bluuebunny/crossref_metadata_2025 huggingface dataset:
Preliminary study of confocal laser endomicroscopy for in vitro specimens of the endometrium
Authors: Wen Jia , Yang Xi , Ye Guiying , Chen Rui , Feng Yu , Liao Qinping
Published: October 2022

Background

This study observed and described the morphological characteristics of the endometrium of the resected uterus using confocal laser endomicroscopy. This included benign endometrium, non-atypical endometrial hyperplasia, atypical endometrial hyperplasia, and endometrial carcinoma, thereby laying a foundation for finding the precise localization and resection of endometrial lesions, given the feasibility of confocal laser endomicroscopy-assisted hysteroscopy.

Methods

This prospective study included 32 patients who underwent hysterectomy. We used confocal laser endomicroscopy to observe the endometrium of resected uteruses and described the characteristics of endometrium in different states by comparing histopathological findings (primary objects). The secondary objects of observation were the myometrium, endocervical canal, and surface of the external os of the cervix.

Results

A total of 32 patients who underwent hysterectomy for different diseases were included: 9 with endometrial carcinoma (5 with endometrioid carcinoma, 1 with endometrial serous carcinoma, 2 with clear cell carcinoma, and 1 with carcinosarcoma), 2 with atypical endometrial hyperplasia, 9 with benign diseases, 7 with cervical cancer, and 5 with ovarian cancer and borderline tumor. The dynamic images of the endometrium were observed and recorded using probe-based confocal laser endomicroscopy (pCLE). Considering histopathology as the gold standard, the diagnostic concordance rate of pCLE was 96.9% in patients with endometrial carcinoma and precancerous lesions and 100% in patients with endometrial carcinoma.

Conclusion

Confocal laser endomicroscopy provides real-time high-resolution images of the benign endometrium and endometrial lesions. Compared with histopathology, confocal laser endomicroscopy has high diagnostic accuracy and may become an auxiliary examination tool for hysteroscopy, as it is useful for early identification of endometrial lesions, real-time diagnosis of tumor, and detection of tumor boundaries for complete tumor resection. These findings can lay a foundation for the feasible use of fertility-sparing local excision of tumor lesions by hysteroscopy.
Economic impact of implementing prescription of single-inhaler triple therapies versus current multiple-inhaler triple therapies for COPD in the Apulia Region
Authors: Resta Emanuela , Scioscia Giulia , Lacedonia Donato , Quarato Carla Maria Irene , Panza Francesco , Resta Onofrio , Lepore Giorgia , Buonamico Enrico , Di Lecce Valentina , Carpagnano Giovanna Elisiana , Barbaro Maria Pia Foschino , Rossi Noemi
Published: October 2022

Background

The most impacting direct costs associated to COPD for the National Health Systems (NHS) are those related to accesses to the emergency room and hospital admissions, due to the onset of one or more COPD exacerbations. At the same time, severe COPD treatment, that often require a combination of medicaments, represents a substantial economic burden for the National Health Systems (NHS). This study aimed to evaluate the potential saving deriving from the implementation in the prescription of the two currently available single-inhaler triple therapies (SITTs) versus the currently used multiple-inhaler triple therapies (MITTs) in an eligible COPD population residing in the Apulia Region.

Methods

A budget impact model was developed hypothesizing the progressive replacement of the different MITTs on the reference market (Scenario A) with the pre-established SITTs, assuming a degree of penetration of 30%, 50% and 100% (Scenario B). Drug costs were based on prices published on the Official Gazette and therapy durations were based on prescribing information over the year 2019 (IQVIA™ prescription dataset).

Results

Our analysis showed that the extemporaneous MITT with the highest prevalence on the reference market was the inhaled corticosteroids/long-acting β2-agonists (ICS/LABA) combination plus a long-acting muscarinic antagonists (LAMA). This association of medicaments was paradoxically also the one associated to the highest expense value. The expanded use of a pre-established ICS/LAMA/LABA SITT was associated to a significant economic saving, ranging from a minimum of -€ 1,108,814 (SITT use: 30%) to a maximum of -€ 3,658,950 (SITT use: 100%). The cheapest pre-established SITT contained the fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI) combination.

Conclusion

A pre-fixed ICS/LAMA/LABA SITT is cost-saving, compared to the different currently used extemporaneous MITTs. Clinicians should consider the potential benefits of finding less expensive regimens while maintaining adequate efficacy in the prescriptive decision making process of COPD patients.
Optimal control for a chemotaxis–haptotaxis model in two space dimensions
Authors: Tang Hui , Yuan Yunfei
Published: October 2022

This paper deals with a chemotaxis–haptotaxis model which described the process of cancer invasion on the macroscopic scale. We first explore the global-in-time existence and uniqueness of a strong solution. For a class of cost functionals, we prove first-order necessary optimality conditions for the corresponding optimal control problem and establish the existence of Lagrange multipliers. Finally, we derive some extra regularity for the Lagrange multiplier.
Peer-Modeled Mindsets: An Approach to Customizing Life Sciences Studying Interventions
Authors: Hecht Cameron A. , Latham Anita G. , Buskirk Ruth E. , Hansen Debra R. , Yeager David S.
Published: October 2022

Mindset interventions can promote diversity in STEM but require customization. A customization protocol was developed and used to create a “peer-modeled” mindset intervention for introductory biology. Underrepresented students randomly assigned to receive the intervention reported better psychological experiences and earned more “A’s” in the class than those assigned to a control condition.
Personalizing Activity Recommendations for Individuals with Type 2 Diabetes
Authors: Knaga Julie , Buresh Robert
Published: October 2022

Apply It!

By reading this article, fitness professionals who work with novice exercisers with type 2 diabetes mellitus (T2DM) will be able to:

• individualize recommendations for activity timing, reducing sedentary time, and modes of exercise to maximize blood sugar control for clients with T2DM;

• summarize the benefits and limitations of step tracking on blood sugar control for individuals with T2DM.
Comparison of different illumination systems for moisture prediction in cereal bars using hyperspectral imaging technology
Authors: Echávarri-Dublhán Jaione , Alonso-Santamaría Miriam , Luri-Esplandiú Paula , Sháiz-Abajo María-José
Published: October 2022

Moisture content and its distribution is a critical parameter in the production of cereal bars. Inappropriate control of this quality parameter can lead to non-conforming products and excess waste on production lines. In the field of hyperspectral imaging, the search for alternative light sources to stabilised-halogen (cheaper and emitting less heat) is a growing need for the application of this technology in industry. This study compares three different illumination systems for moisture prediction in the visible-near infrared (vis-NIR) range (from 400 nm to 1000 nm). The hyperspectral images were acquired using three illumination systems including two halogen-based systems (stabilised-halogen and conventional-halogen) and an LED-based illumination system. The results showed that halogen-based illumination systems combined with a partial least squares model better predicted moisture in bars. Lower accuracies were obtained when the experiment was performed with an LED-based illumination system, which showed double the error of the halogen-based systems. It was concluded that this is a consequence of the information lost in bands appearing above 850 nm that may be revealing information about the moisture in bars since the second overtone of the water O–H is found at 970 nm. The results demonstrate that conventional halogen-based light systems in the vis-NIR range are a promising method for moisture prediction in cereal bars.
Horta da Formiga: um laboratório no ecossistema social da agricultura urbana
Authors: Souza Ana Clara Aparecida Alves de
Published: October 2022

O caso discute o ativismo pela agricultura urbana em uma iniciativa denominada Horta da Formiga, considerada um laboratório social na cidade de Porto Alegre, Rio Grande do Sul. Pode ser aplicado em uma variedade de áreas do conhecimento e disciplinas, dado que a agricultura urbana tem se mostrado um fenômeno de interesse multidisciplinar.
Perdidos no espaço: uma negociação estratégica
Authors: Leite Jaci Corrêa
Published: October 2022

Inspirado num episódio real, este caso apresenta uma situação de conflito entre três empresas que desenvolvem conjuntamente um projeto de alta complexidade e elevado valor. Para cada uma delas, tal projeto é estratégico – não só pelos valores envolvidos, como também pelos possíveis impactos em termos de imagem e reputação. Durante o desenvolvimento, uma divergência técnica gerou um impasse que pode levar todas as três empresas a pesadas perdas. O foco da atuação de cada participante será, então, a busca de uma solução que proteja, da melhor forma possível, os interesses da empresa que representará. Pode ser aplicado em disciplinas de Negociação e de Estratégia de Negócios, e é adequado a alunos que já tenham alguma maturidade, dada a complexidade do problema.
Nota: no material a ser distribuído aos participantes, não há nenhuma menção sobre ser uma negociação estratégica. É parte do aprendizado encontrarem, por si sós, o caminho da solução.
Belo Monte do Xingu
Authors: Duarte Júnior Antonio Marcos
Published: October 2022

O complexo hidrelétrico de Belo Monte, com a quarta maior usina hidrelétrica do mundo em capacidade instalada, e a maior genuinamente brasileira, tem a sua história envolta em muito debate. De um lado seus defensores, munidos de bons argumentos, como a necessidade crescente de energia renovável e limpa do País, e, do outro lado, seus detratores, também munidos de bons argumentos, como os custos ambientais e sociais resultantes da obra. O objetivo do estudo de caso é conduzir o aluno ao longo da tênue linha divisória que contrapõe o desenvolvimento econômico aos seus impactos negativos sobre o meio ambiente e comunidades locais.
Discutindo tecnologia social na periferia: o caso do Jardim Verônia Esporte Clube
Authors: De Morais Holanda Bruna , Nunes Leal Claudio
Published: October 2022

O caso narra a história do Jardim Verônia Esporte Clube, uma organização da sociedade civil localizada no bairro de Ermelino Matarazzo, na periferia da cidade de São Paulo, que trabalha oferecendo aos moradores do bairro atividades culturais e esportivas. Ele destaca os trabalhos desenvolvidos pela entidade e as dificuldades pelas quais ela vem passando para a manutenção de sua sede e da execução das atividades. O caso é indicado especialmente para disciplinas de pós-graduação de Inovação Social que busquem promover a compreensão aprofundada a respeito do conceito de tecnologia social e seu papel na transformação social de contextos vulneráveis, como é o caso das periferias brasileiras, e reflexões acerca de seus desafios e sua permanência.
Acesse as notas de ensino desse caso aqui.
First record of darter goby, Ctenogobius boleosoma (Jordan & Gilbert, 1882) (Gobiiformes: Gobiidae), in the Mediterranean with notes on larval morphology and cryptic diversity
Authors: MAVRUK SINAN , TOSLAK CIHAN , YALIM F. BANU , ÜTÜK ARMAĞAN ERDEM , KARA ALPASLAN , AKTAŞ ÖZGÜR , YÜKSEK AHSEN
Published: October 2022

Darter goby, Ctenogobius boleosoma (Jordan & Gilbert, 1882), is a small euryhaline fish of the Gobiidae family (Gobiiformes). It is naturally found in the shallow marine and brackish waters of the Western Central Atlantic. This study reports the first record of C. boleosoma in the Mediterranean Sea. In August and October 2019, two postflexion stage larvae were sampled during ichthyoplankton surveys in Antalya Bay in the Northeastern Mediterranean. The larvae were identified using the barcoding of cytochrome oxidase 1 gene sequence of mitochondrial DNA (COI). The morphology of the pre-transitional stage larvae was described and compared to previously published data. A phylogenetic analysis revealed that two distinct clades of C. boleosoma exist in its distribution range. The COI records belonging to one of the clades were generally collected within the Caribbean Sea, while the others were collected primarily in North American Western Atlantic waters from Florida to North Carolina. The average divergence between the clades was calculated to be 9.36 ± 1.34 (± 95% confidence interval), which likely indicates the existence of undescribed species. The specimen from the Mediterranean was identified as most closely related to the North American clade. This study shows how the integrative taxonomy of ichthyoplankton can improve knowledge about non-indigenous fish in the Mediterranean.
Assessment of the Sabellaria alveolata reefs’ structural features along the Southern coast of Sicily (Strait of Sicily, Mediterranean Sea)
Authors: BORGHESE JACOPO , ARDUINI DANIELE , SCHIMMENTI EUGENIA , IACIOFANO DAVIDE , MIKAC BARBARA , BADALAMENTI FABIO , GIANGRANDE ADRIANA , GRAVINA MARIA FLAVIA , MUSCO LUIGI , LO BRUTTO SABRINA
Published: October 2022

The honeycomb worm Sabellaria alveolata is a gregarious tube-dwelling polychaete that builds remarkable biogenic reefs in marine coastal waters. Sabellaria alveolata reefs are considered valuable marine habitats requiring protection measures for their conservation, as they play a key role in the functioning of coastal ecosystems. Sabellarid reefs are extensively developed along the Atlantic coasts of Europe and reported for the Mediterranean Sea and the Italian coasts, where large reefs have been recorded in several localities. Fragmentary information is available on their health status, Sabellaria reefs thus being listed as “Data Deficient” in the Red List of Marine Habitats. To fill this knowledge gap, this study focused on the analysis of the structure of three reefs found along the southern coast of Sicily. In particular, we aimed to assess their phases with respect to the natural cycle that characterizes the sabellarid reefs. Reef features were analyzed both on the macroscale, based on the bioconstruction size (diameter and thickness) and degree of fragmentation, and on the microscale, based on the measurement of worm density, opercular length and sand porch presence. This study reveals relevant differences among reefs of the studied locations. These differences we attributeto the temporal shift linked to the natural reef phases, albeit further analyses are needed to understand the possible effect of natural and anthropogenic sources of variation on the Southern Sicilian reefs. In conclusion, Sabellaria reefs are a unique and persistent habitat along the Sicilian coast requiring proper management and conservation measures.
The Eternal Struggle for Supremacy between Creditor and Debtor
Authors: Paulus Christoph G.
Published: October 2022

Presenting a historical summary of the relationship between debtors and creditors, the article is aimed at evidencing the nature of contracting. The author argues that it has always been an attempt at both establishing and settling a power relationship. Conclusion of a contract, therefore, is not always a peace-maker, and by no means does it fulfil this function automatically.
The Independence of the Judiciary: Meaning and Threats
Authors: Fernández Jesús Manuel Villegas , Rodríguez-Blanco Victoria
Published: October 2022

What an ‘independent’ judiciary means in a democratic society is a complex question, bringing in such elements as the governing of high courts, recruitment of judges, and their susceptibility to disciplinary action. Those subjects are not isolated items but components of a wider system, with its functioning ruled by political principles. Therefore, it is essential to identify the ideological conceptions beneath the diverse theses offered. The paper examines recent events in Poland and Spain that offer valuable data to illustrate the problem. In synthesis, two broad theoretical tendencies emerge: on one side, judges ought to be controlled by politicians, at least to a certain extent, in aims of safeguarding the democratic foundations of the Constitutional legal frame; on the other side, the emphasis is on judicial self-government as a means of preserving courts from corruption associated with pressure exerted by political, economic, or social lobbies. The paper presents a proposed solution to the controversy, involving characterisation of the minimum standards for a free judiciary in a democratic legal order, and for detecting the risks inherent to both politicisation and corporatism. The model is constructed by means of legal methodology that entails comparison among legal systems of different sorts in light of international documents, among them reports by the Council of Europe. A particularly significant contrast is visible in the distance between Continental and Common Law traditions, illuminated via consideration also of the United States.
The Duty of Diligence of a Tenderer in EU Public Procurement Law
Authors: Härginen Kadri
Published: October 2022

The article analyses the duty of diligence of a tenderer under EU public procurement law. Hitherto, the subject has not been examined in the academic literature, with such exceptions as a brief introduction to the topic in a 2009 presentation by M.A. Simovart. Therefore, the article focuses primarily on a certain duty of diligence of tenderers that has been recognised by the CJEU as an independent legal requirement under the EU’s public procurement law. Emphasis is placed on elucidating which types of obligations the duty of diligence imposes on a tenderer, which requirements a diligent tenderer shall not be subjected to, and the situations in which obligations may occasionally arise under specific circumstances – such as those in light of the tenderer’s right to review.
‘Protection of Employee Privacy in the Digital Workplace’: Arguments and Comments Presented during the Defence of Seili Suder’s Doctoral Thesis
Authors: Otto Marta
Published: October 2022

The contribution is based on the opinion presented in the author’s role as designated opponent to the dissertation of Seili Suder, defended at the University of Tartu on 6 December 2021. The dissertation contributes to employment-specific discussion of privacy and data protection by exploring the main legal concerns and practical challenges that deployment of the ‘newest’ digital monitoring technologies poses under the current European privacy and data-protection framework. That framework, while indeed being among ‘the most substantial and thus influential around the world’, still leaves open the question of the need for establishment of specific/sectoral provisions at EU level that regulate privacy and data protection.
Possibility of using sweeteners in the prevention of obesity development
Authors: Staśkiewicz Wiktoria , Wyleżoł Magdalena , Bielaszka Agnieszka , Kiciak Agata , Kardas Marek
Published: October 2022

Background. The problem of the 21st century both in Poland and around the world is overweight and obesity, and diabetes. Due to the increased incidence of these diseases, the consumption of intense sweeteners, which are used as substitutes for sucrose, has increased. The purpose of this study was to evaluate the sweet taste intensity of selected sweeteners in comparison with the benchmark - beet sugar. Methods. The material for the study consisted of four sweeteners: sugar, xylitol, stevia, and cane sugar. The substances were subjected to dilution in an infusion of black tea. This tea was then divided into 4 portions and each portion was sweetened with a different sweetener at a rate of 20g per 1l of infusion. The samples were coded with 3-digit codes, and the paired method was used for sensory evaluation. A total of 78 people participated in the study. Results. Differences in the intensity of sweet taste between beet sugar and the substitutes used were confirmed. Cane sugar and xylitol were characterized by a lower intensity of sweet taste, but these substitutes were preferred compared to beet sugar. Stevia is characterized by greater sweetness than beet sugar, while survey respondents strongly preferred beet sugar. Conclusions. Consumers, participating in the survey, prefer products with a less intensely sweet taste. Learning about consumers' preferences for sweet taste will allow the use of appropriately preferred substances in the production of food and dishes. This will have a positive effect on the sugar content of the daily ration and its overall consumption.
Doświadczenia bibliotek akademickich z bibliograficzno-dokumentacyjnej i sprawozdawczej działalności w kontekście współpracy z Polską Bibliografią Naukową w latach 2012-2020/2021 – analiza wybranych zagadnień
Authors: Woźniak Barbara , Zawadzka Agnieszka
Published: October 2022

Zmiany dotyczące nauki w Polsce, szczególnie kwestie związane z jej zarządzaniem, finansowaniem czy procesem oceny i parametryzacji wymuszały na bibliotekach akademickich szereg modyfikacji. Dostosowanie do zmieniających się przepisów prawnych i wymogów było trudnym przedsięwzięciem zwłaszcza w przypadku bibliotek, które stały się partnerem w transferze danych i chciały sprostać wyzwaniom stawianym uczelniom przez Ministerstwo ds. Nauki. Artykuł przedstawia doświadczenia bibliograficzno-dokumentacyjne i sprawozdawcze w kontekście kooperacji z PBN w latach 2012–2021. Wskazuje problemy i korzyści wynikające z działań synergistycznych, których efekty zorganizowanej pracy zespołowej widoczne są we współtworzeniu PBN. Opiera się częściowo na ankiecie przeprowadzonej wśród bibliotek akademickich, która dotyczyła zagadnień: współpracy, zaangażowania, roli, zadań bibliotek w procesie ewaluacji i parametryzacji w powiązaniu z odpowiedzialnością za prawidłowy przebieg sprawozdawczości Uczelni. Szerzej odnosi się także do aspektów związanych ze współpracą w ramach wszystkich modułów PBN i ich funkcjonowaniem.
THE ROLE OF FRICTION IN THE STRENGTH SIZE EFFECT IN FIBER COMPOSITES FAILING BY COMPRESSION KINK BANDS
Authors: XUE JING , KIRANE KEDAR
Published: October 2022

Prior studies have provided experimental evidence of the size effect on the nominal strength of fiber composites, failing by the formation of a kink band under compression. This size effect is analyzed here computationally with the goal to understand and quantify the role of crack face friction. The mechanism of kink band formation is modeled by the semi-multiscale cylindrical microplane model, recently calibrated and experimentally validated for its predictions of the failure geometry as well as strength size effect. The kink band initiation in the model is driven by damage triggered on cylindrical microplanes. The model embodies a combined damage friction formulation on the microplane level, which assumes a parallel coupling between the two mechanisms. The model is used here to predict the strength size effect with and without friction effects. In the friction-free models, the predicted strength is found to scale in accordance with linear elastic fracture mechanics, suggesting brittle fracture. On the other hand, in the models embodying friction, the fracture process zone size is found to be enlarged, and the predicted strengths are found to not only obey the Bažant size effect law, but also match the test data. The strengths are found to fall in the transitional portion, suggesting quasibrittle fracture. Thus, the inclusion of friction is found to considerably increase the degree of quasibrittleness, and the combined friction/damage based microplane model employed here, is found to be useful to quantify this increase.
IMPROVED BUCKLING RESISTANCE IN WIND TURBINE BLADES THROUGH THE PRODUCTION OF GFRP COMPOSITES WITH ENHANCED RESINS
Authors: MORRIS JOSHUA , CHENEY WILLOUGHBY , AMIRKHIZI ALIREZA V.
Published: October 2022

The shear and transverse stiffnesses of unidirectional glass fiber reinforced polymer (GFRP) composites, which constitute a significant portion of wind turbine blades, are dominated by the resin properties. Accurate analysis and therefore optimized usage of such materials are critical in design of super-sized offshore blades, whose macro-structural properties may be improved through use of enhanced resins. In this paper, the properties of GFRP composites made using resins with assumed enhanced properties are accurately predicted using the Continuous Periodic Fiber Model (CPFM) and inserted into macroscopic finite element blade models of 33 and 100 meter lengths. Changes to blade performance in terms of buckling, bending, torsion, and trailing edge shear are quantified. Resins of increasing Young's modulus demonstrated increased blade transverse stiffness and postponed the buckling failure onset. Delayed buckling provides the opportunity to decrease the overall blade mass, reduce the required core foam, and optimize cost/performance for large offshore turbines.
IMPACT PERFORMANCE COMPARISON OF FIBER REINFORCED COMPOSITE SANDWICH STRUCTURES IN ARCTIC CONDITION
Authors: BANIK ARNOB , KHAN M. H. , TAN K. T.
Published: October 2022

About 40% of sea ice-covered areas have been reduced over the last three decades due to the effect of global warming. The Northern Sea route has been considered as a more effective, quicker, and economical sea route for marine vessels. But it is not safe to operate in such a cold and harsh environment due to the potential risk of collision with ice chunks, resulting in damages in the marine structures. It is therefore important to understand the behavior of marine composites at low temperatures, with the overarching goal that leads to improved design for marine structures and materials that can operate safely and effectively in the Arctic environment. This study investigates the low-velocity impact performance and damage mechanisms of woven carbon fiber reinforced polymer (CFRP), glass fiber reinforced polymer (GFRP), and carbon-glass fiber hybrid face sheets sandwich panel at both room temperature (23 °C) and low temperature (-70 °C) to mimic the Arctic environment. A series of low-velocity impact tests (3.46 m/s and 4.92 m/s) is performed at 15 J and 30 J energy using a drop tower testing machine. A relative comparison of the impact response due to different face sheet materials is presented in terms of force, displacement, and energy. Force-time and force-displacement plots show that GFRP sandwich composites have the highest damage initiation force and peak force values across different temperatures and impact energies. Furthermore, the lowest energy absorption for GFRP composites is found responsible for the least impact-induced damage. X-ray microcomputed tomography reveals severe fiber breakage on the compression side of CFRP sandwich panel and back face spitting at both temperatures for 30 J impacts. By replacing carbon fibers with glass fibers, the damage mechanism switches from fiber breakage to delamination as the dominant failure mode. The findings from this work will aid in a better understanding of the impact failure modes of composite sandwich structures at extremely low-temperature conditions.
CORRUGATED CORE MADE BY 4D PRINTING OF COMPOSITES FOR FLEXIBLE AIRCRAFT WING
Authors: HOA SUONG V. , ABDALI MARJAN , JASMIN ANICK , PRATS VICTOR , RADESCHI DANIEL , KOBAISSI BACKER , FAOUR HADI
Published: October 2022

This paper presents a procedure to make composite corrugated core without the need for a mold with corrugated shape. The technique is called 4D printing of composites. The corrugated composite is intended to serve as the core for flexible aircraft wings. A demonstrator sample was manufactured and tested. It was shown that the flexible wing can morph up to 20o and can withstand loads for small unmanned arial vehicles.
RADICAL INDUCED CATIONIC FRONTAL POLYMERIZATION FOR RAPID OUT-OF-AUTOCLAVE PROCESSING OF CARBON FIBER REINFORCED POLYMERS
Authors: STAAL JEROEN , CAGLAR BARIS , MICHAUD VÉRONIQUE
Published: October 2022

Radical induced cationic frontal polymerization (RICFP) is considered as a promising method for processing of fiber reinforced polymers (FRPs). Optimization of the local heat flow is required to pave the way for its adaptation to an industrial processing method. In this work we present an overview on the role of the mold design on the frontal polymerization characteristics and resulting chemical properties. Mold properties were found of significant influence on the front characteristics. Highly insulating molds allowed for the highest front temperatures and velocities while consequent delayed cooling is suggested beneficial for the monomer conversion in neat polymer and FRP systems. An optimized mold configuration was subsequently used for FRP production, allowing for self-sustaining RICFP in FRPs with fiber volume fractions (Vfs) up to 45.8%. A processing window was moreover defined relating the Vf and required heat generation to the potential formation of a self-sustaining or supported front.
MODELING COLD SPRAY DEPOSITION OF THERMOPLASTIC POLYMERS: EFFECTS OF IMPACT ANGLE AND TEMPERATURE
Authors: MUTHULINGAM JEEVA , SINGH NAND KISHORE , JHA RATNESHWAR , KOOHBOR BEHRAD
Published: October 2022

Cold spray additive manufacturing is gaining popularity for polymers due to its low operating temperature and reduced manufacturing time. In the present study, the likeon- like impact of single thermoplastic polymer (polyether ether ketone, PEEK) particles on PEEK substrates is modeled to explore the effects of impact angle, initial particle temperature, and impact velocity on cohesion. The particle impact angle varies from 30o to 90o with 15o intervals for impact velocities ranging from 200 to 1000 m/s. Particle temperature in each case is varied from room temperature to the glass transition temperature of PEEK. Results obtained herein provide an insight into the energy balance and the temperature-velocity conditions likely to lead to bond formation. Modeling results demonstrate that the likelihood of bond formation increases with an increase in impact angle, particle temperature, and velocity, at the cost of bond strength.
REACTIVE MOLECULAR DYNAMICS MECHANICAL PROPERTIES PREDICTION OF FURAN RESIN
Authors: KEMPPAINEN JOSH , GALLEGOS IVAN , KRIEG AARON , ODEGARD GREGORY
Published: October 2022

During the reentry of aerospace vehicles into the earth’s atmosphere, the outer shell surface temperature can reach up to 2700°C, which would melt or degrade most materials. The high temperatures that aerospace vehicles face during reentry mean that these vehicles need a thermal protection system (TPS) to shield the rest of the structure and occupants. There are many categories of thermal protection systems and many materials have been used over the years, but the most notable are carbon-carbon composites (CCC). CCCs are usually manufactured by curing a polymer in a fiber preform and then heat-treating the composite until all non-carbon atoms are burnt out. Due to the complexity, it is desired to model the polymerization and carbonization process to fine-tune composite materials. The first step in modeling a CCC involves the polymerization of precursor material, and an atomistic model is to model the polymerization. Therefore, reactive molecular dynamics (MD) has been used to model the polymerization of precursor material. The precursor material selected for benchmarking and validation is furan resin (polyfurfuryl alcohol – PFA). Furan resin has been of interest for CCC ablatives since the 1950s due to its ability to achieve relatively high carbon yields, which reduces the number of carbonization cycles. Furan resin has also found uses in adhesives, corrosion protection, fuel propellants, and foundry molds. In this paper, you will find experimental curing of furan resin and an MD modeling approach for polymerization of furan resin.
PUNCH CRUSH OF UNIDIRECTIONAL COMPOSITES AT SUB-MILLIMETER LENGTH SCALE: EXPERIMENTS AND SIMULATIONS
Authors: GILLESPIE, JR. JOHN W. , ALI MOLLA A. , O’BRIEN DANIEL J. , HAQUE BAZLE Z. (GAMA)
Published: October 2022

An experimental methodology has been developed to fabricate unidirectional (UD) S-2 glass/epoxy composite films at sub-millimeter length scale, and to study the micromechanical punch crush damage mechanisms of UD ribbons of width 1mm (machined from sub-millimeter UD composite films) under transverse compression loading. Quasi-static micro-mechanical crush damage mechanisms includes: (i) fiber-matrix debonding, (ii) non-linear large-deformation of matrix resins, (iii) punch-shear of fibers, (iv) crush of fibers under diametric compression and (v) crush of matrix resins. Modeling these micro-mechanical damage mechanisms are challenging. Finite element (FE) models of UD composite ribbons of sub-millimeter thickness have been developed by modeling individual fibers through the thickness, fiber-matrix interface debonding with zero-thickness rate-dependent cohesive elements, transverse fibers fracture with stochastic zero-thickness cohesive elements, and fiber crush is modeled by erosion of elements. Micro punch crush experiments on UD S-2 glass composites show formation of a sheared plug which undergo through-thickness crush damage yielding about 1.4 GPa crush strength. Micromechanical 3D FE model can predict this crush damage mode at a matrix erosion strain of 0.99.
LOW VELOCITY IMPACT ON PLAIN WEAVE S-2 GLASS/DER353 COMPOSITES WITH THE CORNER OF A CUBE AND A HEMI-CYLINDER: EXPERIMENTS AND SIMULATIONS
Authors: STACK ANDREW J. , BOGETTI ELI D. , ALI MOLLA A. , QUABILI ABIR M. , YARLAGADDA SHRIDHAR , GILLESPIE, JR. JOHN W. , HAQUE BAZLE Z. (GAMA)
Published: October 2022

An experimental methodology has been developed to investigate the low velocity impact (LVI) damage behavior of plain weave (PW) S-2 Glass/DER353 composite laminate using a hemi-cylinder (HC) and the corner of a cube impactor. Ultrasonic Cscan images of the LVI specimens have been used to determine the extent of interlaminar delamination. LS-DYNA finite element (FE) models of the LVI experiments have been developed and simulated for different impact scenarios in conjunction with rate dependent progressive composite damage model MAT162. A Python code has been developed to reduce the experimental data and automatic determination of different LVI parameters to validate the FE models. In addition, another Python code has been developed to automate the processing of layer-by-layer damage modes and LVI simulation parameters to validate with experimental data. Computational models have been validated with LVI experimental force-time data which shows a good correlation. The relationship between computational damage prediction and LVI experimental damage has been established.
A TECHNIQUE FOR REAL-TIME DEFECT DETECTION OF COMPOSITE MATERIAL USING MACHINE LEARNING AND TRANSFER LEARNING
Authors: KASHEFINISHABURI FARZAD , HOA SUONG V.
Published: October 2022

In this study, the aim is to develop a method that is capable of locating the defects in composite plates by using a minimum number of wires and contact points. The reason is that previously there was not a method that can be used to detect defects with a reasonable number of wires and connections. To do so, measurements are restricted to be done only on the edges of the composite plates to predict the location of the defect within the plate. In this work, Single-walled carbon nanotubes (SWNT) were mixed with epoxy resin. By doing so, electrical conductivity was introduced to the resin. The prepared resin is then incorporated with woven fiberglass fabrics to make nanocomposite plates. Probes to measure the electric resistances were placed on the edges of the plates. The 4-probe method was used to measure the electrical resistance between the probes. Due to the complexity of the electrical behavior of composites and having multiple numbers of inputs, Machine Learning (ML) and Deep Learning (DL) methods were used. Data Augmentation (DA) was used to increase the number of labeled data examples that are needed to train the Neural Network (NN) model. Coupled with DA, Transfer Learning (TL) was used. A simulation model of the grid of resistors was developed in LTspice software. In the simulation, the defect was represented by increasing the resistors’ value of the defected cell. The data from the simulation was used for the initial training of the NN and then the experimental data is used in the second stage of Transfer Learning to train and test the final NN. The model's performance in locating the defects is 78.57% while the precision is 2”x2”.
PHASE FIELD BASED COHESIVE ZONE FRACTURE APPROACH TO MODEL ANISOTROPIC EFFECT AND INTERFACE FRACTURE IN FIBER REINFORCED POLYMER COMPOSITES
Authors: KUMAR AKASH , SAIN TRISHA
Published: October 2022

Among multiple damage mechanisms in fiber reinforced polymer composites (FRPCs), delamination is the major failure mode that occurs very often due to low interlaminar strength of these materials. Prediction of this failure mode through computational modeling is not straight forward. In this work we aim to use the phase field fracture method (PFF) to model interfacial fracture in FRPCs. In PFF, the crack is assumed as a diffused entity rather than discrete discontinuities. In the present work, a unified phase field based cohesive zone model (PF-CZM) has been utilized to characterize the interlaminar fracture of carbon fiber reinforced epoxy composite. A Double cantilever beam (DCB) geometry has been simulated for 0◦ fiber orientation to determine mode I interfacial fracture toughness. To meet the requirement, two laminas of unidirectional FRP were bonded together using an adhesive (resin rich region) for different adhesive layer thicknesses and the corresponding energy release rates are computed. The area method suggested by Whitney [1982] was used to measure the energy release rate (R-curve). The results show different GI values for different thickness of adhesive layer and remains within a specified limit. The peak load is also different for different thicknesses of adhesive. Prior to the DCB simulations, open hole tension (OHT) simulations for different fiber orientations (0◦, 45◦ and 90◦) were also performed for carbon-fiber reinforced epoxy composite to validate the PF-CZM model prediction with the experimental data available in literature.
MULTI-NOZZLE ELECTROSPINNING OF CARBON NANOTUBE/EPOXY SUBMICRON FILAMENTS FOR COMPOSITE REINFORCEMENT APPLICATIONS
Authors: LIYANAGE ASEL ANAND HABARAKADA , BISWAS PIAS KUMAR , AGARWAL MANGILAL , DALIR HAMID
Published: October 2022

Nanocomposites are gaining tremendous attention in structural applications from the automotive to aerospace industries. In this research, we used multi-nozzle electrospinning using Lateral Belt Driven (LBD) approach to fabricate mass production of submicron thermoset epoxy filaments with carbon nanotubes (CNT) to enhance the mechanical properties of Carbon fiber reinforced polymer (CFRP). Electrospinning is one of the most versatile, low-cost, and well-recognized technologies for producing continuous filaments with diameters ranging from submicron. These Nanofilaments were precisely incorporated into the prepreg layers to improve adhesion and interfacial bonding. In this study, the deposition characteristics of the multi-nozzles were observed and analyzed to understand the fiber formation of each nozzle on the multi-nozzle (10 nozzles in 50 mm apart) platform, as shown in Figure 1. Figure 2 represents the summarized fiber diameters of the SEM images at 6,000× magnification from each nozzle while the electrospinning parameters were kept constant; Voltage: 17kv; nozzle gauge: 25G, working distance: 12 cm, and time of spinning: 5min. ImageJ software was used to analyze the SEM images and was plotted using Origin Pro software. CNT/Epoxy Fiber mean diameter was 128.3 nm ±35.4 nm resulting in a 29% improvement in Interlaminar Shear Strength (ILSS) of the multi-nozzle electrospun CNT/Epoxy enhanced CFRP laminates.
EXPERIMENTAL VALIDATION OF THE DYNAMIC MOLECULAR STATE OF WATER IN DAMAGED POLYMER COMPOSITES USING NEAR INFRARED SPECTROSCOPY
Authors: OLUWAJIRE OLUWATIMILEHIN , BERKOWITZ KATHERINE , GUHA RISHABH D. , GRACE LANDON
Published: October 2022

Safety has long been a key factor in the design, manufacturing and maintenance of products that are made from composite materials. The exceptional properties these materials exhibit compared to their metal counterparts is enabling widespread adoption across civil infrastructure, oil & gas, marine, automotive, and aerospace industries. But the lack of a definitive and accurate technique to predict damage progression in a polymer-matrix composite (PMC) during their service life continues to pose a major risk and creates a gap in the long-term integrity of the structures produced. Although there is widespread consensus regarding the deleterious effects of the ingressed moisture on the overall properties of a composite, recent studies have revealed that the inevitable presence of moisture in a PMC can be leveraged for damage characterization. This work aims to employ Near-Infrared spectroscopy for quantifying molecular moisture in polymer composites for submicron scale damage detection. Prior to moisture absorption, a drop tower was used to induce a barely visible impact damage (BVID) in the center of dry E-glass/epoxy specimens. Three different specimens were subjected to 1J, 1.5J, and 2J of damage, respectively. The NIR Nano EVM Spectrophotometer was used to obtain spectral scans between wavelengths of 900-1700 nm for each of the three damaged samples, as well as an undamaged sample, in their dry state. The samples were then exposed to moisture contamination via water bath, and subsequent spectral scans were acquired at consistent intervals of gravimetric moisture gain. The spatial variation of the moisture content was evaluated from the characteristic peak for water in the damaged samples at various levels of absorbed moisture. The absorbance area obtained from the NIR spectral shows quantitative values to represent increasing damage and spatial maps indicating different states of absorbed moisture in each sample.
PROPER TENSILE TESTING OF UNIDIRECTIONAL COMPOSITES
Authors: FAZLALI BABAK , ASHODIA SAGAR ASHOKBHAI , CARVELLI VALTER , LOMOV STEPAN V. , SWOLFS YENTL
Published: October 2022

Tensile tests are a basic characterization method for composite materials, but the specimens often do not fail properly. Obtaining reliable results in tensile testing requires avoiding stress concentrations near the grips. The material near the tabbed section is under longitudinal, transverse and shear stress concentrations, which leads to underestimated results and conservative design. This study therefore examines different geometries to find the best testing method that yields the maximum failure strain. The experimental results show that the novel arrow shape end tabs and continuous tab specimens allow reaching the highest failure strain value.
EFFECT OF NEGATIVE POISSON’S RATIO ON THE TENSILE PROPERTIES OF AUXETIC CFRP COMPOSITES
Authors: LIN WENHUA , WANG YEQING
Published: October 2022

Carbon fiber reinforced polymer (CFRP) matrix composites have become increasingly popular across industries such as aerospace and automotive industries due to its outstanding mechanical properties and significant weight saving capability. CFRP composites are also widely known to be highly tailorable. For instance, different laminate-level mechanical properties for CFRP composites can be achieved by varying the individual carbon fiber laminar arrangements, among one of them is the Poisson’s ratio. Conventional materials have a positive Poisson’s ratio (PPR), visualize any conventional materials in a 2D block shape, when stretching that material in longitudinal direction, contraction follows on the transverse direction, whereas for materials with a negative Poisson’s ratio (NPR), stretching in the longitudinal direction leads to expansion in the transverse direction. Materials with NPRs have been shown to improve the indentation and impact resistances, when compared to equivalent materials with PPRs. However, producing NPRs could potentially compromise other properties, such as tensile properties, which has not been reported. The current work investigates the effects of NPR on the tensile properties of CFRP composites. Specifically, a laminatelevel NPR of -0.4094 in the in-plane direction is achieved through ply arrangement of CFRP composites using classical lamination theory (CLT). The non-auxetic counterpart CFRP composites are designed to produce an PPR of 0.1598 in the in-plane direction while simultaneously match their elastic moduli in three directions with those of the auxetic composites. Results show that the predicted tensile modulus and in-plane Poisson’s ratio were in excellent agreement with the experiment results. It was found that the ultimate tensile strength and failure strain or ductility of auxetic specimens were on average 40% lower than those of the conventional CFRP composites.
GAS PERMEABILITY OF 3D PRINTED THERMOPLASTIC COMPOSITES FOR CRYOGENIC APPLICATIONS
Authors: SAHA SHUVAM , SULLIVAN RANI W.
Published: October 2022

Thermoplastics have shown promise as a choice of material for production of lightweight structures for cryogenic storage. To fully utilize thermoplastics for such applications, cryogenic fuel leakage through transverse cracks in these structures must be studied. Thermoplastic composites (carbon fiber reinforced PEEK and Nylon) were 3D printed using fused deposition modeling. Test specimens were thermally cycled from ambient (23ºC) to cryogenic (-196ºC) temperatures and gas permeability measurements were conducted at selected cryogenic cycles. Results show that carbon fiber/PEEK specimens had the lowest gas permeability after 50 cryogenic cycles with no through-thickness crack networks. The gas permeability of 3D printed thermoplastic composites was several magnitudes lower than the leak rate allowables for different launch vehicles. Tensile tests, post cryogenic cycling, revealed a reduction in the tensile strength and modulus of the 3D printed specimens with CF/PEEK having the best mechanical and permeability performance.
THE EFFECT OF PROCESS PARAMETERS ON FIRST PLY DEPOSITION IN AUTOMATED FIBRE PLACEMENT
Authors: VALVERDE MARIO , SUN RIC , TRETIAK IRYNA , NGUYEN DUC , KRATZ JAMES
Published: October 2022

Automated Fibre Placement (AFP) is widely recognised as one of the most advanced processes for manufacturing structural composite components. Understanding the process remains at the forefront of academic/industrial investigation due to the myriad of parameters that affect the quality of the deposited tape. A novel AFP testbench, which included a heated glass tool, was developed to aid in the investigation of the material behaviour underneath the roller during compaction. The material behaviour was captured by using a camera directed at the compaction region, where the data was subsequently analysed using a vision analysis technique during a post-processing step. The results indicate that the use of a glass tool can help in quantifying the tape spreading when subjected to varying process temperatures as well as identifying various defects and features that can arise in a typical AFP manufacturing cycle.