In this project, an investigation will be performed about how to improve thermal properties of recycled composite material. First, a literature study was performed about the potential techniques to improve the heating efficiency of the composites. Heating  techniques,  fibres  and  possible  fillers  were  investigated.    Secondely, an experimental method was set with the material available.   In the laboratory a precedent  work  was  performed  on  the  thermal  conductivity  of  polyamide  12 reinforced  with  glass  fibres.   The  conductivity  of  polyamide  12  reinforced with carbon fibres is measured using the same experimental method to compare the thermal conductivity. In theory, carbon fibres have a better thermal conductivity than glass fibres, this was confirmed by the experiments performed.  During the recycling of thermoplastic fibre composites the scrap will be grinded.  Therefore, the thermal conductivity of small pieces of carbon fibre composites was measured, the  thermal  conductivity  is  reduced  due  to  the  increase  of  air  fraction  and the shortening of the fibres.  The thermal conductivity of small pieces of glass fibre composite was investigated in the previous work, by mixing the grinded pieces of carbon fibre composite and the small pieces of the glass fibre composite the effect on the thermal conductivity was investigated.  It was noticed that using smaller pieces of grinded material allows to reduce the air fraction between the bigger pieces and increase the thermal conductivity. / I detta projekt kommer en undersökning att göras om hur man effektivt kan   åter­vinna fiberförstärkta termoplaster. Först genomfördes en litteraturstudie om de potentiella teknikerna för att förbättra kompositernas uppvärmningseffektivitet. Uppvärmningstekniker,   fibrer  och  möjliga  fyllmedel  undersöktes.     Därefter genomfördes experiment med tillgängligt material.  I laboratoriet hade tidigare ett arbete  genomförts  för  att  mäta  värmeledningsförmågan  hos  polyamid  12 förstärkt  med  glasfibrer.    Ledningsförmågan  hos  polyamid  12  förstärkt  med kolfibrer   kommer   här   att   mätas   med   samma   experimentella   metod   för att      jämföra      värmeledningsförmågan.   I      teorin      har      kolfibrer     bättre värmeledningsförmåga    än    glasfibrer,     detta    bekräftades    av    de   utförda experimenten.     Under  återvinning  av  kompositer  av  termoplastfibrer maldes restmaterialet  ner.    Därför  mättes  värmeledningsförmågan  hos  små bitar  av kolfiberkompositer,  värmeledningsförmågan  minskades  på  grund  av ökningen av luftfraktion och förkortningen av fibrerna.  Värmeledningsförmågan hos små bitar  av  glasfiberkomposit  undersöktes  i  det  föregående  arbetet,   genom  att blanda   de   slipade   bitarna   av   kolfiberkomposit   och   de   små   bitarna   av glasfiberkompositet     undersöktes     effekten     på värmekonduktiviteten. Det noterades   att   användning   av   mindre   bitar   av   slipat   material   gör   det möjligt    att    minska    luftfraktionen    mellan    de större    bitarna    och    öka värmeledningsförmågan.

Composite materials are increasingly used in primary structure of modern commercial aircraft. Its excellent material characteristics enables reduction of structural weight compared to traditional metal solutions and thereby offers reduction of fuel consumption and carbon dioxide (CO2) emissions. In the aerospace industry, carbon fibre reinforced plastics or CFRP is the most commonly used composite material, where the reinforcement is held together by a thermoset resin, often epoxy, referred to as the matrix. When manufacturing aircraft composite parts, the curing temperature is usually in-between 120°C to 180°C. As the constituents, i.e. fibre and matrix, have significantly different thermal expansion, the temperature difference from manufacturing of parts to assembly and in-service use results in shape distortions and/or development of residual stresses. With an increased size and complexity of structural parts used in modern aircraft, the development of efficient methods for shape distortion analysis are therefore becoming increasingly important. Shape distortions come from numerous sources and some of them like thermal expansion and chemical shrinkage during curing are fairly well studied and understood. The focus of this thesis is on less researched parameters such as the laminate bending stiffness and effects of moisture content. The bending stiffness of a laminate can be controlled by varying the thickness of the laminate, or by changing the layup sequence of individual plies. Paper A presents an experimental study on shape distortion were the effect of laminate bending stiffness is separated from that of the laminate thickness. The results show that it is possible to tailor the laminate layup in a way that is beneficial for in-plane loads, while still reducing the built-in stresses that occur in a composite component due to shape distortions. The second parameter investigated in this thesis is the laminate moisture content. Composite materials used in aircraft structures will be exposed to environmental effects such as varying temperatures and moisture. The exposure is seldom constant but varies over time, depending on seasonal change and geographical area of aircraft operation. In Paper B, the influence of laminate moisture content on shape distortions is experimentally investigated. It becomes clear that laminate moisture content has such a strong effect on shape distortions that it is important to control and predict for all composite structures. The results presented in this thesis show that both laminate bending stiffness and laminate moisture content have a great influence on shape distortions, and that further research and development is needed to improve the simulation methodology used within the aerospace industry. This is key to future cost-efficient production and assembly of large composite parts. / Kompositmaterial utgör viktiga konstruktionsmaterial i moderna flygplansstrukturer. Deras goda mekaniska egenskaper leder till minskad strukturell vikt och därmed minskad bränsleförbrukning och utsläpp av koldioxid (CO2). Ett vanligt använt kompositmaterial inom flygindustrin är kolfiberarmerad plast eller CFRP. CFRP består av lastbärande kolfiber sammanbundna av en härdplastmatris bestående av epoxi. Vid tillverkning av kompositartiklar inom flygindustrin används härdningstemperaturer på vanligtvis mellan 120°C till 180°C. Då den termiska expansionen hos kompositens delar, fiber och matris, skiljer sig mycket, resulterar stora temperaturskillnader under tillverkningen i formförändringar hos kompositdetaljen och/eller uppbyggnad av restspänningar. Allt eftersom kompositdetaljernas storlek och komplexitet ökar i moderna flygplan så blir behovet av att förstå dessa formförändringar och kunna modellera dess effekter allt större. Det är många faktorer som påverkar uppkomsten av formförändringar, där de mest kända innefattar skillnader i termisk expansion och kemiskt krymp hos den härdande matrisen. I denna avhandling är dock fokus på två mindre undersökta faktorer; laminatböjstyvhet och påverkan från laminatets fukthalt. Böjstyvheten hos ett laminat kan varieras genom att ändra laminattjockleken och/eller uppläggningssekvensen av enskilda lager. I artikel A presenteras en experimentell studie där inverkan av ett laminats böjstyvhet på formförändringen separeras från laminattjocklekens inverkan på formförändringen. Resultaten som presenteras i artikel A visar att det är möjligt att anpassa laminatupplägget på ett sätt som är fördelaktigt för i-planet laster samtidigt som det minskar de inbyggda spänningarna som uppstår i en komplex kompositartikel på grund av formförändringar. I den andra delen av denna avhandling så har kopplingen mellan laminatets fukthalt och formförändring undersökts. Kompositmaterial som används i flygplanstrukturer kommer att utsättas för miljöeffekter såsom varierande temperaturer och fukt. Exponeringen är sällan konstant utan varierar över tid beroende på årstid och i vilket geografiskt område flygplanet befinner sig i. I artikel B sammanställs resultat från en experimentell studie där påverkan av laminatfukthalt på formförändringar har undersökts. Det är tydligt att fuktinnehållet har så stor inverkan på formförändringar att det måste beaktas vid analys av komplexa kompositstrukturer för att kunna nå tillförlitliga prediktioner från modeller och simulering. Resultaten som presenteras i denna avhandling visar på att ytterligare forskning och utveckling behövs för att förbättra de beräkningsmodeller som används inom flygindustrin för att förutsäga formförändringar hos kompositartiklar. Detta är viktigt för att möjliggöra en mer kostnadseffektiv tillverkning och sammanbyggnad av stora kompositdelar i framtiden. / <p></p><p>QC20200302</p>

Saab AB levererar lösningar, produkter och tjänster inom militärt försvar och civil säkerhet. Affärsområdet Aeronautics producerar förutom det militära stridsflygsystemet Gripen även komponenter till civila flygplan, dels sina egna men även andra flygplansproducenter som Airbus och Boeing. Projektets mål är att utveckla ett multifunktionellt robotgripdon för att undersöka automationsmöjligheter kring uppläggning av kolfiberskikt på ett plant underlag, en uppläggning som idag sker för hand. Processen som önskas automatiseras innefattar tillskärning av skikt, förflyttning från skärbord och placering på uppläggningsmall samt borttagning av skiktets skyddspapper. En systematisk konceptutvecklingsmodell har använts som grund för produktutvecklingsprocessen. Modellen har bestått av problemgranskning, undersöka ”state of the art”, upprättande av konstruktionskriterielista, nedbrytning av huvudproblemet i delproblem och framtagning av lösningar på delproblemen. Lösningarna har sedan kombinerats ihop till koncept. De genererade koncepten har utvärderats och en funktionsprototyp av det vinnande konceptet har konstruerats och testats på en robot. Prototypen är uppbyggd av aluminiumprofiler och kolfiberskikten hanteras med hjälp av vakuumsugkoppar vilkas placering anpassats efter skiktens form. Det beslutades att tillskärningen av skikten inte borde integreras i gripdonet utan lämpligast utförs av en programmerbar skärmaskin. Borttagningen av skyddspappret sker sedan i tre steg. Sedan placeras skiktet på mallen och kompakteras genom att en roller jämnar ut eventuella ojämnheter och får skiktet att fästa bättre mot underlaget. Därefter lyfter en sugkopp upp skyddspappret i det hörn som behandlats och en klo griper tag i det upplyfta hörnet varpå pappret avlägsnas. Slutsatsen är att automation av uppläggningen med hjälp av en robot är möjlig. Som fortsättning på detta projekt föreslås att en testcell byggs där automatisk uppläggning av hela processen kan testas. / Saab AB delivers solutions, products and services in military defence and civil security. In addition to the military aircraft system Gripen, the business area of Aeronautics also produces components for civil aircraft. Customers include Airbus and Boeing. The aim of the project is to design a multifunctional robot end-effector in order to investigate whether the degree of automation in the layup of a composite component can be increased. The layup is today a predominantly manual process. In the targeted production step, the pre-impregnated carbon fiber are cut into plies at a cutting table and accurately placed on a layup template. In this step, the backing paper attached to one side of the ply also has to be removed. A systematic model has been used as a foundation of the development process. The model has consisted of problem definition, a “state of the art” study, defining a design specification, and a functionality analysis. Results from the functionality analysis have then been combined into concepts and evaluated. Finally a prototype based on the winning concept has been built and tested on an actual robot. The prototype’s structure is based on aluminum profiles. The carbon fiber plies are handled with vacuum cups whose placing has been adjusted to fit the geometries of all plies. The step where plies are cut was excluded from the multifunctional end-effector since an automated cutting machine, which is already in use, was considered a more viable option at this stage. Removal of the backing paper is done in three steps. Then the ply is placed on a lay-up template and compacted by a roller to remove any unevenness and to attach the ply better to the surface. Finally, a vacuum cup lifts the previously treated corner of the backing paper and a mechanical claw secures the grip whereupon the paper is removed. A conclusion from this project is that automation of the lay-up with a robot is possible. As a continuation of this project it is suggested that an automated robot cell is constructed to test the automated layup process.

In this work four fiber-reinforced polymers and one polymer were tested with four different mechanical testing methods, namely; vickers harness test, scratch test, fatigue test and tensile stress. The testing methods were evaluated according to their applicability on the materials mentioned. The purpose of the work is to give the reader an insight of what mechanical properties of materials mean and what kinds of properties one can expect from fiber-reinforced polymers. The purpose is also to give the reader a good sense of what can be expected from the methods tested on fiber-reinforced polymers. Vickers harness test was found to be a valid method as long as the surface of the material was neither uneven nor processed. Scratch test was found to be an overall good method but was recommended to be used in combination with scanning electron microscope, or other imaging tool for strong magnification. Processing of surfaces proved to affect the results. Tensile test was proved to give the user a good perception of the properties of the material, as long as the material not was woven. Woven materials found to differ a lot from each other. One conclusion from this result is that woven materials are best to be tested several times. Fatigue test was found to require more preparatory time and calculations to be able to give the user any useful results, the loads used in the project was found to be too light weight. Processed surfaces were found to be hard to examine in a scanning electron microscope.

Detta examensarbete beskriver undersökningen av kärnmaterial i en sandwichpanel under belastning. Arbetet har utförts tillsammans med CCG i Laholm, Sverige. Kärnmaterialen lämpar sig vid design av sandwichpaneler på grund av sin låga vikt och sin förmåga att klara av högt tryck. Då materialet uppvisar ett ickelinjärt beteende skapar det problem vid design av sandwichpaneler och leder till att materialsammansättningarna tillverkas konservativa mot verkligheten. Projektet har gått ut på reducera designprocessen genom att bygga upp och simulera materialmodeller i programvaran ABAQUS för att kunna analysera och förutse materialets beteende. Resultaten har presenterats i kraft- och förskjutningsdiagram samt visualiseringar och har försvarats med hjälp av teorier för kontaktmekanik samt matematik. Projektet har utförts på ett vetenskapligt sätt där hypotes verifieras mot teori för att sedan verifieras i experiment, allt för att säkerställa resultatet. / This thesis describes a study of the core materials used in composite panels under static indentation. The work was conducted together with CCG in Laholm, Sweden. These materials work well when designing sandwich panels due to their low weight and high compression strength. As the cores show a non-linear behavior problems can arise when constructing panels and oftentimes lead to choosing very conservative solutions that are not optimized.The main focus of this thesis has been the modelling and simulation of materials in the software ABAQUS to analyze and predict the materials behavior and reduce the time needed for the design of new panels. The result is presented in force- displacement plots as well as von Mises visualization plots and is sustained by theories of both contact mechanics and mathematics. The group endeavored to work in a scientific manner by verifying the hypotheses through theory and experiments in order to accomplish accurate results.

No description available.

Reinforced polymer composites consist of continuous fibers embedded in a polymer matrix. The matrix is usually a thermoplastic or thermosetting resin. When thermosetting matrices are cured during the manufacture of composite parts, residual stresses develop within the part during the manufacture due primarily the thermally and chemically induced volumetric strains imposed on them. This can lead to shape distortions and sometimes weakening of the structure itself. Curing is the manufacturing process in which the thermoset resin is transformed from a liquid to a solid material. The molecular mechanisms involved in this process are quite complex and not well understood. In the macro-level, in addition to volumetric strains, heat is also generated since most thermoset polymerization reactions are exothermic. The mechanical properties of the thermoset also undergo dramatic changes. The material changes from an initial liquid state to a rubbery gel and finally to a vitrified glassy state. In modern day composite manufacturing, to accommodate for the shape distortions caused due to residual stress formation, the mold geometry is compensated. To do this, accurate predictions of the distortion behavior is preferred via computer simulations. This in turn requires simple mathematical models that can replicate the complex processes that take place during manufacture. One such process that requires attention is the curing of the thermoset. While models exist that assume elastic behavior during cure, they are not accurate throughout the entire cure process. Models based on viscoelastic material during cure offer better prospects in this perspective. However, currently models that are based on full viscoelasticity are either not well defined or are computationally tasking. Viscoelastic materials can be classified further in to thermorheologically simple and complex materials depending on their molecular weights. In simpler terms, thermorheologically simple materials are those that obey the principles of time-temperature superposition (TTS). TTS requires that all response times (i.e., all relaxation or retardation time), depend equally on temperature. This is expressed using the temperature shift function. Master curves can be then generated extending the time scale beyond the range that could normally be covered in a single experiment. However to fully understand the development of viscoelasticity during cure it is also necessary that the effects of the degree of cure of the thermoset on these times be included in the model definition. This requires defining a cure shift function along with the temperature shift function. In the presented work, an attempt is made to develop a simplified methodology to characterize the viscoelastic material properties during curing. Two different methods are investigated in a DMTA instrument to determine the effects of curing on the glassy state of the resin system LY5052/HY5052. A cure shift function was identified in the process. Based on observations it was concluded that the total shift function could be possibly defined as a product of the temperature and cure shift functions. Unique super-master curves were generated as a result. However, these curves showed a dependency of the rubbery modulus on the degree of cure. Hence, in the second paper, the effect of the degree of cure on the rubbery modulus was investigated. Subsequently a model was reformulated from an existing one and this was used to further simplify the super-master curves. Following dynamic testing, it was necessary that macroscopic testing is performed to corroborate the results. The macroscopic experiments utilized for this purpose was stress relaxation tests to determine the viscoelastic Poisson’s ratio of neat resin. The Poisson’s ratio in particular is an important property to study, since it’s interaction with the fiber during curing is critical in the study of residual stresses. The focus of the study is to determine if there is a dependency of the Poisson’s ratio on degree of cure and whether master curves can be generated by horizontal shifting of data. Literature pertaining to the dependency of the Poisson’s ratio on degree of cure is scarce. If appropriate horizontal shifting can be performed, it can be easily compared to the results from dynamic testing to check if the shift factors are truly universal. Also presented is a brief study of the effect of degree of cure and time on the development of viscoplastic strains during curing. This is done by performing creep tests on composite specimens with varying degrees of cure. The experimental results were then used to validate the well-known Zapas-Crissman model for viscoplastic strain evolution with time and investigate how it is influenced by the cure state.

Syftet med arbetet är att designa ett elektrolytflödesbatteri som möter kraven att den perforerade laddningsuppsamlaren i batteriet ska ska ha en resistans väl under 3 ohm samt ha god kontakt med kompositelektroden gjord av ett aktivt elektrodmaterial belagt på kolfiltsubstrat utan att påverka elektrolytens flödesmöjligheter. Det finns också krav på att cellen ska vara tät, tåla en syrakoncentration på 3,3 M (H_2SO_4) samt att flödet skapat av en pump ska ske vinkelrätt mot kompositelektroden och laddningsuppsamlaren. Först skapades en design som inte gav utrymme till mer elektrolyt än vad som fick plats i kompositelektrodens porer och hade kontakter som var en del av laddningsuppsamlaren. Den slutliga designen är utformad så att det finns utrymme för mer elektrolyt och kontakter i som är skilda från laddningsuppsamlarna för att möjliggöra lättare rengöring av cellen vid behov. Behållaren är förslagsvis gjord i Teflon då det är ett material som tål kemisk påverkan och är omformbart, men om konstruktionen sker genom uppvärmning så är PEEK ett bättre alternativ. Laddningsuppsamlaren föreslås vara gjord i grafit, men kan också tillverkas av rostfritt stål vilket är det material som fördelaktigt används till kontakterna.

Improved fracture toughness at a given strength level is one of the most important properties of cemented carbides. Large number of different testing methods (both theoretical and experimental) has been proposed to determine fracture toughness of cemented carbides and it has been always a topic of interest to relate fracture toughness with mechanical properties. In this report method such as Palmqvist toughness, chevron notch, toughness determination through Hertzian indentation and different theoretical toughness models have been utilized in order to investigate fracture characteristics and is also compared with other mechanical properties by varying cobalt content and grain size. This study has provided some new and interesting results as well as new information about hardmetals in different loading conditions.

Fiber-reinforced concrete is a construction material that holds high promise in progressing theconstruction industry. The fibers impact on crackproperties as well as strength means there isa wide array of application areas. Still this material holds a very limited area of application asof today. One of the main reasons for this is the lack of examples and tests in new applicationareas. This work therefore aims to identify whether fiber-reinforced lattice girder elementscan compete with an element reinforced in the traditional way in any of the categories cost,work environment, strength or environmental impact. Through literature study andcalculations, we were able to see that this method of reinforcing lattice girder elements couldbe applicable at least in some of the areas. The study saw that the steel fiber came with anincrease in cost, decrease in time, bigger impact on the environment and a better workenvironment. This means that this method could be used in some specific cases where timeand work environment is of importance. We also see that further advancements in this methodcan be made if the fibers are combined with normal rebar.