bluuebunny/crossref_metadata_2025 huggingface dataset:
Playing the Edge
Authors: Ewert Alan W.
Published: March 2007

Activities in a natural environment that involve risk and danger to the participant have become more popular over the last decade. This article describes a study on the motivations for high-altitude mountaineering at Mount McKinley in Denali National Park, Alaska. Using a principal components factor analysis, five factors emerged, accounting for 92% of the explained variance. Overall, scale items such as exhilaration, excitement, and accomplishment appeared as important motivating variables. Risk taking as a motivating variable did not generate a high level of motivational importance. Based on experience levels in mountaineering, a number of differences were observed in the patterns of motivational importance. The findings suggest that participants in risk recreation report different patterns of motivations that are contingent on their levels of experience.
Preference for Urban Buildings as a Function of Age and Nature Context
Authors: Herzog Thomas R. , Gale Theresa A.
Published: March 2007

Preferences for urban buildings were studied as a function of building age and nature context. The primary finding was that old buildings were preferred over contemporary buildings when building care was equated statistically, but the reverse was true in the absence of such control. Thus, when older buildings are disliked, poor maintenance is likely to be a contributing factor. A natural context enhanced building preference, but only when it was well maintained. In general, rated building care and nature care were positively related to preference and to each other. Thus the results highlighted the substantial impact of building age and both building and nature care on building preference. Other analyses suggested that the positive impacts of age and nature context on preference were at least party mediated by their generally positive impacts on variables such as complexity, mystery, and coherence.
Black Environmentalism in the Local Community Context
Authors: Arp Wiwam , Kenny Christopher
Published: March 2007

In this article it is argued that existing studies of Black environmentalism do not appropriately measure the environmental concerns and activities most relevant to Blacks and hence do not accurately reflect the extent to which African Americans are responsive on environmental issues. Using data that measure Black environmental concern and activity in communities threatened by hazardous industries to various degrees, the authors evaluate 2 competing sets of expectations regarding the manner in which these concerns and activities are affected by differential environmental threats to the community. They find that specific local concerns and activities depend, to some extent, on the nature of the threat from nearby industry, but that more general attitudes toward the regulation of industry and concern about the environment do not Reasons as to why this might be the case are discussed.
Windows and Environmental Cues on Performance and Mood
Authors: Stone Nancy J.
Published: March 2007

Task type and the presence of windows and posters were manipulated to examine their effects on individuals' performance, mood, and perceptions. Male and female undergraduates worked either a filing, computational, or creative task in a windowed or windowless room, with or without a poster (i.e., task-relevant cues). As predicted, the presence of windows did not affect performance. Window presence increased perceptions that the room was motivating and the likelihood that one looked about the room for help with the computational task. Unexpectedly, the number of errors on the computational task was reduced when the task-relevant poster was present. Poster presence also increased positive mood and decreased fatigue perceptions for individuals performing the creative task. Overall, poster presence increased confidence. Because perceptions of task demand were related to several outcome variables, the stimulation from windows and posters appears to interact with the task demand.
An Overview of Teenagers and Television Advertising in the United States
Authors: Ferle Carrie La , Li Hairong , Edwards Steven M.
Published: March 2007

Teens in the US are an increasingly important segment of the consumer market because of their size, available disposable income, lifestyle and the potential for lifetime brand loyalty. Recent increases in teen programming across major US television networks have been effective in attracting teen viewership and forming a sizeable market for advertisers. This article examines the development of Generation Y as a profitable consumer market in the US. A discussion on the impact of increases in teen-directed television programming and advertising on the teen socialization process is also presented. Implications for communication specialists, public policy-makers and researchers are considered.
Global vs Local Advertising in Taiwan
Authors: Krishna Vijay , Chuang Reuyling , Axinn Catherine
Published: March 2007

This article investigates the differences in Taiwanese television advertisements for local and global products with regard to the degree of informativeness, type of cues and product class. The sample included advertisements that appeared on the three major networks (CTV, TTV and CTS) in 1993. The majority of the advertisements promote local brands. Results indicate a significant difference between global and local advertisements with regard to the above-mentioned criteria.
Investigating the Determinants of International News Flow
Authors: Wu Haoming Denis
Published: March 2007

Studies investigating the determinants of international news flow in the past few decades are systematically reviewed and analyzed. The factors found in these various studies can be demarcated into two broad categories: gatekeeper perspective and logistical perspective. A synthetic profile of the past studies is also provided, which includes the regions and topics covered by international news, geographic distribution of the studies' locales, space/newshole allotted for different regions, and media examined by the studies. The article ends with a critique of the past studies and offers some prospects for future research on this topic.
The Beijing Conference on Women as Seen by Three International News Agencies
Authors: Giffard C. Anthony
Published: March 2007

Of the seven major United Nations conferences on global issues in the last decade, only one took place in Asia. However, the Fourth World Conference on Women in Beijing in September 1995 was one of the largest multinational gatherings ever held, with 17,000 participants from 189 countries. In hosting the conference, China hoped to overcome the negative publicity it had endured after Tiananmen Square and to showcase the progress made by Chinese women. This study examines coverage of the conference by three international news agencies: the Associated Press, Reuters and Inter Press Service. It seeks to determine the amount and kind of coverage given to conference themes, and to Asian actors, organizations and nations in reports from the three news agencies.
An Information Society in Africa?
Authors: Nulens Gert , Van Audenhove Leo
Published: March 2007

The widespread belief in the benefits of information and communication technologies (ICTs) in a developmental context is shared and fostered by international organizations. In recent years they have introduced a multitude of programmes and initiatives in this field. This article sets out to critically analyse the formal ICT policy of three international organizations, namely the World Bank, the International Telecommunications Union (ITU) and the United Nations Economic Commission for Africa (ECA). In order to do so, policy is analysed according to three dichotomies which are central to the debate on the Information Society: materialism/idealism, technophilia/technophobia and market/state. As is the case for Europe, it is argued that discourses on the Information Societies in developing countries often do not transcend these simplistic dichotomic pairs.
The Impact of Cable Television on Political Campaigns in Taiwan
Authors: Chiu Peilin , Chan-Olmsted Sylvia M.
Published: March 2007

This study examines the impact of cable television on Taiwan's election campaign strategies, the implications of political affiliation/ownership of cable television for political campaigns and cable's role in Taiwan's democratization process. The results show that cable has provided an alternative platform for the opposition parties and encouraged the emergence of rational politics in Taiwan. More campaign media budget has been allocated for this emerging political medium, campaign candidates and staff are taking a proactive role in expending their cable airtime, especially in popular political call-in/debate programs, and the nature of the cable political programming is fostering more issues-based campaigns.
The Effects of Proximal and Distal Goalson Goal Level, Strategy Development, and Group Performance
Authors: Weldon Elizabeth , Yun Seokhwa
Published: March 2007

It was hypothesized that team members working toward short-term and long-term goals would perform better than teams only working toward long-term goals, because the former would invest more time and energy in efforts to develop effective task strategies. Thirty-one teams of nurse surveyors working in a state department of health set goals to improve the accuracy of their reports. One-half the groups set a long-term goal for accuracy (the level of accuracy they would ultimately try to achieve over the next 6 to 9 months). The other groups set a long-term goal and one or two short-term goals to serve as intermediate steps. Results showed that although team members in the short-term-plus-long-term-goal condition performed better than those in the long-term-goal condition, strategy development did not mediate this effect. Instead, group members in the short-term-plus-long-term-goal condition set more difficult long-term goals, and more difficult goals led to better performance.
The Role of Environment in Mental Health
Authors: Nikelly Arthur G.
Published: March 2007

Despite substantial progress in developing empirically validated psychotherapeutic treatments for specific mental health problems, most current efforts are based largely on treatment with drugs, which may not produce permanent recovery. The result has been an almost nihilistic attitude that assumes that little can be done to rehabilitate persons with mental health problems. Empirical evidence gleaned from innovative treatment programs and ethnocultural studies indicates clearly that healthy environments that provide meaningful work and a variety of nonmedical interventions offer more lasting health results than medical treatment alone. The supportive and curative influence of the environment has been greatly neglected, in part because of medical dominance in the treatment of emotional problems. More effective is the removal of the social, economic, and professional barriers to mental health and the strengthening of rehabilitative efforts that promote activity and purpose.
Violence is the Language of the Unheard
Authors: Smith Kenwyn K.
Published: March 2007

This article describes a Power Laboratory in the Barry Oshry tradition that has a chilling relevance for the post–September 11 world. In this Lab, the “have-nots” behaved in a way that was totally incomprehensible to the “haves. ” However, when the realities of all involved were understood, it was evident that the physical violence of the Outs was but a shadowymirroring of the systemic violence instituted and perpetuated bythose with power.
Inequality and Control in a Colonial Bureaucracy
Authors: Parris Ronald Glenfield
Published: March 2007

If the free traders cannot understand how one nation can grow rich at the expense of another, we need not wonder, since those same gentlemen also refuse to understand how within one country one class can enrich itself at the expense of another (Marx, 1963: 223).
Transmission Electron Microscopy of Interfacial Areas in Metal-Matrix Composites*
Authors: Hancock J.R.
Published: March 2007

Microtechniques of selected-area transmission electron microscopy have been developed for the study of interfacial areas in a high- strength aluminum alloy reinforced with stainless-steel wires. The specimen-preparation procedures are described and the conditions necessary for the successful production of useful areas of trans mission progressively nearer the interface in the composite foils are discussed. Dislocation arrangements in the aluminum alloy matrix of a composite subjected to fatigue loading have been ob served as a function of the distance from the filament-matrix interface. The dislocation density was not appreciably affected by the presence of the filament-matrix interface to within 25 microns of the interface. The results demonstrate the potential usefulness of such studies to the development of improved design criteria through a better understanding of the micromechanisms of com posite behavior.
Reciprocal Theorem for Displacements In Inelastic Bodies
Authors: Lin T.H.
Published: March 2007

Using the analogy between the inelastic strain gradient and applied body force, the reciprocal theorem for displacement in inelastic bodies is derived. The application of this theorem to find the deflection or slope at a particular point due to given in elastic strain distribution in the body is given. Using this theorem, the coincidence of yield surfaces with plastic potential is derived. This theorem may be applied to solid bodies of both homogeneous and composite materials.
Measurement of Whisker Orientation in Composites by X-Ray Diffraction*
Authors: Schierding R.G.
Published: March 2007

Standard x-ray diffraction techniques have been shown to give a quantitative measure of orientation of α-SiC whiskers in polymeric matrices. The pole distributions of the (1120) planes of SiC have been fitted to a normal bivariate distribution where the standard deviation is taken as a measure of the degree of orientation and the volume under the surface as the volume fraction of whiskers oriented within a given set of limits. A semiquantitative trans mission photographic method was also used and the half-arc lengths are shown to give results comparable with those of the quantitative methods. The specimens were whisker filled strands of cellulose triacetate and cupra-ammonium rayon (Cupram), made by a wet spinning process, and an epoxy composite made from the Cupram strand. The strands are shown to exhibit rotational symmetry about the long axis whereas the composite does not.
The Elastic Constants of Fiber Reinforced Materials
Authors: Chow T.S. , Hermans J.J.
Published: March 2007

The five elastic constants of a composite containing parallel cylin drical fibers are expressed as a series expansion in terms of the volume fraction, c, of the fibers. The coefficients of c2 are estimated on the basis of a "reflection" theory: the disturbance in the stress field caused by the presence of a cylinder creates a reaction around a second cylinder, and this in turn has an effect on the stress around the first one. The approximation is made that the reaction of the second cylinder to the said disturbance can be found by treating this disturbance, locally, as a homogeneous field. Although the numerical results of this procedure are not rigorous, it is believed that it correctly describes the role played by the elastic constants of the matrix and of the fiber material. A comparison with some previously published approximations which were derived on the basis of simple models demonstrates that the results for these models are to be used with reserve. This comparison is made in Section IV.
Longitudinal Shear Deformation of Composites II Stress Distribution*
Authors: Sendeckyj G.P.
Published: March 2007

An exact analytical expression is given for the stress distribution in the matrix for a case of longitudinal shear deformation of an uni directional fiber reinforced composite. The expression takes into account non-uniform spacing between fibers, which can have dif ferent radii, and possible variations in shear modulus from fiber to fiber. For the case of a regular array of equal fibers, the expression simplifies considerably. Detailed results are presented for rectangular and diamond arrays of fibers.
Vibration Characteristics of Aluminum Plates Reinforced with Boron-Epoxy Composite Material
Authors: Clary Robert R. , Cooper Paul A.
Published: March 2007

Vibration characteristics of aluminum plates reinforced with boron epoxy composite material were investigated experimentally and analyt ically. Variations in the natural frequencies, mode shapes, and damping with filament angle were studied. Vibration characteristics of the re inforced plates were also compared with all-aluminum plates.

Results of this study demonstrate the merit of using directional com posite materials in design for controlling vibration characteristics of plates. For example, experimental results show that the frequency of the first mode can be changed 77 percent by adjusting the fiber orientation with no change in the plate mass. Results also showed that the damping coefficients could be controlled with filament orientation and that the maximum damping occurred for modes having maximum straining of the matrix and minimum straining of the filaments. Regardless of the filament orientation, all the reinforced plates had more damping than the all-aluminum plates. However, these damping values tend to be less than those normally associated with conventional built-up aerospace structures.

Analytical results used in this report were in qualitative agreement with experimental trends for nodal pattern and frequency variations with filament orientation. However, in some cases, quantitative frequency corre lation was poor. To obtain better correlation, a more sophisticated finite element, including effects such as interlaminar shear, matrix viscoelasticity, and metal-epoxy interface properties, might be necessary.
Development of a Graphite/Aluminum/Epoxy Hybrid Composite
Authors: Walrath David E. , Adams Donald F.
Published: March 2007

The objective of this program was to develop a graphite/aluminum com posite using epoxy to form an interfacial bond between the fibers and the aluminum. Twenty-two test panels were fabricated and tested for tensile strength and tensile elastic modulus, both in the longitudinal and transverse directions. Although problems were encountered in gripping the longitu dinal tensile samples, strengths of 1490 MPa (216 ksi) and 89.6 MPa (13 ksi) were achieved in the longitudinal and transverse directions, respectively.
Post-Failure Behavior of Laminates: II — Stress Concentration
Authors: Chou Shun-Chin , Orringer O. , Rainey J.H.
Published: March 2007

Experimental and analytical results are presented for the post-failure behavior of quasi-isotropic glass-epoxy laminates with a central circular hole. Load-strain response is predicted by combining a failure model developed from tests of unnotched laminates with a tangent-modulus finite-element analysis of the notched laminate. The prediction is shown to agree both qualitatively and quantitatively with experimental results.
Edge Effects on Thermally Induced Stresses in Composite Laminates
Authors: Wang A.S.D. , Crossman Frank W.
Published: March 2007

Thermally induced stresses in fiber composite laminates play an important role in the strength and failure of such laminates as load carrying members. When laminates have free edges, cutouts or holes, interlaminar stress concentration will usually develop near the free-edge region under service loads. An accurate evaluation of thermally induced edge stresses will further the understanding of the laminates' behavior. The present paper examines the stress field of a finite-width, symmetrical laminate when subjected to a uniform temperature change. A finite-element proce dure employing advanced sparse matrix solution technique is employed to study the singular nature of stresses near the free-edge region. Edge effects on the overall response of the laminate under thermal loading are discussed.
Behavior of Integral Composite Joints-Finite Element and Experimental Evaluation 1
Authors: Gillespie John W. , Pipes R. Byron
Published: March 2007

Experimental evidence indicates that the incorporation of an insert increases the out-of-plane load transfer capability of an integral composite joint [1,2]. The detailed analysis of the integral joint concept has been conducted with linear-elastic finite element techniques for the graphite epoxy material system. Discussion of the finite element model, material properties and strength criteria for the no-insert, titanium insert and graphite-epoxy insert concepts is presented. Correlation with available experimental data shows relatively close agreement with analytical predic tions.
Failure of Glass-Epoxy Lamina - Fractographic Study
Authors: Voloshin Arkady , Arcan L.
Published: March 2007

Scanning-electron microscope (SEM) investigation of the failure surfaces provides information on bidimensional state of stress under which failure of unidirectional fiber reinforced material occurred. The failure occurs by debonding between fibers and matrix for the cases of pure shear and shear + compression bidimensional state of stress. The multitude of small pieces of broken matrix is characteristic for the last case. The matrix failure is observed for the case of shear + tension.
Multi-Material Model Moisture Analysis for Steady-State Boundary Conditions
Authors: Miller R.K.
Published: March 2007

A method is presented for analyzing moisture absorption and desorption in multi-material models with constant boundary conditions. It is shown that a multi-material system can be converted into a single material system where the moisture analysis can be performed with existing theory. The conversion process is accomplished by adjusting the thickness of the dif ferent layers of material accordingly. The effective thickness of the con verted laminate is shown to be governed by the square root of the ratio of the respective material diffusion coefficients. Numerical results are pre sented for a hybrid composite of B/5505 and AS/3501-5.
Experimental Measurement of Elastic Shear Modulus of Graphite/Epoxy Tubes
Authors: Bauchau Olivier A.
Published: March 2007

The elastic shear moduli of graphite/epoxy composite materials have been measured using thin walled tubes of different lay-ups. First a dynamic test was used in which shear moduli were derived from the measurement of the natural frequency of torsional vibrations. Next a static torsional test was performed. In both cases the results correlated very well with classical lamination theory. Dynamic moduli were found to be an average 10% higher than static moduli.
Tubular Joint Design in Carbon Fiber Reinforced Plastic
Authors: Norwood C. J. , Brown K. C.
Published: March 2007

A theoretical and experimental study of the performance of a torsional joint between a CFRP tube and an aluminum end fitting was conducted. Three different types of end fitting joint were compared, one bolted and two bonded. The theoretical analysis was performed using a finite element technique, which provided close agreement between the predicted and the experimental strains. One of the designs gave a considerable improvement in performance, in terms of both weight and strength, over the other designs.
Thermal Response of Graphite Epoxy Composite Subjected to Rapid Heating
Authors: Griffis C.A. , Masumura R.A. , Chang C.I.
Published: March 2007

A one-dimensional finite difference analysis describing the transient ther mal response of fiber-reinforced organic matrix composte plates subjected to intense surface heating is presented. The effects of fiber ablation, matrix decomposition, and radiation and convective heat losses are included in the formulation. Numerical results are in good agreement with mass loss and thermocouple mesurements obtained from laser irradiation tests on AS/3501-6 graphite epoxy coupons. A steady state analytic solution is also given which provides a reasonable estimate of the surface recession rate over much of the surface irradiation period.
A Finite Element Analysis of Single and Two-Hole Bolted Joints in Fibre Reinforced Plastic
Authors: Wong C.M.S. , Matthews F.L.
Published: March 2007

The results are presented of a finite element analysis of bolted joints in fibre reinforced plastic. Although the finite element model uses only two- dimensional elements, through-thickness stresses being ignored, some cor respondence is demonstrated between the calculated strains and experimental data from tests on glass fibre reinforced epoxy resin.
Analysis of Curved Laminated Beams of Bimodulus Composite Materials
Authors: Ramana Murthy P.V. , Rao K.P.
Published: March 2007

Composite materials exhibiting different moduli in tension and in compression, commonly called as bimodular composites are being used in many engineering fields. A finite element analysis is carried out for small deflection static behavior of laminated curved beams of bi modulus materials for both solid and hollow circular cross-sections using an iterative procedure. The finite element has 16 d.o.f. and uses the displacement field in terms of first order Hermite in terpolation polynomials. The neutral surface, i.e. the locus of points having zero axial strain is found to vary drastically depending on the loading, lay up schemes and radius of curvature. As il lustrations, plots of the cross-sections of the ruled neutral-surface are presented for some of the investigated cases. Using this element a few problems of curved laminated beams of bimodulus materials are solved for both solid and hollow circular cross-sections.
Numerical/Experimental Correlation of Three-Dimensional Thermal Stress Distributions in Graphite/Epoxy Laminates
Authors: Griffin O. Hayden , Roberts Jack C.
Published: March 2007

Three-dimensional finite element analysis was used to predict thermal stress distribu tions in thick graphite/epoxy laminates. The laminates analyzed were [On/90n]s and [+45n/-45n]s. For the [On/90 n]s laminates, high thermal in-plane tensile normal stresses were predicted in the transverse (2-) directions in both the 0° and 90 ° plies. High inter laminar normal (z- or 3-direction) tensile stresses were predicted to exist in the 90° plies near the center of two opposite free edges, with large compressive interlaminar normal stresses along the other two edges. Stresses were predicted to be low in all corners. In the [+45n/-45n]s laminates, high in-plane transverse (2-) direction normal tensile stresses were also predicted. High tensile interlaminar normal stresses were predicted to exist at two diagonally opposite corners, with large compressive interlaminar normal stresses at the other corners. Subsequent experiments using thick laminates with similar stacking sequences slowly cooled to -150°C confirmed the predicted stress distribu tions and the existence of a "free corner" effect in angle-ply laminates, an effect which could not have been predicted without performing a fully three-dimensional analysis. Absence of inplane symmetry in mid-plane symmetric angle-ply laminates was predicted analytically and verified experimentally. Failure mode and location were shown, analytically (based on a maximum stress failure criterion) and experimentally, to depend on stacking sequence.
Computed Tomography X-Ray Scanning NDE of Graphite/Epoxy Coupons
Authors: Baumann Kai J. , Kennedy William H. , Herbert David L.
Published: March 2007

Exploratory tests of computed tomography (CT) x-ray scanning of damaged Gr/E coupons demonstrate the potential utility of this NDE method for Gr/E structures. The resulting images are presented with dye penetrant enhanced film radiographs and photographs.
Fiber Stresses in a Cracked Monolayer: Comparison of Shear-Lag and 3-D Finite Element Predictions*
Authors: Reedy E. David
Published: March 2007

Shear-lag and 3-D finite element predictions for the fiber stresses in a cracked monolayer are compared. Results are given for 5-fiber wide boron/aluminum and Kevlar 49/epoxy monolayers containing a single broken fiber. Both methods of analysis are found to predict nearly the same fiber stress distribution along the crack- tip fiber when the monolayer is fully elastic. Results for highly loaded monolayers with extensive matrix yielding are not in quite as good agreement, but even then the predicted stress distributions are within 5%. These calculations show that a shear-lag analysis is accurate even when 1) the matrix is relatively stiff and can carry substantial loads (e.g., boron/aluminum), and 2) the fiber is highly anisotropic, (e.g., Kevlar 49/epoxy).
Failure Analysis of a Graphite/Epoxy Laminate Subjected to Combined Thermal and Mechanical Loading
Authors: Chen J.K. , Sun C.T. , Chang C.I.
Published: March 2007

Quasi-static thermal stress response and failure behavior of graphite/epoxy lam inated plates under combined intense thermal and mechanical loadings are investigated. The temperature field is obtained by using a one-dimensional finite difference code. The effects of ablation, degradation of thermophysical properties at elevated tem peratures, and radiation and convective heat losses are included in the formulation. In the thermal stress and strength analyses, the temperature-dependent mechanical prop erties and temperature-dependent strengths are used. A nine-node isoparametric finite element is employed to calculate the structural responses. The maximum stress criterion is adopted for failure predictions. Numerical results include the temperature distributions over the thickness of the plate, structural responses, and time to failure. The analytical predictions are compared with experimental data.
Fiber Stress Concentrations in Kevlar/Epoxy Monolayers
Authors: Reedy E.D.
Published: March 2007

A stress-based finite element analysis, formulated within the context of a shear-lag theory, is used to analyze a Kevlar 49/epoxy monolayer containing a single, preexisting fiber break. The highest and most localized stress concentration occurs when the epoxy matrix is idealized as linearly elastic and perfectly bonded to the fibers. This calculation suggests, however, that the fiber-matrix bond strength will be exceeded at relatively low load levels and fiber-matrix debonding will occur. Calculations which permit debond ing and also consider a residual frictional interface stress after the primary bond fails are presented. When there is no residual frictional stress, the fiber stress concentration is fully relieved and debonding occurs along the entire fiber length at loads only slightly higher (∼ 10%) than that needed to initiate bond failure. A residual frictional stress stabilizes debond growth. The fiber stress concentration factor decreases as the magnitude of the residual frictional stress decreases, while debond length and the length of fiber subject to the overstress increase.
The Effect of Pin Load Distribution on the Strength of Pin Loaded Holes in Laminated Composites
Authors: Chang Fu-Kuo
Published: March 2007

An analysis was performed to evaluate the effect of the assumed pin load distribution on the calculated strength and predicted failure mode of pin loaded holes in laminated composites. The calculations utilized a finite element method of stress analysis combined with the Yamada-Sun failure criterion applied along the Chang-Scott-Springer char acteristic curve. Strengths and failure modes were calculated for both a cosine load distri bution and a load distribution determined by an iterative procedure. The strengths and failure modes calculated by the two types of load distributions agreed closely.
The Consolidation of Laminate Composites
Authors: Gutowski Timothy G. , Morigaki Tadahiko , Zhong Cai
Published: March 2007

A general mathematical model wich allows for three dimensional flow, and one dimen sional consolidation of the composite, is developed. The model assumes that the fibers make up a deformable, nonlinear elastic network. The resin flow is modelled using Darcy's Law for an anisotropic porous medium, with a resin of time varying viscosity. The general case is then solved for two important molding situations: 1) Compression Mold ing, and 2) Bleeder Ply Molding.
Effect of Fiber Waviness on the Nonlinear Elastic Behavior of Flexible Composites
Authors: Kuo Chen-Ming , Takahashi Kiyohisa , Chou Tsu-Wei
Published: March 2007

The effect of fiber waviness on the elastic moduli of flexible composites is investigated theoretically and experimentally. The flexible composites examined are composed of con tinuous fibers with sinusoidal waviness in an elastomeric matrix. Both iso-phase and random-phase fiber arrangements are used for this study. The constitutive relations for the longitudinal and transverse tensile behavior have been developed for these models. Tensile tests have been conducted to verify the constitutive relations. Carbon fiber and silicone elastomer were used for the experiments. Techniques for specimen fabrication as well as photoelastic tests are also presented. Experimental results show good agreement with the theoretical predictions.
Moisture Absorption of Graphite/Polymer Composites Under 2000 Feet of Seawater
Authors: Tucker Wayne C. , Brown Richard
Published: March 2007

Studies were conducted to determine moisture absorption properties of a vinyl ester graphite fiber composite under 2000 feet of seawater pressure. The results were compared with moisture absorption curves generated on identical specimens soaking in seawater at the surface. After soaking, samples were tested for flexure strength. Results in dicate diffusion coefficients are the same in both cases, but higher equilibrium moisture contents were obtained on deep submergence samples. Also, samples subjected to pressure experienced a 15 % reduction in flexure strength and stiffness. It is proposed that higher moisture content and loss of strength and stiffness were due to the activation of damage dependent mechanisms in the composite under pressure.
Experimental Tests for Damping Measurements on Several Short Glass Fiber Composites
Authors: Balis Crema L. , Castellani A. , Serra A.
Published: March 2007

Some experimental tests on the damping measurements for short glass fiber composites are presented.

The short fiber samples are of three different fiber orientations: aligned longitudinally, aligned transversely and random.

The tested composites have been built for a possible secondary structural use in the field of road transport.

A comparison of the gathered data from the damping measurements with theoretically predicted values, gained with a classical approach, is presented.

The good agreement between the experimental and theoretical values of the three types of composites shows that it is possible to broaden the application of the theoretical ap proach as used in continuous glass fiber for predicting the damping values of aligned and random short glass fibers.

These results also confirm the tight connection between damping and stiffness charac teristics in glass fiber composites.
Fracture Behavior of Extren at Room Temperature and 77 K
Authors: Lau H. , Jiang K. , Rowlands R.E.
Published: March 2007

Unlike most fiber-reinforced polymer composites, the measured inter laminar fracture energy of the glass-polyester Extren is significantly greater at 77 K than at room temperature (298 K). Composite microfailure is adhesive at room temperature but cohesive at 77 K. SEM and acoustic emission results suggest the enhanced interlaminar fracture toughness at 77 K is associated with increased matrix cracking which occurs at cryogenic conditions. The additional fracture surfaces increase the amount of released sur face energy.
Characterization of Creep in Polymer Composites by the Use of Frequency-Time Transformations
Authors: Gibson R.F. , Hwang S.J. , Sheppard C.H.
Published: March 2007

The use of frequency domain vibration test data to obtain time-dependent creep and relaxation properties of polymer composite materials is described. Frequency domain complex moduli are measured over a suitable frequency range by using vibration test techniques on small specimens. Complex moduli are then converted to time-domain relaxation moduli or creep compliances by using an Inverse Fourier Transform and numer ical integration. Several test functions were used to check the accuracy of the transfor mation, which was then used for characterization of an angle-ply graphite/polyimide composite.
Experimental Evaluation of Global Composite Laminate Stiffnesses by Structural Wave Propagation
Authors: Veidt M. , Sayir M.
Published: March 2007

An experimental method based on a consistent second order theory for flex ural waves in an orthotropic fiber reinforced plate is described. The propagation of struc tural waves allows the accurate evaluation of four elastic constants E22, E33, G12, G13 in a single experiment. The flexural waves are induced centrally with a piezoceramic trans ducer. Phase velocities as a function of frequency are determined from the phase spectra of flexural waves measured with a heterodyn laser-Doppler-interferometer along straight lines through the loading point. The theory is developed by means of asymptotic expan sions of the three dimensional equations of linear elasticity and includes shear deforma tion. The measured behaviour and the accuracy of the moduli is shown to be very satisfac tory and in accordance with theoretical expectations.
On the Influence of Stacking Sequence on Notch Sensitivity of Fabric Laminates
Authors: Naik N.K. , Shembekar P.S. , Verma M.K.
Published: March 2007

The effect of stacking sequence on the unnotched and notched strength of E-glass/epoxy fabric laminates has been studied. The stacking sequence alters the un notched and notched strength. The failure mechanisms in these two cases are different. As a result, the hierarchies of unnotched and notched strength based on stacking sequence variation are different. The failure mechanisms have been discussed. The effect of stacking sequence on the unnotched and notched strength of woven fabric composites are compared with the UD tape laminate results reported earlier. Based on the experimental observa tions, some guidelines are given to choose the optimum stacking sequence for unnotched and notched composites.
Failure Mechanisms of Edge Delamination of Composites
Authors: Lee S.M.
Published: March 2007

The mechanisms controlling edge delamination in [± 30°/ ± 30°/90°/90°] s composites have been studied. Edge delamination strength and fracture toughness were strongly dependent on the resin matrices. For the same resin matrix, however, these prop erties drastically and consistently varied with the fibers studied, suggesting a fiber/matrix interface-controlled mechanism. Failure analyses using microscopy techniques revealed corresponding variations of fiber/matrix adhesion and crack paths. As the fiber/matrix adhesion decreased, the dominant crack paths in the laminates changed from straight —30°/90° interply failure to zig-zag 90° intraply failure. The critical role of fiber/matrix adhesion on edge delamination was demonstrated.
Vibration and Low Frequency Acoustic Analysis of Piecewise-Activated Adaptive Composite Panels
Authors: Anders W.S. , Rogers C.A. , Fuller C.R.
Published: March 2007

This paper presents an analytical modeling technique which uses the Ritz method, classical laminated plate theory, and finite panel acoustic radiation theory to pre dict the modal and structural acoustic behavior of locally activated shape memory alloy hybrid composite panels. This technique for performing a spatial integral within the Ritz approximation of the laminated plates with nonlinear material properties can also be ap plied to analysis of laminated plates with stiffeners and other spatially nonlinear character istics. The application of interest for this presentation is structural analysis of laminated plates. However, this technique may also be used for analyzing plates with ribs and stiffeners, etc. By minimizing the total energy functional, integrating piece-wise over dis crete homogeneous panel regions characterized as activated and unactivated and summing these integrals over the total panel area; stiffness matrices are found to determine natural frequencies, mode shapes and steady-state dynamic response to periodic incident plane wave acoustic excitation. This information is then used to determine the structural acoustic response as a function of frequency for a laminated plate with material nonlinearities. Analytical results are presented for balanced symmetric adaptive panels to demonstrate how various localized activation scenarios affect modal and structural acoustic behavior.
Study of the Mechanism by Which an Orthocarbonate Reduces Residual Stress in a Composite
Authors: Chou C.T. , Penn L.S.
Published: March 2007

Orthocarbonates have received attention for their ability to improve com posite properties by a possible mechanism involving ring opening and simultaneous reduc tion of resin cure shrinkage. We conducted a detailed investigation of the physicochemical behavior of an orthocarbonate-epoxy resin blend known to reduce the residual stress in a composite. The orthocarbonate was found neither to undergo chemical reaction, nor to reduce resin cure shrinkage. However, its significant reduction of the resin Tg was found to be the feature that brought about the reduced residual stress in the composite.
Elastic-Plastic Analysis of AS4/PEEK Composite Laminate Using a One-Parameter Plasticity Model
Authors: Sun C.T. , Yoon K.J.
Published: March 2007

A one-parameter plasticity model was shown to adequately describe the plastic deformation of AS4/PEEK (APC-2) unidirectional thermoplastic composite. This model was verified further for unidirectional and laminated composite panels with and without a hole. The elastic-plastic stress-strain relations of coupon specimens were mea sured and compared with those predicted by the finite element analysis using the one- parameter plasticity model. The results show that the one-parameter plasticity model is suitable for the analysis of elastic-plastic deformation of AS4/PEEK composite laminates.
Characterization of Interfacial Bond Strength by Dynamic Analysis
Authors: Kennedy J.M. , Edie D.D. , Banerjee A. , Cano R.J.
Published: March 2007

Short beam shear, double cantilever beam, and torsional dynamic mechanical (DMA) tests were performed on composite materials systems to characterize the interfacial bond strength. The composite materials were unidirectional flat laminate with different fiber surface treatments and sizings. The results indicated that the DMA test was superior to the short beam shear and double cantilever beam test for measuring fiber/ matrix bonding. The DMA tests detected the effect of surface treatment with much greater accuracy than the standard mechanical tests. Also, DMA tests readily detected the differ ence in fiber/matrix bonding of PAN-based and pitch-based fibers. The DMA test had the additional feature of being able to isolate fiber/matrix interface effects from matrix and fiber effects.
Thermoviscoplasticity Based on Overstress Applied to the Analysis of Fibrous Metal-Matrix Composites
Authors: Yeh Nan-Ming , Krempl Erhard
Published: March 2007

The vanishing fiber diameter (VFD) model together with the thermovisco plasticity theory based on overstress (TVBO) are used to analyse the thermomechanical behavior of unidirectional fibrous metal-matrix composites. Fiber and matrix can both be transversely-isotropic, thermoelastic-viscoplastic. All material constants can depend on current temperature. Yield surfaces 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 equilibrium stress, a state variable of the theory. The three- dimensional equations are derived and specialized for various simple loading cases such as isothermal uniaxial and biaxial proportional and nonproportional loadings. The predic tions of this viscoplasticity theory during loading compare favorably with results from the rate-independent plasticity theory. In addition it is capable of predicting creep, relaxation and rate sensitivity.
Simplified Mold Filling Simulation in Resin Transfer Molding
Authors: Zhong Cai
Published: March 2007

A simplified mold filling simulation is developed to estimate the process variables for resin transfer molding (RTM) of structural composite parts. This approach uses very limited calculations and needs only microcomputer facilities. Resin flow in RTM processes is considered to follow Darcy's law. Both Newtonian fluid and power-law fluid are studied. Mold sections are decomposed as a combination of simple geometry shapes, such as rectangular, circular, trapezoid, spheric or conic sections. Closed form solutions are derived for each of these simplified shapes. The total mold filling time can then be esti mated, as well as the required inlet pressure or flow rate. Compared with more sophis ticated simulation programs, the computer time and user interface effort are greatly re duced.
Models of Moisture Transport and Moisture-Induced Stresses in Epoxy Composites
Authors: Myung Cheon Lee  , Peppas Nikolaos A.
Published: March 2007

Mathematical models are presented to describe moisture transport in epoxy composites using concentration and stress dependent diffusion coefficients. These models take into consideration the stresses induced due to moisture and their influence on the transport mechanism. All governing differential equations are solved with appropriate boundary conditions to obtain concentration and stress profiles. It is concluded that non- Fickian and anomalous transport of moisture in epoxy composites can occur under certain conditions, leading to stress accumulation close to the fibers of the composite.
The Cognitive Consequences of Specific Experiences
Authors: Rogoff Barbara , Gauvain Mary
Published: March 2007

This study examines the generalizability of cognitive skills across varying domains by comparing the predictiveness of an everyday skill (weaving) and formal schooling for performance on four pattern continuation tests varying in their similarity to weaving and schooling. The subjects were 79 adult Navajo women from the eastern area of the Navajo reservation. Their schooling varied from 0 to 16 years and their skill in weaving ranged from nonweaver to expert. Multiple regression analyses indicated that weaving skill was the best predictor of performance on the task resembling weaving, as expected, but schooling experience did not predict performance on the task designed to resemble schooling after subject's age was controlled. The results call into question the notion that what is learned in particular experiences automatically improves skills in general.
Perceived Language Proficiency and Person Perception
Authors: Wible David S. , Hui C. Harry
Published: March 2007

A group of native Mandarin Chinese speakers listened to tapes of six American females speaking in Chinese as their second language and evaluated each speaker on a set of 22 traits. Another group of native Chinese speakers listened to the same tapes and evaluated the six speakers on areas of Chinese language proficiency. The trait evaluations were then correlated with the language evaluations. Evaluations of 8 of the 22 traits showed significant correlations with evaluations in every language area. In contrast, seven other traits showed no significant correlations with any language area. Listening order significantly affected ratings on 12 of 22 traits. The results indicate two distinct groups of traits. One group is the traits that the trait judges somehow associated with language proficiency. In evaluating these traits, the judges depended on cues of language proficiency. The other group is the traits that apparently the trait judges evaluated independently of spoken language proficiency.