bluuebunny/crossref_metadata_2025 huggingface dataset:
Educational Programs and Human Response to Natural Hazards
Authors: Sims John H. , Baumann Duane D.
Published: March 2007

That an individual is aware of the risk of a natural hazard and the range of damage mitigation measures is no guarantee that he or she will act on this information. Based on a review of the literature, the available evidence is weak on the relatonship between awareness or knowledge and the consequent adoption of damage mitigation measures. Although substantial sums of money are expended each year on public information programs on natural hazards, little effort has focused on the cost-effectiveness of such programs.
Undermanning Theory and the Workplace
Authors: Oxley Diana , Barrera Manuel
Published: March 2007

Undermanning theory has been identified as a useful tool for organizational and community psychologists. The research described here demonstrated the utility of this theory in two ways. First, it examined the applicability of undermanning theory to work settings. A model of causal relationships among the number of employees in a setting, setting claim, and several attitudinal and behavioral outcome variables was presented and tested using path analysis. The results provided support for the generalizability of undermanning theory and illuminated important linkages between setting claim and more traditional variables of interest to organizational psychologists, such as job satisfaction and organizational identification. Second, this research examined relationships among social support, sharing grievances, and other outcome measures in small and large work settings. These findings indicated that social support may be a mediating process in the relationship between setting size and employee attitudes and behavior.
Household Income, Electricity Use, and Rate-Structure Preferences
Authors: Blocker T. Jean , Koski Patricia R.
Published: March 2007

Using data collected as part of a larger project evaluating the effects of the Public Utility Regulatory Policies Act, this article seeks to explore the relationship between household income, present electricity use (kwh), and preferences for three proposed conservation-promoting electricity rate structures. In considering the adoption of these structures, the respondent would find it necessary to consider the possible losses in comfort versus the lowered costs of electricity. Previous research suggests that income levels and present comfort levels may impact one's willingness to adopt alternative rate structures. Using present electricity use as a measure of the current comfort threshold, we find limited support for the suggestion that kwh use affects willingness to adopt alternative rate structures and stronger support for the hypothesis that income affects rate structure preferences.
Has Environment and Behavior Research "Made a Difference"?
Authors: Kantrowitz Min
Published: March 2007

Environment and behavior research can only "make a difference" if it is utilized and accepted. This article presents a five step pyramidal model of steps toward acceptance and utilization of E&B research. These steps-awareness, interest, exploration, belief and action- help in understanding our progress. The field of E&B research is progressing down the pyramid in application to design, in academic research, and in theory development. E&B research applications in office environments, housing and institutional environments are given, and progress in E&B concept generation and in professional and academic recog- nition is discussed. The article closes with examples of the growing acceptance and utilization of E&B research through institutionalization.
Evaluating Evaluation
Authors: Zimring Craig , Wener Richard
Published: March 2007

Postoccupancy evaluation (POE) has expanded beyond its academic origins and is now routinely performed in government, industry and private design and consulting practice. It is proposed that a POE can be evaluated both by whether it meets its own goals and whether it meets more general methodological standards. Several examples of "successful" evaluations are presented and an overall framework for evaluating evaluation is proposed.
The Perception of Spatial Enclosure As a Function of the Position of Architectural Surfaces
Authors: Thiel Philip , Harrison Ean Duane , Alden Richard S.
Published: March 2007

Two studies were conducted to test a hypothesis that the perceived differential enclosing effect of architectural surfaces is a function of their position, weighted in the ratio 1:2:3 for surfaces in the horizontal under, vertical side, and horizontal over positions, respectively. The stimuli were separate realistic line drawings in one-point eye-level perspective of the same furnished and occupied interior space, differing only in the presence or absence of floor, wall, and ceiling surfaces in all possible combinations. In the first study subjects were asked to arrange the drawings in a left-to-right order ranging from spatial openness at one end to spatial closedness at the other. In the second study the same subjects were given a diagram of the most enclosed case and asked to rank-orderthe surfaces in terms of their importance in enclosing the space. A total of 35 subjects took part in these experiments. The results of both studies confirmed the enclosure hypothesis.
The Incidence of Home Grounds and Experiential Networks
Authors: Stanton Barbara Hadley
Published: March 2007

Approximately 40% of 210 residents interviewed on two streets in different localities of New York City felt a distinction between Lee's socio-spatial "neighborhood" and their "home gound": the mental form and geographical extent of those places that evoke a feeling of being near home. Only residents of blocks 460 feet or less in length were able to think of their home ground form as an "experiential network": a street network without continuous boundaries. These findings suggest that cognition of an experiential network may be influenced by a mental time limit; that the concept of home ground may be a useful adjunct to Lee's concept of neighborhood; and that residents' cognitions of familiar places may not be hierarchically ordered.
Identity Symbolism in Housing
Authors: Sadalla Edward K. , Vershure Beth , Burroughs Jeffrey
Published: March 2007

Upper-middle-class homeowners were asked to rate themselves on an extensive set of bipolar personality and identity dimensions. Photographs were taken of the interior and exterior of each homeowner's dwelling and were developed into color slides. These slides were subsequently presented to subjects who were asked to rate the homeowner on the same set of personality and identity dimensions. Subjects were assigned to one of three conditions, interior, exterior, or combined, depending upon the type of information to which they were exposed. Subjects in all conditions were able to infer the homeowner's selfconcept to a significant degree, with subjects in the interior condition displaying the most accuracy. Results were interpreted in terms of a self-presentational model of housing choice.
Wayfinding without Vision
Authors: Passini Romedi , Proulx Guyltne
Published: March 2007

In a wayfinding experiment a group of 15 congenitally totally blind subjects and a matched control group of 15 sighted subjects were guided through a complex architectural setting. After two guided tours they had to make the journey on their own. An analysis of their decision making showed that the blind subjects tended to prepare theirjourney in more detail, that they made significantly more decisions during the journey, and relied on significantly more units of information. The nature of the decisions made and the information used by the two groups showed some interesting differences: About half of the decisions made by the visually impaired group were not part of the sighted group's repertory; furthermore, certain environmental features important to one group were totally ignored by the other. According to a cognitive mapping exercise and a posttest questionnaire, a third of the congenitally totally blind subjects were not only capable of representing the route taken without errors, but demonstrated as well a general understanding of the spatial attributes of the setting. Although the blind group as a whole tended to make more errors, the overall performance compares favorable with the sighted control group. The findings are discussed in terms of wayfinding theory and design implications.
Changing a Schoolyard
Authors: Weinstein Carol S. , Pinciotti Patricia
Published: March 2007

This article describes the construction of a tire playground on an empty, fenced-in blacktop that had served as the schoolyard for a small primary school. It discusses the parents' and designer's goals for the tire playground, describes the way the playground design supported and reflected these goals, and documents the eventual impact on children's behavior. Construction of the playground led to significant decreases in organized games, uninvolved behavior, and roughhousing, and significant increases in active play and pretend play. Age and sex differences in play behavior are also described.
Comparing Preferences of Neighbors and a Neighborhood Design Review Board
Authors: Stamps Arthur E.
Published: March 2007

Because of increases in participatory, neighborhood, and aesthetic planning, nondesigners are being asked to anticipate architectural preferences of other nondesigners. Neighborhood design review boards are a case in point. This study compared the preferences of a neighborhood design review board to the preferences of other demographic subpopulations. It was found that the overall correlations between the preferences of the review board and the preferences of other respondent groups were statistically significant. However, it was also found that the correspondence between the review board and other people decreased when individual projects and specific design criteria were compared.
Controlling Illegal Parking in Spaces Reserved for the Physically Disabled
Authors: Cope John G. , Lanier Tina M. , Allred Linda J.
Published: March 2007

Messages announcing the possibility of community intervention and the time of its occurrence were used to examine illegal parking in spaces reserved for the disabled, during specified and nonspecified time periods. Observations were recorded during two consecutive 1-hour shifts (4:00 to 5:00 p.m. and 5:00 to 6:00 p.m.). An ABACA reversal design was used at Space 1 and an ABACAB reversal design was used for Spaces 2 and 3. A sign was used to indicate that either the 5:00 to 6:00 p.m. (B) or the 4:00 to 5:00 p.m. (C) shift was under observation. Although the results from Space 1 showed the same pattern as found in Spaces 2 and 3, they were not statistically significant. These findings suggest that illegal parking was probably controlled more by the content of the message than by the increased salience resulting from the addition of a secondary message sign.
A Structural Model of Reuse and Recycling in Mexico
Authors: Corral-Verdugo Victor
Published: March 2007

Direct observations are used to analyze reuse and recycling pattems of 100 families in a middle-sized northwestem Mexico city and reveal that reuse is practiced more than recycling. An inventory administered to housewives examined potentfal predictors of the studied practices, investigating dispositional factors (motives, competencies, beliefs, knowledge), demographic variables (age, income, education), and situational variables (storage facilities, presence of collectors of recyclables, use of radio, TV, newspapers, and books). Each variable was presumed related to conservation behavior. Multiple regression and causal structural models were used to investigate the direct and indirect effects of these factors. Multiple regressions produced a limited number of significant (direct) predictors of reuse and recycling, whereas structural models revealed conservation competencies and motives to reuse/recycle to be the most important direct predictors. Moreover, these analyses showed that situatonal and demographic factors exerted significant indirect influence on conservation behavior through reuse/recycling motives and competencies.
Urban Public Spaces as Representations of Culture
Authors: Low Setha M.
Published: March 2007

This article illustrates how spatial/cultural representations come into being with data collected during a 7-month ethnographic study of two plazas, the Parque Central and the Plaza de la Cultura in San Jose, the capital city of Costa Rica. The comparison of their history, physical and spatial symbolism, user activities and daily behaviors, and news reports and commentaries demonstrates how these cultural representations reflect meanings that change in response to the material conditions and social values of the historical period. Further, the analysis uncovers that moral contradictions in those meanings are expressed first in the traditional plaza setting, and then, are transformed into contradictions across both plazas.
Polar Field Tent Shelters and Well-Being of Users
Authors: Potter James J. , Yan X. Winston , Krug Nathan S. , Kuivinen Karl C. , England Marijane E.
Published: March 2007

Polar research teams often spend extended periods of time away from base stations, living and working in remote field camps of portable tent shelters. This article reports on a study of the design and use of portable field tent shelters being deployed in Antarctica and other circumpolar areas. The purpose of the study was to determine the effect of the shelters on health and well-being of their users from an environment-behavior perspective. Preliminary analysis indicates that although the design and use of field tent shelters were generally satisfactory, there are areas in which the shelters had some adverse bearing on health and well-being of a considerable number of shelter users. This article concludes with suggestions that can be used for future design and manufacture of portable field tent shelters.
The Internet and Public Culture in Kuwait
Authors: Wheeler Deborah L.
Published: March 2007

This article considers the development and impact of the Internet in Kuwait. It argues that even though important cultural filters shape Internet use, experimentation with new social relationships in cyberspace occur. This is true especially among youths. It performs three kinds of analyses to make its main point. First, it performs a content analysis of the major Kuwaiti daily newspapers in both Arabic and English to illustrate the emergence of a public consciousness of the Internet. Second, it uses survey data to describe the scope and character of the Kuwaiti Internet community in relation to the general population of Kuwait, and in relation to regional Internet access/use patterns. Third, it examines the emerging impacts of Internet use in Kuwait. It concludes that the most significant possibilities for change stem from student use of the Internet to transgress gender boundaries, and to protest the state's new gender law.
The Rwanda Crisis
Authors: Wall Melissa A.
Published: March 2007

American media traditionally have created one-dimensional portraits of intracountry conflict in Africa. Worldwide changes since the end of the Cold War have given many media observers hope that African violence might be covered more insightfully. To see whether this was true, news magazine coverage of the 1994 Rwanda crisis was analyzed. Findings suggest that some patterns such as viewing African events through an East-West frame have disappeared, but other types of simplification prevail.
The Independent Press and Politics in Africa
Authors: Kasoma Francis P.
Published: March 2007

The independent press in Africa's multiparty states of the 1990s has developed a confrontational relationship with governments, which is largely being brought about by the press's own unprofessional behaviour. The confrontational relationship is causing governments to introduce measures, legal and otherwise, aimed at making the press behave responsibly, in the absence of effective self-regulating mechanisms by the press itself. These measures are likely to lead to the subjugation of the independent press by governments once again and the reintroduction of dictatorship in Africa at the turn of the millennium and beyond. When this happens, the independent press will have to bear the bulk of the blame for loss of press freedom and democracy.
Liberalization, Regulation and Development
Authors: Hills Jill
Published: March 2007

Markets are social and political constructs and regulation the means to their construction. The article considers why both regulation and telecommunications have been absent from mainstream development theory and looks at some of the practical difficulties of regulating telecoms in a number of low income and lower middle income countries.
The Rural-Urban Dichotomy of Doordarshan's Programming in India
Authors: Rao Sandhya
Published: March 2007

Doordarshan, India's state-run television network, has changed its programming strategies in view of India's economic liberalization policy of the 1990s. This study examines the impact of Doordarshan's shift in programming bias from the `rural' to the `urban' among 800 respondents in Bangalore city and surrounding villages. Findings reveal that urban viewers had a more positive perception of Doordarshan's programming after Doordarshan added cable channels. Doordarshan has to rethink its programming strategies to better serve the rural and urban audiences who cannot afford cable television. Doordarshan has the challenging task of trying to resolve the rural-urban dichotomy by providing more regional Indian language and locally relevant programs that are both entertaining and social goals oriented.
The Media in Asia
Authors: Gunaratne Shelton A.
Published: March 2007

This overview article operationally defines Asia as the three subregions constituting the South, the Southeast and the East. It discusses the Occidental and the Oriental (i.e. Asian values) views of press freedom and argues the case for placing this debate within the framework of Article 19 of the UN Universal Declaration of Human Rights. Moreover, it looks at the relevance of old media, as well as old media theory, in the context of the new media that have become essential for global competition. It provides the rudiments of a structural theory suitable for communication analysis in the era of globalization.
Efficacy in Letter-Writing to an Entertainment-Education Radio Serial
Authors: Law Sweety , Singhal Arvind
Published: March 2007

The influence of efficacy, both self and collective, in the adoption of prosocial behaviors has not been examined in the context of large-scale communication campaigns that use mass media interventions. Our purpose is to identify efficacious dimensions in letter-writers' communication to an entertainment-education radio drama serial in India. An entertainment-education program can influence audience members' sense of efficacy, an effect that can lead them to reconsider their values and behavior. We argue that audience letters represent a possible approach to measuring efficacy. Letters written by listeners can help us understand how they know what they hear and with what psychosocial consequences.
The rhetorical strategy of an autobiography: Reading Satyavati's A tmacaritamu
Authors: Rajagopal Vakulabharanam
Published: March 2007

This article describes and analyses the autobiography of an ordinary woman, perhaps the first autobiography by a woman in Telugu. Despite its unique features, the text, strangely enough, fell into oblivion. Published in 1934, Satyavati's Atmacaritamu contains a radical critique of religion and society. Though a widow, Satyavati claimed the status of pativrata and through this ingenious rhetorical strategy legitimated her critique as internal to tradition. The article also situates the text in the corpus of writings by women all over India in the late nineteenth and the early twentieth centuries, and traces the evolution of the 'women's question'in colonial Andhra in relation to this literature.
A Historical Perspective of the Emergence of Higher Education in Black Colleges
Authors: Harris J. John , Figgures Cleopatra , Carter David G.
Published: March 2007

They prepared the stage for academic development, although none survived to witness the flowering, once their work had been released from the morass of primitive beginnings [Johnson, 1938].
Transverse Normal Loading of a Unidirectional Composite
Authors: Adams Donald F. , Doner Douglas R.
Published: March 2007

The problem of a doubly periodic rectangular array of elastic filaments contained in an elastic matrix material has been formu lated using a theory of elasticity analysis. The filaments can be of arbitrary shape within the restriction of having two axes of symmetry. The composite is assumed to be subjected to normal stress components in directions perpendicular to the direction of the filament axes. A uniform temperature change can also be im posed. A finite difference representation of the governing equi librium and stress-displacement equations has been utilized in obtaining a solution by a systematic overrelaxation procedure. Numerical results have been obtained for various cross-sectional shapes, a number of filament and matrix material properties, and a range of filament spacings (filament volume contents) varying from filaments nearly in contact to extremely wide spacings in which interaction effects between filaments are essentially zero. Theoretical results have been compared with other methods of analysis and with the limited experimental data presently available.
The Elastic Stability of Fibers in a Composite Plate*
Authors: Chung Wen-Yi , Testa Rene B.
Published: March 2007

The stability of unidirectional, equally spaced fibers in the plane of a composite plate is formulated by treating the fibers as beams and the matrix by the theory of generalized plane stress. Critical values of the axial load and the corresponding buckling modes are evaluated numer ically and shown graphically for various values of the parameters. Approximations leading to explicit expressions for the critical values are introduced, and restrictions on the applicability of the approximate results are determined. Experimental evidence of the occurrence of buckling modes of the type considered is presented.
A General Theory of Strength for Anisotropic Materials
Authors: Tsai Stephen W. , Wu Edward M.
Published: March 2007

An operationally simple strength criterion for anisotropic materials is developed from a scalar function of two strength tensors. Differing from existing quadratic approximations of failure surfaces, the present theory satisfies the invariant requirements of coordinate transforma tion, treats interaction terms as independent components, takes into account the difference in strengths due to positive and negative stresses, and can be specialized to account for different material symmetries, multi-dimensional space, and multi-axial stresses. The measured off-axis uniaxial and pure shear data are shown to be in good agreement with the predicted values based on the present theory.
Stress Pulse Attenuation in Cloth-Laminate Quartz Phenolic
Authors: Reed R.P. , Munson D.E.
Published: March 2007

Using flat plate impact techniques and quartz stress gages, a study of the propagation of short-duration stress pulses in a cloth-laminate quartz phenolic composite was made. Propagation characteristics, wave shape and peak stress attenuation, were measured for 14.5 and 7 kbar initial impact stresses and 0.1, 0.2, and 0.3 μsec initial pulse durations for propagation distances up to 52 times the impactor thickness. The experimental results showed marked dispersive spreading of the wave profiles and very strong attenuation of stress, but no evidence of elastic-plastic effects. The amount of attenuation was much greater than could be attributed to "normal" atten uation in homogeneous materials with a modulus equivalent to the com posite modulus.

Experimental results were compared to calculations based on a rate dependent analogy using a generalized Maxwell model. The instantaneous and equilibrium response of the model was defined solely in terms of bulk properties of the components of the composite; while a single relaxation time of 0.023 μsec was determined from experiment. Model predictions agreed extremely well with the measured profiles, giving ± 10% agreement to the measured half-amplitude wave velocities. Attenuation was predicted to better than 20% in stress, which is quite good. Quantitative agreement was found between calculations and the measured results of other investigations, as well.
The Vibration of Cantilever Beams of Fiber Reinforced Material
Authors: Abarcar Rene B. , Cunniff Patrick F.
Published: March 2007

Experimental results were obtamed for the natural frequencies and the mode shapes of graphite-epoxy and boron-epoxy composite materials having fiber orientations of 0°, 15°, 30° and 90° with respect to cantilever beam axes Certain elastic constants were experimentally determined and used in a programmed numerical solution in which rotary inertia, trans verse shear, and coupled bending-torsion effects were included. The experi mental results for the 15° and 30° beams gave a clear indication of the interaction between bending and twisting and good agreement was obtained with the numerical results.
Longitudinal Tensile Behavior of Unidirectional Carbon-Carbon Composites
Authors: Adams Donald F.
Published: March 2007

The increasing interest in utilizing carbonaceous-fiber-reinforced carbon matrix materials in high temperature structural applications has resulted in the generation of an increasing amount of experimental data, primarily for unidirectionally reinforced systems. While the longitudinal tensile strength and stiffness properties presently being achieved are attractive relative to those of unreinforced carbonaceous materials such as bulk graphite, they remain well below their apparent potential. Utilizing micromechanical analyses and taking into consideration the highly anistropic crystallo graphic structure of graphite, possible explanations for the observed properties degradation have been formulated. Suggestions for modifying the fabrication and thermal processing as a means of improving axial properties, and tensile strength in particular, are presented.
Tensile Analysis of an Edge Notch in a Unidirectional Composite
Authors: Ueng C.E.S. , Aberson J.A. , Lafitte B.A.
Published: March 2007

The failure of a notched, unidirectional, boron-epoxy composite sub jected to simple tension along the fibers and perpendicular to the notch is studied. Tension tests are performed and the composite is analyzed using a finite-element crack program. The finite-element model takes into account the effects of layering and heterogeneity in the crack-tip region. Stress- intensity factors are obtained from the crack program and compared with the corresponding one for an isotropic material. Notch insensitivity and the failure mode are discussed and the fracture toughness of the test material is determined.
Influence of Environmental Cycling on the Mechanical Properties of Composite Materials
Authors: Lundemo Christer Y. , Thor Sven-Erik
Published: March 2007

Static and fatigue tests were carried out on CFRP specimens exposed to environmental conditions with the purpose of simulating the real environ mental conditions for today's aircraft.

The investigation has comprised ± 45° reinforced test specimens, 24 mm wide and 1 mm thick, built up from carbon-fiber prepreg THORNELL 300/NARMCO 5208. In the investigation polyurethane-covered specimens were also tested, in order to investigate the protecting ability of that mate rial.

The results show clear deteriorations in both static and fatigue proper ties due to environmental exposure. The material becomes more ductile under the influence of moisture, and after prolonged exposure one can notice a debonding effect between the fibers and the matrix. Environ mental degradation becomes more pronounced if the specimens are pre loaded prior to exposure.
The Correlation of Ultrasonic Attenuation and Shear Strength in Graphite-Polyimide Composites
Authors: Hayford D.T. , Henneke E.G. , Stinchcomb W.W.
Published: March 2007

The buffer rod technique for measuring attenuation in thin specimens is modified here to apply to specimens having intermediate thicknesses and high attenuation. The described procedure, which requires only one access ible surface of the material, was used to determine the initial attenuation values of ultrasonic waves in short beam shear specimens of graphite- polyimide composite material. It is shown that there is good correlation between the initial attenuation values and the shear strengths of the speci mens determined by the standard short beam shear test method. The modi fied ultrasonic buffer block technique offers much potential for service as a quantitative, nondestructive, quality assurance test for composite mater ials.
The Interlaminar Shear Strength of Unidirectional Boron-Aluminum Composites
Authors: Peters P.W.M.
Published: March 2007

The interlaminar shear strength was estimated for four types of B-A1 unidirectional composites. The shear strengths from the short beam shear test and symmetric block shear test sometimes show a considerable differ ence. It is shown that in the case of a matrix of high plasticity and (or) many defects in the shear-plane the short beam shear test gives a much too high shear strength. The symmetric block shear test supplies more realistic values both for the inter- and intralaminar shear strength.
Percolation in a Thin Ply Of Unidirectional Composite
Authors: Joy Thomas , Strieder William
Published: March 2007

A unidirectional composite is modeled as a two-dimensional cartesian square lattice of infinite width and finite thickness. Circular fiber cross sections, each contained completely within a lattice square and touching on all four sides, are placed at random within the lattice according to the fiber volume fraction. Percolation, in this system, is shown to be very sensitive to the lattice thickness. To be regarded as infinitely thick a lattice must be at least 150 fiber diameters across, and for a typical ply thickness of 20 fiber diameters the critical fiber fraction for percolation is shifted by 26% from the infinite lattice value of 0.46 to a smaller value of 0.34.
Environmental Effects on Glass Fiber Reinforced Polyester and Vinylester Composites
Authors: Springer George S. , Sanders Barbara A. , Tung Randy W.
Published: March 2007

The effects of environment on glass fiber reinforced polyester and vinylester composites immersed in liquids and in humid air were investi gated. Tests were performed at temperatures 23 C and 93 C with the materials exposed to humid air at 50 and 100 percent relative humidities, and to five different liquids: saturated salt water, No. 2 diesel fuel, lubrica ting oil, antifreeze, and indolene. Changes in weight, ultimate tensile strength, tensile modulus, short beam shear strength, and shear modulus were measured over a six month period, and the effects of the environment on these parameters were assessed.
Edge Effects in Uniaxial Compression Testing of Cross-Ply Carbon-Fiber Laminates
Authors: Ditcher A.K. , Webber J.P.H.
Published: March 2007

Experimental data from static uniaxial compression tests of cross-ply laminates of two thicknesses and two stacking sequences are presented and compared with theoretical predictions from a non-linear laminated plate analysis and with numerical results from a free-edge solution. The ex perimental data shows the existence of an edge effect in the laminates similar to that predicted theoretically, and which depends upon the laminate stacking sequence and thickness. No evidence was found of transverse cracking or edge delamination prior to total laminate failure.
The Room-Temperature Shapes of Four-Layer Unsymmetric Cross-Ply Laminates
Authors: Hyer Michael W.
Published: March 2007

A previous approximate theory for predicting the room-temperature shapes of unsymmetric laminates is examined in light of the assumptions regarding the inplane strains. The previous theory, which was a geometrically nonlinear extension of classical lamination theory, was felt to be restrictive and this paper develops a new theory in which these restrictions are relaxed. It is shown that despite the previous concern, there is little difference between the previous theory and this theory. This paper presents numerical results for the inplane residual strains of unsymmetric laminates which have cooled from curing into a cylindrical room-temperature shape. It is shown that the residual strains are compressive and practically independent of spatial loca tion on the laminate. In another facet of the paper, the room-temperature shapes of all four-layer unsymmetric cross-ply laminates are predicted. There are only four unique stacking arrangements for this category of laminates and it is shown that their room-temperature shapes are a strong function of their size and their stacking arrangement. Depending on these parameters, the room-temperature shape of a four-layer cross-ply unsymmetric laminate can be a unique saddle shape, a unique cylindrical shape, or a cylindrical shape that can be snapped through to another cylindrical shape.
Strength of Mechanically Fastened Composite Joints
Authors: Chang Fu-Kuo , Scott Richard A. , Springer George S.
Published: March 2007

A method is presented for predicting the failure strength and failure mode of mechanically fastened fiber reinforced composite laminates. The method in cludes two steps. First, the stress distribution in the laminate is calculated by the use of a finite element method. Second, the failure load and the failure mode are predicted by means of a proposed failure hypothesis together with Yamada's failure criterion. A computer code was developed which can be used to calculate the maximum load and the mode of failure of joints involving laminates with different ply orientations, different material properties, and dif ferent geometries. Results generated by the present method were compared to data and to existing analytical and numerical solutions. The results of the pres ent method were found to agree well with those reported previously. Parametric studies were also performed to evaluate the effects of joint geometry and ply orientation on the failure strength and on the failure mode.
Distributions of Fatigue Life and Fatigue Strength in Notched Specimens of a Carbon Eight-Harness-Satin Laminate
Authors: Shimokawa Toshiyuki , Hamaguchi Yasumasa
Published: March 2007

The objective of this research is to investigate the distribution properties of fatigue life and fatigue strength in sharply notched specimens of a carbon fabric laminate, which was made of three layers of eight-harness-satin/epoxy prepreg sheets. Fatigue life distributions were obtained at six stress levels by carefully designed fatigue tests of four point plane bending under a constant temperature and humidity condition. Sample sizes were 30 for the three high stress levels and 12 for the three low stress levels. The amount of scatter and distributional form of fatigue life and fatigue strength are discussed from the test results. It is found that fatigue strength distributions are practically normal and their stand ard deviations are constant regardless of fatigue life.
Load Transfer from a Pin to a Wound Fibre Composite Strip
Authors: Mansfield E.H.
Published: March 2007

A simplified analysis is given of the stresses caused by load transfer into a U-shaped fibre rein forced strip wound round a pin. It is shown that the peak stresses vary markedly with the ratio of the longitudinal to transverse modulus of the composite. Because of this, a design which is satisfactory with glass fibre may not be so with carbon fibre.
Thermal and Photo-Degradation Behaviors of Glass-Fiber Reinforced Rigid Polyurethane Foam
Authors: Morimoto Kiyotake , Suzuki Toshio , Yosomiya Ryutoku
Published: March 2007

Thermal and photo-degradation of rigid polyurethane foams (PUF) and glass fiber reinforced rigid polyurethane foams (FRU) have been studied.
Buffer Strips in Composites at Elevated Temperature
Authors: Bigelow C.A.
Published: March 2007

The present investigation evaluated the buffer strip concept at elevated temperature. Accordingly, graphite/polyimide buffer strip panels were tested at room and elevated (177 ± 3 °C) temperatures. One layup was used: [45/0/45/90]2S. The buffer strip material was 0° S-glass/polyimide. The buffer strips were made by replacing narrow strips of the 0° graphite plies with strips of the 0 °S-glass on either a one-for-one or a two-for-one basis. All panels had the same buffer strip spacing and width. Slits were cut in the center of each panel to represent damage. Each panel was loaded in tension until it failed. During the tests, panels were radiographed and crack-opening displacements were recorded to indicate fracture onset, fracture arrest, and the extent of damage in the buffer strip after crack arrest.

At the elevated temperature, the buffer strips increased the panel strength by at least 40 percent compared to panels without buffer strips. The buffer strip panels tested at 177 °C exhibited stable crack growth until the crack grew into the buffer strip. Com pared to similar panels tested at room temperature, the buffer strip panels tested at 177 °C had lower residual strengths but higher failure strains. The panels with two-for- one buffer strip replacement had slightly lower strengths (by 5 percent) than panels with one-for-one replacement. A shear-lag type stress analysis correctly predicted remote failing strains for buffer strip panels tested at 177°C and at room temperature.
Effect of Microcracks on the Thermal Expansion of Composite Laminates
Authors: Bowles David E.
Published: March 2007

A finite element analysis was used to quantitatively predict the effect of matrix microcracks in the 90° plies of graphite/epoxy composites on the coefficient of ther mal expansion in the 0° direction, α y (perpendicular to the cracks). Results were generated for [0 m/90n]s, [0/±45/90]s and [0/90/±45] s graphite/epoxy laminate con figurations. Analytical predictions were compared with experimental results for the two quasi-isotropic laminate configurations. Both analytical and experimental results showed that microcracks reduced the effective stiffness of the 90° plies, thus causing the laminates, thermal response to be more like that of a [0] laminate. The change in αy was a function of lamina material properties, microcrack density, fiber orientation, and stacking sequence. A combination of classical lamination theory and finite element analysis was used to predict the effect of microcracks in both the 90° and 0° plies. Analytical results showed that the addition of microcracks in the 0° plies do affect αy, but to a lesser extent than those in the 90° plies.
A Stochastic Model for the Growth of Matrix Cracks in Composite Laminates
Authors: Wang A.S.D. , Chou P.C. , Lei S.C.
Published: March 2007

This paper presents a stochastic simulation model for the growth of multiple matrix cracks in composite laminates subjected to both static and fatigue loads. Working within the premise of ply-elasticity, a new concept of effective flaws is introduced which replaces the conventional constant ply strength criterion. Thus, the model con sists of an application of fracture mechanics and a rational representation of material flaw distributions. Simulation examples are presented on [02/902]s and [0 2/903]s graphite-epoxy laminates which undergo characteristic transverse cracking under uniaxial tension.
The Effects of Matrix Plasticity on the Thermal Deformation of Continuous Fiber Graphite/Metal Composites
Authors: Kural M.H. , Min B.K.
Published: March 2007

The thermal deformation behavior of very low expansion, unidirectional and angle- ply metal matrix composites is investigated. The theoretical investigation accounted for the plastic flow in the matrix material resulting from residual thermal stresses and ex posure to thermal cyclic environment. Results indicate that the thermal deformation behavior varies significantly in accordance with the stress state of the matrix material. Plasticity in the matrix material causes large thermal strains and hysteresis loops that are not predicted by the elastic analysis. The effects of plasticity can be minimized, however, by increasing the yield stress of the matrix material and preconditioning the composite consistent with the operating temperatures. This paper also includes test data substantiating the elastoplastic effects of matrix material as predicted by analysis.
Vibration and Damping Analysis of Fibre Reinforced Composite Material Plates
Authors: Alam N. , Asnani N.T.
Published: March 2007

Governing equations of motion for a laminated plate consisting of an arbitrary number of fibre reinforced composite material layers have been derived using the variational principles. Each layer has been considered to be of a specially orthotropic material with its directional elastic properties depending on the fibre orientation. Extension, bending, inplane shear and transverse shear deformations in each layer are considered. The longitudinal translatory and the rotary inertias along with the transverse inertia are taken into account. A solution for simply supported rectangular plate is obtained in series summation form and the damping analysis is carried out by an application of the correspondence principle of linear viscoelasticity. The computer program for the determination of the resonating frequencies and the associated system loss factors for the various families of modes of vibration of a plate consisting of an arbitrary number of layers has been developed. Using the same, investigation for the optimum fibre orientation for maximizing the resonant frequencies and the system loss factors for the flexural and the extensional modes of vibration of a four layered criss cross laminated plate, has been carried out. The variation of the resonant frequencies and the system loss factors with aspect ratio, for the first flexural modes of 2,4 and 6 layered cross-ply laminated plates are also reported.
On the Analysis and Design of the End Notched Flexure (ENF) Specimen for Mode II Testing
Authors: Carlsson L.A. , Gillespie J.W. , Pipes R.B.
Published: March 2007

The end notched flexure (ENF) specimen is examined as a candidate for measuring interlaminar fracture toughness in skew symmetric loading. A simple design study for sizing the ENF specimen to minimize geometric nonlinear response and to avoid nonlinear material behavior or flexural failure is presented. Results indicate that inter laminar shear effects may be significant for tough resin systems requiring large thickness-to-length geometries. The influences of interlaminar shear deformation and fric tion between the crack surfaces on the strain energy release rate are examined.
Mode I and Mixed Mode Energy Release Rate Values for Delamination of Graphite/Epoxy Test Specimens
Authors: Rybicki Edmund F. , Hernandez Tony D. , Deibler John E. , Knight Ronald C. , Vinson Steven S.
Published: March 2007

This study is part of a larger program directed at developing guidelines for preventing web-to-stiffener debonding in stiffened composite panels. An important ingredient needed to attain this goal is the identification of a criterion to predict debonding. The objective of this work is to evaluate the energy release rate as a criterion for predicting debonding. A combined experimental and finite element modelling approach was used. Comparisons of strains and displacements measured prior to debonding and the corresponding values calculated with the finite element models are presented to illustrate the capability of the model to represent the behavior of the test specimens. Energy release rate values asso ciated with debonding of two types of graphite/epoxy composite test specimens were eval uated. One test specimen was the Mode I double cantilever beam. The other was a mixed mode (Mode I and Mode II) cracked lap shear specimen. Test specimens were loaded in laboratory conditions until the onset of debonding was observed. Critical load levels and the geometric and material properties of the test specimens were input data for the finite element analysis which evaluated the Mode I and Mode II components of the energy release rate at the onset of debond propagation. The tests provided a range of ratios of Mode II to Mode I energy release rates from 0 to 5.0. Data are shown in a graph of G, versus G~ for both types of test specimens. A discussion of the energy release rate as a criterion for debonding is presented.
Effects of Cure Pressure on Resin Flow, Voids, and Mechanical Properties
Authors: Tang Jian-Mao , Lee Woo I. , Springer George S.
Published: March 2007

The effects of cure pressure on resin flow, compaction, void content, and mechanical properties of fiber reinforced composites were investigated. Tests were performed on lami nates made of Fiberite T300/976 and T300/934 unidirectional prepreg tape. Data are pre sented on compaction, resin flow, and void content which lend support to the validity of the Springer-Loos model. Data are also given showing the effects of cure pressure on void content and on the compressive strength and short-beam shear strength and modulus.
Rate Effects on Mode I Interlaminar Fracture Toughness in Composite Materials
Authors: Smiley A.J. , Pipes R.B.
Published: March 2007

The Double Cantilever Beam (DCB) test geometry was utilized to investigate the rate ef fects on Mode I interlaminar fracture toughness in graphite/PEEK and graphite/epoxy composites. The tests were performed over a range of crosshead speeds from 4.2 × 10-6 to 6.7 × 10 -1 m/s. The results indicate that the toughness of both material systems is rate sensitive. The Mode I interlaminar fracture toughness of the graphite/PEEK material decreases from 1.5 to 0.35 kJ/m2 over five decades of opening rate. The fracture toughness of the graphite/epoxy material decreases from 0.18 to 0.04 kJ/m2 over four decades of load ing rate.
Environmental Effects on Glass Fiber Reinforced PPS Stampable Composites*
Authors: Lou A.Y. , Murtha T.P.
Published: March 2007

The application of polymer composites in engineering structures are contingent upon their property retention and dimensional stability after extended temperature/humidity exposure in service. Mechanical properties of composites decrease with increasing temperature/humidity and the percent of property reduction generally depends on the ex posure time. In this paper, the properties of compression molded polyphenylene sulfide, stampable composites, a long glass fiber reinforced product and a short glass fiber rein forced version, were evaluated after exposure to elevated temperatures, both in air and in water, for extended time periods. Properties measured included tensile, compressive, flexural, impact and fatigue.

The PPS composites exhibited good dimensional stability, as well as property retention, after exposure to the severe temperature/humidity conditions. Effect of temperature alone was negligible, however, some property reduction was measured in the presence of water at elevated temperatures. These property reductions were observed to level off over time at respectable values. The fatigue performance of PPS composite was unaffected by expo sures to the high temperature/humidity conditions.
The Effects of Laminated Structure on Delamination Buckling and Growth
Authors: Yin Wan-Lee
Published: March 2007

Cylindrical postbuckling solutions are obtained for an arbitrarily structured laminate. The strains of the middle surface contain sinusoidal terms that are in-phase with the out- of plane deflection. Bendmg-stretching coupling significantly reduces the buckling load and enhances the postbuckling deformation. The effects may be characterized by introduc ing an equivalent bending rigidity. The postbuckling solutions for a laminate with clamped ends are applied first to a thin-film strip delamination in a base laminate subjected to uni form membrane loads and next to a mid-plane delamination in a symmetric laminate. The energy release rates at the crack tip are evaluated to determine the stability characteristics of delamination growth.