<p>Composite materials have become widely used for high-performance applications, particularly in the aerospace industry where annual production volumes are low and a higher part cost can be supported. During the last decades composite materials are beginning to see use in a broader range of applications, including the automotive and sports equipment industries. Simultaneously, there is increasing demand from consumers and regulatory bodies to make cars more fuel efficient and in the case of EV’s longer drive range, which can be accomplished by reducing vehicle weight. Composite materials have high specific stiffnesses and strengths, resulting in weight savings when they are used to replace traditionally metal components. However, in order for widespread adoption of composite parts to be viable for the automotive industry, high-rate manufacturing must be realized to reach the required production volumes and part costs.</p> <p>Toward this goal, advanced composite manufacturing techniques have been developed. These techniques typically combine high automation with careful material selection, which can include fast-curing resins and thermoplastics with adapted melt viscosities and thermomechanical properties. They also allow for complex part geometries to be produced in a single step, reducing the need for additional assembly time. Further, they can be used to easily create multi-material components, which can result in parts that benefit from the desirable mechanical properties of the constituent materials without sacrificing performance.</p> <p>This thesis develops a framework for the design and high-rate manufacture of multi-material components. First, a critical literature review is conducted to develop a clear understanding of existing research into combinations of dissimilar materials, including epoxy/polyamide, thermoplastic elastomer/polyamide, and aluminum/thermoplastic. It is shown that, for all material combinations studied, interfacial delamination and subsequent deformation are the primary energy absorption mechanisms and that manufacturing conditions may affect interfacial bond strength. Based on this foundation, adhesion testing is performed on devoted sample configurations fabricated under controlled molding conditions. For these material combinations, interfacial adhesion can be significantly improved with carefully selected processing temperatures, even to the extent that adhesive bond between dissimilar materials can be stronger than the cohesive bond in the constituent materials. Next, impact and quasi-static indentation testing were performed to determine the effects of interfacial adhesion and part design on crash performance. The materials tested all benefit from the placement of a more ductile material on the impacted side of the sample (top surface), indicating a more favorable dissipation of the contact stresses from the impactor, and a higher strength material on the bottom surface where it can withstand tensile stresses imposed by impact-induced bending. </p> <p> Finally, a complex part consisting of a unidirectional polyamide/carbon fiber preform and a thermoplastic overmold is manufactured via a hybrid overmolding process. Interfacial temperature during overmolding is varied to confirm if the same improvements in interfacial bond strength seen in the compression molding test samples are attainable under realistic high-rate manufacture conditions. Additionally, the preform volume is varied to examine the effect of the preform reinforcement on a part’s bending performance. For this system, varying the preform temperature had no effect on interfacial bond strength. A predictive technical cost model is also used to determine the effect of manufacturing changes on part costs. Increasing the tow volume three-fold increased the absorbed energy by more than 30% and requires an increased cost of only 3.8%. </p> <p>This thesis proves that a tough, multi-material part can be rapidly produced via hybrid overmolding. It was demonstrated that a complex shaped part could be produced at a complete line cycle time of approximately 90 secondsmaking it a viable method to produce high-performance, low-cost components. </p>

[ES] Los Nanotubos (CNTs) y Nanofibras de Carbono (CNFs) son materiales de nueva generación que tienen características mejores que los materiales convencionalmente utilizados. Los Nanotubos están formados por carbono, siendo su unidad elemental un plano de grafito enrollado cilíndricamente creando tubos de diámetro nanométrico. Por otro lado, las Nanofibras son materiales intermedios entre las habituales fibras de carbono y los CNTs, las cuales se han desarrollado con la finalidad de obtener fibras de carbono nanométricas y pudiendo reemplazar a los CNTs, de una forma más económica y pudiéndose obtener en grandes cantidades. Todo ello, ha llevado a que estos materiales susciten grandes intereses como consecuencia de sus variadas aplicaciones posibles, provocando que se haya trabajado en optimizar y trasladar su proceso de producción a nivel industrial y cada día sean más atractivos. La conveniencia de utilizar estos productos radica en sus excelentes propiedades mecánicas, alta conductividad térmica y eléctrica, así como buena estabilidad a altas temperaturas. Todo ello hace que este tipo de materiales sea muy interesante para ser empleado como refuerzo en matrices termoplásticas. Sin embargo, los materiales compuestos que se ha conseguido obtener hasta la fecha presentan unas propiedades muy inferiores a las inicialmente esperadas, debido a la naturaleza de los materiales y la elevada incompatibilidad existente entre la matriz polimérica y el nano-refuerzo. Ésta provoca la aglomeración de las partículas y la formación de una interfase polímeronanopartícula de malas propiedades mecánicas, donde la transferencia de tensión entre la matriz y el refuerzo no es efectiva. En busca de alternativas a esta problemática, el presente trabajo trata de evaluar como evolucionas distintas propiedades, como las mecánicas, térmicas, reológicas y/o eléctricas, en los materiales desarrollados tras la incorporación de distintas cantidades tanto de CNFs como de CNTs a una matriz de Polipropileno, mediante un proceso de mezclado en fundido o compounding. En un último estudio, se ha analizado cómo evolucionan las propiedades eléctricas o antiestáticas de estos materiales al ser sometidos a subsiguientes procesados con aportes térmicos (Tª) como son la extrusión de monofilamento y la posterior impresión 3D del mismo, para transformarse en una pieza final. / [CA] Els Nanotubs (CNTs) i Nanofibres de Carboni (CNFs) són una nova generació de materials que presenten unes propietats superiors als materials convencionalment utilitzats. Els CNTs són uns materials formats per carboni, on la unitat bàsica és un pla grafític enrotllat que forma un cilindre, formant uns tubs el diàmetre dels quals és de l'ordre d'alguns nanòmetres. Les CNFs per part seua, es consideren com a materials intermedis entre les fibres de carboni convencionals i els CNTs, desenvolupades a fi de produir unes fibres de carboni de grandària nanométrica alternatives als nanotubs, més econòmiques i amb la possibilitat de ser produïdes en grans volums. Tot això, ha portat al fet que aquests materials susciten grans interessos a causa de les seues múltiples possibles aplicacions, provocant que s'haja treballat a optimitzar i traslladar el seu procés de producció a nivell industrial i cada dia siguen més atractius. La conveniència d'utilitzar aquests productes radica en les seues excel·lents propietats mecàniques, alta conductivitat tèrmica i elèctrica, així com bona estabilitat a altes temperatures. Tot això fa que aquest tipus de materials siga molt interessant per a ser emprat com a reforç en matrius termoplàstiques. No obstant això, els materials compostos que s'ha aconseguit obtindre fins hui presenten unes propietats molt inferiors a les inicialment esperades, a causa de la naturalesa dels materials i l'elevada incompatibilitat existent entre la matriu polimèrica i el nano-reforç. Aquesta provoca l'aglomeració de les partícules i la formació d'una interfase polímer-nanopartícula de baixes propietats mecàniques, on la transferència de tensió entre la matriu i el reforç no és efectiva. A la recerca d'alternatives a aquesta problemàtica, el present treball tracta d'avaluar com evoluciones diferents propietats, com les mecàniques, tèrmiques, reològiques i/o elèctriques, en els materials desenvolupats després de la incorporació de diferents quantitats tant de CNFs com de CNTs a una matriu de Polipropilè, mitjançant un procés de barrejat en fos o compounding. En un últim estudi, s'ha analitzat com evolucionen les propietats elèctriques o antiestàtiques d'aquests materials en ser sotmesos a subsegüents processaments amb aportacions tèrmiques (Tª) com són l'extrusió de monofilaments i la posterior impressió 3D d'aquest, per a transformar-se en una peça final. / [EN] Nanotubes (CNTs) and Carbon Nanofibers (CNFs) are a new generation of materials that present superior properties to conventionally used materials. CNTs are materials made of carbon, where the basic unit is a rolled graphite plane that forms a cylinder, forming tubes whose diameter is of the order of a few nanometres. For their part, CNFs are considered as intermediate materials between conventional carbon fibres and CNTs, developed in order to produce nano-sized carbon fibres that are alternatives to nanotubes, cheaper and with the possibility of being produced in large volumes. . All this has led to these materials arousing great interest due to their multiple possible applications, causing work to be done to optimize and transfer their production process to an industrial level and become more attractive every day. The convenience of using these products lies in their excellent mechanical properties, high thermal and electrical conductivity, as well as good stability at high temperatures. All this makes this type of material very interesting to be used as reinforcement in thermoplastic matrices. However, the composite materials that have been obtained to date have much lower properties than those initially expected, due to the nature of the materials and the high incompatibility between the polymeric matrix and the nanoreinforcement. This causes the agglomeration of the particles and the formation of a polymer-nanoparticle interface with poor mechanical properties, where the transfer of tension between the matrix and the reinforcement is not effective. In search of alternatives to this problem, this work tries to evaluate how different properties evolve, such as mechanical, thermal, rheological and / or electrical, in the materials developed after the incorporation of different amounts of both CNFs and CNTs to a matrix. Polypropylene, through a melt mixing process or compounding. In a last study, it has been analysed how the electrical or antistatic properties of these materials evolve when subjected to subsequent processing with thermal inputs (Tª) such as the extrusion of monofilament and the subsequent 3D printing of it, to become a final piece . / Peris Abad, F. (2021). Desarrollo de materiales compuestos mediante la modificación de matrices de polipropileno por adición de nanofibras de carbono y nanotubos de carbono para su utilización en el sector textil [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/165209 / TESIS

The availability of a considerable amount of waste carbon fiber (CF) and the increased pressure to recycle/reuse materials at the end of their life cycle have put the utilization of recycled CF (rCF) under the spotlight. This article reports the successful manufacturing of hybrid yarns consisting of staple CF cut from virgin CF filament yarn and polyamide 6 fibers of defined lengths (40 and 60 mm). Carding and drawing are performed to prepare slivers with improved fiber orientation and mixing for the manufacturing of hybrid yarns. The slivers are then spun into hybrid yarns on a flyer machine. The investigations reveal the influence of fiber length and mixing ratio on the quality of the card web, slivers and on the strength of the hybrid yarns. The findings based on the results of this research work will help realize value-added products from rCF on an industrial scale in the near future.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Lately numerous studies have been performed to design composite monocoques with high strength and low weight for various student level racing contests. The objective of this paper is to develop an insightful methodology to design and de veloped a light-weight composite monocoque. The monocoque is designed to pass the mandatory static load tests laid down by the International Automobile Feder ation (FIA)Formula 3. These Formula 3 tests are considered the baseline of the desired structural integrity of the composite monocoque. The presented design tech nique emphasises on a monocoque developed for Sports Car Club of America (SCCA) races. The three standard load tests performed on the monocoque are Survival Cell Side test, Fuel Tank test and Side Intrusion test. A sandwich layup of bi-directional woven carbon/epoxy prepreg and aluminium honeycomb is optimized for minimum weight while predicting the unknown properties of layup and ensuring the mono coque doesnt experience failure. The approach intends to achieve minimum weight with high torsional rigidity and is capable of being used for the design and analysis of any kind of formula type composite monocoque.

No description available.

Aluminium matrix composites are among the most promising candidate materials for light weight and high strength applications such as transportation and armour. In a previous study 6061 aluminum matrix composites reinforced with plain weave carbon fiber preform (AS4 Hexcel) were successfully fabricated by squeeze casting using the laminate fabrication technique. This research aims at optimizing the fabrication process in order to achieve improved strength and mechanical properties. It focuses on the liquid infiltration squeeze casting method. Good mechanical bonding between fiber and aluminium is achieved thanks to improved infiltration and impregnation of the fabric by liquid aluminium. Oxidation products at fiber/aluminium interface and porosity are reduced. As a result, composites are produced with overall improved mechanical properties. The flexural strength is increased by up to 19.9% and 15.4% compared to the laminate approach and the reference 6061 aluminium alloy squeeze cast under identical conditions, respectively. Similarly, overall hardness is improved. However, the impact strength is reduced by 7.76% and 25.78% when compared to casts fabricated by the laminate method and the reference aluminium alloy, respectively. The thesis constitutes a good basis for further research on fiber and particle reinforced aluminium matrix composites with the goal of further improving fracture toughness, particularly for gradient materials used in armour applications.

Carbon fibers (CF) are a material with a composition of over 90% carbon, which has high mechanical properties and low density. This unique combination of properties makes it requirable in applications such as vehicles, aerospace, wind power, and space industries. Commercially made CF are made using the fossil raw material polyacrylonitrile (PAN). In order to make a more sustainable precursor fiber (PF), this project has focused on other raw materials; cellulose and lignin. The PFs were produced with a cellulose and lignin mixture (70:30 wt%). In order to make a more green production of PF, cold alkali system was used as the solution in conjunction with wet spinning with an acid:salt coagulation bath. The acid:salt baths used was the P system with phosphoric acid and ammonium dihydrogen phosphate (ADHP), and the S system with sulphuric acid and sodium sulphate with varying concentrations of both acid and salt. The objectives for this thesis was to evaluate the effect of the acid:salt coagulation bath composition, as well as the spin finish. This was done using tensile tests where Young’s modulus, strain to failure, and tensile strength (TS) were determined. The spin finish was evaluated using thermogravimetric analysis (TGA). The results showed that the P system had a significantly higher Youngs modulus and tensile strength compared to the S system, whilst the S system had a higher strain to failure. For the different concentrations of the S system, the tensile tests showed no significant difference between the concentrations. The fibers contained more phosphorus when ADHP was added to the spin finish, making them more flame retardant.

Background and aim The pace of development of distance running shoes has been fast-forward since 2016 when Nike introduced their model Nike Zoom Vaporfly, with an imbedded carbon fiber plate and an advanced newly developed Pebax®-foam. The shoe-development has continued to track events, with the introduction of carbon fiber plate in several shoe-models for running and sprint- events. The research area for track events has not reached the level as for distance running shoes, therefore the aim of this study was to examine the effects on long jump performance when using long jump spikes with (AFT) compared to without (non-AFT) a carbon fiber plate.  Method Nine experienced male (n=6, age 22 ± 4.8 years, body mass 76.4 ± 3.5 kg, height 182 ± 4.9 cm), and female (n=3, age 20.3 ± 3.5 years, body mass 64.8 ± 6.0 kg, height 172 ± 2.0 cm) Swedish long jumpers performed three maximal effort long jumps in AFT and non-AFT long jump shoes. Three-dimensional kinematic data was captured with eight markerless motion capture cameras, and the take-off was performed from a force plate. Run-up velocity was measured using a lidar laser and step characteristics using an optical contact grid. Pearson’s correlation coefficient was calculated for jump distance and maximal run-up velocity and paired samples t-tests and a Wilcoxon rank sum test were conducted to examine differences between the shoes.  Results Peak run-up velocity correlated with jump distance both for AFT (Pearson’s r=0.919, p&lt;0.001) and non-AFT shoes (Pearson’s r=0.910, p&lt;0.001). At a group-level no statistical differences were found between the shoes for the run-up variables. The AFT shoes showed significantly greater horizontal velocity at touchdown (p=0.046) and vertical velocity difference from touchdown to toe-off (p=0.029) compared to the non-AFT shoes. No other significant difference was found on group level for the take-off variables. Conclusion The results in this study did not show a longer jump distance in long jump specific AFT shoes compared to non-AFT on a group level, but individual differences were seen. To further understand the effect of AFT shoes on long jump performance, more studies on different individual characteristics and their relation to long jump performance is needed. Keywords Long jump, super spikes, AFT-shoes, carbon fiber plate, biomechanics. / Bakgrund och syfte Sedan Nike 2016 introducerade sin skomodell Nike Zoom Vaporfly har utvecklingen av löparskor med en inbäddad kolfiberplatta och nyutvecklade med energiåtergivande material snabbt fortskridit. Utvecklingen av skor har fortsatt från löparspåren till friidrottsbanan för flera grenar. Forskningsområdet för grenspecifika skor har inte kommit lika långt som för distanslöparskor, därför var syftet med denna studie att undersöka effekterna på längdhoppsprestation av att använda längdhoppsspecifika spikskor med (AFT) jämfört med utan (non-AFT) kolfiberplatta. Metod Nio erfarna manliga (n=6, ålder 22 ± 4,8 år, kroppsvikt 76,4 ± 3,5 kg, längd 182 ± 4,9 cm) och kvinnliga (n=3, ålder 20,3 ± 3,5 år, kroppsvikt 64,8 ± 6 kg, längd 172 ± 2 cm) svenska längdhoppare gjorde tre maximala längdhopp i AFT och non-AFT längdhoppsskor. Tredimensionell kinematisk data samlades in med åtta markörlösa motion capture-kameror och uthoppet skedde från en kraftplatta. Ansatshastigheten mättes med en laserkamera och steg-specifik data med ett optiskt kontaktnät. Pearson’s korrelations koefficient beräknades for hopplängd och maximal ansatshastighet samt så genomfördes paired samples t-test och Wilcoxon rank sum test för att undersäka skillnaderna mellan skorna. Resultat Maximal ansatshastighet korrelerade med maximal hopplängd både för AFT skor (Pearsons r=0,919, p&lt;0,001) och non-AFT skor (Pearsons r=0,910, p&lt;0,001). På gruppnivå hittades ingen statistisk skillnad mellan skorna vad gäller ansatslöpningens variabler. AFT skorna visade en signifikant högre horisontell hastighet vid första markkontakt med kraftplatta (p=0,046) och vertikal hastighetsdifferens från första markkontakt med kraftplatta till sista markkontakt med kraftplatta (p=0,029) jämfört med non-AFT-skor. Ingen annan signifikant skillnad hittades på gruppnivå vad gäller uthoppsvariabler. Slutsats Resultaten i denna studie visade inte på en längre hopplängd i längdhoppsspecifika AFT skor jämfört med icke-AFT skor på gruppnivå men skillnader sågs på individnivå. För att ytterligare förstå effekten av AFT skor på längdhoppsprestation behövs fler studier om olika individuella egenskaper och dess relation till längdhoppsprestation. Nyckelord Längdhopp, super spikes, AFT-skor, karbonfiberplatta, biomekanik.

Syftet med aktuellt arbete var att kalibrera en kamera i MATLAB, med hjälp av tillägget Computer Vision Toolbox, samt utforma ett skript som kan konvertera pixelkoordinater i MATLAB till rumskoordinater. Resultatet av arbetet agerar som ett komplement till en studie på Gymnastik- och idrottshögskolan, där kompression av skosulor undersöks med hjälp av kamera och MATLAB-skript. Flertalet tester utfördes för att säkerställa kalibreringens tillförlitlighet samt kompatibiliteten mellan de två MATLAB-skripten. Kalibreringen anses tillförlitlig, och kompatibiliteten mellan skripten anses god. Vidare utfördes en mindre kompressionsstudie på löpband. Resultaten från denna studie är ej tillförlitliga, eftersom väldigt stora fel behövde tillåtas för att möjliggöra skriptets så kallade pixelspårning. Detta anses vara på grund av ljussättningen vid testerna, samt att kamerans videoupptagning ej hade hög nog bildupptagning per sekund till att följa skornas höga hastighet på löpbandet. Vidare studier av kompression rekommenderas att utföras på stilla underlag, där foten är huvudsakligen stilla i bildens synfält under markkontakt. / The purpose of this work was to calibrate a camera in MATLAB using the Computer Vision Toolbox add-on and to design a script to convert pixel coordinates in MATLAB into spatial coordinates in the room. The result of this work serves as a complement to a study conducted at Gymnastik- och idrottshögskolan in Stockholm, where they are investigating the compression of shoe soles with a camera and a MATLAB-script. Several tests were conducted to ensure the reliability of the calibration along with the compatibility of the two MATLAB scripts. The calibration is considered reliable, and the compatibility of the two scripts is considered satisfactory. Furthermore, a smaller compression study was performed on a treadmill. The results from this study are considered unreliable, as large errors were allowed in the so-called pixel tracking of the MATLAB script. This is considered to be due to bad lighting, and because the video recording did not have a high enough frames-per-second to follow the high velocity of the shoes on the treadmill. Further compression studies are recommended to be performed on stable, non-moving surfaces, where the foot is principally still in the camera’s field of view during ground contact.