TY - JOUR A1 - Gebhardt, M. A1 - Malolakis, I. A1 - Kalinka, Gerhard A1 - Deubener, J. A1 - Chakraborty, S. A1 - Meiners, D. T1 - Re-use potential of carbon fibre fabric recovered from infusible thermoplastic CFRPs in 2nd generation thermosetting-matrix composites N2 - The research presented here attempts to assess the potential for re-using carbon fibre (CF) fabrics recovered from recycling infusible acrylic thermoplastic carbon fibre reinforced polymer composites (CFRPs) in a universal manner, i.e. by combining with a wide variety of matrices to manufacture 2nd generation composite laminates by resin infusion. The 2nd generation composites have been compared in terms of bulk and interfacial properties against counteparts processed with virgin carbon fibre fabric infused with the same matrices. Generally, an increase in damping (tanδ) was observed in all 2nd generation composites, which can be attributed to a residual thin thermoplastic layer present on the recovered fibres. The interfacial adhesion of the 2nd generation Composites was investigated by shear tests and scanning electron micsoscopy, and also appears to be less influenced by the type of matrix. KW - Composite recycling KW - Thermoplastic matrix KW - Thermosetting resin KW - Fibre/matrix bonding PY - 2021 DO - https://doi.org/10.1016/j.coco.2021.100974 VL - 28 SP - 100974 PB - Elsevier Ltd. CY - Niederlande AN - OPUS4-53639 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kalinka, Gerhard T1 - Optische Beobachtungen der Faser-Matrix-Trennung im Pull-out-Versuch N2 - Der Vortrag behandelt Rissentstehung und Ausbreitung an Faser-Matrix-Interfaces, untersucht mit dem optischen Mikroskop. T2 - Composites United, CU-Arbeitsgruppe/n Faser-Matrix-Haftung & Matrices CY - Online meeting DA - 02.12.2021 KW - Faser KW - Matrix KW - Pull-out KW - Interface PY - 2021 AN - OPUS4-53968 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Plichta, T. A1 - Sirjovona, V. A1 - Zvonek, M. A1 - Kalinka, Gerhard A1 - Cech, V. T1 - The Adhesion of Plasma Nanocoatings Controls the Shear Properties of GF/Polyester Composite N2 - High-performance fibre-reinforced polymer composites are important construction materials based not only on the specific properties of the reinforcing fibres and the flexible polymer Matrix but also on the compatible properties of the composite interphase. First, oxygen-free (a-CSi:H) and oxygen-binding (a-CSiO:H) plasma nanocoatings of different mechanical and tribological properties were deposited on planar silicon dioxide substrates that closely mimic E-glass. The nanoscratch test was used to characterize the nanocoating adhesion expressed in terms of critical normal load and work of adhesion. Next, the same nanocoatings were deposited on E-glass fibres, which were used as reinforcements in the polyester composite to affect its interphase properties. The shear properties of the polymer composite were characterized by macro- and micromechanical tests, namely a short beam shear test to determine the short-beam strength and a single fibre push-out test to determine the interfacial shear strength. The results of the polymer composites showed a strong correlation between the short-beam strength and the interfacial shear strength, proving that both tests are sensitive to changes in fibre-matrix adhesion due to different surface modifications of glass fibres (GF). Finally, a strong correlation between the shear properties of the GF/polyester composite and the adhesion of the plasma nanocoating expressed through the work of adhesion was demonstrated. Thus, increasing the work of adhesion of plasma nanocoatings from 0.8 to 1.5 mJ·m−2 increased the short-beam strength from 23.1 to 45.2 MPa. The results confirmed that the work of adhesion is a more suitable parameter in characterising the level of nanocoating adhesion in comparison with the critical normal load. KW - Mechanical properties KW - Plasma nanocoatings KW - Glass fibre KW - Polymer composite KW - Short-beam strength KW - Interfacial shear strength KW - Work of adhesion PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-521844 DO - https://doi.org/10.3390/polym13040593 VL - 13 IS - 4 SP - 593 PB - MDPI CY - Basel,Schweiz AN - OPUS4-52184 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lamoriniere, S. A1 - Mitchell, P. J. A1 - Ho, K. A1 - Kalinka, Gerhard A1 - Shaffer, M. S. P. A1 - Bismarck, A. T1 - Carbon nanotube enhanced carbon Fibre-Poly(ether ether ketone) interfaces in model hierarchical composites N2 - Poly (ether ether ketone) (PEEK) has a high continuous service temperature, excellent mechanical properties, and good solvent and abrasion resistance, which can be further improved through the addition of carbon nanotubes (CNTs). CNT-PEEK nanocomposites are promising matrices for continuous carbon fibre composites; powder processing can mitigate the high melt viscosities in these systems. In this study, model single fibre (hierarchical) composites were produced by embedding sized and desized carbon fibres in nanocomposite CNTPEEK powders followed by single fibre pull-out tests to assess interfacial characteristics. Carbon fibre-PEEK interfacial shear strength is typically 40–45 MPa. Increasing CNT loadings increased fibre-matrix interfacial shear strength linearly up to ~70 MPa at 5.0 wt%, which was attributed to the CNT-based mechanical modification of the PEEK matrix. Apparent interfacial shear strength was inversely correlated with the embedded fibre length irrespective of carbon fibre sizing or CNT loading, indicating brittle fracture of the fibre-matrix interface. Pulled out carbon fibres were still coated with the matrix, which indicated strong adhesion at the interface in all samples, likely related to a transcrystalline region. Adhesion was, however, negatively affected by the presence of epoxy sizings. Frictional shear strength was independent of embedded fibre length and CNT content for all samples. KW - Keywords: Poly(ether ether ketone) KW - Carbon fibres KW - Carbon nanotubes KW - Interfacial strength KW - Debonding PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-550052 DO - https://doi.org/10.1016/j.compscitech.2022.109327 SN - 0266-3538 VL - 221 SP - 1 EP - 8 PB - Elsevier Ltd. CY - Niederlande AN - OPUS4-55005 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Trappe, Volker A1 - Kalinka, Gerhard A1 - Loose, Florian T1 - Carbon fibre composites exemplarily research at BAM N2 - Lightweighting as a cross-cutting technology contributes significantly to achieve the European Green Deal goals. Based on, but not limited to, advanced materials and production technologies, the demand for natural resources and CO2 emmissions are reduced by lightweighting during production, as well as use phase. Therefore, lightweighting is a crucial transformation technology assisting in decoupling economic growth from resource consumption. In this manner, lightweighting contributes significantly as a key technology of relevance for many industrial sectors such as energy, mobility, and infrastructure, towards resource efficiency, climate action and economic strength, as well as a resilient Europe. To strengthen international partnerships, addressing global issues of today at the edge of science with high performance lightweight material based on carbon fibers, an overview about the BAM expertise in carbon fiber reinforced materials is given. T2 - Meeting KCarbon CY - Berlin, Germany DA - 15.06.2023 KW - Lightweighting KW - Carbon Fibers KW - Recycling KW - Push-out Test KW - multi scale testing PY - 2023 AN - OPUS4-58094 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Taketa, I. A1 - Kalinka, Gerhard A1 - Gorbatikh, L. A1 - Lomov, S. A1 - Verpoest, I. T1 - Influence of cooling rate on the properties of carbon fiber unidirectional composites with polypropylene, polyamide 6, and polyphenylene sulfide matrices N2 - The longitudinal and transverse strength of three unidirectional thermoplastic prepreg systems: carbon fiber/polypropylene (CF/PP), polyamide 6 (CF/PA6), and polyphenylene sulfide (CF/PPS) are studied and analytical formulas are proposed for the estimation of matrix and fiber/matrix interface properties from composites properties. Since the matrices are semi-crystalline thermoplastics, the influence of cooling rate on the strength is statistically evaluated. While the 0° tensile strength is found to be independent of the cooling rate, the 90° tensile strength is strongly influenced by the matrix type and cooling rate. The matrix modulus increases as the cooling rate is decreased; the degree of crystallinity also increases. The matrix residual stress, interfacial shear strength, and mode II interlaminar fracture toughness are also found to depend on the cooling rate, with the trends different for different matrices. KW - Matrix residual stress KW - Thermoplastic prepreg KW - Unidirectional composites KW - Cooling rate KW - Interfacial strength PY - 2020 DO - https://doi.org/10.1080/09243046.2019.1651083 SN - 0924-3046 SN - 1568-5519 N1 - Die originale japanische Version des Artikels erschien in: Journal of the Japan Society for Composite Materials, Jg. 44, Nr. 4 (2018), S. 123-128. - The original Japanese version of the article was published in: Journal of the Japan Society for Composite Materials, vol. 44, no. 4 (2018), pp. 123-128. VL - 29 IS - 1 SP - 101 EP - 113 PB - Taylor & Francis CY - London AN - OPUS4-45433 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Valentini, Martino A1 - De Almeida, Olivier A1 - Kakkonen, Markus A1 - Kalinka, Gerhard A1 - Dorigato, Andrea A1 - Kallio, Pasi A1 - Fredi, Giulia T1 - Effect of fiber surface state on the thermomechanical and interfacial properties of in situ polymerized polyamide 6/basalt fiber composites N2 - This study investigates the thermomechanical properties and interfacial adhesion of novel in-situ polymerized anionic polyamide 6 (aPA6) composites reinforced with basalt fibers (BF). The impact of different BF surface states - as-received (BFa), ethanol-washed (BFw), and thermally desized (BFu) on composite performance is examined through a comprehensive approach. For the first time, anionic PA6/BF composites with very low residual monomer content were successfully produced via thermoplastic resin transfer molding (tRTM). The PA6/BFw composites exhibited the highest interlaminar/interfacial shear strength in short beam shear test (52 ±8 MPa) and fiber push out test (34 ± 11 MPa) tests. Fiber microdebonding test, performed only on PA6/BFw, yielded a low interfacial shear strength (12 ± 4 MPa), which was attributed to droplet porosity resulting from concurrent polymerization and crystallization. Thermal desizing significantly deteriorated interfacial strength (19.6 ± 1.2 MPa in short beam shear test). This multi-technique characterization provides insights into optimizing the fiber–matrix adhesion in these advanced thermoplastic composites. KW - Anionic Polyamide 6 KW - Reactive thermoplastics KW - Basalt fibers KW - Microdebonding KW - Fiber push out KW - Short beam shear test PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-623596 DO - https://doi.org/10.1016/j.compositesa.2024.108681 SN - 1878-5840 VL - 190 SP - 1 EP - 15 PB - Elsevier Ltd. CY - Niederlande AN - OPUS4-62359 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kalinka, Gerhard T1 - Testing the fibre matrix interface of short glass fibre reinforced PMCs with using the push out technique N2 - With this presentation, the push-out technique is explained. The focus of the experimental work is on the characterization of the fiber-matrix interface of short fiber reinforced composites. The reinforcing component was glass fibers and the matrix polymer was PA6.6 and PPA. It is demonstrated for the first time that the push-out technique ca be applied on injection molded short fiber PMC and is sensitive to the mechanical interface properties. Further studies are planned on the influence of multiple processing, the temperature and humidity. T2 - Composirtes United Workshop „Fiber Matrix Interphases“ CY - Online meeting DA - 09.11.2023 KW - Polymer Matrix Composite KW - Glass Fibres KW - PA6.6 KW - PPA KW - Push-out Test KW - Interface Strength PY - 2023 AN - OPUS4-59053 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krauklis, A. E. A1 - Starovka, O. A1 - Gibhardt, D. A1 - Aouissi, H. A. A1 - Burlakovs, J. A1 - Sabalina, A. A1 - Fiedler, Bodo A1 - Kalinka, Gerhard T1 - Reversible and irreversible effects on the epoxy GFRP fiber-matrix interphase due to hydrothermal aging N2 - Epoxy R-Glass Fiber-Reinforced Polymer (GFRP) composite plates were hydrothermally aged at 60 ◦C for 23, 75, and 133 days. The water content reached 0.97 wt%, 1.45 wt% and 1.63 wt%, respectively. The studied GFRP matrix was inert to hydrolysis or chain scission, allowing for investigation of irreversible changes in the fiber-matrix interphase due to hydrothermal aging upon re-drying. During each period, a subset of the specimens was removed from the water bath and dried in a chamber. The weight loss upon drying was explained with epoxy leaching (impurities), sizing-rich interphase hydrolysis, glass fiber surface hydrolysis, accumulated degradation products escaping, and water changing state from bound to free. The influence of hydrothermal aging on the fiber-matrix interfacial properties was investigated. Lower interfacial strength of hydrothermally aged (wet) samples was attributed to plasticization of the epoxy, plasticization and degradation of the sizing-rich interphase (including formation of hydrolytic flaws), and hydrolytic degradation of the glass fiber surface. The kinetics of epoxy-compatible epoxysilane W2020 sizing-rich interphase hydrolysis provided an estimate of ca. 1.49%, 4.80%, and 8.49% of the total composite interphase degraded after 23, 75, and 133 days, respectively. At these conditions, the interface lost 39%, 48%, and 51% of its strength. Upon re-drying the specimens, a significant part of the interfacial strength was regained. Furthermore, an upward trend was observed, being 13%, 10% and 3% strength, respectively; thus, indicating a possibility of partial recovery of properties. KW - GFRP KW - Hydrothermal Ageging KW - Interphase KW - Water Diffusion KW - Desorption KW - Interfacial Strength PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-581554 DO - https://doi.org/10.1016/j.jcomc.2023.100395 SN - 2666-6820 VL - 12 SP - 1 EP - 9 PB - Elsevier B.V. CY - Amsterdam, Niederlande AN - OPUS4-58155 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lüders, C. A1 - Kalinka, Gerhard A1 - Li, Wei A1 - Sinapius, M. A1 - Wille, T. T1 - Experimental and numerical multiscale approach to thermally cycled FRP N2 - Due to the different thermal expansion of the constituent materials, cyclic thermal loading of FRP induces alternating stresses in the material at two scales: at the micro scale (level of fibre–matrix-interaction) and at the macro scale (level of the multidirectional laminate). Especially the micro scale effect is not comprehensively investigated yet. Additionally, computational investigations mostly neglect this effect due to the homogenous modelling of the composite material. As this effect is assumed to significantly contribute to the fatigue of FRP at thermal loads, the present paper suggests an experimental and numerical multiscale approach including Experiments at the different involved material scales to separately observe the effects acting at these scales. The approach also includes numerical modelling for each scale to complement the knowledge gained from the Experiments and to create a basis for the consideration of the micro effect even in macroscopic fatigue models treating homogeneous modelled composites. The main focus of the contribution is to bring the overall Approach up for discussion, rather than to present the multiscale modelling details. KW - Fatigue KW - Thermal cycling KW - Fibre reinforced plastic KW - Cryogenic KW - Carbon Fibre KW - Epoxy Resin PY - 2020 DO - https://doi.org/10.1016/j.compstruct.2020.112303 SN - 0263-8223 VL - 244 SP - 112303 PB - Elsevier Ltd. CY - Niederlande AN - OPUS4-50844 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gebhardt, M. A1 - Manolakis, I. A1 - Chatterjee, A. A1 - Kalinka, Gerhard A1 - Deubener, J. A1 - Pfnür, H. A1 - Chakraborty, S. A1 - Meiners, D. T1 - Reducing the raw material usage for room temperature infusible and polymerisable thermoplastic CFRPs through reuse of recycled waste matrix material N2 - In this work, a closed loop recycling process is investigated, which allows polymerised bulk thermoplastic matrix (Elium 150) from production waste (also referred to as recyclate) to be reused as additive in composite manufacturing by vacuum assisted resin infusion (VARI) of virgin Elium 150 monomer. It is shown that this process can save up to 7.5 wt% of virgin material usage in each processing cycle. At the same time, the thermal stability and stiffness of the composite increases with the proportion of recyclate introduced. Contemporarily, the shear and bending properties have also been observed to improve. Gel permeation chromatography (GPC) showed that the changes observed are due to an increase in molecular weight with the recyclate content. In particular, a correlation between the molecular weight and the shear properties of the composite was discovered using single fibre push-out tests. KW - Mechanical properties KW - Recycling KW - Carbon fibres KW - Fibre/matrix bond PY - 2021 DO - https://doi.org/10.1016/j.compositesb.2021.108877 SN - 1359-8368 VL - 216 SP - 108877 PB - Elsevier Ltd. CY - Niederlande AN - OPUS4-52711 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Guerra, E. S. S. A1 - Silva, B. L. A1 - Melo, J. D. D. A1 - Kalinka, Gerhard A1 - Barbosa, A. P. C. T1 - Microscale evaluation of epoxy matrix composites containing thermoplastic healing agent N2 - Among the strategies to produce healable thermosetting systems is their modification by the addition of thermoplastic particles. This work investigates the influence of poly(ethylene-co-methacrylic acid) (EMAA) on fibermatrix interfacial properties of a glass fiber reinforced epoxy matrix composite. Epoxy-EMAA interactions were evaluated using differential scanning calorimetry (DSC) and infrared spectroscopy. The effects of EMAA on the epoxy network formation were evidenced by changes in glass transition temperature, cure kinetics and alteration of chemical groups during cure. Interfacial shear strength (IFSS) measurements obtained by single fiber pull-out tests indicate similar interfacial properties for pure and EMAA modified epoxy. Additionally, the potential for self-healing ability of an EMAA modified epoxy was demonstrated. However, IFSS after a healing cycle for the EMAA modified epoxy was lower as compared to the pure epoxy, because of the lower fiber-EMAA interfacial shear strength. So, thermoplastic healing agents has not only to fill cracks in the matrix material, but also have to be optimized regarding its interface properties to the reinforcing fibers. KW - Interfacial strength KW - Fiber/matrix bond KW - Self-healing KW - Polymer-matrix composites (PMC) PY - 2022 DO - https://doi.org/10.1016/j.compscitech.2022.109843 SN - 0266-3538 VL - 232 SP - 1 EP - 9 PB - Elsevier Ltd. CY - Niederlande AN - OPUS4-56379 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schraa, Lucas A1 - Rodricks, Carol A1 - Kalinka, Gerhard A1 - Roetsch, Karl A1 - Scheffler, Christina A1 - Sambale, Anna A1 - Uhlig, Kai A1 - Stommel, Markus A1 - Trappe, Volker T1 - Characterisation and Modelling of the Fibre-Matrix Interface of Short Fibre Reinforced Thermoplastics using the Push-Out Technique N2 - This study investigates the suitability of the single fibre push-out (SFPO) test for the determination of the interfacial shear strength (IFSS) of injection moulded short fibre reinforced thermoplastics. It includes a detailed description of the required sample preparation steps and the boundary conditions of the SFPO setup. Experimental SFPO tests were carried out on PA66 GF, PPA GF35 and PA6 GF50 materials. Furthermore, a finite element model was set up to simulate the behaviour of these materials during this test. The numerical results showed that the inhomogeneous stress distribution in the fibre-matrix interphase during the test causes the measured apparent IFSS to underestimate the true strength of the interphase. The simulations put the experimental results into perspective and provide valuable information for the further development of the test setup. This study therefore not only provides new insights into the interphase strength of injection moulded short fibre reinforced thermoplastics, but also an insight into local load conditions during testing and thus an indication of the true IFSS. KW - GFRP KW - Interface KW - fibre matrix bond KW - single fibre push-out PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-626087 DO - https://doi.org/10.1016/j.compositesb.2025.112317 SN - 1879-1069 VL - 297 SP - 1 EP - 8 PB - Elsevier Ltd. CY - Niederlande AN - OPUS4-62608 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kalinka, Gerhard T1 - Moderne Faserverbundwerkstoffe – Reparatur und Recycling N2 - Der Vortrag beschreibt Aktivitäten der BAM zur Reparatur von Rotorblättern von Windkraftanlagen sowie ein Konzept zum Recycling by Design für faserverstärkte Kunststoffe T2 - Reparaturgerechtes Produktdesign CY - Potsdam, Germany DA - 06.11.2024 KW - GFRP KW - Rotorblätter KW - Reparatur KW - Recycling KW - Composites PY - 2024 AN - OPUS4-61533 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kalinka, Gerhard T1 - Recycling von Faserverbundwerkstoffen N2 - Der Vortrag beschreibt Aktivitäten der BAM zum Recycling von carbonfaser-verstärkten Verbundwerkstoffen. T2 - Fachdialog Recycling von Windenergieanlagen CY - Berlin, Germany DA - 23.09.2024 KW - Polymer Matrix Composite KW - Carbon Fibres KW - Recycling KW - Pyrolysis KW - Recycling by Design PY - 2024 AN - OPUS4-61536 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Colombo, Marta A1 - Mostoni, Silvia A1 - Fredi, Giulia A1 - Rodricks, Carol A1 - Kalinka, Gerhard A1 - Riva, Massimiliano A1 - Vassallo, Andrea A1 - Di Credico, Barbara A1 - Scotti, Roberto A1 - Zappalorto, Michele A1 - D'Arienzo, Massimiliano T1 - Interfacial Chemistry Behind Damage Monitoring in Glass Fiber‐Reinforced Composites: Attempts and Perspectives N2 - Glass Fiber Reinforced Polymers (GFRPs) are widely used in structural applications but degrade over time due to internal damage. Structural Health Monitoring (SHM) enables early damage detection, improving reliability and reducing maintenance costs. Traditional SHM methods are often invasive and expensive. An emerging solution involves the embedding of carbon‐based filler like carbon nanotubes and reduced graphene oxide into GFRPs, forming conductive networks that detect damage through resistance changes. However, poor adhesion among GF, filler, and matrix can reduce mechanical performance. Therefore, tailoring GF and filler surface chemistry is essential to enhance durability and enable effective self‐sensing properties. This review summarizes the most recent efforts in modifying GF with carbon‐based filler to design GFRP with improved sensing ability and mechanical performance. After a brief introduction on the role of SHM solutions in early damage detection, an overview of the common GF and filler used in GFRPs will be provided. Then, the most relevant GF modification strategies exploited to incorporate carbon‐based filler in GFRPs will be described, focusing on the chemical grafting approach, which allows a careful optimization of the fiber/matrix interface. Last, a concise summary of the key mechanical and electrical tests to evaluate interfacial adhesion and self‐sensing will be supplied. KW - Review KW - Interface KW - Micromechanics KW - Polymer matrix composites KW - Glass fibre reinforced composites PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-639934 DO - https://doi.org/10.1002/pc.70332 SN - 0272-8397 SP - 1 EP - 30 PB - Wiley AN - OPUS4-63993 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rabe, T. A1 - Kalinka, Gerhard A1 - Mieller, Björn T1 - Manufacturing and deformation behavior of alumina and zirconia helical springs at room temperature N2 - Ceramic helical springs with identical dimensions were produced by hard machining from alumina, alumina toughened zirconia (ATZ), and tetragonal zirconia polycrystals (TZP) stabilized with different oxides. According to the results of the spring constant determination under deformation rates of 3 mm/min, the deformation behavior of all ceramic springs obeys to Hook’s law. However, variation of the deformation rate, tests under constant load, and spring recovery behavior revealed differences in the deformation behavior of alumina, TZP, and ATZ springs. Alumina springs exhibited time-independent deformation in all tests. In contrast, anelastic deformation at room temperature was demonstrated in all springs containing TZP. This deformation is completely reversible over a period of several days. Anelastic behavior is particularly pronounced in Y-TZP springs, whereas Ce-TZP springs exhibit comparatively very low but still reliably detectable anelasticity. Oxygen vacancies in the TZP ceramic are considered the most likely explanation for the anelastic behavior of TZP springs at room temperature. KW - Alumina KW - Creep KW - Elastic properties KW - Zirconia PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-571858 DO - https://doi.org/10.1111/jace.19085 SN - 0002-7820 SP - 1 EP - 14 PB - Wiley-Blackwell CY - Oxford [u.a.] AN - OPUS4-57185 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rodricks, Carol Winnifred A1 - Prockat, Annabell A1 - Kalinka, Gerhard A1 - Trappe, Volker T1 - Novel Recyclable Hierarchical Carbon Fiber/Epoxy Composites: Preserving Fiber Length and Orientation Using Elium N2 - Current recycling methods for polymer matrix composites produce short, unoriented carbon fibers, limiting their use to intermediate‐strength applications. A method is therefore needed to recycle fibers while preserving their original length and orientation, enabling a circular economy for carbon fiber composites. This study proposes a novel hierarchical composite designed to retain fiber length and orientation during recycling. Virgin carbon fibers are encased in an insoluble epoxy matrix to form tapes that act as the primary units of the structure. The primary tape matrix shields the fibers from chemical degradation while preserving their alignment throughout recycling. The tapes are then embedded in a secondary recyclable matrix, Elium, a thermoplastic polymer soluble in acetone with mechanical properties comparable to epoxy. The composite is recycled by dissolving the secondary Elium matrix in acetone and recovering the primary tape units with intact fiber length and orientation. The primary units can then be used to assemble new composites. In this study, hierarchical composite laminates underwent recycling up to three times. Their mechanical properties were assessed after each cycle. Laminates with an Elium secondary matrix retained 60%–90% of the mechanical performance of epoxy‐based laminates. Minimal degradation was observed between cycles, and fiber length, orientation, and volume fraction were fully preserved. Pushout tests confirmed that fibers in the primary tapes were sufficiently shielded during the recycling process. These results validate the feasibility of a hierarchical recyclable composite that combines recyclability with high mechanical performance, serving as a proof of concept and providing opportunities for future development. KW - Review KW - Interface KW - Micromechanics KW - Polymer matrix composites KW - Glass fibre reinforced composites PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655276 DO - https://doi.org/10.1002/pc.70869 SN - 0272-8397 SP - 1 EP - 16 PB - Wiley Periodicals LLC. AN - OPUS4-65527 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -