bluuebunny/crossref_metadata_2025 huggingface dataset:
An Evaluation of the Use of Ordinary Least Squares for Estimating Tourism Demand Models
Authors: Morley Clive L.
Published: July 2017

Estimating tourism demand models involves a set of related equations with errors that may not satisfy the common assumptions of being independent, with constant variance and normal distribution. In such circumstances, seemingly unrelated regression estimation may be considered a better estimation technique than ordinary least squares. Results from a simulation exercise, however, show that generally there is little difference between ordinary least squares and seemingly unrelated regression. The ordinary least squares technique performs well, and the results give little reason to use more complex estimation techniques. Another feature of tourism data is that strong growth in tourist numbers is often observed. This feature implies that models in which such series are the dependent variable are not consistently estimated by least squares methods. A percentage error loss function is proposed as a more appropriate criterion for estimating tourist data of this type.
Tourism Research Inquiries: The Response of the State Office of Tourism
Authors: Van Hoof Hubert B. , Verbeeten Marja J.
Published: July 2017

This article reports on the findings of a 1995 survey of state offices of tourism on how they address research inquiries. Results indicate that most state offices of tourism have a mechanism in place to deal with tourism research inquiries, yet very few of them track the nature of the inquiry or evaluate their own performance in this area.
Gambling on the Internet: A Threat to Tourism?
Authors: Au Norman , Hobson J. S. Perry
Published: July 2017

The limited number of legalized gambling and gaming destinations has resulted in significant tourism flows. In some destinations gambling has been permitted based on the economic benefits associated with increased amounts of tourism. The emerging use of the Internet, and the increasing access to new Internet gambling opportunities may pose a threat to gambling-related tourism. This article examines the issues surrounding the development of Internet casinos and assesses the likely impacts on the tourism industry.
Heading South! Importing Discourse Analysis
Authors: Painter Desmond , Theron Wilhelmina H.
Published: July 2017

Postmodern critiques problematise the import of social psychology into non-western contexts on epistemological and ideological grounds. Yet, British approaches to the discipline remain popular with critical social psychologists in South Africa. One such import product is discourse analysis, which, as a “postmodern” social psychology, seemingly resolves challenges of “intellectual colonialism” by endorsing a constructionist understanding of social psychological phenomena. However, by extending a conception of language into a discursive ontology enables only a partial social psychological understanding of the often insidious nature of experience and social conduct even when discourses change. What is required is an understanding of these aspects of social agency as also pre-reflexively and non-propositionally patterned, making necessary a conception of culture that works, so to speak, directly on the body. This remains impossible in a theoretical system that has to fall back on the notions of reflexivity and ideology in order to explain the social and political determination of experience and meaningful conduct.
Psychological Symptoms in Recently Diagnosed Cancer Patients
Authors: Pillay Anthony L
Published: July 2017

The study sought to empirically evaluate levels of depression, anxiety and hopelessness in adults recently diagnosed with cancer. Fifty newly diagnosed cancer patients (with mixed cancer sites) were compared to a group of non-clinical controls using the Beck Depression Inventory, Beck Anxiety Inventory and Hopelessness Scale. The results showed significantly higher levels of depression, anxiety and hopelessness reported by the cancer subjects. Also significant positive correlations were found across these clinical variables. The findings highlight the psychological symptoms manifested by newly diagnosed cancer patients and emphasize the need for concerted efforts to provide appropriate psychological care to such patients. This aspect of the management of cancer patients, especially in the early stages of coping with the diagnosis, is often ignored or superficially handled.
A Lurian-Piagetian Approach to Assessment of Historically Disadvantaged Black Scholars in English Medium Schools
Authors: Levert Tanya , Jansen Patricia
Published: July 2017

Piagetian and Lurian assessment procedures were employed to evaluate the neurocognitive processes of seven-year-old historically disadvantaged children (n=27), residents of traditionally Black areas who were identified as experiencing learning problems (LP group) in English medium schools. Comparisons were made with a reference group of Black children in the same schools (n=23) currently not experiencing learning problems (NLP). No significant differences were found between factors such as maternal education, occupational status, Home Screening Questionnaire or the amount of English spoken in the homes of the two groups. On Piagetian tasks of conservation and seriation, it was observed that the performances of the NLP group were age appropriate, while the LP children showed a developmental lag, despite the fact that no significant difference was observed on classification tasks. Using Majovski et als (1978) adaptation of Luria's tests, significant differences were noted on all tasks with the exception of Acoustic-Motor organisation and Higher Visual Functions. The results of the Lurian tasks indicated difficulties with basic skills but especially with the regulatory and directional aspects of language which manifested in lower level dysfunctions regarded as prerequisites for gaining higher level skills. The occurrence of different maturation rates and skills for the two groups as shown by Piagetian and Lurian tasks, was also supported by differences obtained on Goodenough's (1929) DAP test (p<.001). Significant correlations were found between conservation and seriation tasks with Lurian functions of motor, acoustic-motor, expressive language, arithmetic and reading /writing skills. The possibility is raised that Piagetian and Lurian approaches can offer greater insight into children's cognitive levels and task performance.
Some Predictors of Mathematics Achievement among Black Secondary School Learners
Authors: Grobler Anneke C. , Grobler Adelene A. , Esterhuyse Karel G.F.
Published: July 2017

This study was conducted to identify predictors of mathematics achievement among grade 9 learners of a random sample of five township schools. A series of regression analyses were performed for boys and girls separately to obtain Cohen's (1992) effect size estimate (uniquely explained criterion variance expressed as a proportion of unexplained criterion variance) for various predictor variables. Cognitive predictors were verbal and non-verbal General Scholastic Aptitude Test scores. Non-cognitive variables included the hierarchical levels of self-concept: Global (Rosenberg Self-Esteem Scale), and academic and mathematics self-concept (relevant scales of Brookover, Erickson and Joiner). Socio-economic predictors included home-related variables (parental education, parental occupation, family size) and school-related factors (class size, teacher's qualification, teacher's experience). Gender differences favouring boys were found. Non-verbal and verbal scholastic aptitude and teacher's general training correlated significantly with mathematics achievement for boys and girls, with nonverbal scholastic aptitude showing the highest correlation and effect size estimate for girls and teacher's general training occupying this position for boys. Teacher's mathematics training and class size showed correlations in excess of 0.35 for boys but not for girls. The negative corrrelation obtained for teacher's general training suggested that learners whose teachers held a three-year teaching diploma performed better in mathematics than did learners whose teachers held a degree and a teacher's diploma.
Nerve growth factor: Increased angiogenesis without improved nerve regeneration
Authors: Santos Perry M. , Winterowd Jack G. , Allen Graham G. , Bothwell Mark A. , Rubel Edwin W.
Published: July 2017

Nerve growth factor (NGF) and laminin are important factors for neural development and regeneration. We examined the effects of increasing the local concentration and duration of action of NGF and laminin on peripheral nerve regeneration in the adult mouse sciatic nerve. A Silastic (silicone rubber) channel with intraiuminal NGF solution was secured between transected nerve ends. The second channel tested, formed from a polysaccharide called chitosan, was prepared with NGF and laminin in the channel walls and provided a sustained release of NGF. At six weeks post‐implantation, no improvement in nerve regeneration was identified in those channels prepared with NGF when comparing electromyographic thresholds (μA), maximum potentials (mV), nerve diameter, myelin sheath thickness, myelinated axon counts, or diameter. However, increased angiogenesis was demonstrated within the chitosan and Silastic channels prepared with NGF compared to those channels without NGF. Silastic exhibited minimal inflammation. Chitosan was associated with inflammation in many nerve channels.
The Numbers Game in Evangelism
Authors: Coote Robert T.
Published: July 2017

Failed expectations about “bringing in the Kingdom” may lie at the root of the decline in the missionary force of mainline denominations. Is a missiological motivation based on “evangelising the world to bring back the King” giving rise to similar unrealistic expectations? Optimistic statistics on aspects of church growth are vulnerable to question. Reports of the numbers of missionaries forget the aspect of proportionality to size of population, reports of church growth include the effect of babies born to Christians of all denominational groups, and increases in the numbers of missionaries include short-termers. The growth of the new category of Great Commission Christians and the reduction in number of unreached people groups are based on faulty descriptive bases. If the world remains unevangelised by 2001, these attempts to motivate Christians to evangelism on the basis of current optimistic statistical improvements will undermine a proper basis for motivating people for evangelism which is based on faith and not on sight.
Can the Evangelist Ignore Socio-Political Issues? I
Authors: Son Bong-Ho
Published: July 2017

The rapid growth of Korean churches and the conflict-ridden Korean society may serve to illustrate how evangelists should face critical socio-political issues. The Korean experience seems to indicate that evangelists are most effective when they concentrate their entire efforts on preaching “Jesus Christ and Him Crucified” alone. Believers in general, however, should be keenly interested in such issues as human rights and social justice, not only for their own sake but also for the sake of effective future evangelism. The Church's involvement in these issues gives a favourable impression of Christianity, which in turn facilitates evangelism.
Can the Evangelist Ignore Socio-Political Issues? II
Authors: Raj Ebenezer Sunder
Published: July 2017

In the nineteenth century, Christian evangelists in India played a major role in influencing the majority Hindu population; although most of their listeners did not know the God they preached about, the listeners knew what values the evangelists stood for. The reverse is true today. Modern Christian preaching tends to emphasise a spiritual commercialism. The respect of the nation and the right to be heard need to be regained.
“Small Is [still] Beautiful In Missions”
Authors: Bonk Jonathan J.
Published: July 2017

A recent re-reading of E. F. Schumacher's classic Small is Beautiful: Economics as though People Matter reminded me that while Western socio-economic systems seem to operate on the assumption that the chief end of a human life is to bring glory to the GNP, no religious person–certainly no Christian–can accept either economic theories or economic practices which functionally regard human beings as mere means to materialist ends. Western mission societies have by no means been exempt from the pressure all about them to become numerically bigger, materially richer, and technologically more powerful in response to the highly competitive world of conflicting world views. That this is not only an inappropriate but dangerous trend is the point of this article.
Scope phenomena in English and Dutch and L2 acquisition: A Case Study
Authors: Haegeman Liliane
Published: July 2017

The aim of this paper is to examine how a revised contrastive analysis, based on Chomsky's Government Binding Theory, can be a contribution to L2 acquisition research.

The paper illustrates in detail how a contrastive approach in terms of parametric variation between languages may explain persistent errors made by Dutch learners of English. Three parameters are considered: the COMP-INFL parameter, the presence of absence of reanalysis in the VP and the categorial status of modals. These three interact in three related areas of English grammar: i) do-insertion, ii) scope of negation, and iii) modal scope (especially as regards conditionals). It is argued that errors made by Dutch learners in these areas of English grammar are due to an inadequate ‘resetting’ of the parameters involved. A prominent feature of L2 parameter setting seems to be the doubling strategy.
Beetlemania of Bygone Times
Authors: Lubetski Meir
Published: July 2017

The biblical terms [Formula: see text] in Deut. 28.42 and [Formula: see text] in Isa. 18.1 were never satisfactorily defined. A thorough analysis of ancient Egyptian texts, classical literature, Aramaic and rabbinic sources, post-biblical texts and archaeological material suggests that [Formula: see text] in the Pentateuch means beetle and Isaiah's phrase can be translated ‘land of the winged beetle’, that is, Egypt. Moreover, the Egyptian beetle metaphorically could represent a (sacred) boat and in Christian commentary, crucified Jesus. Though viewed as abominable, the beetle was used as a potent drug in eastern Mediterranean communities down to the middle ages. Influence of time-honoured Egyptian culture left a distinct mark on the contiguous communities. Small wonder that the Bible, even talmudic literature, incorporated some of its tastes.
Land, Slave Labor and Law: Engaging Ancient Israel's Economy
Authors: Glass Zipporah G.
Published: July 2017

Engaging ancient Israel's economy is important for explicating economic processes in the social and legal composition of the society. Using biblical and extra-biblical texts, archaeological data, and knowledge primarily from the fields of anthropology and economic sociology, scholars have sharply delineated the processes of latifundialization when constructing representations of societal structure and agricultural economy in the ancient world. The purpose of this paper is to be in dialogue with this scholarship, yet move to a level of systemic analysis that treats the pertinence of three factors—land, slave labor and law. In this context, the economy of land and labor is used as an alternative optic for viewing and understanding the manumission laws of Deuteronomy 15.
The Contribution of the Dead Sea Biblical Scrolls to Biblical Studies, with the Preliminary Editions of 4QPsP and 4QPsr-u
Authors: Flint P.W.
Published: July 2017

The first section of this article offers an overview of the biblical scrolls from Qumran and other Judaean sites in the desert and discusses the ongoing contribution of many recently-published biblical scrolls to study of the Hebrew Bible. Brief descriptions of six projects in progress are offered: Biblia Hebraica Quinta The Hebrew University Bible Project, The Oxford Hebrew Bible, The Qumran Bible, The Dead Sea Scrolls Bible and the Text and Interpretation series. The second section presents the preliminary editions of three scrolls that contain ‘Psalms of David’ (4QPsP 4QPsr and 4QPss), and two more that contain ‘Psalms of the Sons of Korah’ (4QPst and 4QPsu).
An Intertextual Reading of ‘A Crushed Reed’ and ‘A Dim Wick’ in Isaiah 42.3
Authors: Paul Kim Hyun Chul
Published: July 2017

The present study proposes a new reading of the ‘crushed reed’ and ‘dim wick’ passage in Isa. 42.3a by examining the interconnections of phrases and metaphors within Isaiah and beyond. Several similar phrases in other texts help one read these seemingly ambivalent phrases as referring to the group of people weakened and shattered, the Judaeans, on an explicit level and to the foreign forces of Egypt and Babylon on an implied level. A deliberate double entendre in the phrases conveys that Israel is assured of consolation, particularly under the coming authority of the individual servant, Cyrus or a Davidic king. At the same time, this double entendre also implies an irony in that Israel, also as the servant, will establish justice over against Egypt and Babylon and on the whole earth with the task that moves beyond anti-Babylonian ideology, a part of the new vision of the prophet.
Sibling Relationships in Classical Athens: Brother-Sister Ties
Authors: Cox Cheryl Anne
Published: July 2017

This article examines the private orations of classical Athens for evidence of the relations between brothers, brothers and sisters, and brothers-in-law. Although affection could exist between male siblings, Athenian inheritance laws, requiring equal division of the paternal estate among male heirs, stimulated conflict between brothers. Females, however, could not inherit if they had brothers, neither were their dowries equal to their brothers' share of the patrimony. The interest of the natal family in giving a substantial dowry and in contracting a secure and prestigious marriage for the daughter often led to ties between brothers and sisters and cooperation between brothers-in-law. When cross-siblings or their descendants contended for the same estate, however, conflicts did arise, at times aggravated by the institution of adoption.
Luther's Reformation and (Un)Holy Matrimony
Authors: Johnson Susan M.
Published: July 2017

How dramatic was Martin Luther's impact on the Reformation family? By moving away from a history of politics and theology to the beliefs and practices of common people, scholars drawing from many disciplines paint portraits of Reformation families that differ little from those that preceded and followed them. Available information on household climate, the divorce rate, the social role of women, child-rearing practices, and education lead one to conclude that Martin Luther affected little enduring change in European families.
Prevalence of the Formal Zadruga in the Village of Vilovo, Vojvodina, Serbia
Authors: Djurdjev Branislav S. , Katic Vesna , Zarkov Dubravka
Published: July 2017

The article describes the use of local historical archives (defters-Turkish tax poll registers, parish registers, and Libri Status Animarum) for reconstructing sociodemographic growth. The changes in the household structure of Vilovo village have been studied on the basis of the household typology developed by the Cambridge Group. Both the incidence and the longstanding tradition of the category of zadruga have been attributed to the influence of Turkish and Austrian state regulations favouring the zadruga organization, especially in the period when the village was a part of the Military Border. This resulted in its prevalence over other household categories.
Industry, Family, and Class: The Working-Class Community in Barreiro
Authors: de Almeida Ana Nunes
Published: July 2017

Frequently placed on the edges of scientific debate and analyzed in relation to problems or theoretical constructs specific to other social groups, the portrait of the “working-class family” is too often the product of logical deductions and a sort of no-man's land. The research project described by the present article concerns factories, working-class groups, and family strategies in Barreiro, a Portuguese industrial town near Lisbon, the Portuguese capital. Special attention is given to reconstructing the industrial experience at a regional level and to the study of workers in the cork and heavy metallurgical industries of Barreiro. The results suggest the internal diversity of the working-class world and two different kinds of linkeage between family and workplace life—the survival strategy of cork workers in the 1920s, and the promotion strategy of the metal workers in the 1950s.
Peasant Stem Families in Northwestern Portugal: Life Transitions and Changing Family Dynamics
Authors: Wall Karin
Published: July 2017

The article analyzes data on family forms and individual life experiences in two rural communities of the Baixo Minho (northwest Portugal) during the 20th century. It examines how social and economic differentiation shaped norms and practices, giving rise to a variety of family forms rather than a regional family pattern. The stem family is found to be characteristic of wealthy peasant farmers. Drawing on individual life histories in two different generations, the article traces changes in stem family dynamics under the impact of industrialization and modernization over the last thirty years.
Racial Differences in First Names in 1910
Authors: London Andrew S. , Morgan S. Philip
Published: July 2017

This research examines concentration and similarity in the first name distributions of African Americans and whites resident in Mississippi in 1910. Data are drawn from the Public Use Sample of the 1910 Census, with names added from microfilm copies of original Census manuscripts. We find little difference in the degree of concentration of the name distributions and only modest dissimilarity in name choice. Multivariate analysis using age as a proxy for period of name assignment (birth cohort) indicates that racial differentiation in name choice increased over the period 1870 to 1910 primarily as a result of changes in the name choices of whites. We discuss these results in conjunction with the recent work of Lieberson and Bell (1992) on contemporary racial differences in naming patterns. Lieberson and Bell (1992) argue that African Americans in the contemporary period emphasize group differences by choosing “African” or “African sounding” names. In Mississippi in the period between the abolition of slavery and 1910, we argue that whites distanced themselves from African Americans by choosing increasingly the “whitest” names (e.g., those disproportionately chosen by whites). Changing naming patterns are not orchestrated group responses. Instead, they reflect emergent cultural responses to fundamental social change.
How Separate a Sphere? Poor Women and Paid Work in Late-Victorian London
Authors: August Andrew
Published: July 2017

The essay traces patterns of poor women's employment in late-nineteenth-century London. It shows that employment was common among single, married and widowed women, except among mothers of young children. Unpaid domestic work and paid employment dovetailed into a constant burden of work facing poor women. This challenges the prevalent argument that married women earned wages only at moments of severe crisis in the household economy. It reveals a culture of women's work among the poor that contrasts sharply with the ideology of separate spheres that excluded middle-class women from employment.
Simulation of Non-Linear Viscoelastic Flow Behavior in the Buss Kneader
Authors: Lyu Min-Young , White James L.
Published: July 2017

We seek to simulate the non-linear viscoelastic characteristics of molten thermoplastics in the Buss Kneader in which the screw has both rotating and oscillating motions. Non-linear viscoelastic effects are considered using a convected Maxwell model. Calculations are made first in a basic screw element and subsequently in the special Kneader screw modules where we consider leakage flows by drag and pressure flows through the interrupted screw flights.

Our study predicts screw pumping characteristics of Kneader screw elements which vary with material properties such as viscosity and relaxation time. It also considers pressure and fill factor profiles along the screw axis in the modular Kneader machine.
Hygrothermal Expansion Coefficients of Composite Materials Studied by a Simple Statistical Approach
Authors: Yeh Hsien-Liang , Yeh Hsien-Yang
Published: July 2017

In this article, an investigation of the coefficients of hygrothermal expansion for a general class of randomly-oriented composite laminate is presented. A simple random statistical analysis has been used to demonstrate that under certain conditions, for instance, a laminate with 40 plies or more, the mean values of the coefficients of hygrothermal expansion in the randomly-oriented laminate are close to those values evaluated from the classical hygrothermal-elastic lamination theory. Also, the influence of the various lamina material properties E2JEI, G12/E1 and v12 as well as the lamina hygrothermal expansion coefficients axl/(i2 and 41/2 to the coefficients of hygrothermal expansion of the laminate are investigated. The results from this statistical analysis provide a set of general guidelines for designing the coefficients of hygrothermal expansion of the composite laminates to meet different environmental conditions in engineering application.
Effect of Foam Density and Skin Material on the Damping Behavior of Polyurethane Sandwich Structures
Authors: Sharma S. C. , Murthy H. N. Narasimha , Krishna M.
Published: July 2017

In this article, the effects of polyurethane foam (PUF) density and skin materials, namely, e-glass/epoxy and e-glass/polyester on the damping behavior of PUF sandwich structures were investigated in the temperature range 20 to 100 C using Rheovibron dynamic mechanical analyzer. Three types of specimens, viz. Epoxy/Glass-PUF-Epoxy/Glass (EPE), Polyester/Glass-PUF-Polyester/Glass (PPP) and Epoxy/Glass-PUF-Polyester/Glass (EPP) with three foam densities (0.6, 0.65 and 0.7 gm/cc) were considered. The effects of the skin material, the density of foam, the interface bonding between the skin, and the foam and the operating temperature on the damping mechanism of the sandwich structures are discussed. The experimental results showed the maximum peak damping capacity at 0 C in case of PPP specimens for a foam density 0.6 gm/cc. The damping capacity initially increased in the temperature range 20 to 0 C, attained peak value at 0 C, further decreased marginally up to 60 C and finally, drastically decreased in the temperature range 60-100 C.
A Relational Expression between the Fatigue Life and Stress Level, Temperature, Humidity for Composite Materials
Authors: Huimin Fu , Wei Huang
Published: July 2017

The prediction and evaluation of fatigue life for composite materials under hydrothermal environment are of importance in engineering practice. So far fatigue life in given conditions can generally be obtained by tests. In this paper, a relational expression between the fatigue life and stress level, temperature and humidity is proposed and the parameters in the formula are then determined by least square method. Verification based on a great amount of test data indicates that the expression can effectively describe the relation between the fatigue life of composite materials and the effects of loading and environmental conditions. The calculation results show that the expression reaches a satisfactory precision. As an example, resin-matrix composite laminates is utilized to show the applicability. With the proposed formula, the information of fatigue life can be obtained by limited test data. The reduction in experiment numbers will result in a great saving, which is significant for engineering practice.
Buckling Response of Stitched Polyurethane Foam Composite Sandwich Structures
Authors: Sharma S. C. , Krishna M. , Murthy H. N. Narasimha
Published: July 2017

Edgewise compression (buckling) tests were performed on unstitched and stitched sandwich specimens made of glass/epoxy face-sheets and polyurethane foam core. The buckling characteristics of the specimens with through-the-thickness stitches and the influence of strain rate on buckling were investigated. Ultimate load carrying capacity of the specimens was determined. Modes and causes of failure along with their relation to the buckling properties were identified. The effect of stitch row spacing on the instability preceding the crush failure was investigated using finite element analyses, which were found to explain the fracture and debonding phenomena accurately. The average sustained critical compression load increased with reduced stitch row spacing and the total buckling load decreased with decrease in strain rate, as revealed by the buckling experimental studies.
An Elastic-Plastic Stress Analysis of Symmetric Aluminum Metal-Matrix Composite Laminated Plates under Thermal Loads
Authors: Topcu Muzaffer , Ondurucu Ayse
Published: July 2017

In this study, a thermal elastic-plastic stress analysis is carried out on symmetric cross-ply (0°/90°)2 and angle-ply (30°/30°)2, (45°/45°)2, (60°/60°)2 aluminum metal-matrix composite laminated plates. Temperature changes parabolically from T0 up to T0 along the thickness. It is zero on the middle axis. The composite material is assumed to be linear strain hardening. The Tsai-Hill Theory is used as a yield criterion. The elastic-plastic solution is carried out for small plastic deformations. The distributions residual stress components of σ x and σ y are illustrated along the thickness of the laminated plates. All the residual stress moments are in static balance with respect to middle plane of the laminates since they are symmetric in opposite signs.
A Viscoelastic Macro-Microfracture Delay Mechanism Approach in Particulate Epoxy Composites
Authors: Kytopoulos V. N.
Published: July 2017

By adopting a theoretical model of the elastic-plastic Fracture Mechanics as a reference one concerning the viscoelastic crack growth in cracked plates and by relating this model with a certain viscoelastic as well as macro-microfailure parametric transitional approach, seems to be possible to “gross simulate” the real crack growth behavior in a polymeric composite system by means of the adopted model.

This possibility is based on the relative good “general viscoelastic response” of the reference model to the material and experimental conditions. This “viscoelastic response” in turn is consistent with the proposed fracture delay mechanism which is deduced by means of a semiquantitative gross estimation approach methodology. In this methodology the basic assumption that the main contribution to the proposed fracture delay mechanism is given by viscoelastic loss effects and less by the plastic flow and/or adiabatic thermal blunting effects localized at the propagating crack tip seems to be consistent with the material and experimental conditions. In this context it can be reasonably assumed that this delay mechanism in fact may consist of two consecutive phases. The first one which gives the microcrack growth is controlled by short-range intramolecular rearrangements which in turn are expressed by local (crack tip) characteristic relaxation time. The second one which gives the macrocrack growth is controlled by longrange intermolecular rearrangements which in turn are expressed by a characteristic “bulk” relaxation time. The experimental evidence and modeling of these phases was assisted by in situ scanning electron microscopy (SEM) tensile observations and related measurements. Related to these observations was the statement that the proposed delay mechanism is enhancing assisted by the microvoid-microcrack coalescence “submechanism” ahead of the crack tip (notch root). As a result of all the above, an operational mode for the experimental fracture delay characterization of the polymeric composite system by means of a nomogram-aided evaluation technique is introduced.
Finite Element Based Sub-Laminate Damage Model for Intraply Cracking
Authors: Yang Qinghui , Engblom John J.
Published: July 2017

An analytical sublaminate model of intralaminar cracking, i.e., representative of a particular ply or sub-set of adjacent plies (layers) of equal orientation, is developed by an internal state variable (ISV) approach. Furthermore, a finite element based plylevel damage formulation is established to represent the variation of material properties with intralaminar cracks. Simple linear and parabolic "layer" material models are shown to be useful in providing for a smooth transition in stiffness characteristics as crack densities increase. The utility of the formulation is established in the comparison of predicted laminate stiffness variation and constitutive relations with experimental results. In addition, some results are presented based on implementation of the ply-level damage model in a finite element formualtion.
Sensitivity of the Acoustic Impact Technique in Characterizing Defects/Damage in Laminated Composites
Authors: Haque A. , Raju P. K.
Published: July 2017

The sensitivity of the Acoustic Impact Technique (AIT) has been investigated in detecting delaminations, impact and moisture induced damage in laminated composites. The use of Acoustic Impact Technique has shown encouraging results by previous investigators in identifying defects like delamination and disbonds in honeycomb structures. Very limited work has been reported in the literature about the utility of AIT as a NDT tool for testing laminated structures. The present work investigates the sensitiveness of the AIT method in detecting delamination in laminated composites in terms of size, shape, position and degree of concentration. The technique has also been applied in identifying low velocity impact and moisture induced damage in laminated composites. The significant advantage of AIT is that this technique is attractive for field applications. The AIT method involves striking the structure with an instrumented impacter in the region of interest and recording the time history of the impulse. The response of the signals received from both good and defective zones of a specimen were anlayzed in the time domain. The experimental configuration used by previous investigators was very restrictive. In this study a different experimental set up for studying AIT is developed. The effectiveness of AIT was evaluated by making a comparative study with ultrasonic measurement in detecting similar types of defects.

The results indicate the sensitiveness of AIT in detecting delamination in laminated composites in terms of size, depth and degree of concentration. The low velocity impact damage can also be identified using the AIT method. Moisture induced damage, shape of delamination and position of delamination along the edges and the center appear to be less sensitive for detection by the AlT method.
Thermal Behaviors of the Resin and Mold in the Process of Resin Transfer Molding
Authors: Young Wen-Bin
Published: July 2017

The manufacture of polymer composites through the process of the resin transfer molding (RTM) involves the impregnation of the reactive polymer resin into a mold with preplaced fibrous reinforcements. Determination of RTM processing conditions requires the understanding of various parameters, such as material properties, mold geometry, and mold filling conditions. Modeling of the entire RTM process provides a tool for analyzing the relationship of the important parameters. This study developed a nonisothermal simulation model to simulate the thermal behaviors of the resin and mold during the resin transfer molding process based on the control volume finite element method. The model will be able to simulate the thermal and chemical changes of the resin and the thermal variations of the mold during the filling and curing stages. Thermal effect of the epoxy mold was shown to have large influence on the temperature distribution and curing process of the resin. Results of some numerical studies in RTM show the applications of the proposed model.
Experimental Evaluation of Stiffness of Laminated Composite Beam Elements under Flexure
Authors: Lopez-Anido Roberto , Davalos Julio F. , Barbero Ever J.
Published: July 2017

The objectives of this study are: (1) to define upper and lower bounds for the stiffness of laminated beam elements under flexure, (2) to correlate experimental effective beam moduli with analytical predictions, and (3) to obtain a threshold aspect-ratio that limits the range of application of various analytic methods. Experimental tests were conducted to characterize the load-displacement response of laminated beam elements under flexure, and the results were correlated with available analytic approaches. Angle-ply laminated beam elements were chosen to distinctly show the differences between various analytic methods. Three-point bending tests were performed, both flatwise (out-of-plane) and edgewise (in-plane), on rectangular lay-up specimens made of AS-4/3501-6 carbon-epoxy. Recommendations are made for the analytical prediction of stiffness under various conditions.
Tests on Deep I-Shape Pultruded Beams
Authors: Zureick A. , Kahn L. F. , Bandy B. J.
Published: July 2017

The paper describes the full-scale tests conducted to study the behavior and recommend design criteria for deep I-shape reinforced plastic (RP) pultruded beams subjected to transverse loads in the plane of the web. The beam utilized in these experiments was made of a vinylester matrix reinforced with E-glass, and their cross sections consisted of a 610 mm x 9.5 mm (24 in. x 3/8 in.) web and 190 mm x 19 mm (7 1/2 in. x 3/4 in.) flanges. Beams were instrumented at various locations using strain gages, LVDTs and potentiometers. Both finite element analysis and approximate beam theory for composite sections predicted deflections within 5 percent of those observed. Engineering beam theory may be used for design of such RP beams.
A Case Study of Structural Core Application in Marine Vessels
Authors: Zvanik Marco
Published: July 2017

Fiber reinforced composite sandwich construction (FRP Sandwich) is the most common method of fabrication for the worldwide marine industry. Marine governing bodies such as The American Bureau of Shipping and Det norske Veritas in response to the widespread use of FRP Sandwich construction have established precise guidelines with regards to skin and core material requirements for various types of vessels. However, the methodology that is used by each builder to design the sandwich laminate can vary considerably. The purpose of this paper is to evaluate the real world use of semi-rigid PVC foam core in vessels ranging in size from 5' to 200' in length. The typical skin thickness for each skin will also be evaluated.
Effects of Material and Manufacturing Variations on Dimensionally Stable Composite Structure
Authors: Mcmanus Hugh L. , Abernathy Erik
Published: July 2017

Composites offer the major advantage of tailorable coefficients of thermal expansion (CTE's). Theoretically, zero-CIE composite structures can be designed, but in practice their CTE's deviate from zero due to variations in materials and manufacturing techniques. An analytical technique to find laminate elastic, thermoelastic, and hygroelastic properties and their standard deviations from ply properties, manufacturing variables, and their standard deviations and correlations is presented. Attention is concentrated on the in-plane coefficients of thermal expansion and the analogous coefficients of out-of-plane thermal bending and warping. Based on statistical information about the materials and manufacturing processes used, both the mean values and, more significantly, the standard deviations of these values are computed. In the case of laminates designed with zero mean values the standard deviations become the performance metrics. Experimental results are presented which verify the analytical techniques. The out-of-plane thermal deformations of over 90 specimens cut from both unsymmetric and symmetric laminates are measured. The experimental and analytical results are correlated, and show good agreement. The analysis is also used in sensitivity studies to aid in the understanding of the mechanisms of thermally induced deformations, and to identify the manufacturing factors and material properties that are most important to minimizing them.
Deformation Modes in Fiber glass, under Weak Impact
Authors: Zaretsky E. , Igra O. , Zhuk A. Z. , Lash A. A.
Published: July 2017

Spall strength and shock front structure of commercial fiberglass were studied at pressures between 0.3-0.8 GPa, using Doppler velocity interferometer technique (VISAR). Substantial changes in the spall strength and shock front rise time were observed. These changes allow us to propose that fiberglass performs three modes of the deformation at the different levels of compression curve similar to porous materials and some dispersed composites.
Failure of Composite Stiffened Plates Loaded in Compression
Authors: Habib S. S. , Nahas M. N.
Published: July 2017

The buckling and ultimate failure characteristics of composite stiffened panels loaded in compression are investigated analytically and experimentally. Three different parameters are considered. These are stiffener pitch, type of stiffener and panel lamination. For the stiffener pitch two values are considered. Also, two stiffener types are investigated, namely angle stiffeners and Z-shaped stiffeners. For the last parameter two different stackings are studied, namely (+45O), and (00/900)s. The analytical and experimental results for the critical buckling stresses are close to each other. The (+ 450)s gives higher buckling stress than the (00/900)s laminates. The final failure stress also follows the same trend.
The Energy Release Rate of the Fiber/Polymer Matrix Interface: Measurement and Theoretical Analysis
Authors: Hampe A. , Marotzke C.
Published: July 2017

A new method for the experimental determination of the fracture toughness in the fiber/matrix interface by means of the single fiber pull out test is presented. To achieve this aim, two problems had to be overcome: the measurement of the compliance of a partial debonded fiber, which necessitates a stable crack propagation, and the determination of the corresponding crack length.

Stable crack propagation along the interface of a single fiber is achieved using an advanced test equipment exhibiting an extremely high stiffness. This is obtained by using a piezo translator and a piezo force cell in combination with a very short free fiber length. The experimental data and a theoretical analysis of the pull out process under these conditions reveal that the commonly used compliant pull out equipment is hiding important details of the force displacement trace and, thus, leading to a wrong interpretation and wrong results.

The most important result is that in the case of a brittle interfacial fracture the maximal force cannot be used for the determination of an interfacial strength as it is common practise till now.

The crack length is measured with the aid of a polarisation microscope. A combination of the advanced pull out experiment with a simultaneous monitoring of the photoelastic patterns of the embedded fiber enables the determination of G -values as a function of the crack length. For the calculation of G, the compliance data are obtained by the force displacement trace and the crack length data by the correlated photo-elastic patterns. The discrimination between the failure modes is obtained by finite element analysis. The energy release rates for different fiber/matrix combinations are presented.

In addition the photoelastic patterns give evidence, that in the case of a glass fiber the crack starts at the matrix surface and in the case of a carbon fiber with an embedded length < 150 jAm the crack starts at the fiber tip.
Prediction of Extensions in 3-D Blow Moulding Simulation
Authors: Debbaut Benoît
Published: July 2017

A fluid membrane element is presented for the blow moulding simulation of a geometrically complex gas tank. A Lagrangian formulation of the equations is used. We concentrate on the prediction of extension components in both machineand cross-directions. The contact between parison and mould is handled by a robust algorithm which is also applied to moving moulds, for capturing the pinch-off. Next to the prediction of parison motion, thickness and extension distributions are typical simulation outputs.
The Breaking Down and Agglomerating of Fillers in Polymer Melt: A Physical Model for Mathematical Description
Authors: Potente H. , Flecke J.
Published: July 2017

The filling and reinforcement of polymers represents an essential process task in manufacturing technology. For this reason, in the course of working in the filling substances, the distribution should also be accompanied by a break down of agglomerates. A description of the dispersion process during manufacture is of great importance for the design of process zones in a production machine.

In addition to the basic principles, a mathematical description of the dispersion of additives in a polymer melt will be presented. Here, because of the complexity of the dispersion process, the form of the model assumes simple physical theorems for description of the problem. This procedure leads to a description employing mathematical relationships, with the help of which the agglomerate size can be calculated in relation to material and process values.
Injection and Transport in Glassy Polymeric Coatings
Authors: Abkowitz Martin A.
Published: July 2017

Organic electrophotographic receptors have been enabled by the development of unique classes of high dielectric strength glassy polymer coatings which, through insulating are nevertheless capable of transporting injected charge with relatively high mobility and negligible loss to deep traps. Key features of electronic transport in these materials and the underlying physics are described. Additionally, it is demonstrated that these trap free transport polymers provide a unique venue for the exploration of contact behavior and the factors controlling injection efficiency in disordered organic solids.
Soft Body Impact Damage on CF/PEEK Laminates using Gelatin Projectile
Authors: Morita Hideo , Tsang P. H. Wilson
Published: July 2017

In order to use composite materials in aeronautical turbo engines, their resistance to impact damage caused by soft bodies (birds) must be understood. In this work the subperforation flat wise soft body impact resistance of two kinds of carbon fiber/PEEK systems were evaluated using a gelatin projectile. Tested systems were AS4/PEEK (APC2/AS4) and AS4/PEEK + IL, which consists of APC 2 prepreg and PEEK film inserted between layers as an interleave. To investigate the effects of stacking sequence on resistance, three lay ups were tested. A gas gun system was used for the impact tests, where the velocity range was between 90 and 190 m/s. Mass of the projectile was about 3 g. The projected damage area was measured with an ultrasonic C Scan. The dynamic strain response was also measured for some of the impact tests. The impact resistance to soft body impact is compared with that of hard body impact investigated in a previous study by the first author.