During machining operation, cemented carbide tools are exposed to high loads and temperatures, which eventually leads to plastic deformation of the tool material. The aim of this work was to investigate if the microstructures of creep deformed micro grain cemented carbides can be linked to alloying elements and mechanical properties. Eleven different fine-grained Tungsten carbide (WC) and Cobalt (Co) based materials have been exposed to compressive creep tests at application relevant temperature. The WC grain size, Sigma 2 (∑2) boundary fraction, and crystallographic structure of the creep deformed materials were investigated with scanning electron microscopy equipped with an electron backscatter diffraction detector. Furthermore, the microstructure of some materials was analysed before and after creep deformation using scanning electron microscopy. A screening of alloying elements that have the potential to increase creep resistance was performed. Growth perpendicular to the load axis was observed in several creep deformed materials, and it could be linked to lower creep resistance. Transition metals from group 4 and 6 limited grain growth, and therefore, improved creep resistance. It was found that a high ∑2 boundary fraction is related to higher creep resistance. The ∑2 boundary fraction was observed to be affected by grain size and alloyingelements. / Under skärande bearbetning utsätts hårdmetallsverktyg för höga tryck och temperaturer. Över tid leder det till att materialet plastiskt deformeras. Syftet med det här arbetet var att undersöka om mikrostrukturen i krypdeformerade hårdmetallsmaterial kan kopplas till legeringsämnen och mekaniska egenskaper. Elva olika finkorniga Volframkarbid (WC) och Kobolt (Co) baserade material har utsatts för tryckbelastade kryptest vid applikationsrelevant temperatur. WC kornstorleken, andelen Sigma 2 (∑2) korngränser samt kristallstrukturen i de krypdeformerade materialen undersöktes med hjälp av bakåtspridd elektrondiffraktion (EBSD). Några av materialen analyserades också med hjälp av elektronmikroskopi före och efter deformation. En screening av vilka legeringselement som har potential att förbättra krypmotståndet utfördes. Korntillväxt vinkelrätt mot lastriktningen observerades i ett flertal av de krypdeformerade materialen, och denna korntillväxt kunde kopplas till lägre krypmotstånd. Övergångsmetaller från grupp 4 och 6 begränsade korntillväxten och förbättrade därav krypmotståndet. Det visade sig också att en högfraktion av ∑2 korngränser är relaterat till bättre krypmotstånd. Det observerades att fraktionen av ∑2 korngränser påverkas av kornstorlek och legeringsämnen.

The quest for lighter materials and structures to reduce climate impacts in the automotive industry has paved the way for multifunctional solutions. Mass saving on a system level can be achieved by materials or structures having more than one primary function, thus reducing the number of components used. Structural batteries are composite materials that simultaneously carry mechanical loads while delivering electrical energy. While carbon fiber is a commonly used reinforcing material in high-performance composite materials, it also possesses excellent lithium intercalation properties. Therefore it is possible to use carbon fiber to develop structural batteries based on the lithium-ion battery technology.  In the micro-battery, which is one of several design solutions, the carbon fiber is employed as a negative electrode of the battery and also as a composite reinforcement material. It is coated with a solid polymer electrolyte working as an ion conductor and separator whilst transferring mechanical loads. The coated fiber is surrounded by additional matrix material acting as cathode and transferring loads to the fibers, composed of conductive additives, active electrode material and electrolyte. This assembly of materials allows for the necessary electrochemical processes to occur simultaneously, including electrochemical reactions at the surface of the active electrode material, mass transport within active electrode material by diffusion, mass transport in electrolyte by diffusion and migration, and electronic conduction.  During electrochemical cycling the electrodes undergo volume changes as a result of lithium transport. The work in this thesis addresses modeling of the effects of volume changes on internal mechanical stress state in the structural battery, potentially causing micro-damage formation in the material, which degrade both electrical and mechanical performance of the structural battery composite.  In this work, a physics-based mathematical model employing a number of coupled nonlinear differential equations has been set-up and solved numerically to investigate performance in the structural battery material. The resulting transient Li concentration distributions were used in combination with linear elastic stress analysis in order to assess the mechanical stresses in the fiber, coating and matrix caused by non-uniform swelling and shrinking of the micro-battery.

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>

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.

No description available.