optical lithography
Authors: Vollenbroek F. A. , Spiertz E. J. , Kroon H. J. J. 
Published: May 2005

AbstractA method is described to modify profiles of resist patterns in novolac and diazo‐oxide containing systems. After patterning of the resist, two successive uniform flood exposures are given, one with deep UV (254 nm) at water‐free conditions and the next with near UV (λ > 300 nm) at normal atmospheric conditions. The profile which results after development is vertical, concave or overhanging depending on flood exposure conditions and development processing. As the method includes a flood near UV exposure at atmospheric conditions the imagewise exposure energy can be reduced to approximately 35 percent of the normal value. Furthermore it gives also the possibility of using the resist as a deep UV resist. Another important implication is that standing wave effects are completely eliminated.
Azide‐phenolic resin UV resist (MRL) for microlithography
Authors: Iwayanagi Takao , Hashimoto Michiaki , Nonogaki Saburo , Koibuchi Shigeru , Makino Daisuke 
Published: May 2005

AbstractPoly(4‐vinylphenol) sensitized by an aromatic monoazide compound (4‐azidochalcone), called MRL (Micro Resist for Longer wavelengths), has been prepared and evaluated as a negative UV resist. The resist is sensitive to radiation in the 300 to 400 nm region. The sensitivity of MRL is comparable to that of a positive quinonediazide photoresist under exposure to unfiltered light from a high pressure Hg lamp. An aqueous base developer removes the unexposed areas of MRL with no evidence of swelling of the exposed areas, indicating its high resolution capability. The main products in the exposure of MRL films are found to be primary and secondary amines. It is concluded that the formation of secondary amines attached to the polymer chain is responsible for the insolubilization of the exposed MRL in the base developer.
Plasma developable photoresist containing electronic excitation energy quenching system
Authors: Tsuda Minoru , Oikawa Setsuko , Yokota Akira , Yabuta Mitsuo , Kanai Wataru , Kashiwagi Ken‐Ichi , Hijikata Isamu , Nakane Hisashi 
Published: May 2005

AbstractA dry developable negative working resist composition comprised of poly(methyl isopropenyl ketone) (PMIPK) and 4‐methyl‐2,6‐di(4′‐azido‐benzylidene) cyclohexanone‐1 was examined. The main photochemical product formed in the resist pattern was found to be a secondary amine which crosslinks PMIPK. Post‐annealing forms a hydrogen‐bonded product which shows a powerful electronic excitation energy quenching effect. The quencher is more powerful than the aromatic compound arising from the azide by post‐annealing only. The residual resist thickness of the negative pattern is about 80 percent of the initial thickness of the coating in spite of all the azide compound remaining in the resist coating. The obtained dry developed resist pattern has a high dry etch resistance. Etchings of Si and SiO2 were performed by plasma and reactive ion etching, respectively.
Design of a positive resist for projection lithography in the mid‐UV
Authors: Willson Grant , Miller Robert , McKean Dennis , Clecak Nicholas , Tompkins Terry , Hofer Donald , Michl Josef , Downing John 
Published: May 2005

AbstractThe design, synthesis, formulation, and process optimization of a new mid‐UV resist are described. The synthesis of a spectrally matched sensitizer was guided by semiempirical quantum mechanical calculations that predict the effect of structural changes on optical absorption characteristics. The formulation was guided by computer profile simulation studies and the process development by a response surface analytical procedure. These techniques allowed formulation optimization to be achieved on the basis of an understanding of the complex interactions between the resist dissolution response functions and the modulation transfer function of the exposure tool for which the resist was designed.
Ultrafast deep UV lithography using excimer lasers
Authors: Jain K. , Rice S. , Lin B. J. 
Published: May 2005

AbstractVarious excimer laser wavelengths have been used, both in mid‐ and deep‐UV regions—308 nanometers (nm) from XeCl, 249 nm from KrF and 222 nm from KrCl–to delineate images in a number of resists. The quality of the images obtained with the laser exposures, the absence of speckle, and the insignificant loss of resist reciprocity make excimer laser lithography an attractive technique. The ultrafast exposures possible with this method significantly lessen the sensitivity requirements on deep UV resists, making the choice of the resist more flexible.
Poly(4‐chlorostyrene), a new high contrast negative E‐beam resist
Authors: Liutkus J. , Hatzakis M. , Shaw J. , Paraszczak J. 
Published: May 2005

AbstractPCS(poly‐4‐chlorostyrene) has previously been evaluated as a negative e‐beam resist, but although the sensitivity was good [2 to 5μC/square centimeter (cm2)], the contrast (γ) was poor (1.1 to 1.5). Recent experiments have shown that contrast is not only a function of molecular weight distribution (MWD), but can also be affected by polymerization conditios. Among these are: branching, head to head linkages, and oxygen in backbone. PCS was prepared via thermal free radical solution polymerization, and then fractionated by differential solvation techniques. Reactions occurring during polymerization and crosslink formation on irradiation will be discussed. For molecular weights of 700 and 300K respectively (same MWD), the sensitivity was 2 and 5μC/cm2, while the contrast (γ) was 3.5 for both. This is the highest reported contrast for a polymeric negative resist. The resist can then be UV hardened after development, and will not flow at 200°C. The RIE etch rate is ∼1/2 that of PMMA in various plasmas.
Kinetics of crack tip craze zone before and during fracture
Authors: Döll W. 
Published: May 2005

AbstractIrreversible deformations form the main energy consumption routes for absorbing supplied energy and thus determine the resistance of materials to fracture. In many polymeric materials under mode‐I loading conditions three regions of irreversible deformation behavior can be distinguished as a function of the stress intensity factor KI or strain energy release rate GI, respectively:

no crack growth for Ki < KIo
slow crack growth for KIo < KI < KIc
rapid crack propagation for KI < KIc

In the three regions the amount and geometrical extent of irreversible deformations may be different and the influence of time, crack speed, and temperature may generate different results.In this paper the influences of time and crack speed on the kinetics of the craze zone at the crack tip will be considered in some detail, with respect to results mainly obtained for poly(methyl methacrylate), PMMA, of high molecular weight under quasi‐static loading conditions.
Diffraction studies of craze structure
Authors: Brown H. R. , Sindoni Y. , Kramer E. J. , Mills P. J. 
Published: May 2005

AbstractRecent work using small angle scattering techniques to study craze structure is reviewed. Three different radiations, electrons, X‐rays, and neutrons were used to study four problems in the area. These were (1) the structure of crazes in thin films, (2) the structure of a single craze/crack in a bulk material, (3) the effect of organic environments, and (4), the effect of mechanical fatigue on craze structures. It is shown that the high intensity of a synchrotron source permits the examination of the process of growth and breakdown of a single craze in polystyrene and also the study in real time of the short‐ and long‐term changes during fatigue of crazes. The H/D neutron contrast effects for neutrons were used to study environmental crazes with the environment still present.
Orientation in amorphous polymers II. Characterization of orientation
Authors: Vrentas J. S. , Vrentas C. M. , Bhombal A. H. 
Published: May 2005

AbstractA method based on network theory is developed for characterizing molecular orientation in amorphous polymers. The proposed procedure gives not only the orientation distribution function for the chain segments in the polymer network (and hence the average orientation) but also a quantitative measure of how this orientation is distributed among the various types of entanglement junctions. The orientation of chain segments can be characterized by two parameters, one which gives the average orientation and another which reflects how much orientation is concentrated in long time entanglement junctions. The new method of characterizing orientation is used to interpret tensile strength data for both brittle and ductile failures.
Non‐isothermal flow of a molten polymer in a coat‐hanger die
Authors: Vergnes B. , Saillard P. , Agassant J. F. 
Published: May 2005

AbstractThe non‐isothermal flow of a power‐law fluid in a coal‐hanger flat die is studied. Equilibrium and thermal equations are solved by using an iterative finite difference method. The pressure distribution, the flow lines, the residence time distribution, the temperature distribution, and the flow uniformity at the end of the die are obtained, with a stress on the effect of thermal regulation and of temperature dependence of the viscosity.
Mechanical properties and molecular aggregation of soluble aromatic polyimide
Authors: Kochi Masakatsu , Mita Itaru , Yokota Rikio 
Published: May 2005

AbstractDynamic and static mechanical properties of a soluble aromatic polyimide (PI 2080) were investigated. It, unlike poly(pyromellitimide) (PI), was essentially amorphous in X‐ray diffraction and did not exhibit any heterogeneous two‐phase structure having ordered phases after annealing at temperatures around its glass transition temperature. The mechanical properties including thermal‐distortion temperature and elastic recovery were not much affected by the annealing. The difference in molecular aggregation and mechanical properties between PI 2080 and PI may be due to their different chemical structures. The flexible carbonyl group and the statistical distribution of copolymeric repeating units in the main chain of PI 2080 seem to prevent the formation of molecular order.
Surface‐modified kevlar fiber‐reinforced ionomer: Dynamic mechanical properties and their interpretation
Authors: Takayanagi Motowo , Katayose Teruo 
Published: May 2005

AbstractA quasi‐three‐dimensional model was applied to the composite of ionomer and isotropically oriented discontinuous poly(p‐phenylene terephthalamide) (PPTA) fibers having the surface modified by carboxymethyl groups in order to predict the Young's modulus from the properties of the constituent materials over a wide temperature range. The model in which the modified PPTA fibers are dispersed in ionomer matrix in a three‐dimensional network is composed of series and parallel models. A good agreement between calculated and experimental values was eventually obtained. For comparision, the complex modulus of the composite was also evaluated by application of the Halpin‐Tsai equation modified by Nielsen. The calculated values agreed with the observed values below 240 K, whereas the calculated values above 260 K were significantly lower than the observed moduli.
Effects of thermal history on structural recovery of glasses during isobaric heating
Authors: Hutchinson J. M. , Kovacs A. J. 
Published: May 2005

AbstractThe response of glass‐forming systems to isobaric three‐step thermal cycles involving cooling, isothermal annealing, and subsequent reheating has been investigated comprehensively using numerous combinations of the experimental and material parameters. The latter include the retardation spectrum or response function and the parameter x which determines the relative contributions of temperature and structure to the retardation times. The results show that, on heating, multiparameter systems can display three kinds of peak in the expansion coefficient α or the heat capacity Cp originating from the interactions of the elementary retardation processes with the thermal history of the glass. The conditions under which these peaks occur, their shifts with x, and the experimental variables have been investigated in detail. In particular, it has been shown that for a thoroughly stabilized glass reheated rapidly, the temperature at which the main peak occurs is strongly dependent on the experimental variables and on x, and that this dependence can lead to an estimate of the value of x. For poorly stabilized glasses reheated slowly, on the other hand, the main peak apparently vanishes and allows an upper peak to appear, which is small and insensitive to x and the experimental variables. Intermediate situations in which the main and the upper peaks occur separately give rise to a range of effects which may become quite complicated as the two peaks approach each other. The occurrence of such multiple peaks, which has usually been overlooked or misinterpreted in the past, is discussed and explained in detail and is compared with some experimental observations reported in the literature.