Diss. (sammanfattning) Stockholm : Tekn. högsk., 2004. / Härtill 7 uppsatser. I häftet felaktigt ISBN: KTH/FTP/R--2004/37--SE.

<p>A baggy paper web has parts that are longer than neighboring parts. One of the assumed reasons for bagginess is thickness variations of the paper. In the roll the thicker streaks then add up to form a ridge. In the ridges the paper is strained and during storage the strain may become permanent. When the paper unreeled it is then baggy. Runability problems because of baggy webs is a common problem in the paper industry. Baggy webs can result in corrugations appearing when the paper is passing through nips during converting processes. Ridges have been simulated in this project by reeling thin plastic film into selected parts in the roll. Plastic was reeled in near the core, in the middle of the roll and in the periphery of the roll. To see if the paper web had got length differences the web was divided into stripes and with a special device the length of each stripe was measured. Even other paper properties were tested to determine if the ridges had other influences on the paper. Two of this properties was thickness and grammage, which were determined to see if the paper had got higher density in the baggy parts. The measurements show that the plastic results in bagginess but also that after a couple of days, the paper more or less has recovered to the initial thickness and sometimes also to the initial length. The most bagginess appeared near the core and it resulted in relatively large length differences, but even here the paper has likely recovered to some extent.</p> / <p>Då en pappersrulle har partier där pappret är längre kallas det ibland för slappa stråk. Det finns flera orsaker till slappa stråk och en av dessa orsaker är att pappret har en ojämn tjockleksprofil. I dessa fall uppstår de slappa stråken eftersom den ojämna tjockleksprofilen gör att pappersrullen på de positioner där pappret är tjockare får en större diameter än i övrigt. Då papper rullas över dessa åsar eller valkar som har en större diameter töjs pappret ut och då det rullas av rullen är det slappt. Körbarhetsproblem till följd av att pappret är slappt i vissa partier är ett stort problem inom pappersindustrin. Dessa körbarhetsproblem kan t.ex. vara att det uppstår veck i pappret då det passerar valsnyp.</p><p>I detta projekt har slappa stråk skapats genom att en viss mängd plast rullats in i pappersrullar dels i botten, dels i mitten samt ett parti närmast rullens periferi. Banspänningsmätningar har utförts för att se hur slappt pappret blivit där plast rullats in. För att se om pappret fått bestående längdskillnader i de slappa stråken har tvärsbanor tagits ur rullen och varje tvärsbana delats upp i remsor för att mäta längden på. Även andra pappersegenskaper har testats i dessa partier för att se om de slappa stråken påverkar papprets egenskaper. Bland annat har tjockleksprofilen mätts upp för att se om pappret komprimerats och fått en bestående densitetsökning i de slappa stråken. Mätningar visar dels att pappret blir slappt i partier där plast rullats in, men också att pappret efter några dagar i stort sätt helt återgått till sin ursprungstjocklek och vissa fall även i längdled. Pappret var som slappast i botten av rullarna och där uppmättes relativt stora längdskillnader även om pappret troligtvis återhämtat sig till en stor del även där.</p>

A baggy paper web has parts that are longer than neighboring parts. One of the assumed reasons for bagginess is thickness variations of the paper. In the roll the thicker streaks then add up to form a ridge. In the ridges the paper is strained and during storage the strain may become permanent. When the paper unreeled it is then baggy. Runability problems because of baggy webs is a common problem in the paper industry. Baggy webs can result in corrugations appearing when the paper is passing through nips during converting processes. Ridges have been simulated in this project by reeling thin plastic film into selected parts in the roll. Plastic was reeled in near the core, in the middle of the roll and in the periphery of the roll. To see if the paper web had got length differences the web was divided into stripes and with a special device the length of each stripe was measured. Even other paper properties were tested to determine if the ridges had other influences on the paper. Two of this properties was thickness and grammage, which were determined to see if the paper had got higher density in the baggy parts. The measurements show that the plastic results in bagginess but also that after a couple of days, the paper more or less has recovered to the initial thickness and sometimes also to the initial length. The most bagginess appeared near the core and it resulted in relatively large length differences, but even here the paper has likely recovered to some extent. / Då en pappersrulle har partier där pappret är längre kallas det ibland för slappa stråk. Det finns flera orsaker till slappa stråk och en av dessa orsaker är att pappret har en ojämn tjockleksprofil. I dessa fall uppstår de slappa stråken eftersom den ojämna tjockleksprofilen gör att pappersrullen på de positioner där pappret är tjockare får en större diameter än i övrigt. Då papper rullas över dessa åsar eller valkar som har en större diameter töjs pappret ut och då det rullas av rullen är det slappt. Körbarhetsproblem till följd av att pappret är slappt i vissa partier är ett stort problem inom pappersindustrin. Dessa körbarhetsproblem kan t.ex. vara att det uppstår veck i pappret då det passerar valsnyp. I detta projekt har slappa stråk skapats genom att en viss mängd plast rullats in i pappersrullar dels i botten, dels i mitten samt ett parti närmast rullens periferi. Banspänningsmätningar har utförts för att se hur slappt pappret blivit där plast rullats in. För att se om pappret fått bestående längdskillnader i de slappa stråken har tvärsbanor tagits ur rullen och varje tvärsbana delats upp i remsor för att mäta längden på. Även andra pappersegenskaper har testats i dessa partier för att se om de slappa stråken påverkar papprets egenskaper. Bland annat har tjockleksprofilen mätts upp för att se om pappret komprimerats och fått en bestående densitetsökning i de slappa stråken. Mätningar visar dels att pappret blir slappt i partier där plast rullats in, men också att pappret efter några dagar i stort sätt helt återgått till sin ursprungstjocklek och vissa fall även i längdled. Pappret var som slappast i botten av rullarna och där uppmättes relativt stora längdskillnader även om pappret troligtvis återhämtat sig till en stor del även där.

Thesis (M. Sc.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 68-71).

In Luftfahrzeugen werden häufig Sandwich-Strukturen verwendet, da somit vergleichsweise hohe gewichtsspezifische Steifigkeiten und Festigkeiten erreicht werden können. Hierbei werden für Deckschichten überwiegend Faserverbund-Kunststoffe angewendet. Die Kerne bestehen zumeist aus Honigwaben, welche aus phenolharzbeschichtetem Aramid-Papier gefertigt sind. Somit können Anforderungen an die Feuer- und Korrosionsresistenz erfüllt werden. Sandwich-Strukturen im Allgemeinen sind dabei anfällig für lokale Belastungen, sowie Lasten senkrecht zur Struktur. Dies können beispielsweise Schlagbelastungen, Lasteinleitungen durch Verbindungselemente oder Druckunterschiede sein. Folglich bedarf die Zertifizierung von Luftfahrtstrukturen zumeist umfangreiche experimentelle Untersuchungen zum Nachweis des Tragverhaltens und der Schadenstoleranz. Dieses Vorgehen ist äußerst zeitaufwendig und somit kostenintensiv. Virtuelle Tests, welche durch einzelne reale Versuche validiert werden, können den experimentellen Aufwand erheblich reduzieren. Dazu bedarf es fundierter Kenntnisse der mechanischen Eigenschaften der einzelnen Komponenten der Sandwich-Struktur. Während diese für Faserverbund-Kunststoffe als gegeben angenommen werden kann, trifft dies für Honigwabenkerne bestehend aus Aramid-Papier nicht zu. Demzufolge wird in dieser Arbeit ein Vorgehen vorgestellt, welches eine mechanische Charakterisierung und numerische Simulation von papierartigen Materialien ermöglicht. Dabei werden zunächst anwendbare Prüfmethoden für Aramid-Papier evaluiert. Darauf aufbauend werden ein verbessertes Schubprüfverfahren und ein neuartiges Druckprüfverfahren für Papier erarbeitet. Anschließend werden verschiedene luftfahrttaugliche Papiere mechanisch charakterisiert und Anforderungen an ein Materialmodell für die numerische Simulation abgeleitet. Daran anknüpfend wird ein spezielles Materialmodell entwickelt, welches das elastisch-plastische orthotrope Materialverhalten mit unterschiedlicher Druckplastifizierung und regressivem Versagen abbilden kann. Dieses Modell wird in LS-DYNA implementiert und validiert. Darauf aufbauend werden Validierungsrechnungen am Aramid-Papier sowie an Honigwaben- und Faltkern-Strukturen durchgeführt. Abschließende exemplarische Simulationen von Deckschichtablöseversuchen demonstrieren die mit dem Vorgehen erreichbare Qualität der Ergebnisse sowie Möglichkeiten zum virtuellen Testen und virtuelle Parameterstudien. / A variety of components in aircraft are made out of sandwich structures because of its high weight-specific stiffness and strength. In many cases, fiber composite plastics are used for face-layers and cores consist of honeycombs, which are made of phenolic resin coated aramid paper. Thus, requirements for fire and corrosion resistance can be met. Sandwich structures in general are prone to local loads as well as loads perpendicular to the structure. This can be, for example, impact loads, load applications by connecting elements or pressure differences. Consequently, certification of aerospace structures usually requires extensive experimental tests to demonstrate structural behavior and damage tolerance. This procedure is extremely time-consuming and therefore cost-intensive. Virtual tests, which are validated by individual experiments, can significantly reduce the experimental effort. This requires a knowledge of the mechanical properties of the individual components of the sandwich structure. While this is given for fiber composite plastics, this is not true for honeycomb cores consisting of aramid paper. Consequently, this work presents a procedure that allows mechanical characterization and numerical simulation of paper-like materials. First, applicable test methods for aramid paper are evaluated. Based on this, an improved shear test method and a novel compression test method for paper are developed. Subsequently, various paper-like materials are mechanically characterized. The requirements for a material model for numerical simulation are derived. Following on from this, a special material model is developed that can reproduce the elastic-plastic, orthotropic material behavior with different plastification for compressive loads and a regressive failure model. This material model is implemented and validated in LS-DYNA. Based on this, validation calculations are carried out on aramid paper, honeycomb and foldcore structures. Final exemplary simulations of single-cantilever-beam tests demonstrate the achievable quality of the results as well as possibilities for virtual testing and virtual parameter studies.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2016-08-04T18:12:55Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação RC14351382449.pdf: 7587259 bytes, checksum: 789b264977a2ad73f76f667b13299806 (MD5) / Made available in DSpace on 2016-08-04T18:12:55Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação RC14351382449.pdf: 7587259 bytes, checksum: 789b264977a2ad73f76f667b13299806 (MD5) Previous issue date: 2016-03-03 / Facepe / Estudos anteriores sempre buscaram elucidar a degradação do papel em aspectos como cor, resistência à tração ou alongamento. Todavia, a literatura conhecida não apresenta estudos sistemáticos de degradação do Papel Japonês, material largamente utilizado nos processos de restauração. Nestes processos, o papel Japonês é aplicado ao objeto de papel e a partir deste momento tem-se a evolução temporal das propriedades de um sistema duplo onde os materiais estão embebidos ou conectados fisicamente. Nesta situação, é de grande relevância a compreensão do comportamento em termos de cor e de propriedades mecânicas dos papeis Japonês de modo que permita uma escolha mais adequada para uma dada restauração. Assim, apresentamos um estudo, que consideramos inicial, sobre a alteração de cor em amostras de papel Branco, comumente usado em impressora de escritório, em amostras de papel Whatman e em amostras de seis tipos de papeis Japonês. As amostras dos papeis foram submetidas a um processo controlado de degradação artificial que teve como agente catalisador a irradiação por luz UV. A evolução temporal da cor das amostras foi medida semanalmente. As cores foram medidas no espaço de cores L*a*b*. Além disso, foram realizados ensaios mecânicos, em quase todas as amostras, como função do tempo de irradiação ultravioleta. Para análise dos dados de cor, foram utilizados o conceito de contraste de cor, ΔE*, e foi definido um novo parâmetro nomeado IDC – Índice de Degradação da Cor. Para a análise dos dados de comportamento mecânico, foi definido um novo parâmetro nomeado FQM – Fator de Qualidade Mecânica. No final, é apresentado um diagrama onde os papeis são classificados em regiões de qualidade com relação à cor e à resistência mecânica. / Previous studies have always sought to elucidate the degradation of paper on aspects such as color, tensile strength and elongation. However, the known literature shows no systematic studies of degradation of Japanese paper, material widely used in the restoration process. In these processes, the Japanese paper is applied to the paper object and from that moment there has been the evolution of dual system properties where the materials are physically embedded or attached. In this situation, it is of great importance to understanding the behavior in terms of color and mechanical properties of Japanese papers in order to allow a choice most appropriate for a given restoration. Thus, we present a study, which we consider initial on the color change in White paper samples, commonly used in office printer, on Whatman paper samples and samples of six types of Japanese papers. Samples of the papers were subjected to a controlled artificial degradation process which had as a catalyst to irradiation by UV light. The temporal evolution of the color of the samples was measured weekly. The colors were measured in the colors space L*a*b*. Furthermore, mechanical tests were performed in almost all samples as a function of ultraviolet irradiation time. To analyze the color data, we used the concept of color contrast, ΔE*, and defined a new parameter named CDI - Color Degradation Index. For the analysis of the mechanical behavior of data, a new parameter named QFM - Quality Factor Mechanics has been set. In the end, a diagram where the papers are classified into quality regions regarding the color and the mechanical strength is displayed