Depth-resolved characterization of carbon fiber reinforced polymer (CFRP) laminates remains challenging due to signal superposition from multiple layers in conventional eddy current testing. This letter presents a novel multicoil sensor architecture that enables simultaneous measurements at different penetration depths. The sensor comprises one transmitter coil and four receiver coils. One concentric coil with the transmitter arranged around the receiver for shallow layer sensitivity, and three additional receivers arranged concentrically around each other but with an offset to the primary pair for enhanced depth discrimination. By exploiting the distinct electromagnetic coupling characteristics of each receiver configuration and combining this spatial diversity with frequency-multiplexed excitation, the sensor provides complementary information about layer-specific fiber orientations and defects. Experimental validation on symmetric multilayer CFRP laminates with deliberately introduced anomalies demonstrates the sensor's capability to distinguish features in individual layers that were previously indistinguishable with single-coil approaches.

Low productivity and increasing labour shortages present major challenges in the traditional production of thin-walled structures. The CRC-Transregio 280 is therefore developing new design principles for carbon concrete that rely on robot-assisted, digitalised fabrication technologies and are complemented by customised material solutions. One example of this is the production of versatile, bionically inspired 3D textile reinforcements using a cooperative robotic system. In this process, the robot-assisted yarn placement is synchronised with the curing phase of the impregnation. The 3D textile reinforcement structure provides the general shape and support for the fresh concrete in a formwork-free construction method. This is applied to the textile in thin strips by extrusion from a robot-guided print head. The rheological properties are manipulated in such a way that both the textile is enclosed and the concrete stays in place. Comprehensive controls of material flow, spatial positioning of the textile reinforcement structure and the applied concrete layers are intended to enable real-time adjustments to be made. This innovative manufacturing method is intended to produce shell-like, self-penetrating lightweight components for a modular construction method using 3D printing. The combination of the precision and speed of robotics and the technological flexibility of advanced materials will pave the way for a more sustainable, resource-efficient future through carbon-reinforced concrete construction.

Although hybrid yarns containing recycled carbon fibres (rCF) and thermoplastic fibres offer significant potential for sustainable composites, their use in thermoset composites remains challenging due to fibre shortening, poor inter-fibre cohesion, and difficulties in producing textile reinforcements with high rCF content. This study investigates the mechanical behaviour of thermoset composites reinforced with a 2/2 twill woven fabric manufactured from a high-rCF-content yarn and compares it with a unidirectional (UD) composite from the same yarn and a woven-fabric composite reinforced with a virgin carbon filament yarn. A homogeneous 100% rCF sliver was prepared by carding and drawing and processed into a friction-spun yarn containing more than 90 wt% rCF, which was woven into a 2/2 twill fabric. Thermoset composites were manufactured by resin transfer moulding and evaluated by tensile and Charpy impact tests. The UD composite based on rCF yarn achieved the highest tensile strength (1173 MPa), Young’s modulus (100 GPa), and impact strength (87.7 kJ/m 2 ). The composite based on rCF woven fabric exhibited a tensile strength of 227 MPa and a Young’s modulus of 27 GPa, compared with 677 MPa and 55 GPa, respectively, for the composite based on virgin carbon filament woven fabric. Despite its lower tensile properties, the composite based on rCF woven fabric exhibited a comparable impact strength (70.1 kJ/m 2 ) to the virgin carbon filament woven-fabric composite (66.2 kJ/m 2 ). These findings demonstrate the influence of the reinforcement architecture on composite performance.

Carbon reinforced concrete (CRC) is characterized by its corrosion resistance, material efficiency, and high load-bearing capacity. To fully leverage the potential of high-performance carbon reinforcement structures, load-specific and component-adapted textile reinforcement structures are essential. For retrofitting and reinforcing planar structural elements, biaxial grid structures and rebars have been established as effective solutions. However, for three-dimensional, more complex geometries, these reinforcement structures often require complex subsequent forming processes and often result in overdimensioning and therefore an inefficient use of the carbon reinforcement structure. For the tailored and efficient reinforcement of components with complex 3D geometries, such as hollow-core slabs and beams, load-path-based reinforcement structures are needed, according to the biological principle of “form follows force.” A particularly promising reinforcement structure is the so-called “Netzgitterträger”. First Netzgitterträger were fabricated manually as well as using advanced multi-axial warp-knitting technology with specialized warp thread manipulation and shaping systems for hollow-core slab systems. This reinforcement structure, consisting of branched and alternating, diagonally offset roving paths with overlapping edge area, enables high material efficiency and advantageous anchorage of the reinforcement. This principle of branched and merged reinforcement paths can also be found in botanical structures such as the transition zone between petiole and lamina of peltate leaves. Thus, biologically inspired load-path designed reinforcement layouts can also be applied to slab systems such as T-beams. For high performance and more complex, branched reinforcement structures, robot-based automated yarn deposition is particularly suitable. This paper presents the Netzgitterträger principle through examples of slab and beam systems, selected experimental results on load-bearing behavior and productive manufacturing processes for the fabrication of complex, biological inspired reinforcement structures.

ABSTRACT Twisted and Coiled Polymer Actuator (TCPAs) are recognized as a promising class of soft actuators due to their high energy efficiency, low weight, and actuation performance. These actuators are typically based on thermally or electrothermally responsive polymer fibers and combine high strain and force output with tunable stiffness. As a result, they are considered for applications in robotics, prosthetics, and wearable systems. This article provides a comprehensive overview of the principles, fabrication strategies, and materials characterization methods of TCPAs, including thermomechanical, structural, and morphological analysis at different length scales. It further correlates polymer microstructure, processing history, and actuator geometry with key performance metrics such as stroke, blocking force, and cyclic stability. Furthermore, recent advances in performance optimization are discussed, covering approaches to accelerate thermal management, mitigate creep and fatigue, and improve controllability through integrated sensing and modeling. The application landscape of TCPAs in biomedical engineering, soft robotics, and adaptive textile structures is highlighted, followed by a critical assessment of current challenges and future research directions in materials design, scalable manufacturing, and standardized characterization protocols. The present work serves as a resource for researchers seeking a materials science perspective on the design, characterization, and application of twisted coiled polymer actuators.

Efficient resin infiltration in complex textile reinforcements remains a persistent challenge in liquid composite molding. This study investigates flow-front development in biaxial non-crimp fabrics incorporating temporary flow channels (TFCs). The proposed approach exploits the fabric architecture and associated dual-scale flow phenomena to improve in-plane permeability. Flow behavior is examined through experiments conducted using a custom in-house setup and numerical simulations employing a dual-domain porous/free-flow model with Volume of Fluid tracking in ANSYS Fluent. Two physics-based modeling simplifications are considered: a representative volume element with periodic boundary conditions and a simplified three-dimensional plate model incorporating User-Defined Function–based porosity assignment. Numerical results show good agreement with experimental observations, demonstrating that TFC-modified fabrics promote flow-front advancement and significantly reduce mold filling time relative to the reference configuration.

Recent advances in fiber-based actuators have spotlighted twisted, coiled polymer actuators (TCPAs) as a promising technology, offering a combination of high energy density, cost-effectiveness, and environmental sustainability. A comprehensive review of current literature underscores the potential of TCPAs while also revealing significant drawbacks in scaling production and maintaining stability for widespread textile integration. Our research directly addresses these challenges through an innovative manufacturing concept rooted in false-twisting techniques. The approach enables rapid, continuous production of intensely twisted polymer monofilaments, simultaneously allowing for the seamless incorporation of functional elements for thermal actuation and sensory capabilities. The study delves into the impact of this additional helical tier, alongside critical parameters, such as twist intensity, thermal processing conditions, and chirality, on the actuator’s contractile behavior. Exploiting the inherent structural integrity of plied yarns, we demonstrate the feasibility of processing these advanced TCPAs using conventional textile equipment. This may facilitate the creation of complex, multi-yarn contractile systems through circular braiding techniques, effectively producing artificial muscles at a scale previously unattainable. The findings reveal that monofilament coils can achieve remarkable contraction rates of up to 60

This study presents a novel hierarchical strategy for the design and manufacture of sustainable complex-shaped Structural Supercapacitors (SSCs) via an additive manufacturing approach using vertically aligned carbon nanotube (VACNT)-functionalized carbon fiber electrodes. The SSC core, based on a poly(vinyl alcohol)-NaCl gel polymer electrolyte, is integrated within a load-bearing polyethylene terephthalate glycol-modified carbon fiber (PETG-CF) reinforcement hull. While the VACNT functionalization effectively boosted the component-level integral specific capacitance to 5.75F/g, the process induced a 70% reduction in fiber’s tensile strength. This limitation was mitigated through topology optimization, which minimized the composite reinforcement hull mass while ensuring the required structural integrity for complex geometries. Additive-manufacturing successfully overcomes the geometric constraints of traditional lamination methods. However, the study identifies a manufacturing bottleneck: device performance (415 µF/g) was limited by process losses, specifically high current collector contact resistance and gel polymer swelling-induced short-circuiting. A demonstrated closed-loop system, including the mechanical recycling of the PETG-CF hull and chemical recovery of the water-soluble PVA, establishes a strong sustainability profile for this novel multifunctional composite system. This work provides a scalable pathway for designing weight-efficient, energy-storing structures in aerospace and automotive applications.

Warp knitted fabrics are used in a variety of ways, including knitted garments, home textiles, medical textiles, technical fabrics, and non-crimp fabrics, enhancing their durability, functionality, and aesthetic appeal. However, when developing a finite element method (FEM) model for these types of fabrics, accurately creating the geometry of the warp knitted structure can be challenging. Careful approximation of the stitch geometry is essential, as it significantly influences the final simulation results. This paper presents an approach to develop the geometry of the warp-knitted fabric structure to better reflect reality. To validate this approach, two FEM models are developed in LS-DYNA: one for a warp-knitted fabric for a medical application and another for a unidirectional non-crimp fabric, both of which incorporate a pillar stitch type. The warp-knitted fabric is utilized as an attachment tube for the fixation of muscle tissue during hip replacement surgery. A tensile test is conducted on one half of the warp-knitted fabric, and the results are compared with the simulation outcomes for validation. Additionally, the attachment tube is fitted over a endoprosthesis and visually compared with real-time experiment. The non-crimp fabric is used as a reinforcement for a composite material. A hemisphere drape test is performed on the non-crimp fabric both in real life and through simulation. Finally, a visual comparison is made to assess how the pillar stitches in the fabric behave during the draping process. Simulation results confirm the reliability of the developed models and their ability to predict the forming behavior of the fabrics.

Twisted and coiled polymer actuators (TCPAs) are thermally driven artificial muscles capable of generating large reversible strains, making them attractive for soft robotics and adaptive systems. Their actuation behavior strongly depends on the thermomechanical properties of the precursor fibers, which are governed by polymer processing and drawing conditions. In this study, polyamide 6 (PA6) precursor fibers were melt-spun and systematically drawn at different temperatures and draw ratios to tailor their geometry, crystallinity, and thermal contraction behavior. The resulting fibers were characterized using tensile testing, microscopy, dynamic mechanical analysis, and differential scanning calorimetry. Selected fibers were then converted into TCPAs using a twist and autocoiling process and electrically actuated via Joule heating. Their thermally induced strain behavior was compared with TCPAs made from a commercial nylon filament. Results show that increasing draw ratio reduces fiber diameter while increasing strength, crystallinity, and thermal contraction. Maximum thermal contraction occurred for fibers drawn at 85 circle C and a draw ratio of 4.5, indicating that contraction is not governed by crystallinity alone. TCPAs from tailored PA6 fibers achieved actuation performance comparable to commercial nylon, with slightly higher strain but somewhat lower reproducibility. The overall actuation strain remained limited by coil geometry and spring index. These findings demonstrate that precursor fiber drawing provides an effective pathway to tailor TCPA performance and supports the development of tunable polymer-based artificial muscles.

Lignin is a natural biopolymer that is the third most abundant in nature after cellulose and chitin. Despite its widespread occurrence, it has been little used industrially to date, as it is usually regarded as a by-product of the paper industry and is generally only exploited thermally. However, there have recently been many efforts to make further technical use of this biopolymer. Besides applications in the food industry (reduction to vanillin as a flavoring agent), as a binder in asphalt or as a filler in elastomers, research into lignin as a precursor material for carbon fibers has been carried out for many years. Due to the wide range of possible applications, new processes have been developed to extract the lignin specifically from the biomass. The properties of the lignin obtained in this way depend on the extraction process on the one hand and on the original source of the biomass on the other. This results in a broad spectrum of commercial lignin qualities with different properties. For the use of lignin in textile applications, the solubility and fiber formation properties are of essential importance. Therefore, the solubility of several commercial lignins in different organic and inorganic solvents were investigated in order to further process them in a wet spinning process. The results show, that the origin and pulping method of the lignins have a huge impact on their suitability and consequently on the processing into spinning dope for the manufacturing of precursor fibers.

Textile‐integrated sensors are investigated as functional elements in engineering textiles, enabling monitoring in deformable systems, including biomedical applications. While most current research focuses on material choice, mounting evidence shows that the textile architecture also plays a decisive role in affecting sensor stability and reliability. This study compares two textile architectures designed for sensor integration: a weft‐knitted pocket structure and a weft‐knitted tunnel‐routing structure. These architectures employ different sensor integration approaches, such as embroidered capacitive sensors and braided sensor yarns, which reflect their respective structural integration strategies. The integrated textile samples were subjected to tensile, bending, and compressive loads, as well as thermal sterilization and exposure to chemical environments relevant to wound care applications. Under these conditions, the two textile architectures exhibited stable resistance behavior under mechanical stress, whereas their capacitive responses differed according to the integration strategy. The pocket structure demonstrated lower signal drift and higher repeatability, whereas the tunnel design offered higher sensitivity at the cost of increased variability. Notably, both architectures retained sensing functionality after sterilization and chemical exposure. These results emphasize that textile architecture is a key factor in determining sensor reliability, with the pocket‐type design providing a robust platform for capacitive sensing in functional engineering textiles.

Carbon-fiber-reinforced polymer (CFRP) reinforcements offer high potential for resource-efficient and durable concrete structures due to their superior tensile properties and corrosion resistance. However, existing CFRP tendons and rope systems are limited in terms of bond performance, anchorage efficiency, bending capability, and applicability to filigree and modular concrete structures. This paper presents the development of novel CFRP rope structures based on preconsolidated, partially profiled carbon rovings combined with thermoplastic and elastomeric impregnation systems. The proposed rope concept features a spiral configuration of seven rovings, consisting of one central unprofiled strand and six surrounding profiled strands to enhance bond behavior. A laboratory-scale rotational manufacturing process is introduced, allowing controlled variation of spiral geometry and structural fixation. In addition, modified tensile testing and load introduction concepts based on segmented grouting were developed to enable reliable characterization of CFRP rope structures with increased diameters up to failure. Experimental investigations focus on tensile and bending behavior relevant to reinforcement and prestressing applications. The novel CFRP ropes achieve Young’s moduli between approximately 140 and 180 GPa and tensile strengths of about 2,350 MPa, exceeding a commercial epoxy-based reference by 10–30 %. Bending tests demonstrate that soft polymer-based impregnation enables small bending radii suitable for coiling and continuous production, while stiffer matrices provide higher axial stiffness at reduced flexibility. Overall, the results highlight the potential of thermoplastic-based CFRP rope systems for material efficient prestressing systems in combination with shaping, modular construction, demountability, recyclability, and future integration of sensor functionalities.

Textile based actuators have emerged as promising candidates for biomedical applications such as ventricular assist systems or artificial myocardium. This study investigates the mechanical coupling between Liquid Crystal Elastomer (LCE) fibers and a soft anatomical model of the human left ventricle (LV). In this work, a simplified LV geometry was modeled as a hyperelastic and wrapped with beam element textiles representing plain and atlas weave types. LCE contraction was simulated via thermally induced strain along the yarn axis. Simulations were performed using LS-DYNA, to evaluate surface contact coverage, mean and peak contact pressures, and resultant displacements across increasing LCE strain levels. Results show that the plain weave achieve superior conformity and more efficient force transmission. This work provides new insights into fiber geometry coupling and offers a simulation driven foundation for designing textile LCE systems tailored for soft robotic and cardiac applications.

Compared to the mechanical properties of composites from recycled carbon fibres (rCF) based on moulding compounds and nonwovens, hybrid yarns from rCF and thermoplastic fibre with adjusted yarn properties offer an excellent potential for high fibre orientation, fibre length, compactness, high fibre volume content resulting in a high level of performance in composites. However, the spinning of hybrid yarns from rCF and thermoplastic fibres for carbon fibre rein-forced composites (CFRP) is based on modified roving frame spinning technology with high yarn twists, which are indispensable to ensure sufficient yarn strength and a stable spinning process. However, high yarn twist results in undefined damage to the rCF, increased short fibre content during spinning and poor fibre alignment in the composite. These lead to drafting error, uneven fibre structures and irreproducible manufacturing processes as well as low mechanical properties of CFRP. Therefore, one of the main objectives of this work is to develop zero twist hybrid yarns from recycled carbon fibres for high performance thermoplastic composites. For this purpose, a new concept of false twisting spinning process for the production of twist-free ( 0 T/m) hybrid yarns from rCF and thermoplastic fibres based on thermal activation of thermoplastic fibres is developed and patented. This spinning process consists of a modified drafting unit with adjustable gauges and fibre guidance elements for fibres up to 120 mm, a thermo-module, a false twister, a nozzle, take-up rollers and a winder. The new process is expected to help achieve higher tensile strength and modulus in composites compared to rCF hybrid yarns produced on conventional roving frame machines with twists. As a result, the potential of rCF to achieve the high mechanical properties of CFRP can be realised.

Abstract Computerized flat knitting offers advantages in programmability, integrative forming, and multi-material integration. Here, we present rigid–soft hybrid knitted origami structures that combine stiffness-tunable spacer panels with soft folding lines of predefined curling direction, all fabricated in a single knitting process. This design addresses a key limitation of conventional knitted foldable structures, in which the high compliance of loop-based fabrics allows deformation to spread beyond the intended crease regions. The panels are reinforced with spacer fabrics to suppress unintended bending, and their bending stiffness can be tuned through knitting parameters. The soft folding lines, by contrast, curl intrinsically toward either a mountain or a valley fold, with the curling direction programmed by switching stitch formation between the front and back needle beds. Using these two mechanisms, we develop seven fundamental foldable units as modular building blocks for more complex origami structures and demonstrate them in three prototypes: a vacuum-driven folding actuator, a Kresling-inspired adjustable lampshade, and a Miura-inspired foldable structure. The Miura structure deploys to 60 × 40 × 0.5 cm and folds to 38 × 20 × 5 cm, showing compact shape transformation and preliminary qualitative stability under static loading. This strategy provides a scalable route to programmable foldable knitted fabrics for adaptive structures, soft robotics, and functional architecture.

Cardiovascular stents are often produced using a technique called maypole braiding. Maypole braiding is a highly productive manufacturing method in comparison to laser cutting but not versatile as laser cutting. Due to design and machine-specific limitations, these braiding machines are not suitable for versatile stent production and patient specific requirements, insofar a new flexible 3D rotatory tunnel braiding machine is developed. The novel machine is therefore including new operation principles to control carrier transfers, as well as an electronic fibre tension control system. Different aspects of the machine development such as structure possibilities, constructive requirements and consequences were observed. Various algorithms have been developed to enable collision-free carrier tracks during the automated set-up of the machine and in production. Furthermore, a variety of other structure formation options can be realised, such as flat braiding with identical horn gears rotating at different speeds. Utilising the new machine manufactures are enabled to produce versatile and patient specific cardio vascular implants in a highly productive way.

The increasing need for effective recycling strategies for carbon fiber reinforced composites has become essential to minimize waste volumes and sustainably enhance raw material efficiency. Spinning yarns from discontinuous recycled carbon fibers (rCF) has shown significant potential for use in thermoplastic and thermoset composite applications. However, despite their high deformability resulting from fiber-fiber slippage mechanisms, there is a lack of investigation into the deformability of fabrics made from rCF spun yarns. The current study, thus, addresses this gap by examining the fabric forming behavior through a combination of experimental forming tests and meso‑scale modeling. The developed model incorporates the elastic-plastic behavior of the yarns and captures their stochastic mechanical properties introduced by the manufacturing process. Parameter studies on blank holder force and stochastic material properties were conducted in forming simulations to identify critical areas within the textile structure with a higher probability of damage initiation. The probabilistic approach adopted in this study provides insights into the localized behavior of the material under forming conditions, enabling a more accurate prediction of failure-prone regions. These findings contribute to advancing the understanding of rCF-based textile structures and their application in composite manufacturing processes.

The presented research provides an investigation into the interface between shape memory alloys (SMA) and epoxy resin based matrix system representative as used in adaptive composite structures. The wire, made of a Nickel-Titanium alloy, is treated with mechanical, chemical and physical methods with the goal to adjust the adhesion between actuator and matrix. Two different experimental plans are designed. One aims at increasing the adhesion for a better force transmission. The second one investigates methods to lower the interfacial shear strength to reduce movement resistance while the SMA contracts. The different treatments are not only tested individually, but also in combination to determine possible synergies. The quality of the interface is tested using pull-out tests, where a single wire is pulled-out of a pure epoxy resin block. The results are then compared in terms of the maximum pull-out force. It shows that the adhesion can be increased through the use of mechanical sanding, plasma treatments and application of a bonding agent. The maximum effect results in an increase of 130% in pull-out force from a combination of sanding and bonding agent. On the opposite, the processes for the adhesion reduction show less effective. Only the usage of a release agent with or without a previous plasma treatment resulted in a slight decrease in interfacial shear strength. The interfacial shear strength appears already low for the origin state of the SMA. In the result, the present research provides successful routines to increase the adhesion for epoxy-based composites with integrated SMA wire actuators but does not recommend any procedures for the reduction of adhesion as the investigated approaches only showed marginal effects.