Today, numerous carbon fiber (CF) reinforced plastic (CFRP) components are in continuous usage under harsh environmental conditions. New components often replace damaged structural parts in safety-critical applications. In addition to this, there is also no effective repair method to initially restore the mechanics of these structures using dry fiber material. The high costs of CFRP components are not in proportion to their lifetime. The research project IGF-19946 BR “CFRP-Repair” addresses this specific challenge. By using an oxide semiconductor that is activated by ultraviolet (UV) irradiation, the thermoset matrix can be depolymerized and thus locally removed from the damaged CFRP component. Afterward, the harmed fibers can be physically removed from the laminate in this certain area. A load-adjusted tailored fiber reinforcement patch is subsequently applied and consolidated by local thermoset re-infiltrating. Using this procedure, the structure can be locally repaired with new CF. As a result, repaired CFRP structures can be obtained with reduced mechanics and an approximately original surface. This article gives an insight into the developed repair procedure of CFRP components in an innovative and more efficient way than the state-of-the-art.

The present study proposed a novel process for the matrix decomposition of carbon-fiber-reinforced plastics (CFRPs). For this purpose, the influence of ultraviolet (UV) radiation paired with semiconductors on CFRP was analyzed. Then, suitable process parameters for superficial and in-depth matrix decomposition in CFRP were evaluated. The epoxy resin was decomposed most effectively without damaging the embedded carbon fiber by using a UV light-emitting diode (LED) spotlight (395 nm, Semray 4103 by Heraeus Noblelight) at a power level of 66% compared to the maximum power of the spotlight. Using a distance of 10 mm and a treatment duration of only 35–40 s achieved a depth of two layers with an area of 750 mm², which is suitable for technological CFRP repair procedures. In addition to the characterization of the process, the treated CFRP samples were analyzed based on several analytical methods, namely, light microscopy (LM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Subsequently, the prepared carbon fibers (CFs) were tested using filament tensiometry, single filament tensile tests, and thermogravimetric measurements. All analyses showed the power level of 66% to be superior to the use of 96% power. The gentle (“fiber friendly”) matrix destruction reduced the damage to the surface of the fibers and maintained their properties, such as maximum elongation and maximum tensile strength, at the level of the reference materials.

The Cluster of Excellence ‘Centre for Tactile Internet with Human-in-the-Loop (CeTI)’¹ addresses developments and inventions for the use in or as smart devices in many areas, such as Industry 4.0, medicine and skill learning. The application of sensor units in smart textiles is widespread and used in various industry branches. Besides sensors, the development of textile actuating units is a relevant research topic. This paper discusses a theoretical actuator concept that leads to a ready-to-implement fiber-based electrostatic brake concept (passive actuator). Generally, the set-up is similar to a capacitor. Two different variants are presented according to the design of the dielectric and outer electrode layer. The dielectric material, its thickness, manufacturing process, future properties and implementation possibilities of the concepts are considered. Finally, a proof of concept with first results is presented.

Hybrid yarns, combining stainless steel with glass fibers, are promising for impact-resistant composites. Inside the yarn, the thermoplastics matrix is provided in the form of endless filaments. Thermoplastics gained popularity as composites' matrix due to recyclability. The study emphasizes customizing adhesion between stainless steel and polypropylene for desired properties in the composites. Tailored adhesion is crucial for optimizing the performance of stainless steel/polypropylene composites. Within this contribution, a selection of adhesion promoters and preventers is analyzed to generate adjustable adhesion between polypropylene matrix and stainless steel filaments. The characterization is fulfilled using contact angle measurements on films of coating agents and coated stainless steel filaments. Furthermore, surface free energy is calculated and theoretical adhesion is analyzed between coating agent and stainless steel filaments and coated stainless steel filaments and polypropylene matrix. The results are validated by single fiber pullout tests.