bluuebunny/crossref_metadata_2025 huggingface dataset:
Greener Still?
Authors: Grendstad Gunnar , Wollebaek Dag
Published: March 2007

Perspectives on green political thought distinguish between anthropocentrism and environmentalism on one hand, and ecocentrism and ecology on the other. Green theorists argue for a difference in kind between the two domains, whereas survey researchers identify a difference in degree, as they carefully extend environmental scales to incrementally include ecological items. Eckersley's (1992) theory of green political thought identifies resource conservation, human welfare ecology, preservationism, and animal liberation as subtypes of anthropocentrism; and it identifies transpersonal ecology, autopoietic intrinsic value, and ecofeminism as subtypes of ecocentrism. The empirical results of testing Eckersley's framework indicate that the subtypes cannot be coherently subsumed under a general green dimension but that anthropocentrism and ecocentrism, to a large degree, are independent of one another. Young age and high education are inversely related to ecocentrism. This contradicts previous research on environmental concern.
Age and Gender-Related Differences in Strategy Use for Route Information
Authors: Brown Lenora N. , Lahar Cindy J. , Mosley James L.
Published: March 2007

Adults, ranging in age from 20 to 78 years, were required to give directions to a hypothetical stranger while looking at a map. The direction giving was scored according to the strategies employed by the direction giver (e.g., landmarks, relational turns, road names, and cardinality). The "map present" direction-giving paradigm was employed to reduce the influence of memory. The results suggest that the aging decline in spatial abilities does not influence direction-giving strategies when memory demands are minimal. Older adults are as proficient as young adults when employing direction-giving strategies. Middle-age females employed a significantly higher frequency of strategies relative to young males, young females, middle-age males, and older females. When accuracy was examined, gender-related differences favoring males were obtained for the relational strategy.
Controversial Facility Siting in the Urban Environment
Authors: Takahashi Lois M. , Gaber Sharon Lord
Published: March 2007

Conflict over facility siting has become increasingly common across facility types and neighborhoods throughout the United States. This article posits that the conflict about facility siting stems from the distinct roles played by the state (with a central role played by planners), the shadow state (consisting of voluntary and nonprofit organizations), and interest groups (primarily community residents). This article explores the similarities and differences in perception toward controversial facilities for two of these three actors: the state (represented by planning directors) and interest groups (in this case, community residents). To investigate the similarities and differences between resident and planner perceptions, this article analyzes the first national survey of resident attitudes, which included both environmental and human service facilities, and a recent national survey of planning directors. Implications of this analysis for understanding facility siting, community opposition, and planning responses are discussed.
Subtitling Rap
Authors: Havens Timothy
Published: March 2007

This article reports the findings of a pilot study of a single African-American situation comedy, The Fresh Prince of Bel-Air, among a small number of young viewers in the nation of Kuwait. It is intended as a first step toward investigating the popularity of black and African-American youth styles among young people from various parts of the globe, and the conclusions that the author reaches are intended to be suggestive rather than definitive. Throughout the article, the author focuses on questions that his research has raised about the pleasures and meanings that these young people derive from the series, and how the series might be implicated in the expression of distinct ethnic, generational and gender identities.
International Radio Broadcasting in Arabic
Authors: Boyd Douglas A.
Published: March 2007

This study updates five others by the author that provided information about governments and private organizations transmitting an Arabic-language radio service to the Middle East. For the purpose of analysis, these broadcasters were placed in six groups: Western Europe, the Commonwealth of Independent States and Eastern Europe, Asia and the Middle East, the Americas, Sub-Saharan Africa and Christian religious broadcasters. In addition to a discussion of the history of international broadcasting in Arabic and information about each service, survey data on Arab audiences are supplied.
The `Troubles' as Portrayed in Four Irish Newspapers
Authors: Vincent Richard C.
Published: March 2007

This article is an exploratory analysis of the linguistic treatment of the `troubles' by the Irish print media. It studies the national news reported by four different Irish newspapers published during a two-month period immediately following the violation of the cease-fire agreement by the IRA in February 1996. In an effort to understand better the many issues underlying the crisis, each newspaper's treatment of `the troubles' are studied and similarities and differences are examined. Computer-assisted content analysis is employed to survey the large volume of news stories for relevant news, and to help examine tendencies in specific language utilization, particularly as it exemplifies selected theories of conflict resolution. By utilizing certain language and focusing on particular issues, it appears that the press has the power to help promote community dialog and potentially resolve conflicts. At the moment, however, stronger efforts are needed since the newspapers examined often reflect the biases of particular communities and readerships.
Ethnic Minorities and Television
Authors: Halloran James D.
Published: March 2007

The use of and attitudes to television of 182 people of `Asian origin' in the city of Leicester, UK, purposively selected with regard to age, gender and ethnic group, were studied by means of interviews and discussion groups. Although there were marked differences at all levels between and even within the various minority groups, there was a well nigh unanimous criticism of the negative way television was perceived as portraying ethnic minorities and Third World countries. Looking to the future, although there was no unanimity about the use of language, special provision or the establishment of separate channels, there was a widespread wish for more `Asian involvement' and a more balanced presentation which would `present us as we really are, an integral part of a multicultural society, not in well-worn stereotypes or in special slots'. Television was not seen as contributing to the development of a multicultural society.
Vision Revisited
Authors: Levin Ira M.
Published: March 2007

Organization vision has been a topic much discussed and written about over the past couple of decades. Yet, confusion still exists regarding what it is and how it is most effectively conveyed. Vision is often confused with the similar constructs of organization mission, philosophy and values, strategy, and goals. This article examines the key differences among these frequently confused constructs and the inherent weaknesses of traditional vision statements to provide the sense of meaning and motivation for organization members. A different concept of organization vision is presented—vision as a descriptive story of the desired future in action. Several examples of such vision stories are presented. A case example is used to illustrate how to develop the vision story and deploy it through-out an organization to gain shared commitment to it.
Self-Fulfilling Prophecy and Escalating Commitment
Authors: Edwards John C.
Published: March 2007

In this article, the author extends the work on self-fulfilling prophecy and escalating commitment as cognitive phenomena that can cause organizational crisis. A detailed description of the FBI standoff with the Branch Dividians at Waco, Texas, provides a unique setting in which to examine the phenomena of self-fulfilling prophecy and escalating commitment. Based on this detailed description, an analysis of the cognitive processes of key decision makers during the Waco standoff reveals that both self-fulfilling prophecy and escalating commitment interacted to cause organizational crisis. The analysis further suggests that variances in perceived behavioral control and cognitive categorization altered the likelihood of a self-fulfilling prophecy or an escalating commitment being enacted by decision makers. These two deviation-amplifying loops, escalating commitment and self-fulfilling prophecy, can interact if decision makers implement bipolar decision alternatives or exclude expert advice. The article concludes with a discussion of the implications for academic researchers and organizational leaders.
The Prison Birth of Black Power
Authors: Johnson Roberta Ann
Published: March 2007

If ever America undergoes great revolutions, they will be brought about by the presence of the black race on the soil of the United States; that is to say, they will owe their origin, not to the equality, but to the inequality of condition.
Investigation of Acoustic Emission During Fatigue Loading of Composite Specimens
Authors: Williams R.S. , Reifsnider K.L.
Published: March 2007

Strain and load controlled fatigue tests were run on boron-aluminum and boron-epoxy angle-plied specimens. Acoustic emission data was recorded using a gating technique that eliminated most extraneous noise. Various material parameters were monitored during the test. A good corre lation between acoustic emission and damage extent and propagation was obtained. This was evidenced by an apparent first order linear relationship between dynamic compliance and totalized acoustic emission. A basis for an energy based failure model is formulated and discussed.
Dynamic Mechanical Behavior of Fiber-Reinforced Composites: Measurement and Analysis
Authors: Gibson Ronald F. , Plunkett Robert
Published: March 2007

This paper describes analytical and experimental efforts to find the internal damping and elastic stiffness of E-glass fiber-reinforced epoxy beams under flexural vibration. Stiffness and damping are expressed in terms of effective complex moduli. The parameters considered in the study are geometric configuration, vibration frequency, and vibration amplitude. Comparison. of measured values of the complex moduli with predicted moduli and with predicted bounds on the moduli shows that, for small amplitudes, the predicted values are reasonably accurate. Damping and stiffness are independent of amplitude as long as the maximum strain amplitude does not exceed the threshold strain for material damage. Once this threshold strain is exceeded, however, permanent changes occur in damping and stiffness. The resulting increase in damping is much more significant than the corresponding reduction in stiffness.
Effects of Moisture and Temperature on the Tensile Strength of Composite Materials
Authors: Shen Chi-Hung , Springer George S.
Published: March 2007

The ultimate tensile strengths of Thornel 300/Fiberite 1034 graphite epoxy composites were measured with material temperatures ranging from 200 K to 422 K and moisture contents from 0% (dry) to 1.5% (fully saturated). All measurements were performed using 0°, 90° and π/4 laminates. A survey was also made of the existing data showing the effects of temperature and moisture content on the tensile strength of different composites.
Deformation and Fracture of Resin Matrix Composites in Combined Stress States*
Authors: Guess T.R. , Gerstle F.P.
Published: March 2007

The analytical prediction of elastic constants and strengths in highly anisotropic composites is complex and always requires experimental verifi cation. This paper describes a study of the room-temperature mechanical characterization of high performance reinforced-resin composite materials. The composites were fabricated from three high strength filaments: Union Carbide's graphite fibers, Thornel 75S and Thornel 400 and duPont's organic fiber, Kevlar 49. The matrix was a filament-winding epoxy resin, Dow Chemical DER-332 room-temperature cured with Jeffamine T-403. Test specimens were thin-walled, cylindrical tubes fabricated with unidirec tional (90° or hoop wound) or quasi-isotropic [±30/90] S filament orienta tions. Specimens were tested in uniaxial and biaxial tension; axial loads were applied with an electrohydraulic testing machine and circumferential loads by internal pressurization. Deformations were monitored with strain gages.

Data from uniaxial tests and from the literature provided the elastic properties and strengths of the unidirectional composite. The stiffness data were used to calculate, from lamination theory, the macroscopic elastic stiffnesses of the quasi-isotropic tubes which were in good agreement with experimental values. Strength data are compared to four empirical strength criteria.
Buckling of Rotationally Restrained Orthotropic Plates Under Uniaxial Compression
Authors: Simitses G.J. , Giri J.
Published: March 2007

A solution methodology is developed to predict critical conditions for rotationally restrained orthotropic plates loaded by a uniform axial com pression. In addition, parametric studies are performed to find the effect, on the critical load, of various elastic constants for a practical range of aspect ratio values and the entire range of rotational restraint, including the extreme cases of simply supported and clamped plates. The generated data are based on the assumption of symmetric boundary conditions (the amount of rotational restraint is equal for opposite sides) although the methodology is not limited by this assumption. Among the conclusions one may list that the most significant effect is that of the ratio of Young's moduli and amount of rotational restraint.
Effect of Cracks on Thermal Conductivity
Authors: Hasselman D.P.H.
Published: March 2007

Expressions are derived for the effect of penny-shaped cracks of various orientations on the thermal conductivity of solid materials.
A Numerical Study on Effects of Fiber-Orientation of a Unidirectional Elastic Solid Under Impact
Authors: Chen Y.M. , Lee Kelvin J.
Published: March 2007

A numerical study on effects of fiber-orientations of a unidirectional linear-elastic solid, not perpendicular to the direction of impulsive loading, on the wave propagation is performed by using a finite difference method, the AWMP code. A two-dimensional case of the penetration of a rigid punch into a unidirectional linear-elastic solid is used as the example. The fiber-orientation is found to play an important role in causing asymmetric wave patterns and generating asymmetric surface waves under symmetric loads. These asymmetric wave patterns resemble those in isotropic solids caused by asymmetric loads.
A Vibration Technique for Non-Destructive Testing of Fibre Composite Structures
Authors: Cawley Peter , Adams Robert D.
Published: March 2007

A vibration technique for non-destructively evaluating the integrity of structures is described and applied to components fabricated from fibre reinforced plastics. The method uses measurements of changes in the lower structural natural frequencies, which can be made at a single point in the structure, in conjunction with a dynamic analysis of the system to detect, locate and roughly to quantify damage. The mathematical model of the structure need not be sophisticated and only one analysis is required for each type of structure to be tested. It is shown to be possible to detect and locate a variety of types of damage in structures which are representative of the use of fibre reinforced materials in the aerospace industry.

An indication of the severity of damage is also obtained.
Analysis of the Thermal Expansion Coefficients of Particle-Filled Polymers
Authors: Takahashi Kiyohisa , Harakawa Kazuhisa , Sakai Tetsuya
Published: March 2007

An attempt has been made to predict the thermal expansion coefficients of particle-filled polymers in which particles have various types of orienta tion distributions. The calculation is based on Eshelby's theory and a kind of self-consistent method is introduced to estimate the effect of the orien tation distribution together with the interaction among particles. The ex pression for the space random orientation of disk-shaped particles with infinitesimal aspect ratio, which is derived here, agrees with lower bound of isotropic composites predicted by Schapery. The calculated results are also compared with existing experimental data for glass particle-epoxy resin composites, and these are almost in good agreement.
Stress Wave Damage in Graphite/Epoxy Laminates
Authors: Roylance David
Published: March 2007

A series of unidirectional graphite/epoxy laminates of various fiber moduli have been subjected to uniaxial-strain shock loading to assess their resistance to dynamic loading. All of the laminates were found to exhibit nearly identical values of wave attenuation and shock hardness, and the resistance to impact in the through-thickness direction was ascribed prima rily to the response of the epoxy matrix.
An Advanced Shear-Lag Model Applicable to Discontinuous Fiber Composites
Authors: Fukuda Hiroshi , Chou Tsu-Wei
Published: March 2007

This paper develops an analysis for predicting the stress distribution in unidirectional discontinuous fiber composites. Although the basic ap proach is based upon the shear-lag analysis, the load transfer at fiber ends is taken into consideration. This consideration becomes important if the bonding between the fiber and matrix at the fiber end is perfect such as the cases often observed in metal matrix composites, as well as during the early stage of loading of polymeric matrix composites. The present analysis in cludes the ordinary shear-lag analysis as a special case.
On Stiffness and Strength of an Aligned Short-Fiber Reinforced Composite Containing Penny-Shaped Cracks in the Matrix
Authors: Taya Minoru
Published: March 2007

A model study is conducted on the prediction of the stiffness and fracture toughness of an unidirectional short-fiber reinforced composite containing numerous cracks in the matrix. It is assumed in our model that short-fibers are aligned in the uniaxial loading direction and that cracks in the matrix are perpendicular to the loading axis and are penny-shaped. Then the longitudinal Young's modulus of the composite weakened by those cracks and the energy release rate of a representative penny-shaped crack are com puted by a combination of Eshelby's equivalent inclusion method and Mori- Tanaka's back stress analysis. The interaction between fibers and that be tween fibers and cracks are taken into account by Mori-Tanaka's back stress analysis. Hence our results are valid even for a large volume fraction of fiber and crack.
Elastic Behavior of Woven Hybrid Composites
Authors: Ishikawa Takashi , Chou Tsu-Wei
Published: March 2007

Basic geometrical and material parameters are identified to characterize the structure of hybrid fabrics. Analysis of the elastic behavior is made based upon a mosaic model and the fabric composite can be regarded as an assemblage of assymetrical crossply laminates. Upper and lower bounds of elastic properties have been obtained and the results compare very favorably with experiments. The influence of fabric parameters on the elastic behavior has been demonstrated especially for the bending-stretching coupling effect. Essential considerations for fabric design also have been discussed.
Buckle Pattern of Biaxially Compressed Simply Supported Orthotropic Rectangular Plates
Authors: Libove Charles
Published: March 2007

Simply supported orthotropic elastic rectangular plates in biaxial compres sion are considered, and it is proved that such plates will buckle with m or n (or both) equal to 1, where m and n are the number of half waves in the two prin cipal directions. While this theorem may be known to many as an empirical computational fact, it does not appear to have been explicitly stated or proved heretofore in the literature on orthotropic plates
The Damping and Dynamic Moduli of Symmetric Laminated Composite Beams—Theoretical and Experimental Results
Authors: Ni R.G. , Adams R.D.
Published: March 2007

A method for predicting the dynamic properties of laminated composite beams has been developed in this work.
Evaluation of the Tensor Polynomial Strength Theory for Wood
Authors: Liu J.Y.
Published: March 2007

The tensor polynomial (Tsai-Wu) strength theory with the interaction stress coeffi cient, F12, determined from the Hankinson formula, has been applied in this study to predict the strength of wood under plane-stress conditions. The biaxial failure envelope for Sitka spruce, based on this choice of F12 and the mechanical properties from the Wood Handbook, is presented. F12 is very sensitive in biaxial loading tests and can be extremely difficult to obtain in such tests on wood. Since the Hankinson formula has been verified repeatedly and has been popular in the wood industry, it is recommended that F 12 be based on the Hankinson formula.
Prediction of Tensile Matrix Failure in Composite Laminates
Authors: Flaggs D.L.
Published: March 2007

A conceptually simple mixed mode fracture analysis method is presented for the prediction of tensile matrix failure in composite laminates. The analysis technique, which makes use of a mixed mode strain energy release rate fracture criteria in con junction with an approximate two-dimensional shear-lag model, is cast in terms of a tensile matrix strength criterion. In contrast to presently available point stress tech niques, surprisingly accurate predctions of mode I matrix failure in the 90° lamina of (±θ/90 n) s and mixed mode matrix failure in the θ° lamina of (02/θ) s T300/934 com posite laminates are observed.
Delamination Growth in Angle-Ply Laminated Composites
Authors: Kim K.S. , Hong C.S.
Published: March 2007

Delamination, a frequently observed failure mode in composite laminate, is a key issue in structural design and integrity consideration. In this paper, the stability of delamination crack is investigated for angle-ply laminates subjected to uniform displacement and ther mal loading. Due to the complexities of the problem, a quasi three-dimensional finite ele ment method is used to obtain strain energy release rate. The effect of parameters, such as temperature drop, loading type, stacking sequence, laminate width and laminate thick ness will be considered. Also, the effect of delamination crack on the tensile strength of angle-ply laminate for small fiber orientation is evaluated by using a rule of mixtures and energy release rate concept in classical fracture mechanics. Finally, failure mode and ten sile strength are predicted and compared with known experimental data to assess the pre diction accuracy of the delamination growth model.
Transverse Thermal Expansion Coefficients for Composite Laminates
Authors: Wetherhold Robert C. , Boss Christopher S.
Published: March 2007

A simplified derivation has been performed for the transverse thermal expansion coeffi cient for a symmetric composite laminate. In numerically evaluating the resulting expres sion, it was noticed that the dominant term for the transverse expansion of each lamina was invariant with respect to the lamina orientation. Subsequent manipulation of the analytical expression has proven this. This result limits the flexibility for designing laminates with unusual transverse expansion properties. Simple bounds on the transverse expansion coefficient are suggested.
Strength and Response of Cylindrical Composite Shells Subjected to Out-of-Plane Loadings
Authors: Chang Fu-Kuo , Kutlu Zafer
Published: March 2007

An investigation was performed to study the response of cylindrical composite shells subjected to out-of-plane loads. During the investigation, an analytical model was devel oped to predict the mechanical behavior of the structures from the initial failure, through post-failure, to the final collapse. The model is also capable of predicting the residual stiffness and strength of the structures after a preload. Basically, the model consists of a structural analysis for calculating the global response of the structures, and a failure analysis for predicting local damage of the structures and their residual stiffnesses and strengths. A nonlinear finite element code based on the updated Lagrangian formulation was developed for the model. To verify the model, experiments were also conducted. An excellent agreement was found between the computer simulations and the test results. It is expected that the model can be extended to more complicated structures with various load ing conditions.
The Influence of Matrix Fracture Strain and Interface Strength on Cross-Ply Cracking in CFRP in the Temperature Range of -100°C to +100°C
Authors: Peters P.W.M. , Andersen S.I.
Published: March 2007

Cross-ply cracking in specimens out of the laminate 0/904/0 was in vestigated at -100°C, -40°C, RT, 60° and 100°C. The thermal strain in the transverse ply at these temperatures was determined with the thermal expansion coefficients in fibre direction and transverse to the fibre of a unidirectional laminate. These thermal expansion coefficients were found to vary approximately linearly with the temperature.

Multiple fracture of the 90°-ply of 0/904/0 specimens was registered with the aid of a piezo-electric transducer in connection with a computer during a displacement-controlled quasi-static tensile test. The 904-ply is divided in a number of elements N all of which can break. The registered crack data ( n cracks, n < N, with their respective fracture strains) can be described by two-parameter Weibull distributions of the fracture strain ( = thermal plus mechanical strain). From the Weibull distributions and an available model for the transverse fracture strain distribution it was found that at increasing test temperature two phenomena influence the transverse fracture strain. These are the fracture strain (and duc tility) of the matrix and the strength of the interface, which at increasing temperature im proves and reduces the transverse fracture strains respectively. First ply failure proved to be dominated by the increasing fracture strain of the matrix from -100°C to RT. Above RT, however, the influence of the decrease in interface strength dominates over the in fluence of the increased matrix fracture strain.
Fatigue Degradation in Centrally Notched Quasi-Isotropic Laminates
Authors: Jen Ming-Hwa R. , Hsu J.M. , Hwang D.G.
Published: March 2007

The aim of this research is first to model the degradation of the elastic modulus of quasi-isotropic [0/90/ ±45]2 s graphite/epoxy centrally notched composite lam inates subjected to tension-tension ( T-T) fatigue tests. Then we can predict the fatigue life in terms of elastic modulus as a non-destructive parameter of failure criterion and express the residual strength by using the elastic modulus degradation model. Extensively, the concept of cumulative damage is adopted to expand these models for wide applications to any sequence of loading spectrum instead of the constant stress amplitudes. These models have been modified from the existing models, they possess the features of accuracy, sim plicity and applicability. Basically, part of them are verified satisfactorily in comparison with the experimental data. They still have sound theoretical bases and simply applicable to engineering problems.
Prediction of Notched Strength of 3D Carbon Carbon Materials Under Tension with Large Off-Axis Angle, Part I
Authors: Gu Z.L. , Jianfeng Chen
Published: March 2007

The experimental observations show that a notched 3D carbon carbon spec imen under tension with large off-axis angles will fail due to shear fracture of the fiber bundle. To analyse the failure mechanism, the stress field in front of the notch tip was computed using the finite element method based on a global-local concept. Finally Zwe ben's statistical strength criterion was employed to predict the notched strength based on the shear strength of fiber bundles measured on a specially designed setup. The predicted results are in good agreement with the experimental results.
Process Simulated Laminate (PSL) : A Methodology to Internal Stress Characterization in Advanced Composite Materials
Authors: Manson Jan-Anders E. , Seferis James C.
Published: March 2007

Solidification, under nonisothermal conditions and pressure gradients present during processing, is shown to be a major contributor to the generation of internal stresses in advanced composite materials. These stresses may be amplified in composite materials with significant anisotropic characteristics. Using the process simulated lami nate (PSL) technique, a methodology was developed for the evaluation of the residual stress distributions induced during processing. The PSL contained separation films placed between certain layers of the laminate, enabling separation of the laminate after process ing. Using a strain gage attached to the laminate, the residual stress distribution over the laminate was calculated. The detached laminates served as specimens for the evaluation of through-thickness morphological and property distributions. The direct relationship be tween the residual stresses and the investigation of stress releasing phenomena such as voids, microcracks and/or fiber buckling was important for a complete evaluation of pro cess induced effects. Different techniques for residual stress evaluation were presented and compared for pressformed 40-ply unidirectional composites cooled at a rate of 20-50°C/s. A pronounced skin-core stress profile was observed in unidirectional PEEK/AS4 compos ites demonstrating compressive stresses at the surface and tensile stresses at the center of the laminate.
Fiber-Matrix Adhesion and Its Effect on Composite Mechanical Properties: IV. Mode I and Mode II Fracture Toughness of Graphite/Epoxy Composites
Authors: Madhukar Madhu S. , Drzal Lawrence T.
Published: March 2007

To optimize the level of fiber-matrix adhesion an understanding of the relationship between fiber-matrix interfacial bond strength and the mechanical and frac ture behavior of composites is essential. This study establishes the relationship between fiber-matrix interfacial shear strength (ISS) and interlaminar fracture toughness (both Mode I and Mode II) and failure modes for graphite/epoxy composites. A well defined and characterized graphite fiber/epoxy system was chosen in which the level of adhesion be tween fiber and matrix was changed by using the same graphite fibers with different sur face treatments. These surface treatments changed the level of adhesion between the fiber and matrix thus resulting in an increase of the fiber-matrix ISS by over a factor of two while the fiber and matrix properties remained unchanged. The Mode I and Mode II tests were conducted by the double cantilever beam (DCB) and end-notch flexure (ENF) tests methods, respectively. The Mode I fracture toughness ( GIC) of composites having low fiber-matrix ISS could not be determined from the DCB test because of extensive fiber bridging and crack meandering. For the composites having higher values of the ISS, the GIC increased with the ISS. The experimental results demonstrated that there is a strong dependency of Mode II fracture toughness ( GIIC) on fiber-matrix adhesion. Increased fiber-matrix adhesion in one group of composites significantly improved the GIIC , but the presence of brittle interphase around graphite fibers in another group of composites tended to cancel part of the improvement resulting from increased adhesion. Based on the major failure modes occurring during the Mode I and Mode II loading conditions, a causal link age between fiber-matrix adhesion and interlaminar fracture behavior of graphite/epoxy composites is established.
Reduction of Thermal Residual Stresses in Advanced Metallic Composites Based upon a Compensating/Compliant Layer Concept
Authors: Arnold S.M. , Arya V.K. , Melis M.E.
Published: March 2007

High residual stresses within metal and intermetallic matrix composite systems can develop upon cooling from the processing temperature to room temperature due to the coefficient of thermal expansion (CTE) mismatch between the fiber and matrix. As a result, within certain composite systems, radial, circumferential, and/or longitudinal cracks have been observed to form at the fiber-matrix interface region. The compliant layer concept (insertion of a compensating interface material between the fiber and matrix) has been proposed to reduce or eliminate the residual stress buildup durmg cooling, and thus minimize cracking. The present study investigates elastic-plastically the viability of the proposed compliant layer concept.

A detailed parametric study was conducted utilizing a unit cell model consisting of three concentric cylinders to determine the required character (i.e., thickness and mechanical properties) of the compliant layer as well as its applicability. The unknown compliant layer mechanical properties were expressed as ratios of the corresponding temperature depen dent Ti-24Al-11Nb (a/o) matrix properties. The fiber properties taken were those corre sponding to SCS-6 (SiC). Results indicated that the compliant layer can be used to reduce, if not eliminate, radial and circumferential residual stresses within the fiber and matrix and therefore also reduce or eliminate the radial cracking. However, with this decrease in in-plane stresses, one obtains an increase in longitudinal stress, thus potentially initiating longitudinal cracking. Guidelines are given for the selection of a specific compensating/ compliant material, given a perfectly bonded system.
Non-Uniform Finite Strip Method for Flexed Composite Plates
Authors: Avrashi J. , Lin C.H. , Rauch B.J. , Rhee J. , Rowlands R.E.
Published: March 2007

This article presents a new non-uniform finite strip technique for analyz ing composite laminates having both material and geometrically non-uniform cross sec tions. This is an extension of the conventional concept of the finite strip method which deals with uniform cross sections only. The application of the proposed method for flexed composite plates is illustrated. Numerical results are demonstrated for a transversely loaded circular composite plate containing an eccentric hole and are compared with those from an independent finite element analysis and with measured data. The spectral conver gence characteristics of the non-uniform strips are discussed, and the enhanced accuracy and reduced computer efforts are compared with those for the conventional finite element method.
An Investigation of the Existence of a Work Potential for Fiber-Reinforced Plastic
Authors: Lamborn M.J. , Schapery R.A.
Published: March 2007

Experimental data from axial and torsional deformation tests on inelastic, angle-ply fiber-reinforced plastic laminates and related theory are used to show that mechanical work is independent of path for suitably limited deformation paths, and thus is a potential. First, results from proportional deformation tests are shown to support the existence of a work potential. Domains of path-independence are then established for non- proportional deformation tests of laminates strained well into the range of nonlinear in elastic behavior. Lastly, a study is described in which a work potential-based theory is used to determine critical mixed-mode energy release rates for laminates subjected to axial and torsional deformations. This relatively simple analysis is shown to provide qualitative correlation between fracture surface morphology and calculated energy release rates.
An Experimental Study on the Use of Static Effective Modulus Theories in Dynamic Problems
Authors: Ditri John J. , Rose Joseph L.
Published: March 2007

In a recent paper [1] the effective elastic constants of a [0, ±45,0] 36 graph ite epoxy laminated composite were determined by ultrasonic wave velocity information, and the Young's moduli calculated from these constants were compared to those obtained using a quasi-static loading technique for six different directions. In this article, the previ ously obtained results are compared to those predicted using a three-dimensional static effective modulus theory [2]. It is shown that, if low frequency ultrasonic waves are used, the calculated Young's moduli compare favorably with both the static measurements and those predicted by the effective modulus theory. Comments on the applicability of the various measurement techniques for different purposes are also discussed.
A Study on the Application of Work Factor Approach to Composite Laminates
Authors: Rhee K.Y. , Ernst H.A.
Published: March 2007

Static fracture tests using the cracked lap shear (CLS) specimens made of thermoplastic composite APC-2 were conducted to verify if the elastic work factor devel oped previously is a valid parameter to calculate energy release rate from a single speci men. Also, the elastic work factor was derived theoretically based on a beam analysis. The experimentally determined elastic work factor, (η el)exp was compared with those calculated from a beam analysis and a finite element analysis. The results showed that the elastic work factors determined from these three ways are comparable to each other. In ad dition, the elastic work factor was applied to determine a critical energy release rate, and it was found that the elastic work factor approach can be used to determine energy release rate from a single specimen.
The Influence of Cool-Down Temperature Histories on the Residual Stresses in Fibrous Metal-Matrix Composites
Authors: Yeh Nan-Ming , Krempl Erhard
Published: March 2007

The vanishing fiber diameter model together with the thermoviscoplastic ity theory based on overstress including a recovery of state formulation is introduced. They are employed to analyze the effects of temperature rate and of annealing at constant temperature on the residual stresses at room temperature when unidirectional fibrous metal-matrix composites are cooled down from 1000°C during the manufacturing process. For the present analysis the fibers are assumed to be transversely isotropic thermoelastic and the matrix constitutive equation is isotropic thermoviscoplastic including recovery of state. All material functions and constants can depend on current temperature. Yield sur faces and loading/unloading conditions are not used in the theory in which the inelastic strain rate is solely a function of the overstress, the difference between stress and the equi librium stress, a state variable of the theory. Assumed but realistic material elastic and vis coplastic properties as a function of temperature which are close to W/9Cr-lMo steel com posite permit the computation of residual stresses. Due to the viscoplasticity of the matrix time-dependent effects such as creep and change of residual stresses with time are found. It is found that the residual stresses at room temperature change considerably with temper ature history. The matrix residual stress, upon reaching room temperature, is highest for the fastest cooling rate, but after 30 days rest the influence of cooling rate is hardly notice able since relaxation takes place. Annealing periods can reduce the residual stresses com pared to continuous cooling.
Predicting High Temperature Ultimate Strength of Continuous Fiber Metal Matrix Composites
Authors: Barbero Ever J. , Kelly Kevin W.
Published: March 2007

A model to predict the high temperature ultimate strength of a continuous fiber metal matrix composite (CFMMC) has been developed. The model extends the work of Rosen by including high temperature processes such as matrix creep, fiber-matrix de bond, and the effects of randomly spaced fiber breaks which typically exist in the MMC prior to loading. A finite element model (FEM), developed in the form of a representative volume element (RVE), is used to calculate the time-dependent stress field surrounding a fiber break. Variables included in the calculation are process-related parameters such as the fiber diameter, the fiber-matrix interface strength, and interface roughness. Statistical analysis is used to infer the strength of a large composite sample from the stress analysis of a single break provided by the FEM.
Cavitation Erosion Performance of Fiber Reinforced Composites
Authors: Hammond Douglas A. , Amateau Maurice F. , Queeney Richard A.
Published: March 2007

The cavitation damage resistance of several fiber reinforced polymeric composite systems was evaluated before and after seawater immersion via a modified ASTM G-32 method utilizing a stationary specimen. For both dry and saturated condi tions, a carbon fiber/thermoplastic toughened epoxy matrix composite (IM7/977-2T) was found to perform the best under cavitation attack, while carbon fiber/thermoplastic matrix (AS4/PEEK) was found to be the least resistant. Glass/epoxy composites (E-Glass/5920, Scotch Ply 1002) were intermediate in erosion resistance. Moisture absorption was seen to decrease the erosion resistance of both E-Glass/5920 and AS4/APC-2 materials, while increasing the resistance of SP 1002; IM7/977-2T was not affected by immersion. All mate rials show decreasing erosion rates due to material recession from the cavitation cloud and increasing collapse-shielding with exposure time. A reduction in water hammer pressure was estimated by incorporating finite material impedance into the water hammer equation. Using simplifying assumptions, a 15 percent reduction in water hammer pressure is calculated.
The Reduction of Environmental Effects on Tension-Twist Coupled Composite Tubes
Authors: Hill Stephen C. , Winckler Steven J.
Published: March 2007

A method is presented for designing composite laminates which will pro duce tension-twist coupling in tubes but show reduced variation in that coupling due to hygrothermal effects. Experimental results are presented which demonstrate coupling vari ations due to changes in temperature and moisture content. These effects are modeled the oretically as the variation of constituent shear moduli since shear modulus dominates cou pling behavior. This model predicts the same form of variation as seen in the experimental measurements of coupling. Based on laminates which do not exhibit thermally induced shear deformation, hybrid laminates were developed that can reduce or eliminate hygro thermal sensitivity while retaining coupling.
Do We Need a Concept of Culture?
Authors: Jahoda Gustav
Published: March 2007

Rohner's analysis of the concept of culture is critically examined, considering in particular the distinction drawn between culture and social system. His view is contrasted with that of Segall, who regards the concept of "culture" as redundant for cross-cultural psychology. It is argued that neither of these positions is adequate, and suggestions are made for ways out of the dilemma.
Provision for Adversity
Authors: McGuire Martin C.
Published: March 2007

As contemporary globalization of the world economy continues, each nation enjoys the benefits of greater exploitation of scale economies and of specialization and exchange. But equally true, globalization causes greater dependence among regions, nations, and localities, and this necessarily implies greater vulnerability to disruption of supply to and from each other. Alternative actions that countries might take or actually have taken to manage this vulnerability include (1) stockpiling of goods that might be lost due to political, economic, or natural causes; (2) protection of domestic industries that otherwise could not compete in world markets (the classical “national security” argument for protectionism); (3) maintenance of standby production capabilities, itself closely related to stockpiling; and (4) formation of special economic unions or contingency agreements to guarantee stable supply and exchange. This article develops a unified analysis of the first two of these alternative policies. The analysis examines and summarizes how all these factors combine to determine the optimal level and mix of policies.
The Evolution of Heterogeneity in Biodiversity and Environmental Regimes
Authors: Arce M. Daniel G.
Published: March 2007

Biodiversity and environmental protection are examples of international public goods problems that comprise a symmetrical system of rights and obligations. Moreover, the underlying scientific, economic, and political conditions do not necessarily lead to a prisoner's dilemma. Yet from this symmetrical beginning, voluntary (Nash) equilibria often require heterogeneous actions, the resolution of which is often couched as a North-South or East-West issue. The author uses evolutionary game theory to examine how heterogeneous behavior can emerge over time and finds that asymmetries need not be universally determined in terms of economic or technological differences. In particular, the author finds that the evolution of international environmental protocols is a function of scale: the ability to achieve a cooperative solution depends on the distribution of signatories (namely, nonparticipants in the population at large). Such scale considerations reveal an organizational pattern of collective action that does not require across-the-board contribution or abatement levels.
International Bargaining with Two-Sided Domestic Constraints
Authors: Tarar Ahmer
Published: March 2007

Putnam revived interest in the “Schelling conjecture” that in international bargaining, a domestic ratification constraint provides a negotiator with a bargaining advantage. However, existing formal analyses of the Schelling conjecture generally allow only one side in the bargaining to be constrained. In this article, a model is analyzed in which both negotiators are constrained. A generalized version of the Schelling conjecture holds that if one negotiator's constraint is high and the other's is only low or medium, the former gets a better deal than if neither side were constrained, and the latter is worse off. With incomplete information, however, the complete opposite of what the Schelling conjecture predicts can occur, and there is an equilibrium in which delay in reaching an agreement results in both sides being worse off than if neither side were constrained. Incomplete information can but does not always completely eliminate the advantage of having a high constraint.
Learning About the Value of Global Cooperation
Authors: Volgy Thomas J. , Quistgaard Jon E.
Published: March 2007

As a corollary to Robert Angell's measures of world order, this article examines nation-state differences in support for world order as a function of learning through involvement in the United Nations. Differences in national support for world order are analyzed in terms of "role-taking" and "cue-taking" in the United Nations. The authors identify seven types of roles, based on the degree to which nation-states approximated support for the norms of the organization. Correlational analysis indicates that these roles function as good predictors to variance among nations in their support for world order. Alternatively, nations which could not be classified as taking on a definitive role were hypothesized to be "taking cues" about the value of global cooperation from their regional counterparts. This predicted outcome was also supported. Finally, analysis of "deviant" cases indicated that for some nations, both role-taking and cue-taking may be equally salient for supporting world order.