Due to their excellent strength, rigidity, and damping properties, as well as low weight, carbon fiber reinforced composites (CFRCs) are being widely used for load bearing structures. On the other hand, with an increased demand and usage of CFRCs, effective methods to re-use waste carbon fiber (CF) materials, which are recoverable either from process scraps or from end-of-life components, are attracting increased attention. In this paper, hybrid yarns consisting of waste staple CF (40 and 60 mm) and polyamide 6 staple fibers (60 mm) are manufactured on a DREF-3000 friction spinning machine with various process parameters, such as spinning drum speed, suction air pressure, and core–sheath ratio. The relationship between different textile physical properties of the hybrid yarns, such as tensile strength, elongation, and evenness with different spinning parameters, core–sheath ratio, and input CF length is revealed.

No description available.

Against the background of global warming and the associated need to drastically reduce energy and resource consumption, action must also be taken in the building sector. Resource-efficient construction methods must be used that nevertheless allow the increasing construction tasks in areas such as infrastructure and housing to continue to be fulfilled. In order to successfully introduce a new construction method to the market, the aspects of recyclability and economic efficiency are essential, in addition to important government requirements for climate neutrality and technical performance. Above all, the economic viability, that is, the economic advantageousness, as well as its simple applicability compared to competing systems, decides on the success and widespread use of a new technology. Carbon reinforced concrete, with its outstanding technical properties and simultaneous material efficiency, is an important building block toward climate neutrality in the construction industry. It is a promising technology that still has to prove its economic advantages and robust applicability under market conditions. In addition to the infrastructure sector, there is great potential in the area of housing creation, which needs to be tapped for carbon reinforced concrete. For this challenge, it is necessary to design a competitive value chain that allows the realization of marketable products in mass production on existing plant technology. The article gives a short overview of the economic and ecological status quo in the field of prefabricated construction with carbon concrete, using the example of the C3-result building CUBE. In particular, the CUBE-BOX, which is made of prefabricated and semi-prefabricated parts, is examined in more detail and the carbon reinforced concrete components used are compared with classic reinforced concrete constructions in terms of sustainability. In this context, the conceivable global climate protection contribution of the carbon reinforced concrete construction method is forecast based on potential market segments.

Roller conveyors are critical components in various industries for material handling, enabling the efficient transportation of items in assembly lines, warehouses, and distribution centers. Traditionally constructed from materials such as steel, aluminum, or plastic, roller conveyors are now being innovatively designed using composite materials. This study investigates the design, analysis, and optimization of roller conveyors utilizing composite materials to achieve weight reduction while maintaining or enhancing structural integrity and operational efficiency. Composite materials offer enhanced properties compared to their individual components. Typical composites include fibers like carbon, glass, or aramid within a matrix of epoxy resin, providing superior strength, corrosion resistance, and customization capabilities. The research employs finite element analysis (FEA) and other advanced modeling techniques to evaluate the performance of composite roller conveyors under various loading conditions. The findings suggest that using composite materials can significantly reduce the weight of roller conveyors, leading to decreased energy consumption, lower operational costs, and improved handling efficiency. The optimized design enhances productivity and contributes to sustainability by minimizing environmental impact. This thesis advances the understanding of composite-based roller conveyors, demonstrating their potential to replace conventional materials and achieve higher efficiency in industrial applications.

[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

Yes / To investigate the shear performance of poplar laminated veneer lumber (LVL) beams with holes in bending-shear spans, six specimens were designed and tested by four-point bending tests. Among these, five specimens were provided with a single hole of varying diameter-to-height ratio in the bending-shear span and two of these beams were also reinforced with circumferential carbon fiber reinforced polymer (CFRP) wrap layers. Furthermore, a 3D finite element models for poplar LVL beams with a hole were established, based on the extended finite element method (XFEM) using ABAQUS software. The validated model was utilized to conduct parametric studies on the diameter-to-height ratio, the hole shape, and the vertical eccentricity ratio. A simplified theoretical analysis for predicting the cracking and ultimate loads for LVL beam with a hole was also proposed. The results indicated that beams without a hole failed due to bending, characterized by mid-span tension cracks, whereas beams with a hole exhibited shear failure along the beam's grain direction due to stress concentration around the holes. The maximum normal tensile strain perpendicular to grain around the hole had an angle of 45° or 225° relative to the beam's longitudinal axis, consistent with the crack initiation angle. As the diameter-to-height ratio increased, the cracking and ultimate loads of beams with a hole decreased, indicating more brittle failure characteristics. The circular hole beam showed significant improvements in cracking and ultimate loads compared with the square hole beam with side length equal to the diameter of the circular hole. When the hole center's vertical eccentricity was in the compression zone, an increase in vertical eccentricity led to enhancements in both the cracking load and ultimate loads. Wrapping the beam with CFRP sheet around the hole effectively mitigated crack propagation, enhancing the load-bearing capacity of beams. The simplified formulas provided accurate prediction for the ultimate load, but highly overestimated the cracking and ultimate loads for poplar LVL beams with a hole. The research findings can be provided as a technical support for the design and application of LVL beams with holes. / The full text will be available at the end of the publisher's embargo: 13th Nov 2025

Six poly(ether ketone ketone)/carbon composite panels were manufactured from powder coated towpreg. All six panels were initially processed using a hot press equipped with controlled cooling. Four of the panels were used to investigate the effect of cooling rate on crystallinity. A fifth panel was used to investigate the effect of annealing the composite after completion of the standard fabrication process. The sixth panel was used to investigate changes in toughness due to manufacturing towpreg with polymer that had been reclaimed from the towpreg fabrication system’s air cleaner. Cooling rates of 2°C/min, 4°C/min, 6°C/min, and 8°C/min resulted in composites with crystallinities of 33%, 27%, 24%, and 23%, respectively. The principal investigation of the effect of cooling rate on crystallinity and mode I and mode II strain energy release rates, G_Ic and G_IIc, respectively, showed that G_Ic and G_IIc values increase with increasing cooling rate. Comparison of the toughness values as a function of crystallinity showed that the dependence of toughness on crystallinity is approximately equivalent to the dependence of toughness on cooling rate. Comparison of the data from the annealed panel to that from the analogous principal panel showed that annealing increased the crystallinity and decreased the mode I strain energy release rate. There was no effect, however, on the mode II strain energy release rate. Comparison of the data from the panel made with reclaimed polymer to that from its analogous principal panel showed that the reclaimed polymer panel had equivalent crystallinity and G_Ic values. On the other hand, the G_IIc values in this panel were lower than in the analogous principal panel. / Master of Science

Mineralisch getränkte Carbonfasern (MCF) stellen eine vielversprechende Alternative zu herkömmlichen Stahlbewehrung in Beton dar. Für eine effiziente industrielle Herstellung von MCF muss eine ausreichende Verarbeitungszeit für die Imprägniersuspension gewährleistet sein. In der vorliegenden Untersuchung wurde zu diesem Zweck ein aus Metakaolin hergestelltes Geopolymer (GP) entwickelt und getestet. Die Tränkung von Carbonfasergarnen wurde kontinuierlich und automatisiert durchgeführt. Anschließend wurden die MCF bei 75 °C wärmebehandelt, um die Reaktionsprozesse zu beschleunigen. Die mechanische Leistung von MCF nahm im Verlauf des Aushärtungsprozesses von 2 auf 8 Stunden allmählich zu, was auf das größere Ausmaß der Geopolymerisation zurückzuführen ist. Bei einer solchen verlängerten Aushärtung zeigten thermogravimetrische und mikroskopische Analysen zwar eine stärkere 'reagierte' Mikrostruktur, aber auch einen höheren Gehalt an Hohlräumen. Nach 8-stündigen Erhitzen erreichten die Zugfestigkeit und der Young-Modul von MCF 2960 MPa bzw. 259 GPa, bezogen auf die Garnquerschnittsfläche.:Abstract Schlagwörter 1. Einleitung 2. Experimentelles Programm 2.1. Materialien 2.2. Herstellung von MCF 2.3. Testen der Geopolymermatrix 2.4. Mechanische Prüfung von MCF 2.5. Morphologische Charakterisierung 3. Ergebnisse und Diskussion 3.1. Charakterisierung der Geopolymermatrix 3.2. Hergestellte MCF mit Geopolymer und Wärmebehandlung bei 75 °C. 3.3. Chemische und morphologische Analyse 4. Schlussfolgerung Erklärung des konkurrierenden Interesses Literaturen / Mineral-impregnated, carbon fiber composites (MCF) are a promising alternative to conventional concrete reinforcements. For the efficient industrial production of MCF, sufficient processing time for the impregnation suspension must be ensured. In the present investigation, a metakaolin-made geopolymer (GP) has been developed and tested for this purpose. The impregnation of carbon-fiber yarns was performed continuously and automated. Subsequently, the MCF were heat-treated at 75 °C to accelerate the reaction processes. The mechanical performance of MCF gradually increased in the advancement of the curing process from 2 to 8 h, which is attributed to the greater extent of geopolymerization. In such extended curing, thermogravimetric and microscopic analysis showed indeed a more “reacted” microstructure but also a higher content of voids. After heating for 8 h, the tensile strength and Young's modulus of MCF reached 2960 MPa and 259 GPa, respectively, when related to the yarn cross-sectional area.:Abstract Schlagwörter 1. Einleitung 2. Experimentelles Programm 2.1. Materialien 2.2. Herstellung von MCF 2.3. Testen der Geopolymermatrix 2.4. Mechanische Prüfung von MCF 2.5. Morphologische Charakterisierung 3. Ergebnisse und Diskussion 3.1. Charakterisierung der Geopolymermatrix 3.2. Hergestellte MCF mit Geopolymer und Wärmebehandlung bei 75 °C. 3.3. Chemische und morphologische Analyse 4. Schlussfolgerung Erklärung des konkurrierenden Interesses Literaturen

Because of a growing demand and usage of carbon fiber, effective methods to re-use waste and recycled carbon fiber recoverable either from process scraps or from end-of-life components are attracting increased attention. The development of different hybrid yarn structures consisting of recycled carbon fiber and thermoplastic fibers (recycled carbon fiber content approx. 50% by weight) for thermoplastic composites have been reported earlier. Yarns with high recycled carbon fiber content (>90% by weight) required for thermoset composites are still not realizable due to high shortening in recycled carbon fiber length (≥70%) during different processing steps of spinning. The reason lies in low shear strength, smooth fiber surface and high brittleness of recycled carbon fiber. Second, a lack of crimp in recycled carbon fiber leads to drafting errors during the drawing and spinning process. In this paper, the spinning limit regarding the core to sheath ratio of noble yarns with a recycled carbon fiber content greater than 90% by weight based on friction spinning technology for thermoset composites is reported. Slivers of recycled carbon fiber solely required for the development of yarns are produced on carding and drawing machines optimized for the gentle processing of recycled carbon fiber. Furthermore, different spinning parameters such as spinning drum speed and suction air pressure are investigated and their effect on tensile properties of yarn is analyzed. The results show that yarns with high recycled carbon fiber content (>90% by weight) can be produced with reproducible quality on the DREF-3000 friction spinning machine.

Im Luftfahrtbereich haben sich kohlenstofffaserverstärkte Kunststoffe (CFK) wegen ihrer hohen spezifischen Festigkeiten und Steifigkeiten längst als Konstruktionswerkstoffe etabliert. In der Großserienfertigung von Automobilkarosserien kommt diese Materialgruppe jedoch nur zögerlich zum Einsatz. Offensichtlich sprechen noch viele Argumente für den Einsatz von metallischen Werkstoffen: Denn auch Leichtmetalle und pressgehärtete Stähle ermöglichen immer höhere Leichtbaugrade, ohne dabei signifikante Kostensteigerungen zu generieren. Zudem sind Fertigungs- und Montageabläufe für Metallkarosserien etabliert und weitgehend frei von Entwicklungsrisiken. Vor diesem Hintergrund erscheint es schwer, mit neuen Leichtbaumaterialien und den zugehörigen Bauweisen einen Durchbruch erzielen zu können. Dabei zeigt das Produktsegment der Supersportwagen schon deutlich, dass zusätzliche Leichtbaupotentiale durch beanspruchungsgerecht gestaltete und optimierte CFK-Strukturen für den Automobilbau eröffnet werden. Bislang lassen sich derartig optimierte CFK-Strukturen jedoch kaum wettbewerbsfähig in Großserie realisieren. An dieser Stelle ergeben sich Chancen und zugleich neue Herausforderungen für die Produktentwickler: Zum einen sind Faserverbundbauweisen zu erarbeiten, mit denen die Leichtbaupotentiale von CFK weitgehend ausgereizt werden. Zum anderen ist die automatisierte Fertigung bei hohen Taktraten zu ermöglichen. Die Lösung beider Teilaufgaben setzt den Einsatz geeigneter materialspezifischer Konstruktionsmethoden voraus.