bluuebunny/crossref_metadata_2025 huggingface dataset:
Post-Buckling of Composite I-Sections. Part 2: Experimental Validation
Authors: Papila Melih , Akgün Mehmet A. , Niu Xiaokai , Ifju Peter
Published: July 2004

An experimental investigation was conducted in order to verify the theoretical model described in Part 1 as well as to obtain experimental insight and to generate a database for the post-buckling behavior of composite I-sections. The experiments were performed using a combination of the shadow moiré technique, strain gages, LVDTs (linear variable differential transformer), and dial gages. A total of twenty carbon-fiber/epoxy I-section columns were manufactured and tested with seven specimens from woven fabric and thirteen from unidirectional (UD) tape. The initial buckling load, lateral deflection of the web and flange as well as the crippling load were measured. The experimental results were compared with those of the theoretical model described in Part 1. Agood agreement was observed.
A-Religion
Authors: Nancy Jean-Luc
Published: July 2004

This article attends to the film’s re-reading of Melville in terms of a presentation of an a-religious religion. The film’s display of beauty and its engagement with both the sufficiency and vulnerability of this beauty is seen to partake of a philosophical and cinematic questioning of an aesthetic of auto-sacralization and the chances of an atheist art.
Good Work, Little Soldier
Authors: Lack Roland-François
Published: July 2004

This article reads the relation between Denis’sBeau Travail and Jean- Luc Godard’s 1960 filmLe Petit Soldat as a film-on-film variant of film-on-book adaptation. The model informing this reading is not so much intertextual as pretextual. The principal points of contact between the two films discussed are ‘actor’ (Michel Subor), ‘character’ (Bruno Forestier) and ‘narrator’ (Forestier/Galoup). The use inBeau Travail ofLe Petit Soldat is compared with and differentiated from the use of Melville’s ‘Billy Budd, Sailor’. The conclusion arrived at is that the film-on-film relation can be read as a development of the mirror motif borrowed from Godard by Denis, in order to replace abyssal models of intertextual infinity with the finitudes of abyssal reflexivity. This is to offer a model of pretextuality that is not dependent on privileging the pretext: implicit is the suggestion thatBeau Travail andLe Petit Soldat may be read as a single, if hybrid, text.
‘O Heave! O Heave away, Heave! O Heave!’
Authors: Williams James S.
Published: July 2004

This article argues that the full significance ofBeau Travail only becomes clear if it is placed within both the history of Denis’s evolving commentary on the film and its specificauteur context: that is to say, as a fully assumed intervention by a female director in a male artistic tradition. A study of the processes of intertextual ‘translation’ and ‘graft’ in the extended project ofBeau Travail reveals that Denis’s engagement with masculinity at different levels, including that of the cinematic apparatus itself, constitutes the very basis of her filmic practice which is always sexually charged and must negotiate the fundamental destructiveness of desire through the sublimation of aesthetic form.
Solid Cinema
Authors: Morlock Forbes
Published: July 2004

What forms can solidarity take in the least solid of the plastic arts? Claire Denis asks this question in the images of the human body’s solidity in her films and, more specifically, in her discussions ofBeau Travail . Projecting thoughts onto a pair of short sequences from her ‘African’ films,Beau Travail andChocolat , this paper touches on Denis’s answers.
Love of the Soldier
Authors: Borossa Julia
Published: July 2004

This paper examines belonging and non-belonging as set out in Claire Denis’sBeau Travail , in the context of the Enlightenment ideal of citizenship and the historical development of the Foreign Legion. Inclusion and exclusion are also treated in terms of the Oedipal family formation of psychoanalysis, in order to further question just who it is that belongs and why. The characters of Galoup, Sentain and Forestier are used to illustrate the ambiguities that arise from such questioning.
From the Universal to the Cosmic
Authors: Rooney Caroline
Published: July 2004

This article is in two parts, where the first part offers a reading of the film in terms of an inversion of genre. This de-centring inversion of genre is extended to an inversion of generality and universality, and it is further envisaged that the generic appears encompassed within a generativity that may be said to be cosmic. Whilst this is explored with reference to scenes in the film and to Melville’s ‘Billy Budd, Sailor’, the second half of the article considers the implications of the analysis for a theorization of the cinematic genre. Here, Deleuze’s understanding of the cinematic in terms of temporal duration is juxtaposed with an African understanding of time towards a theory of spectatorship in terms of relaxation.
Isaiah Berlin's Cosmopolitan Ethics
Authors: Zakaras Alex
Published: July 2004

This essay offers a reinterpretation of Isaiah Berlin’s value pluralism. It argues that pluralism is above all an ethical stance by means of which Berlin asserts the importance of empathy, imagination, and freedom in any good human life. Emphasizing these elements of Berlin’s thought draws out his deeply cosmopolitan outlook, which his critics have often ignored. On this reading, Berlin is no defender of cultural particularism—rather, he prefers individuals who understand their choices and aspirations against a broad background of incommensurable yet valuable alternatives. It is on this pluralist sensibility that he rests his hopes for a tolerant, humane politics.
Pity's Pathologies Portrayed
Authors: Boyd Richard
Published: July 2004

Jean-Jacques Rousseau is renowned for defending the pity of the state of nature over and against the vanity, cruelty, and inequalities of civil society. In the standard reading, it is this sentiment of pity, activated by our imagination, that allows for the cultivation of compassion. However, a closer look at the “pathologies of pity” in Rousseau’s system challenges this idea that pity is a pleasurable sentiment that arises from a recognition of the identity of our natures and leads ultimately to communion with our fellow-creatures. Instead, pity rests inexorably on a sense of difference, is fueled by an aversion to suffering, and is more likely to yield a world of “reluctant spectators” than one of simple souls eagerly rushing to the aid of others. Because compassion is unlikely to encourage the moral equality and willful agency requisite to democracy, trying to make compassion central to democratic theory may very well prove counterproductive.
Prudes, Perverts, and Tyrants
Authors: Tarnopolsky Christina
Published: July 2004

In certain contemporary theories of the politics of shame, shame is considered a pernicious emotion that we need to avoid in, or a salutary emotion that serves as an infallible guide to, democratic deliberation. The author argues that both positions arise out of an inadequate notion of the structure of shame and an oversimplistic opposition between shame and shamelessness. Plato’s dialogue, the Gorgias, actually helps to address these problems because it supplies a deeper understanding of the place of shame in democratic politics in ways that address our contemporary dilemmas. It does this first, by avoiding the simple opposition between shame and shamelessness and secondly, by articulating three different kinds of “politics of shame” that can characterize democratic deliberations. Finally, Plato’s treatment of shame extends upon contemporary ethical and psychoanalytic notions of shame in ways that are directly relevant to the our contemporary political situation.
A Single Mathematical Model Predicts Physicians’ Recommendations and Postmenopausal Women’s Decisions to Participate in a Clinical Trial to Prevent Breast Cancer or Coronary Heart Disease
Authors: Veit Clairice T.
Published: July 2004

Few eligible postmenopausal women participate in clinical trial research to prevent breast cancer or coronary heart disease, making it impossible to adequately assess the efficacy of tested interventions for this vulnerable group. To elucidate the causal factors and decision model underlying participation behavior, 180 white, African American, and Hispanic postmenopausal women judged their likelihood of participation in a breast cancer or coronary heart disease prevention clinical trial in scenarios with varied cost/remuneration, perceived risk, doctor’s recommendation, and expected toxicity. In addition, 293 white, African American, and Hispanic male and female physicians judged the strength of their participation recommendation in scenarios with varied cost/ remuneration, expected toxicity, patient’s age, and the source of the information about the clinical trial. An additive and constant-weight-averaging model were rejected. The same configural-weight-range model accounted for judgments in both breast cancer and coronary heart disease scenarios, with different parameter values for each group. According to this model, white and Hispanic women under 70 years of age are most likely to participate, even under somewhat adverse conditions; costs and high toxicity levels act as severe barriers to physicians’ positive recommendations and women’s participation. Perceived risk was the most important factor for women, yet only 8% and 15% reported ever having received risk information from their doctor for breast cancer and coronary heart disease, respectively. For these two diseases, respectively, 75% and 48% of women rated their risk of the disease as low and 76% and 88% reported they had never heard of a randomized clinical trial or of a prevention clinical trial being conducted. These results have implications for education, information dissemination, and prevention clinicaltrial planners.
Classification Algorithms for Hip Fracture Prediction Based on Recursive Partitioning Methods
Authors: Jin Hua , Lu Ying , Harris Steven T. , Black Dennis M. , Stone Katie , Hochberg Marc C. , Genant Harry K.
Published: July 2004

This article presents 2modifications to the classification and regression tree. The authors improved the robustness of a split in the test sample approach and developed a cost-saving classification algorithm by selecting noninferior to the optimum splits from variables with lower cost or being used in parent splits. The new algorithmwas illustrated by 43 predictive variables for 5-year hip fracture previously documented in the Study of Osteoporotic Fractures. The authors generated the robust optimum classification rule without consideration of classification variable costs and then generated an alternative cost-saving rulewith equivalent diagnostic utility. A6-fold cross-validation study proved that the cost-saving alternative classification is statistically noninferior to the optimal one. Their modified classification and regression tree algorithm can be useful in clinical applications. A dual X-ray absorptiometry hip scan and information from clinical examinations can identify subjects with elevated 5-year hip fracture risk without loss of efficiency to more costly and complicated algorithms.
Exploration of a Bayesian Updating Methodology to Monitor the Safety of Interventional Cardiovascular Procedures
Authors: Resnic Frederic S. , Zou Kelly H. , Do Daihung V. , Apostolakis George , Ohno-Machado Lucila
Published: July 2004

Appropriate methods for monitoring of the safety of medical devices introduced into clinical practice have been elusive to develop and implement. A novel approach is the application of Bayesian updating, which incorporates existing knowledge regarding event rates into the estimation of risk. This framework has been shown in other domains to be data efficient and to address some of the limitations of conventional statistical methods. In this article, the authors propose a methodologic framework for developing initial prior probability distributions in risk-stratified patient groups and a mechanism for incorporating accumulating procedure safety experience. In addition, they use this methodology to retrospectively analyze the clinical outcomes of 309 patients undergoing an infrequent interventional cardiology procedure, rotational atherectomy. These exploratory analyses demonstrate the feasibility of Bayesian updating applied to medical device safety evaluation and indicate that the methodology is capable of generating stable estimates of risk in a variety of patient risk groups.
Positive Association between Current Health and Health Values for Hypothetical Disease States
Authors: King Joseph T. , Tsevat Joel , Roberts Mark S.
Published: July 2004

Background: Valuations of hypothetical health state scenarios can be affected by participant characteristics. Methods: The authors interviewed 108 veterans using the visual analogue scale (VAS), standard gamble (SG), time tradeoff (TTO), and willingness to pay (WTP) tomeasure health values for 1) current health and 2) 3 hypothetical health states portrayed in written scenarios describing cervical spondylotic myelopathy (CSM), a degenerative spine condition. They used bivariate rank order and multivariate regression analyses to assess the relationship between CSM values, participants’ characteristics, and participants’ current health values. Results: Participants were predominantly male (89.8%) and Caucasian (75.9%), with a median age of 58.3 years and a median annual income of $15,000. Median values for current health were VAS, 0.75; SG, 0.80; TTO, 0.80; and WTP, $25,000. In the multivariate analysis, higher CSM values were associated with better current health as measured with the SG, TTO, and WTP (for all,P < 0.001); there was no association with VAS values (P = 0.157). Conclusions: Health values for CSM are positively associated with the current health of the study population.
Novel BEM Simulation of Mixing in Polymer Flows Including Non-Linear Effects
Authors: Rios Antoine C. , Osswald Tim A.
Published: July 2004

When numerically analyzing mixing in polymer processes, there are several difficulties that the engineer will encounter; such as moving boundaries, complex geometries and non-linear material behavior. The Boundary Element Method (BEM), as a technique which requires only boundaries (surfaces) to be meshed, is ideal to simulate problems with moving boundaries and complex geometries. However, the introduction of non-linear material behavior requires domain information. This study applies the Monte Carlo technique to integrate the domain and keep the boundary-only discretization. Results show the influence of non-linear effects, such as shear-thinning viscosity, when characterizing mixing in polymer processing equipment.
Time-Dependent Strain Distribution in Polymers under Complex Stress History: Experimental Study by Moire Fringe Method and Finite Element Predictions
Authors: Chaikittiratana A. , Buckley C. P. , Dooling P. J.
Published: July 2004

A combination of experimental and computational methods are developed, for predictions of nonlinear viscoelastic creep of polymers in sheet form, subjected to inhomogeneous stress states and stress history. A recently proposed multiaxial constitutive model for glassy polymers was implemented in a commercial finite element (FE) package. The model was tested by means of creep experiments on PMMA at elevated temperature, using specimens with a central circular hole. The experiments were performed using a tensile creep machine, and the geometric Moire fringe method was employed for measuring strain distribution. The results obtained from the experiment and FE analysis were compared.
Application of the Taguchi Method to Optimize the Surface Quality of Gas Assist Injection Molded Composites
Authors: Liu Shih-Jung , Chang Jer-Haur
Published: July 2004

Gas assist injection molding of short glass fiber reinforced composites has become an important process in industry, because it enables the production of parts with thick and thin sections and with a good structural rigidity. However there are some unsolved problems that confound the overall success of this technique. Part roughness of the composites caused by inappropriate mold design and processing conditions is one of them. An L' 18 experimental matrix design based on the Taguchi method was conducted to optimize the surface quality of gas assist injection molded composites. The material used was a 35% glass fiber reinforced Nylon-6 composite. Experiments were carried out on an 80-ton injection molding machine equipped with a high-pressure nitrogen-gas injection unit. A float-shape mold cavity was used. After molding, the surface quality of the parts was characterized by a roughness meter. For the factors selected in the main experiments, melt temperature and gas injection delay time were found to be the principal factors affecting the surface quality of gas assist injection molded composites. Experimental investigation of a gas assist injection molding problem can help reveal the formation mechanisms of surface roughness, so that steps can be taken to improve the surface quality of molded parts.
Elasto-Plastic Behavior of Thermoplastic Matrix Plates with Rectangular Hole
Authors: Arslan Nurettin
Published: July 2004

The elasto-plastic stress analysis of the thermoplastic matrix plates with rectangular hole is carried out by using finite elements. A two-dimensional finite element computer program is developed for elasto-plastic stress analysis. Isoparametric quadratic element with nine nodes is used with Lagrange polynomial as an interpolation function. The spreads of the plastic zones and variations of the residual stresses are obtained in different orientation angles and loads. It is shown that the path around the hole location can be designed to decrease the stress concentrations. The results are presented in diagrams and compared with some of the relevant studies in the literature.
Effect of Aqueous Environment and Temperature on Glass-Fibre Epoxy Resin Composites
Authors: Ellyin F. , Rohrbacher C.
Published: July 2004

The main objective of this experimental investigation is to study the absorption behaviour of fibre-glass reinforced epoxy matrix composite laminates immersed in distilled water, in ambient and 90'C temperatures, and its effect on the mechanical properties. A comparative study is carried out to evaluate the properties of dry and water immersed specimens, and to investigate damage caused by the aqueous environment and temperature. It is found that the degree of damage strongly depends on the immersion temperature. The fracture surfaces in three different environments are studied using a scanning electron microscope and micro-macro damage correlation is established. The threshold strain for the matrix crack initiation increases when the laminated are immersed in ambient water in comparison to that of a dry environment. Immersion at high water temperature leads to embrittlement of the glass fibres and matrix blistering resulting in a slight decrease in threshold crack initiation strain.
A Melting Rate Model Based on Extrusion Data
Authors: Derezinski Stephen J.
Published: July 2004

To design an extruder screw for a given polymer, the barrel length for melting is needed for a given flow rate and speed. The melting rate needed for calculating the length is given through the conservation laws in cylindrical coordinates based on defined fundamental average parameters. Extrusion machine data are used to calculate the functions of the parameters. Results based on polyethylene data are given.
Viscoelastic Properties of Multiphase Polymeric Blends
Authors: Pieroni Paula , Ercoli Daniel , Goizueta Graciela , Capiati Numa
Published: July 2004

Rheological analysis of multi-phase systems is very difficult because the morphology is strongly related to the flow history. The small amplitude oscillatory shear flow does not affect the morphology and is very useful to predict the viscoelastic behavior of immiscible blends.

In this work we study the dynamic rheological properties of polypropylene based ternary blends with linear low density polyethylene and ethylene/propylene terpolymers of different viscosities taking into account the effects of changing the composition and concentration of the dispersed phase.

The predictions of a constitutive equation for emulsions of viscoelastic fluids are also included.
Free Edge Effect on the Post Failure Behavior of Composite Laminates Under Tensile Loading
Authors: Joo Sang-Gun , Hong Chang-Sun , Kim Chun-Gon
Published: July 2004

It is necessary to understand the complete load response and failure mechanism of composite laminates to enhance the full potential of composite materials. Progressive failure algorithm for the post failure behavior of composite laminates was developed in the present study such that the damaged layer with many micro-cracks is replaced with an equivalent layer of degraded properties. Stresses and strains are calculated by the 3-D finite element method based on the generalized layerwise plate theory (GLPT) in order to consider the local effect near the free edges. The types and size of damage in composite laminates are predicted in the failure analysis that consist of a set of failure criteria and property degradation models for each mode of failure. In the case of matrix cracking, the macroscopic stiffness reduction model based on the shear-lag method is introduced to the finite element method in order to consider nonlinear progressive reduction of stiffness at each strain level. In order to predict the failure load and the damage accumulation accurately, the refined finite element model with 3-D stress field is used. The distribution of stress considering free edge effect is presented. The failure mechanism and ultimate failure loads of the cross-ply and quasi-isotropic laminates for different stacking sequences with the same thickness are investigated.
Discrete-Wavelet Analysis of Acoustic Emissions During Fatigue Loading of Carbon Fiber Reinforced Composites
Authors: Kamala Girish , Hashemi Javad , Barhorst Alan A.
Published: July 2004

Wavelet transform decomposition was used to gather time-frequency-based information from acoustic emission signals generated during fatigue loading of unidirectional Carbon Fiber Reinforced Composite (FRC). The acoustic emissions were detected using a resonant sensor and were digitized for analysis. The sensor response was de-convolved from the acquired signal using a point-by-point divisional spectral method. The analysis of the collected signals revealed that friction-related emissions due to the fretting of fractured surfaces are of very high frequency and can mask emissions due to actual damage.

Through utilization of wavelet transforms, it became possible to present the spectral composition of a transient signal (AK signal) in a time-frequency map which is not easily achieved through conventional spectral analysis techniques. It was determined that most of the acoustic energy (95%) was localized in levels corresponding to central frequencies of 120, 250, and 310 kHz. Results indicate friction-related emissions are associated with levels 8 and 9 and have a frequency range of 250-300 kHz. There are indications that matrix related emissions are of high frequency and high acoustic energy. The results indicate that wavelet analysis would be an effective tool in the analysis of AE by providing information relative to the frequency of the emissions.
Measurements of Ballistic Impact Response of Novel Coextruded PC/PMMA Multilayered-Composites
Authors: Hsieh Alex J. , Song John W.
Published: July 2004

Ballistic impact behavior of coextruded composites consisting of alternate layers of ductile polycarbonate (PC) and brittle poly(methyl methacrylate) (PMMA) were investigated. These PC/PMMA composites were 256, 1024, 2048 and 4096 layers; each consisted of various component compositions and their corresponding layer thickness was on the order of micron or sub-micron scale. Individual layer thickness of PMMA was determined to be critical for the impact response of these ductile/brittle hybrids. A brittle mode of failure was encountered as the thickness of PMMA layers reached 0.5 mm or higher, regardless of their composition or layer configuration. Damage zone size increased significantly as the PMMA layer thickness reduced to approximately 0.36 mm; a mixed mode of failure resulted in these PC/PMMA composites. With the PMMA layer thickness further reduced to approximately 0.14 mm, ductile deformation, which was predominant in the pure PC, occurred in these coextruded composites. Ballistic impact energy data showed that the extent of energy absorption or dissipation increased with an increase in either the PC content or the total number of layers. These results further revealed that the individual layer thickness of PMMA was the critical material parameter, and the determined impact energy values were consistently higher for the composites with PMMA layer thickness being 0.14 mm or thinner. Adhesion between the layers appeared to be very good since delamination did not occur whether these PC/PMMA composites failed in a brittle or a ductile mode.
Continuous Curing and Induced Thermal Stresses of a Thick Filament Wound Composite Cylinder
Authors: Kim Cheol , White Scott R.
Published: July 2004

A new composite manufacturing technique called continuous curing is discussed and analyzed. This method is especially suited to the manufacture of thick composite materials in which thermal spiking is a common problem. Thermal and cure fronts are propagated in the thickness direction as material is accreted on the outer surface. An experimental apparatus was designed and built for use with a filament winder to continuously cure thick composite cylinders. A demonstration experiment was carried out using IM6/3501-6 graphite/epoxy prepreg tow. A hoop-wound composite cylinder with 152 mm wall thickness was manufactured and embedded thermocouples and strain gages were monitored throughout the cure process. Results indicate that very thick and good quality composite cylinders can be fabricated without long manufacturing time, material degradation due to thermal spiking, and high level of thermally induced residual stresses.
Integrated Simulations of Gas Injection Molding Process and Part Structural Performance under a Unified CAE Model
Authors: Chen Shia-Chung , Hu Sheng Yan , Chang Yeon-Pun
Published: July 2004

Integrated simulations of gas injection molding process and part structural performance under a unified CAE model were carried out. An analysis algorithm based on DKT/VRT elements superimposed with beam elements representing gas channels of various section geometries was first developed to evaluate the structural reinforcement of gas channel in the design stage. During melt/gas filling process, a mixed control-volume/finite-element/finite-difference method combined with dual-filling-parameter technique was implemented to trace the advancement of melt and gas fronts. For the prediction of secondary gas penetration, flow model of isotropic-shrinkage origin was introduced. Mold cooling analysis was executed utilizing cycle-averaged boundary element method considering the cooling system. Both cooling channel and the hollowed core gas channel were modeled using line-source approach. Thermal residual stresses calculated from part temperature distribution were then combined with the structural analysis to predict part warpage. The monitor support was used as the case study. The analysis accuracy from this unified model of 2-1/2D characteristics were examined experimentally. The only difference between process simulation and structure/warpage analyses is that different values of equivalent diameters assigned to a circular pipe representing gas channel should be used, respectively.
Effect of Imperfect Interfaces on Elastothermodynamic Damping of Particulate Metal-Matrix Composites
Authors: Srivastava S. K. , Mishra B. K. , Jain S. C.
Published: July 2004

Most of the works related to the evaluation of elastothermodynamic damping in particle-reinforced metal-matrix composite assume perfect interfaces between reinforcement and matrix. On the contrary, composite materials do have imperfect interfaces because of debonding between the reinforcement and matrix. With passage of time, debonding becomes more extensive. In the present work, imperfect mechanical and thermal interface has been considered for the calculation of energy dissipation in the composite sphere model subjected to the uniform time-harmonic excitation. Two non-dimensional parameters quantifying the mechanical and thermal imperfectness at the interfaces have been identified. It is observed that specific damping capacity increases due to mechanical imperfection whereas it decreases due to thermal imperfection and hence the two types of imperfection have compensatory effects on the specific damping capacity.
Acoustic Attenuation for Ultrasonic NDI Detection of Delaminations on Composite Laminates
Authors: Briotti G. , Scarponi C.
Published: July 2004

The purpose of the paper is to show the importance of the acoustic attenuation and probe frequency for the reliable evaluation of delaminations on composite materials subjected to NDI ultrasonic investigation.

An original ultrasonic NDI methodology has been applied to some composite materials of wide application, characterized by a high acoustic attenuation. The materials are based on Kevlar/polyester and glass/polyester systems; the fiber form is woven fabric, and the thicknesses are between 5 and 6 mm. All the specimens are made by RTM technology. The specimens have been subjected to low-velocity impact tests, and then the extension of delaminated areas has been evaluated.

The ultrasonic test apparatus operates in the form of reflection, using two different probes at 5 and 15 MHz. The results point out how the higher frequency probe has a greater resolution and higher sensibility; nevertheless, the higher attenuation at 15 MHz causes a lower inspection depth along the specimen thickness. Thus, for materials with high attenuation the 5 MHz probe is preferable in order to have accurate ultrasonic maps along the thickness and reliable values for the delaminated areas.
Fatigue Fracture Mechanisms of Particle and Fiber Filled PTFE Composites
Authors: Gan Y. X. , Aglan H. , Faughnan P. , Bryan C.
Published: July 2004

The effect of filler type on the fatigue fracture mechanisms of polytetrafluoroethylene (PTFE) composites was studied. The two composites were a silica particle filled PTFE (Garlock 3502‘) and a glass fiber filled PTFE (Garlock 8573‘). Tension-tension fatigue crack propagation tests were conducted on both materials at room temperature at a frequency of 3 Hz. The maximum stress was 6 MPa and the ratio of minimum load to maximum load was 0.1. It was found that the fatigue lifetime of the particle filled PTFE is approximately four times higher than that of the fiber filled PTFE. The fatigue data also revealed that the crack speed of the particle filled composite is always lower than that of the short fiber filled composite. Microscopic analysis on representative fracture surface of each material was performed to identify different fracture surface features. The three fracture regions, crack initiation, stable crack growth and unstable crack growth were examined. In the first region, both composites displayed extensive plastic deformation and severe debonding at the filler/matrix interface. In the second region, stable crack propagation, torn ligament bundles, fibrillation and debonded fillers are the main fracture surface features. The fracture surface of the fiber filled PTFE in the unstable crack propagation region has a more smooth appearance with extensive fiber pull-out. This indicates a fast fracture process and a brittle fracture mechanism dominating this region. The third region of the fracture surface for the particle filled PTFE displayed more severe matrix deformation. The particle filled PTFE displayed more intensive fibrillation in the second region than the fiber filled PTFE, indicating more damage formation and thus higher energy consumption in the stable crack propagation stage. Consequently, the crack speed of the particle filled PTFE is lower than that of the fiber filled PTFE composite.
Pure Mode I, II and Mixed Mode Interlaminar Fracture of Graphite/Epoxy Composite Materials
Authors: Yum Young-Jin , You Hee
Published: July 2004

Pure mode I, II and mixed mode fracture tests were performed to characterize the delamination of unidirectional graphite/epoxy composite. Double cantilever beam specimens were used for the pure mode I test and end loaded split specimens were used for the pure mode II test. The critical strain energy release rates were evaluated by beam theory and compliance method and the values were 333 J/m2 and 1105 J/m2 respectively. Modified mixed mode bending tests were performed to investigate the mixed mode I/II delamination. Various mixed mode ratios could be produced by simply changing the applied load position on the loading lever and the bending load position on the specimen. A new analytical method was presented that can decompose the total strain energy release rate into mode I and mode II components. Experimental and finite element results agreed well with the theoretical ones.
Fractal Description of Interlaminar Contact Development during Thermoplastic Composites Processing
Authors: Yang F. , Pitchumani R.
Published: July 2004

Fabrication of layered thermoplastics and thermoplastic-matrix composites using processes such as tow placement, tape laying, and resistance welding, is fundamentally based on the principle of fusion bonding, which involves applying heat and pressure to contacting thermoplastic surfaces. One of the important processing steps— intimate contact—is considered in this paper. Interlaminar intimate contact development is a strong function of thermoplastic surface geometry. Profilometric measurements of thermoplastic prepreg tows show that surface roughness features can be found at several length scales, which implies that the surfaces have a fractal structure. In this paper, principles of fractal geometry are used to describe prepreg surfaces. Based on this description, an axisymmetric squeeze flow model is developed to relate degree of intimate contact to the process parameters—pressure, temperature, and time—and the fractal parameters of the surface. The model development and comparisons with available experimental data are presented and discussed in this paper.
Finite Element Dynamic Analysis of Submerged Laminated Composite Plates
Authors: Pal N. C. , Sinha P. K. , Bhattacharyya S. K.
Published: July 2004

The influence of the fluid medium in modifying the dynamic characteristics of composite plates considering fluid-structure coupling effect is discussed in this paper. The complete plate-fluid system is discretised as an assemblage of finite elements assuming fluid pressure and generalised displacements as the nodal unknowns for the fluid and structural domain, respectively. The resulting coupled equations of motions for these two domains in the absence of any viscous damping are then integrated using Newmark’s algorithm. Transient analysis of both submerged isotropic and composite plates are carried out to study the effect of submergence on the dynamic characteristics namely, natural frequencies as well as amplitudes and period of response.
Cumulative Damage of Short Glass Fiber Reinforced Thermoplastics
Authors: Zago Alessandro , Springer George S. , Quaresimin Marino
Published: July 2004

Tests were conducted measuring the fatigue lives of 150 mm by 10 mm by 2 mm short glass fiber reinforced Copolyamide coupons under different types of cyclic loads. The fatigue lives measured in these tests were compared to those provided by the Generalized Miner’s Rule, and good agreements were found between the test and model results.
Fatigue Lives of Short Fiber Reinforced Thermoplastics Parts
Authors: Zago Alessandro , Springer George S.
Published: July 2004

The fatigue lives of two different parts (made of short glass fiber reinforced Copolyamide) were investigated. The first one was a 150 mm by 10 mm by 4 mm coupon with a 2 mm hole at the center. The second one was an automotive gear shift link. The fiber orientations and the stresses inside these parts were calculated, respectively, by the commercial softwares C-Mold and by ABAQUS. The fatigue lives under different cyclic loads were measured; they were also estimated by a model based on the Generalized Miner’s Rule, the results of C-Mold and ABAQUS, and the S-N data generated as part of this study [1,2]. Comparisons between the measured and estimated (by the model) fatigue lives are in reasonable agreement, indicating that the procedure employed is a useful tool for estimating the fatigue lives of parts made of short fiber reinforced thermoplastics.
High Quality Flax Fibre Composites Manufactured by the Resin Transfer Moulding Process
Authors: Oksman Kristiina
Published: July 2004

In this work the use of high quality natural fibres as reinforcements was studied using the resin transfer moulding (RTM) processing technique. The fibres were unidirectional high quality Arctic Flax and the matrix was an epoxy resin. The mechanical properties of the composites were compared to conventional RTM manufactured glass fibre composites, traditionally retted UD-flax fibre composites and to the pure epoxy. The results from mechanical testing showed that the (50/50) high quality ArcticFlax/epoxy composite has a stiffness of about 40 GPa compared to the stiffness in pure epoxy of 3.2 GPa. The same composite has a tensile strength of 280 MPa compared to 80 MPa of the epoxy. RTM showed to be a suitable processing technique for natural fibre composites when high quality laminates are preferred.
Postbuckling Strength of Composite Plate with a Hole
Authors: Kong Cheol-Won , Hong Chang-Sun , Kim Chun-Gon
Published: July 2004

Buckling and postbuckling behaviors were analyzed numerically and experimentally for composite plates with a hole. In the finite element analysis, the updated Lagrangian formulation and the eight-node degenerated shell element were used. For the progressive failure analysis, the maximum stress criterion was applied to the average stress in each layer of all the finite elements and then stiffness and stress corresponding to the failure mode were reduced to zero for the failed layers of all the elements. In the experiments, the shadow Moiré technique was used to monitor the out-of-plane deformation. PVDF sensors were used to detect the events of internal damage. The major finding was that when a plate has low bending stiffness in the axial direction, the local instabilities caused a change of mode shapes in postbuckling range. Experiments showed good agreement with the finite element results in the buckling load and the postbuckling strength. The influence of hole sizes and stacking sequences was investigated on the compression behavior of the plate. The postbuckling strength was dominated by the value of the bending stiffness in the axial direction.
Influence of Doubly Periodic Array Aspect Ratio on the Transverse Anisotropy of Continuous Unidirectional Fiber Reinforced Composites
Authors: Lim T. C.
Published: July 2004

A modified mechanics-of-materials approach is developed for analyzing the influence of fiber arrangement in a rectangular array on the transverse anisotropy of transversely-isotropic unidirectional fiber reinforced-composites. The class of material under discussion is one of which is transversely isotropic only when the fiber array aspect ratio is unity. The method takes a one-dimensional approach akin to the slab analysis of metal forming studies—with the exception that the present material being considered is heterogeneous and that deformation is within linear elastic range. Compared to the conventional mechanics-of-materials approach, the present modified model, at unity array aspect ratio assumption for randomly arrayed fibers, gives better agreement with experimental results. Theoretical curves for other array aspect ratios are further plotted and discussed in regard to the fiber array and its relation to transverse anisotropy.
Experimental and Numerical Analysis of Heat Transfer in Bulk Molding Compound Injection Process
Authors: Millischer Arnaud , Delaunay Didier
Published: July 2004

The injection of B.M.C. material represents an important industrial and economic stake. It is used for car parts, electric components, and other products. The knowledge of the material properties (chemical, thermodynamical, mechanical) and of its molding process is essential in order to optimize the manufacture of the pieces. This is the subject of this work. We will show the importance of heat transfer in this transformation process.
Film Casting of a Low Density Polyethylene Melt
Authors: Canning Kathleen , Bian Baigui , Co Albert
Published: July 2004

Film casting is one of the major commercial film manufacturing processes. Although various investigators have studied the process, no comprehensive set of data is available. In this study, film casting experiments of a LDPE polymer melt are conducted. The rheological properties of the melt, the film tension, the velocity profile, and the film width profile due to necking in will be presented. The thickness profile of the solidified film and the edge bead profile will also be reported. These experimental data will be useful for process analysis and verification of film casting simulation.
Prediction of Viscoelastic Behaviour of Thermorheologically Complex Polymeric Materials
Authors: Dutta Naba K. , Choudhury N. Roy , Matisons Janis , Edward G. H.
Published: July 2004

A simplified numerical computational technique based on a Gaussian spectral distribution model developed by Dutta and Edward [1] has been used to describe the stress relaxation behavior of polystyrene (PS) and isotactic polypropylene (iPP) over a wide range of time and temperature. An excellent fit between experimental data and the mathematical model is observed. The method may be applied generally for any linear viscoelastic property and for any polymer.
Effect of the Addition of a Polycarbonate on the Cure of an Epoxy Thermoset System
Authors: Amaral M. J. , Espejo A. , Gonzalez-Alvarez A. , Arellano M.
Published: July 2004

During the cure of a thermoset-thermoplastic blend two-phase morphologies may be formed. The phase separation process can be controlled by manipulation of the rate of polymerization of the thermoset system. In this work, the effect of the addition of different amounts of polycarbonate (PC) on the rheokinetics of an epoxy thermoset system is presented. The reactive system used was diglycidyl ether of bisphenol-A cured with 4-4 diaminodiphenylsulfone. The blends of the PC and the epoxy resin were prepared using two different procedures: (a) hot melt blending and (b) dissolution in a common solvent. The kinetics was followed by differential scanning calorimetry and the change in the rheological properties during the curing by dynamic rheometry.
Elastic-Plastic Stress Analysis of Metal Matrix Laminated Plates Under In-Plane and Transverse Loading
Authors: Sayman O. , Özbay M. , Akbulut H.
Published: July 2004

Metal matrix composites reinforced by fibers give high strengths, specific stiffness, ductility, yield point and a good temperature performance. They provide a relatively new way of strengthening metals. In recent years several low cost manufacturing techniques have been developed.

In this study, continuous stainless steel reinforced aluminum matrix composite manufactured by die casting process has been used as a simply supported symmetric and antisymmetric laminated plate loaded by in-plane and transverse forces. An elastic-plastic numerical solution has been carried out by finite element technique for several iteration numbers. Residual stresses and the expansion of the plastic zone have been illustrated in tables and figures.
Model of Delamination Propagation in Brittle-Matrix Composites Under Cyclic Loading
Authors: Andersons J. , Hojo M. , Ochiai S.
Published: July 2004

A model of interlaminar fatigue crack growth based on damage accumulation ahead of the crack is proposed. Linear cumulative assumption is used for damage estimation, and a quadratic failure criterion is applied for complex interlaminar loading. Model parameters are determined from mode I and mode II fatigue tests, and used to predict mixed-mode delamination propagation rate. Comparison of theoretical prediction with mixed-mode test results for different brittle graphite FRP at several mode- and load ratios show reasonable agreement.
Effect of Matrix Plasticity on Ultimate Strength of Composite Laminates
Authors: Huang Zheng-Ming
Published: July 2004

Prediction of ultimate strength of a multidimensional composite laminate subjected to arbitrary load condition is difficult in nature. A fundamental reason is that the load share by each lamina in the laminate depends on the lamina instantaneous stiffness matrix which is not a constant throughout in most cases. The lamina nonlinear response is mainly caused by the inelastic deformation of the matrix material in the lamina. The primary objective of the present paper is to investigate the effect of matrix plasticity on the progressive failure process in the laminate. The study is based on a recently developed micromechanics model, the Bridging Model, which provides the instantaneous stiffness of the lamina at any load level using its constituent properties and the fiber volume fraction only. Another purpose of this paper is to compare predictive capability of different failure criteria for the laminate ultimate strength. Two typical failure criteria, i.e., the Tsai-Wu criterion applied to the lamina level and the maximum normal stress criterion applied to the constituent level, are incorporated in this paper. It is found that the matrix plasticity affects heavily the laminate strength if the laminate does not have 0 lamina plies in the loading direction or if the stiffness of the matrix does not differ significantly from that of the fibers. It is also found that the maximum normal stress criterion is generally more efficient for composite failure analysis.
Simulation of Planar Entrance Flow Using Strain-Rate-Dependent Shear and Elongational Viscosities
Authors: Gupta Mahesh
Published: July 2004

A finite element simulation of the flow in a planar channel with an abrupt contraction is presented. The effect of the elongational viscosity of a polymer on the entrance flow is analyzed employing a truncated power-law model. The power-law index and the strain rate characterizing the transition from Newtonian to power-law behavior for the elongational viscosity are treated as being independent of the values of these two parameters for the shear viscosity. The effect of flow rate on planar entrance flow is also analyzed. It is confirmed that Trouton ratio is important in determining the recirculating vortex and the extra pressure loss in entrance flow. Extra pressure loss and vortex length predicted by a finite element simulation of a planar entrance loss are compared with the corresponding predictions from Binding’s approximate analysis.
Flow Fields of Polymer Melt Flowing through Wedge Converging Channel
Authors: Huang Han-Xiong
Published: July 2004

Simple formulae are proposed for the velocity and extensional strain rate profiles for a power-law fluid in a converging wedge channel. Trajectory images are obtained of a colored strand in the high density polyethylene melt flowing through a tapered slit die. The theoretically predicted trajectories are in reasonable agreement with the experimental results. The varying trends of the extensional strain rate with the radial and angular positions in the converging channel are then theoretically revealed.