bluuebunny/crossref_metadata_2025 huggingface dataset:
Units of Analysis and the Individual Differences Fallacy in Environmental Assessment
Authors: Richards James M.
Published: March 2007

The "Ecological Fallacy" is the error of interpreting results based on ecological entities, such as environmental settings, as though the results apply to individuals. This article argues that it is equally erroneous to interpret results based on individuals as though the results apply to settings, and suggests this error be labelled the "Individual Differences Fallacy." Hypothetical data were used to illustrate two conditions for an instrument intended to assess the characteristics of classroom environments. In the first condition, the instrument actually measured differences among individuals; in the second condition, it achieved its goal of measuring differences among settings. When individuals were the units of analysis, results either were inconclusive or incorrectly suggested that the measure of individual differences was superior. Correct and interpretable results were obtained only when environmental settings were the units of analysis. Therefore, future research on environmental assessment should use settings as the primary units of analysis.
Studies of Individual Environmental Concern
Authors: Schahn Joachim , Holzer Erwin
Published: March 2007

The article deals with analyses concerning the interplay of environmentally relevant knowledge, attitudes, and behavior as well as gender differences in environmental concern and the role of "background variables" for the prediction of (self-reported) behavior. In a sample of 167 German adults, the results showed that knowledge and gender moderated the relationship between attitudes and behavior. For a second sample of 105 people active in conservation groups, these moderator effects were not as clear. For both samples, women were more environmentally concerned in those topical areas that refer to household behavior, whereas men knew more about environmental problems. Possible reasons for these effects are discussed. Finally, the role of "background variables" is investigated by means of stepwise regression and discriminant analyses, using self-reported behavior as the central dependent variable. For the purpose of this study, a new measurement instrument was constructed and validated. Compared with other scales, a new aspect is the substantially broader spectrum covered. Moreover, various topical areas of environmental concern (e.g., residential energy conservation, environmentally aware purchasing, recycling of solid wastes, and so forth) can be measured simultaneously with the well-established conceptual variables (knowledge, attitude, behavior).
Social Facilitation Effects in Shopping Behavior
Authors: Sommer Robert , Wynes Marcia , Brinkley Garland
Published: March 2007

Unobtrusive observation was used to compare time in the store and load size of lone and group shoppers. Consistent with social facilitation theory, groups spent more time in the store and purchased larger loads than did lone individuals. The larger loads of group shoppers held up with shopping time controlled. Women and older people spent more time in the store and bought larger loads than did men and younger people.
Urban Residence and Housing Improvement in a Lae Squatter Settlement, Papua New Guinea
Authors: Kaitilla Sababu
Published: March 2007

The process of housing improvement in Papua New Guinea (PNG) is a moderate one. This moderate rate of housing activity is largely due to an acute shortage in PNG of affordable, industrially produced modern building materials. The process is further hampered by increasingly changing personal consumer choice behavior. A survey was administered to a random sample of residents of the Burnbu settlement, one of the oldest and largest squatter settlement in Lae, PNG. The results of the study lend support to available evidence that a number of environmental factors play a major role in individual choice behavior.
Environmental Psychology and Health
Authors: Quirk Mark , Wapner Seymour
Published: March 2007

This article reviews a program of research that takes a transactional person-in-environment approach to the study of disease prevention and health promotion. Four areas of research are described: smoking cessation, AIDS prevention, compliance with magnetic resonance imaging (MRI), and prognosis after hip fracture. The findings demonstrate that this approach can shape health care interventions that address the patents thoughts, feelings, and values, and can successfully influence patents' health-related behaviors.
Childhood Foraging as a Means of Acquiring Competent Human Cognition about Biodiversity
Authors: Chipeniuk Raymond
Published: March 2007

With informants from metropolitan Ottawa and the Niagara Peninsula, Canada, tests were made of the hypothesis that broad foraging for natural things in childhood develops personal competence in assessing the biodiversity of local habitats. Responses from initial groups of informants were used to compile region-specific checklists of natural kinds of things foraged. These checklists then became the basis for questionnaires administered to samples of teenage informants, who were also asked to complete a quiz indexing sense of biodiversity by comparing local habitats. Mean breadth of foraging proves to be around 30 natural kinds, and the hypothesis linking breadth of childhood foraging with sense of biodiversity, tested by analysis of variance, is accepted at modest to fairly high confidence levels. Persons who forage more natural kinds in childhood have a better sense of biodiversity as adults.
Images of the Neighborhood and Activity Patterns of Chronically Ill Schoolage Children
Authors: Holaday Bonnie , Swan James H. , Turner-Henson Anne
Published: March 2007

This article deals with chronically ill schoolage children and their parents' perceptions of their neighborhood. Three hundred and sixty-five chronically ill children (ages 10 through 12) were interviewed about their neighborhood. The children described aspects of their neighborhood that they liked and disliked, and their activity pattems alone and with peers. The parents also evaluated neighborhood safety. Regression analysis was used to identify parentand child-reported items that may have influenced images of neighborhood safety. The findings demonstrate that chronically ill children's activity patterns in their neighborhoods are influenced by child factors (perception of the neighborhood and its safety, gender, type of illness) and by parental factors (perception of neighborhood safety, income, home ownership). The findings also suggest that the patterns of interaction of chronically ill children with their neighborhood may be a source of developmental risk.
Nature is Scary, Disgusting, and Uncomfortable
Authors: Bixler Robert D. , Floyd Myron F.
Published: March 2007

The relationships between fear expectancy, disgust sensitivity, desire for modem comforts, and preference for wildland and built environments and related activiffes were examined. Using a population of predominantly suburban and rural eighth-grade students (n =450), all three variables were found to be significantly related to preferences for wildland environments, recreational activifies, and vocational preferences. Those with high fear expectancy, disgust sensitivity, and desire for modem comforts were more likely to prefer manicured park settings and urban environments and to dislike wildland environments. They were also more likely to prefer indoor social recreation activities and express significantly less interest in future careers working in outdoor environments. Finally, they were less likely to prefer appropnate water bodies for conductng an aquatic entomology lab. Studying negative perceptions may complement existing environmental preference research, which has tended to focus on why people prefer certain environments.
Effects of Emotional Mood States in Recognizing Places
Authors: Anooshian Linda J. , Seibert Pennie S.
Published: March 2007

The effects of emotional mood states on remembering scenes along a route of travel were examined in two experiments. For Experiment 1, 48 participants were exposed to a route of travel following a sad, happy, or neutral mood-induction procedure. Process dissociation (Jacoby, 1991) was used to derive separate estimates of the relative roles of conscious recollection and sense of familiarity (unconscious retrieval) in recognizing scenes. Conscious recollection, but not familiarity, was adversely affected by being in an emotional mood state during exposure. For Experiment 2, 24 participants given neutral mood induction were divided according to self-reports of induced mood. Participants in the sad mood group selected more old frames such as "looking sad" in a later test of implicit memory (unconscious retrieval) than did those in the happy mood group. These results reinforced that researchers must address diverse memory processes to understand the role of emotional mood states in spatial cognition.
Rethinking Canadian Magazine Policy
Authors: Acheson Keith , Maule Christopher
Published: March 2007

This article examines the recent magazine dispute between Canada and the USA that was the subject of a World Trade Organization panel ruling in 1997. Canada withdrew or amended the offending measures and subsequently introduced new legislation which the USA claimed to be a replacement of one of the banned measures. This led to the continuation of the dispute and finally to a negotiated settlement in 1999. After examining the underlying facts and the arguments used in this and previous trade conflicts involving periodicals, the article concludes that a continuation of past protectionist policies offers only the possibility of more conflict. In order to bring about a rationalization of the Canadian magazine industry, a reorientation is needed towards a more open perspective. Comment is made on the relevance of these events for other countries.
Mass Media Use, Gender and Religiosity as Predictors of Attitudes Towards Israel in Kuwait
Authors: Al-Menayes Jamal J.
Published: March 2007

This study examines the effects of religious practice and media exposure on attitudes towards normalizing relations with Israel in Kuwait. Results show that frequency of prayer was a strong predictor of holding negative attitudes towards normalizing relations with Israel. Exposure to religious media programming was also a significant predictor of negative attitudes towards Israel. However, ownership of a satellite receiver and exposure to art and culture programming were significant predictors of holding positive attitudes towards this issue. The findings raise questions about the role of mass media in shaping attitudes about international relations.
The Era of Global Communication as Perceived by Muslims
Authors: Ghaffari-Farhangi Sétareh
Published: March 2007

Modern times had not yet finished disrupting life in the Muslim world when a new era arrived, the era of globalization. Technological innovations, especially in the field of communication, are expected exercise a profound cultural impact. From this perspective, Muslims are not the initiators but the victims of change. Their value system is being profoundly affected and many Muslim governments feel threatened by Western hegemony. Some have chosen isolation and have tried the impossible, that is to say the complete closing of their frontiers to the products of Western media (Iran, Saudi Arabia), while others select, censor and adapt these products to conform to their own tastes. However, nearly all Muslim communities are trying to disseminate their own cultures and to carve out a place for themselves in the immense world market of films and television programmes by appropriating the new technologies of communication. Thus can one affirm that a homogenization of cultures will take place? This article concentrates on the new tools of communication and concludes that the use that we make of these tools can effectively allow for both the preservation of one particular culture and its participation in a universal culture.
The Fourth World in the USA: need for convergent generalist, feminist and social development approaches
Authors: Billups James O. , Julia Maria C.
Published: March 2007

Approximately fifty million Americans fall below the poverty line at some time during a given year, while more than thirty-three million are impoverished over any twelve-month period. The disparity between rich and poor is greater in the United States than all but one other industrialized nation. No other developed country has so many poor people or treats them so badly as we do (Brown and Pizer, 1987).
Plotting the Organization
Authors: O’Connor Ellen S.
Published: March 2007

This article uses the literary form of the embedded narrative to link a particular text to the larger texts in which it is embedded, or the surrounding story situation. The article thus addresses a continuing problem in organizational discourse, which is the need to interpret discourse in relation to its context. It also shows how this construct sheds light on the complexity and dynamics of organizational change. The data are from a year-long ethnographic study of a high-technology research organization in Silicon Valley.
Chic, Mystique, and Misconception
Authors: Lipshitz Raanan
Published: March 2007

Few names are more closely associated with organizational learning than those of Argyris and Schön. Nevertheless, their impact on the literature of organizational learning has been fairly tenuous. Examination of references to Argyris and Schön shows that they are frequently drafted to support an author’s or authors’ arguments rather than to be followed or critiqued (“Chic”). From an analysis of Argyris and Schön’s conceptual framework, and of their use of this framework in their consulting practice, the author suggests that the superficiality of Argyris and Schön’s influence is due to their focusing on important, attractive, but hard-to-realize aspects of organizational learning (“Mystique”). As a result, the literature overlooks some important and more feasible substantive lessons that may be learned from Argyris and Schön (“Misconception”).
The Leveling of Organizational Culture
Authors: Feldman Steven P.
Published: March 2007

Critical postmodern organization theory posits the increasing rationalization of organizational life as a threat to individual choice and well-being. Organizational knowledge is seen as a carrier of power relations that subjugate individuals for organizational purposes. Thus, individual resistance through the cultivation of egalitarian forms of self-knowledge is advocated. In this article, the author reviews the arguments and suggestions put forward by critical postmodern organization theorists. He concludes that critical postmodern organization theory’s power/knowledge critique destroys the basis of moral culture in its attack on the dehumanizing processes of rationalization. A more balanced approach that limits critical fervor through the appreciation of moral traditions is suggested.
Employee Participation and Assessment of an Organizational Change Intervention
Authors: Coyle-Shapiro Jacqueline A.-M.
Published: March 2007

Amid the debates on total quality management (TQM), empirical investigations of the process of change have been largely neglected. This article examines the process of change involved in implementing TQM and employees’experience of participation, and it evaluates the impact of employee participation in TQM on their commitment to the organization. The research design involved a survey of employees in a U.K. manufacturing setting, with three measurement occasions: 6 months prior to and 9 months and 32 months after the introduction of TQM. The findings suggest that supervisory participative style is positively related to employee participation. The extent of employee participation is positively related to the assessment of the benefits of TQM. Furthermore, how employees assess the beneficial impact of TQM is more important in predicting subsequent participation in TQM than is their initial participation. Finally, no relationship is found between employee participation in TQM and organizational commitment.
Deflection Limits on the Plate-Twisting Test
Authors: Foye R.L.
Published: March 2007

This note discusses the valid displacement range of the plate- twisting test for estimating shear moduli. The post-linear behavior of this test exhibits some interesting features.
Analysis of The Flexure Test of Bidirectional Composites
Authors: Pagano N.J.
Published: March 2007

Equations are presented which permit a more realistic evalua tion of flexure experiments on bidirectional composite beams. The influence of shear deflection is discussed, and predicted results are compared to experimental data.
Interaction and Fracture of Titanium-Boron Composites
Authors: Metcalfe Arthur G.
Published: March 2007

A model is presented to explain premature fracture of titanium- boron composites as a result of interaction to form titanium boride. Three failure modes are identified. The titanium boride cracks at a strain of 2500 x 10-6 but the cracks result in a smaller stress concen tration than the preexisting flaws in the boron up to a boride thick ness of 1000 Å. Between 1000 and 5000 Å, failure initiates at the cracks in the boride at a strain that varies inversely with the square root of the thickness. Above 5000 Å of boride simultaneous failure of boride and boron filaments occurs.
Bending-Extensional Coupling in Laminated Plates Under Transverse Loading
Authors: Whitney J.M.
Published: March 2007

Anti-symmetric cross-ply and angle-ply laminates under transverse loading are analyzed. By expanding the load in a double Fourier series a closed form solution is obtained for special types of simple-supported boundary conditions. Results show that coupling can increase maxi mum deflections by as much as 300% compared to analogous ortho tropic plates in which coupling is neglected. The severity of the coupling effect depends on the degree of anisotropy of the individual layers, and the total number of plies in the composite
Statistical Theory of Strength of Laminated Composites II
Authors: Scop Peter M. , Argon Ali S.
Published: March 2007

The statistical theory for fracture of laminated composites devel oped previously has been extended to take account of stress enhance ment in neighboring elements around primary fractures. The results show that: a) the effective stress enhancement is less for an elastic matrix than for a rigid-plastic matrix, b) for constant length the strength of the composites rise with increasing numbers of parallel reinforcing elements for all flaw distributions and for both plastic and elastic matrices; c) for the same flaw distribution function the composite with the elastic matrix is stronger than the one with the plastic matrix. Experimental results in support of the theory, on boron sheet com posites and glass fiber tapes are reported.
The Importance of Signs of Shear Stress and Shear Strain in Composites
Authors: Pagano N.J. , Chou P.C.
Published: March 2007

The definition and physical significance of the sign conventions for stress and strain components, in particular, shear stress and shear strain, are of vital importance in studying the response of anisotropic composite materials. Designers and analysts who must predict the strength and stiffness characteristics of laminated systems should be thoroughly familiar with the physical interpretations of these signs. In this paper we elaborate on these sign conventions and demonstrate their importance with several illustrative examples.
Analysis of Anisotropic Plates II
Authors: Ashton J.E.
Published: March 2007

The energy formulation presented earlier is extended to include the analysis of plane anisotropic rectangular plates with non-uniform plate properties and non-uniform in-plane and distributed normal loadings. The formulation includes linear theory stability analysis, the calculation of natural frequencies and mode shapes, and analysis of displacement due to lateral loads. The extension presented in the present paper is formulated in a manner such that the non-uniform properties and loadings can be handled with no appreciable increase in difficulty over the formulations previously presented except for the evaluation of certain more general integrals. An easily automated method of evaluating these more general integrals is presented.
Dislocation Arrays and Elastic-Plastic Cracks in a Two-Phase System
Authors: Chou Tsu-Wei , Tetelman Alan S.
Published: March 2007

A dislocation model is used to study the propagation of elastic- plastic shear cracks in composite materials. It is found that the ex tension of plastic zones in ductile matrices is governed by both the yield strength and rigidity of the matrix phase. Knowing the length of plastic zone, the crack opening displacement can be found. For a constant length of plastic zone, the crack opening displacement in creases as the rigidity of the matrix material decreases. Suppose the fracture of the two-phase system under consideration is caused by reaching a critical crack opening displacement at the crack tip, the critical fracture strength can be determined from the knowledge of fracture toughness of the matrix material.
Dynamic Compressive Strength and Failure of Steel Reinforced Epoxy Composites
Authors: S R.L. , Nevill G.E. , Ross C.A. , Jones E.R.
Published: March 2007

Results of an experimental program systematically evaluating the deformation and fracture of steel wire reinforced epoxy composite systems are presented. The program involved mechanical testing in the strain rate range 10-5 to 103/sec and impact testing of composite specimens using massive elastic targets at strain rates approximately 104/sec. Specific results presented include static and dynamic prop erties, strain rate sensitivity, information on the nature and character of dynamic fracture, influence of specimen geometry and reinforce ment spacing, and high speed photographs of dynamic failure modes. Further, a simplified energy criterion is proposed for predicting failure modes and critical velocities.
The Yield Criterion of Laminated Media
Authors: Chou P.C. , McNamee B.M. , Chou D.K.
Published: March 2007

This study examines the yield criteria for anisotropic laminated media. It will be shown that for laminated media with isotropic layers, the cri tenon of Tsai and Wu is a direct extension of Von Mises'. Also presented here is a set of equations governing the relative positions of the yield ellipses. Furthermore, a general expression for the yield condition of a laminated medium composed of generally anisotropic layers is obtained.
Post-Failure Behavior of Laminates I — No 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 unnotched quasi-isotropic glass-epoxy laminates. The analysis is based on a simplified tangent modulus method and a maximum stress ply failure criterion. Several ply failure models are considered, involving vari ous combinations of stiffness reduction. The most significant finding is that matrix failure in the 90° layers must be supplemented by reduction of E11 as a result of a fiber instability mode.
An Energy Release Rate Approach For Stable Crack Growth in the Free-Edge Delamination Problem
Authors: Rybicki E.F. , Schmueser D.W. , Fox J.
Published: March 2007

An experimental and analytical study was conducted to examine the free-edge delamination mode of failure in a (±30/±30/90/90) S Boron/ Epoxy laminate. The initiation and stable growth of the delamination for static tension loading conditions were identified using ultrasonic tech niques. A finite element representation for the test specimen was con structed using conventional elements. The interlaminar stress distribution at the laminate midplane was found to be in agreement with published results. The finite element representation was used to model the initiation and stable growth of the delamination. An applied force versus longitudinal strain curve was obtained from the model based on the data for the longi tudinal strain versus the extent of the delamination. The applied force versus longitudinal strain curve obtained from the model was between the two sets of data obtained from the specimens. The model also predicted the strain level at which the laminate showed a marked decrease in stiff ness. Energy release rates were evaluated by a simple computational scheme that does not require a special singular element or knowledge of the existence of a stress singularity in the solution. The results of these computations are combined with the experimental data and discussed in terms of the initiation and stable crack growth characteristics of the delamination.
On the Elastic Constants of Plane Orthotropic Elasticity
Authors: Krenk Steen
Published: March 2007

The four independent material parameters of plane orthotropic elasti city are introduced as the effective stiffness, the effective Poisson ratio, the stiffness ratio and the shear parameter. It is proved that stress boundary value problems with zero resulting force on internal contours lead to stress fields that are independent of the effective stiffness and the effective Poisson ratio, and a general transformation is described which is equivalent to a change of the stiffness ratio. These properties suggest the importance of the remaining shear parameter, that has the interesting property of being invariant with respect to a 90 degree rotation of the principal axes of the material.
Moisture Absorption of Graphite-Epoxy Composites Immersed in Liquids and in Humid Air
Authors: Loos Alfred C. , Springer George S.
Published: March 2007

Moisture absorption of graphite-epoxy composites immersed in liquids and in himid air were investigated. The moisture content as a function of time and temperature was measured for three materials: Fiberite T300/1034, Hercules AS/3501-5 and Narmco T300/5208. Tests were per formed a) with the materials immersed in No. 2 diesel fuel, in jet A fuel, in aviation oil, in saturated salt water, and in distilled water (in the range of 300 to 322 K) and b)with the materials exposed to humid air (in the range 322 to 366 K). The results obtained were compared to available composite and neat resin data.
Stress Field Evaluation in Photoelastic Anisotropic Materials: Experimental Numerical Technique
Authors: Voloshin Arkady
Published: March 2007

An experimental numerical technique is developed for stress field evalua tion in photoelastic anisotropic materials. The method is based on using ex perimental data and basic equations of elasticity to obtain an overdetermined solution. Applications of the experimental numerical technique for stress field evaluation in disk under diametral pressure and balanced laminate coupon under tension is presented. Good agreement with the available theoretical solution for the first example was found. An ability of the present method to overcome some inaccuracy in experimental data near free bound ary is shown.
Coefficient of Thermal Expansion for Composites with Randomly Oriented Fibers
Authors: Craft William J. , Christensen Richard M.
Published: March 2007

The effective coefficient of thermal expansion is derived for fiber com posites in two dimensional quasi-isotropic form and three-dimensional isotropic form. These systems represent constructions that have fibers ran domly oriented in a plane and in three dimensions. The effective coeffi cients of thermal expansion are related to the thermal-mechanical proper ties of individual fiber and matrix phases. These results are put into asymp totic forms appropriate to very stiff fiber systems. The asymptotic predic tions are evaluated against the complete forms, and both results are com pared with an experimental result.
The Interlaminar Fracture Energy of Glass Fiber Reinforced Polyester Composites
Authors: Han Kyung S. , Koutsky James
Published: March 2007

This study deals with the interlaminar fracture energy of a glass fiber reinforced polyester composite. Width tapered double cantilever beam (WTDCB) specimens are used for the test. The compliance and fracture behavior of the specimen as well as the effect of specimen geometry on fracture energy are studied. The fracture energy at liquid nitrogen temperature (77°K) is also studied.

It is found that the fracture energy obtained decreases with increasing height of specimens, finally reaching a constant value. The minimum height requirement for the fracture test of Extren is one half inch.

The fracture energy slightly decreases with a decrease in specimen taper. A load-deflection hysteresis is observed to increase with specimen width. Hysteresis is dependent on the beam volume, i.e., height, taper and crack length.

The fracture energy at liquid nitrogen temperature (77°K) is about 3 times higher than that at room temperature and the fracture energy transverse to the fiber direction is slightly higher than in the fiber direction.
Probabilistic Burst Strength of Filament-Wound Cylinders Under Internal Pressure
Authors: Uemura M. , Fukunaga H.
Published: March 2007

This paper presents an analytical approach for predicting the probabilistic ultimate strength after initial failure of the carbon fiber helical-wound cylinders under internal pressure.

First, the initial failure strength distribution is analysed according to the maximum stress and the Tsai-Wu criteria, based on the scatter of basic data of unidirectional composites. The analysis is performed by using the piecewise linar method, taking account of the nonlinear shear stress-strain relation.

Secondly, the ultimate strength is analysed by assuming the degradation of stiffness corresponding to the initial failure modes.

The analytical predictions are compared with the burst test results of CFRP cylinders with some different winding angles. Good agreements are obtained both in the burst pressures and in the pressure-strain curves up to fracture.
Quantitative Nondestructive Evaluation of Automotive Glass Fiber Composites
Authors: Williams James H. , Lee Samson S. , Wang Tony K.
Published: March 2007

Thermographic, ultrasonic and acoustic emission nondestructive evalua tion (NDE) characterizations of flawed and unflawed SMC-R25, SMC-R50 and XMC-3 composites are conducted. For various flawed and unflawed states of the composites, these NDE characterizations are correlated with both flaw state and tensile fracture strength. Drilled-holes and V-notch flaws of various sizes result in correspondingly lower tensile strengths; however, in creases in fabrication temperature up to 177 °C and pressure up to 13.8 MPa, post-fabrication thermal exposure at 191 °C for up to 24 hours, water immer sion at 21 °C for up to 45 days and aluminum foil inclusions are found to have no significant effects on the tensile strength.

For all three materials, the maximum number of thermographic color dif ferences is correlated linearly with the flaw size to specimen thickness ratio and with the tensile fracture stress for the drilled-holes and V-notch flaws. For all three materials, the ultrasonic through-thickness attenuation at 2 MHz is correlated linearly with the tensile fracture stress, independent of the material flaw state. And, for all three materials, the acoustic emission stress delay is correlated linearly with the tensile fracture stress, independent of the material flaw state. Thus, the NDE of fiber reinforced plastics (FRP) for structural integrity assessment is demonstrably feasible.
Moisture Gradient Considerations in Environmental Fatigue of CFRP
Authors: Edge E.C.
Published: March 2007

The evolution of the techniques of conditioning composite material in the laboratory to simulate in service degradation is briefly summarized. The development of environmental fatigue programs, involving simultaneous loading and environmental cycling is seen as introducing new problems, par ticularly if acceleration of ground dwell leads to input frequencies which dif fer from real life values. The frequency effect is illustrated by theoretical ex amples which attempt to evaluate and compare the moisture gradients in duced by an environmental fatigue regime and a typical aircraft outdoor en vironment.

The theoretical method used in this paper would appear to be of general applicability in assessing the realism of accelerated conditioning and testing of CFRP specimens.
Fracture of Random Short-Fiber SMC Composite
Authors: Wang S.S. , Chim E.S.-M. , Yu T.P. , Goetz D.P.
Published: March 2007

The fracture behavior of random chopped-strand, glass-fiber reinforced SMC composites was studied. Experiments were conducted on notched SMC-R50 composite plates subjected to in- plane loading. Fracture mechanics analyses based on recently developed conservation laws of solid mechanics were performed to evaluate notch-tip stress intensities in the specimens. Fracture toughnesses, KIQ and KIIQ, of this material under individual mode-I and mode-II loading were determined. Fracture tests and subsequent analyses were also conducted on the notched SMC- R50 subjected to combined-mode loading. Mixed-mode fracture criteria were investigated for the random short-fiber composite. The suitability of the Whitney-Nuismer two-parameter model was also examined for determination of notched SMC composite strength.
Experimental and Analytical Studies On the Onset of Delamination in Laminated Composites
Authors: Kim R.Y. , Soni S.R.
Published: March 2007

A large number of laminates prone to delamination under uniaxial loading have been tested. The onset of delamination is determined on the basis of acoustic emission data. A two parameter failure criterion, i.e. average interlaminar normal stress failure criterion on σ=, has been used in conjunction with the stress analysis done by applying the global local model [5]. A comparison between the experimental and the predicted edge delamination threshold strengths has been made. For the class of laminates studied, the onset of edge delamination load can be accurately predicted.
Buckling of a Sublaminate in a Quasi-Isotropic Composite Laminate
Authors: Shivakumar K.N. , Whitcomb J.D.
Published: March 2007

Buckling of a delaminated region can cause high interlaminar stresses which, in turn, lead to delamination growth. Hence, buckling strain is an important parameter in assessing the potential for strength loss due to the delamination. The objective of this study was to predict the buckling of an elliptic delamination embedded near the surface of a thick quasi-isotropic laminate. The thickness of the delaminated ply group (the sublaminate) was assumed to be small compared to the total laminate thickness. Finite- element and Rayleigh-Ritz methods were used for the analyses. The Rayleigh-Ritz method was found to be simple, inexpensive, and accurate, except for highly anisotropic delaminated regions. Effects of delamination shape and orientation, material anisotropy, and layup on buckling strains were examined. Results showed that (1) the stress state around the delaminated region is biaxial, which may lead to buckling when the laminate is loaded in tension, (2) buckling strains for multi-directional fiber sublaminates generally are bounded by those for the 0 deg and 90 deg unidirectional sublaminates, and (3) the direction of elongation of the sublaminate that has the lowest buckling strain correlates with the delamination growth direction.
The Fracture Energy of Pultruded Rod
Authors: Outwater J.O.
Published: March 2007

The pronounced anisotropy of pultruded material permits the propagation of a diametral crack along its length by torsion. It is shown that the torque required to propagate this crack is independent of the crack length. Accordingly, the fracture energy of pultruded material is easily approximated by a simple torsion testing system and can provide a measure of the glass-resin interaction and bonding.
Stress Singularity in Composite Laminates by Finite Element Method
Authors: Yeh J.R. , Tadjbakhsh I.G.
Published: March 2007

A compact finite element formulation based on singularity transformation is presented and is used to analyze the stress singularity at the boundary-layer of an interface between adjacent layers in a laminated composite. The composite is subjected to uniform axial ex tension in the plane of the layers. For illustration, results from few elements are shown to demonstrate the accuracy and efficiency of the present approach. Excellent agreement between the present results and the analytical solutions is obtained.
The Dynamic Response of Graphite Fiber-Epoxy Laminates at High Shear Strain Rates
Authors: Werner S.M. , Dharan C.K.H.
Published: March 2007

The split Hopkinson bar was used to determine the stress, strain and strain rate response of woven graphite-epoxy laminates during high shear strain rate deformation. The specimens were oriented and tested in both interlaminar shear and in transverse shear at strain rates ranging from 6000 to 18000 sec-1. The results show that the strain rate effect in interlaminar shear is small. The fracture surface is characterized primarily by interfacial failure between the fibers and the matrix. In transverse shear, however, the strain rate effect is significant due to the greater role played by the resin matrix in the deformation process. In both cases, at the high strain rates imposed in this investigation, sparks were produced by the specimens during deformation. These are believed to be caused by the combustion of fragments resulting from the high rate deformation.
The Effects of Moisture Induced Swelling Upon the Shapes of Anti-Symmetric Cross-Ply Laminates
Authors: Harper B.D.
Published: March 2007

This paper presents an investigation of the effects of moisture-induced swelling upon the out-of-plane warping of general anti-symmetric cross-ply composite laminates. The analy sis assumes linear elastic material behavior and includes non-linear geometric effects. Ap proximate solutions are obtained by assuming kinematically admissible expressions for the mid-plane displacements in terms of several generalized coordinates which are subse quently found by requiring a minimal value for the total potential energy of the laminate. It is shown that any specific anti-symmetric cross-ply lay-up will assume either a unique "saddle" shape or one of two possible approximately cylindrical shapes depending upon the in-plane dimensions of the laminate and the amount and distribution of moisture within the laminate.
On Computation of Stresses Around Holes in Anisotropic Plates
Authors: Tung T.K.
Published: March 2007

In plane elasticity analyses, the effects of anisotropy can be embodied in two characteristic roots. The classical solution by Lekhnitskii and Savin for open holes becomes indeterminate when these roots are equal, also when either root is equal to √-1 for a circular opening. This note presents a limiting procedure and a root modifica tion scheme that give accurate results with ordinary machine precision for any plate material. The latter scheme works well also for loaded holes.
Material Damping in Aluminum and Metal Matrix Composites
Authors: Crawley Edward F. , Van Schoor Marthinus C.
Published: March 2007

The material damping in beam-like specimens of aluminum and metal matrix com posites was measured. A unique apparatus to determine damping by free decay while the specimens are in free fall in a vacuum was used. The specimens tested include 2024-T3 and 6061-T4 aluminum, and unidirectional graphite/metal matrix specimens with P55 and P100 fibers and 6061 Aluminum and AZ91C Magnesium as matrix materials. Tests were conducted to determine the dependence of damping on frequency and stress level. For the aluminum specimens, the material damping followed the Zener model at very low stress levels. Below the Zener relaxation frequency, a strong dependence of damping on stress was found for even moderate stress levels. Damping for the aluminum matrix materials was slightly above that predicted by the Zener model for a homogeneous bar of the matrix aluminum. For the magnesium matrix specimens, damping significantly above the Zener prediction for the homogeneous matrix material was observed.
Mechanical and Electrical Properties of Graphite Fiber-Epoxy Composites Made from Pristine and Bromine Intercalated Fibers
Authors: Jaworske Donald A. , Vannucci Raymond D. , Zinolabedini Reza
Published: March 2007

The mechanical and electrical properties of pristme and bromine intercalated graphite fiber-epoxy composites were compared. The two types of composite were similar in terms of tensile modulus, tensile strength, and Poisson's Ratio. However, the interlaminar shear strength of the brominated composite was 18 percent greater than its pristine counterpart. Only slight differences were observed in flexural properties. A five-fold decrease was observed in the electrical resistivity of the brominated composite parallel to the axis of the fibers, resulting in a unidirectional resistivity of about 90 μΩ-cm. Transverse resistivity was unaffected. Both types of composite were subjected to a simulated lightning strike of 10 KJ (at a peak current of 150 kA), and the composite with the intercalated graphite exhi bited less damage.
Post-Failure Analysis of Bolted Composite Joints in Tension or Shear-Out Mode Failure
Authors: Chang Fu-Kuo , Chang Kuo-Yen
Published: March 2007

A progressive damage model was developed for bolted joints in laminated composites which may fail in either tension mode or shear-out mode. The model is capable of assess ing damage accumulated in laminates with arbitrary ply orientations during mechanical loading and of predicting the ultimate strength of the joints which failed in tension or shear-out mode. The model consists of two parts, namely, the stress analysis and the failure analysis. Stresses and strains in laminates were analyzed on the basis of the theory of finite elasticity with the consideration of material and geometric nonlinearities. Damage accumulation in laminates was evaluated by the proposed failure criteria combined with a proposed property degradation model. Based on the model, a nonlinear finite element code was developed. Numerical results were compared with available experimental data. An excellent agreement was found between the analytical predictions and the experimental data.
On Low-Velocity Impact Testing of Composite Materials
Authors: Sjoblom Peter O. , Hartness J. Timothy , Cordell Tobey M.
Published: March 2007

The importance of understanding the response of structural composites to impact cannot be overstated. This understanding includes both the impact phenomena themselves and the influence of materials properties on the impact response. This paper presents the need for instrumented testing to optimize our understanding of the impact event, especially the response of the impacted material. The conclusion is drawn that the impact force history is a more relevant measure of a materials characteristics than is the total kinetic energy of the impactor. Static and dynamic impact phenomena are assessed to lay the foundation for the eventual development of a standardized test method focused on the lower velocity range impact response behavior of composites. In addition, a relatively inexpensive but very versatile low-velocity, instrumented pendulum impact tester is described and actual test data for both graphite fiber/thermoset matrix and graphite fiber/thermoplastic matrix are compared. Actual energy absorption curves are shown. A simple method is described to allow direct measurement of the total energy exchanged during the impact event, and the use of these data to permit the vital dynamic calibration of the load cell for every different impact event is illustrated. The different stages in the damage process are characterized, for the first time, for the two materials systems studied.
Residual Strength of a Carbon/Epoxy Composite Material Subjected to Repeated Impact
Authors: Wyrick David A. , Adams Donald F.
Published: March 2007

The residual tensile and compressive strengths of specimens cut from composite plates subjected to repeated impact at various energy levels were measured. The 16-ply quasi- isotropic composite plates were 2 mm thick, fabricated from Hercules AS4/3501-6 car bon/epoxy prepreg. Impact energy level and number of impacts were found to be major factors influencing strength degradation. However, strength degradation was limited to the region near the impact point.
Quadratic Stress Criterion for Initiation of Delamination
Authors: Brewer John C. , Lagace Paul A.
Published: March 2007

The initiation ofdelamination in graphite/epoxy specimens was investigated both analyt ically and experimentally. Three specific laminate families were investigated: [±15 n] s, [± 15 n /0n]s, and [0n / ± 15n] s with the normalized effective ply thickness, n, varying from one to five. Delamination initiation was determined to have occurred when a drop in load was detected and a delamination was observed on a replication of the specimen edge. Measured initiation stresses were correlated using the strain energy release rate approach and the Quadratic Delamination Criterion introduced herein. The strain energy release rate approach was unable to accurately correlate data for two of the three laminate fami lies. The data clearly shows that the critical value of strain energy release rate is dependent on ply thickness. The Quadratic Delamination Criterion, an average stress criterion which compares the calculated out-of-plane interlaminar stresses to their related strength param eters, is proposed and shows excellent correlation with the delamination initiation stress data.
Fiber Orientation Control of Short Fiber Composites: Experiment
Authors: Yamashita Shu , Hatta Hiroshi , Sugano Toshiyuki , Murayama Kunihiko
Published: March 2007

Orientation control of short fibers in a liquid matrix has been carried out by loading a magnetic field. Nickel coated graphite short fiber was used as a magnetic inductive fiber. From a practical point of view, main attention was placed upon the determination of the critical volume fraction of the fibers Vfc , which was the maximum value at which the ori entation control was possible. Vfc was experimentally shown to increase rapidly with decrease of aspect ratio of the fibers. Then, in order to force the increase of Vfc , ultrasonic vibration combined with the magnetic moment was loaded to loosen tangled fibers. The loading of the ultrasonic vibration had a remarkable effect in raising the Vfc .
Squeeze Cast Metal Matrix Composites: Evaluation of Their Strength, Damping Capacity and Corrosion Resistance
Authors: Bhagat R.B. , Amateau M.F. , Conway J.C. , Paulick J.M. , Chisholm J.M. , Parnell J.M. , Seidensticker D.G.
Published: March 2007

Several graphite fiber reinforced (planar random) metal matrix composites employing copper, aluminum, tin and babbitt matrices were fabricated by a newly devel oped high-pressure squeeze casting method. The fiber volume fraction of these composites ranged from 5 to 55%. These composites had relatively weak fiber-to-matrix bonding because of the near-absence of interfacial reaction between fiber and matrix materials. The tensile strength of these composites increased with fiber volume fraction up to about 25% followed by a gradual decrease for higher fiber volume fractions.

Experiments were designed to evaluate various mechanical and physical properties of high pressure squeeze cast composites including the damping capacity and corrosion re sistance. Measurements of logarithmic decrement values at reasonant frequencies on can tilevered beam specimens have demonstrated that the damping capacity of the composites is much superior to that of wrought 6061-T6 Al and mechanically alloyed aluminum. Results on corrosion resistance of the composites in distilled water and 3.5% NaCl solu tion over a range of voltages and temperatures are presented and discussed.