Search Results (4)

While carbon fibers (CFs) are still the most attractive reinforcement material for lightweight structures, they are mostly manufactured using crude oil-based process chains. To achieve a higher eco-efficiency, the partial substitution of polyacrylonitrile (PAN) by renewable materials, such as lignin, is investigated. So far, this investigation has only been carried out for batch manufacturing studies, neglecting the transfer and validation to continuous CF manufacturing. Therefore, this work is the first to investigate the possibility of partial substituting lignin for PAN in a continuous process. Lignin/PAN-blended CFs with up to 15 wt.-% lignin were able to attain mechanical properties comparable to unmodified PAN-based carbon fibers, achieving tensile strengths of up to 2466 MPa and a Young’s Modulus of 200 Pa. In summary, this study provides the basis for continuous Lignin/PAN-blended CF manufacturing. Full article

For several decades, carbon fibers have been used for lightweight engineering in aircraft automotive and sports industries, mostly based on high-quality polyacrylonitrile (PAN). We investigated a novel PAN-based precursor fiber (PF) modified with a polycyclic aromatic hydrocarbon, namely hexabenzocoronene (HBC), which is expected to improve the thermal conversion process and to create a carbon fiber (CF) with enhanced mechanical properties. For this purpose, the novel PF and a spun-like homopolymeric PAN-based PF were thermally stabilized and carbonized in continuous lab-scale plants. The effect of the additive HBC on the conversion processes, fiber diameter and shape, density, and mechanical properties were investigated. The results showed that HBC seems to support stabilization reactions, and HBC/PAN-based PF show potentially higher stretchability of PF and stabilized fiber. The modified CF showed an improvement in Young’s modulus of about 25% at the same tensile strength compared to the unmodified PAN-based CF, resulting from enhanced crystalline orientation. The results showed a high potential of the HBC/PAN for energy-efficient production. In particular, the influence on tensile strength and modulus under optimized process conditions, as well as the possibility to use low quality PAN, need to be further investigated. Full article

The building sector accounts for approx. 40% of total energy consumption and approx. 36% of all greenhouse gas emissions in Europe. As the EU climate targets for 2030 call for a reduction of greenhouse gas emissions by more than half compared to the emissions of 1990 and also aim for climate neutrality by 2050, there is an urgent need to achieve a significant decrease in the energy use in buildings towards Nearly Zero-Energy Buildings (nZEBs). As the energy footprint of buildings includes the energy and greenhouse gas consumption both in the construction phase and during service life, nZEB solutions have to provide energy-efficient and less carbon-intensive building materials, specific thermal insulation solutions, and a corresponding design of the nZEB. Carbon reinforced concrete (CRC) materials have proven to be excellent candidate materials for concrete-based nZEBs since they are characterized by a significantly lower CO₂ consumption during component production and much a longer lifecycle. The corresponding CRC technology has been successively implemented in the last two decades and first pure CRC-based buildings are currently being built. This article presents a novel material system that combines CRC technology and suitable multifunctional insulation materials as a sandwich system in order to meet future nZEB requirements. Because of its importance for the life cycle stage of production, cost-efficient carbon fibers (CF) from renewable resources like lignin are used as reinforcing material, and reinforcement systems based on such CF are developed. Cutting edge approaches to produce ultra-thin lightweight CF reinforced concrete panels are discussed with regard to their nZEB relevance. For the life cycle stage of the utilization phase, the thermal insulation properties of core materials are optimized. In this context, novel sandwich composites with thin CRC layers and a cellular lightweight concrete core are proposed as a promising solution for façade elements as the sandwich core can additionally be combined with an aerogel-based insulation. The concepts to realize such sandwich façade elements will be described here along with a fully automated manufacturing process to produce such structures. The findings of this study provide clear evidence on the promising capabilities of the CRC technology for nZEBs on the one hand and on the necessity for further research on optimizing the energy footprint of CRC-based structural elements on the other hand. Full article

Carbon concrete polyacrylonitrile (PAN)/lignin-based carbon fiber (CF) composites are a new promising material class for the building industry. The replacement of the traditional heavy and corroding steel reinforcement by carbon fiber (CF)-based reinforcements offers many significant advantages: a higher protection of environmental resources because of lower CO₂ consumption during cement production, a longer lifecycle and thus, much less damage to structural components and a higher degree of design freedom because lightweight solutions can be realized. However, due to cost pressure in civil engineering, completely new process chains are required to manufacture CF-based reinforcement structures for concrete. This article describes the necessary process steps in order to develop CF reinforcement: (1) the production of cost-effective CF using novel carbon fiber lines, and (2) the fabrication of CF rebars with different geometry profiles. It was found that PAN/lignin-based CF is currently the promising material with the most promise to meet future market demands. However, significant research needs to be undertaken in order to improve the properties of lignin-based and PAN/lignin-based CF, respectively. The CF can be manufactured to CF-based rebars using different manufacturing technologies which are developed at a prototype level in this study. Full article