TY - JOUR A1 - Shirshova, N. A1 - Bismarck, A. A1 - Greenhalgh, E.S. A1 - Johansson, P. A1 - Kalinka, Gerhard A1 - Marczewski, M.J. A1 - Shaffer, M.S.P. A1 - Wienrich, Malte T1 - Composition as a means to control morphology and properties of epoxy based dual-phase structural electrolytes N2 - Structural electrolytes were prepared using a fully formulated commercially available high performance epoxy resin (MTM57) and an ionic liquid based electrolyte: lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) dissolved in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI). Through a systematic study, the composition of the formulations was found to have a greater effect than the curing temperature on the morphology and properties of the resulting structural electrolytes. The presence of lithium salt is essential to form a structurally homogeneous electrolyte. Bicontinuous morphologies containing continuous (coarse) epoxy networks surrounded by connected spherical epoxy nodules were obtained with different length scales upon varying the lithium salt concentration. Increasing the LiTFSI concentration improved the miscibility of MTM57 with the electrolyte and decreased the characteristic length scale of the resulting bicontinuous microstructure. The properties of the structural electrolytes correlated with the morphology, showing increased Young’s modulus and decreased ionic conductivity with increasing lithium salt concentration. The miscibility of the epoxy system with the electrolyte was also improved by substitution of EMIM-TFSI with an equal weight of an aprotic organic solvent, propylene carbonate (PC); however, the window of PC concentrations which resulted in structural electrolytes with bicontinuous microstructures was very narrow; at PC concentrations above 1 wt %, gel-like polymers with no permanent mesoporosity were obtained. KW - Functional composites KW - Mechanical properties KW - Elastic properties KW - Epoxy KW - Morphology KW - Electrolyte PY - 2014 DO - https://doi.org/10.1021/jp507952b SN - 1932-7447 SN - 1089-5639 VL - 118 IS - 49 SP - 28377 EP - 28387 PB - Soc. CY - Washington, DC AN - OPUS4-34565 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Radl, S. A1 - Kreimer, M. A1 - Manhart, J. A1 - Griesser, T. A1 - Moser, A. A1 - Pinter, G. A1 - Kalinka, Gerhard A1 - Kern, W. A1 - Schlögl, S. T1 - Photocleavable epoxy based materials N2 - The present study aims at the development of photodegradable epoxy based materials comprising o-nitrobenzyl ester links that undergo well defined bond cleavage in response to UV irradiation. New bi-functional epoxy based monomers bearing o-nitrobenzyl ester groups are synthesized and thermally cured with an anhydride hardener to yield photosensitive polymers and duromers. The UV induced changes in solubility are exploited for the preparation of positive-type photoresists. Thin patterned films are obtained by photolithographic processes and characterized by microscopic techniques. The results evidence that sensitive resist materials with good resolution and high contrast behavior can be accomplished. Along with resist technology, the applicability of o-nitrobenzyl chemistry in the design of recyclable polymer materials with thicknesses in the millimeter range is evaluated. By monitoring the thermo-mechanical properties upon UV illumination, a distinctive depletion of storage modulus and glass transition temperature is observed with increasing exposure dose. Additionally, single fiber pull-out tests are carried out revealing a significant decrease of the interfacial adhesion at the fiber-matrix interface due to the phototriggered cleavage reaction. KW - Epoxy based network KW - Photocleavage KW - o-Nitrobenzyl ester KW - Adhesion KW - Mechanical properties KW - Interfacial shear strength PY - 2015 DO - https://doi.org/10.1016/j.polymer.2015.05.055 SN - 0032-3861 SN - 1873-2291 VL - 69 SP - 159 EP - 168 PB - Elsevier Ltd. AN - OPUS4-34566 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Greenhalgh, E.S. A1 - Ankersen, J. A1 - Asp, L. E. A1 - Bismarck, A. A1 - Fontana, Q.P.V. A1 - Houlle, M. A1 - Kalinka, Gerhard A1 - Kucernak, A. A1 - Mistry, M. A1 - Nguyen, S. A1 - Qian, H. A1 - Shaffer, M.S.P. A1 - Shirshova, N. A1 - Steinke, J.H.G. A1 - Wienrich, Malte T1 - Mechanical, electrical and microstructural characterisation of multifunctional structural power composites N2 - Multifunctional composites which can fulfil more than one role within a system have attracted considerable interest. This work focusses on structural supercapacitors which simultaneously carry mechanical load whilst storing/delivering electrical energy. Critical mechanical properties (in-plane shear and in-plane compression performance) of two monofunctional and four multifunctional materials were characterised, which gave an insight into the relationships between these properties, the microstructures and fracture processes. The reinforcements included baseline T300 fabric, which was then either grafted or sized with carbon nanotubes, whilst the baseline matrix was MTM57, which was blended with ionic liquid and lithium salt (two concentrations) to imbue multifunctionality. The resulting composites exhibited a high degree of matrix heterogeneity, with the ionic liquid phase preferentially forming at the fibres, resulting in poor matrix-dominated properties. However, fibre-dominated properties were not depressed. Thus, it was demonstrated that these materials can now offer weight savings over conventional monofunctional systems when under modest loading. KW - Carbon fibres KW - Functional composites KW - Mechanical properties KW - Elastic properties KW - Fractography PY - 2014 DO - https://doi.org/10.1177/0021998314554125 SN - 0021-9983 SN - 1530-793X SP - 1 EP - 12 PB - Sage CY - London AN - OPUS4-34567 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Qian, Hui A1 - Bismarck, A. A1 - Greenhalgh, E.S. A1 - Kalinka, Gerhard A1 - Shaffer, M.S.P. T1 - Hierarchical composites reinforced with carbon nanotube grafted fibers: The potential assessed at the single fiber level N2 - The feasibility of reinforcing conventional carbon fiber composites by grafting carbon nanotubes (CNTs) onto the fiber surface has been investigated. Carbon nanotubes were grown on carbon fibers using the chemical vapor deposition (CVD) method. Iron was selected as the catalyst and predeposited using the incipient wetness technique before the growth reaction. The morphology of the products was characterized using scanning electron microscopy (SEM), which showed evidence of a uniform coating of CNTs on the fiber surface. Contact angle measurements on individual fibers, before and after the CNT growth, demonstrated a change in wettability that can be linked to a change of the polarity of the modified surface. Model composites based on CNT-grafted carbon fibers/epoxy were fabricated in order to examine apparent interfacial shear strength (IFSS). A dramatic improvement in IFSS over carbon fiber/epoxy composites was observed in the single fiber pull-out tests, but no significant change was shown in the push-out tests. The different IFSS results were provisionally attributed to a change of failure mechanism between the two types of tests, supported by fractographic analysis. KW - Composites KW - Nano tubes KW - Grafting KW - Interface PY - 2008 DO - https://doi.org/10.1021/cm702782j SN - 0897-4756 SN - 1520-5002 VL - 20 IS - 5 SP - 1862 EP - 1869 PB - American Chemical Society CY - Washington, DC AN - OPUS4-34568 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 - Blaker, J. J. A1 - Anthony, David B. A1 - Tang, G. A1 - Shamsuddin, S.-R. A1 - Kalinka, Gerhard A1 - Wienrich, Malte A1 - Abdolvand, Amin A1 - Shaffer, M. S. P. A1 - Bismarck, A. T1 - Property and shape modulation of carbon fibers using lasers N2 - An exciting challenge is to create unduloid-reinforcing fibers with tailored dimensions to produce synthetic composites with improved toughness and increased ductility. Continuous carbon fibers, the state-of-the-art reinforcement for structural composites, were modified via controlled laser irradiation to result in expanded outwardly tapered regions, as well as fibers with Q-tip (cotton-bud) end shapes. A pulsed laser treatment was used to introduce damage at the single carbon fiber level, creating expanded regions at predetermined points along the lengths of continuous carbon fibers, while maintaining much of their stiffness. The range of produced shapes was quantified and correlated to single fiber tensile properties. Mapped Raman spectroscopy was used to elucidate the local compositional and structural changes. Irradiation conditions were adjusted to create a swollen weakened region, such that fiber failure occurred in the laser treated Region producing two fiber ends with outwardly tapered ends. Loading the tapered fibers allows for viscoelastic energy dissipation during fiber pull-out by enhanced friction as the fibers plough through a matrix. In these tapered fibers, diameters were locally increased up to 53%, forming outward taper angles of up to 1.8°. The tensile strength and strain to failure of the modified fibers were significantly reduced, by 75% and 55%, respectively, ensuring localization of the break in the expanded region; however, the fiber stiffness was only reduced by 17%. Using harsher irradiation conditions, carbon fibers were completely cut, resulting in cottonbud fiber end shapes. Single fiber pull-out tests performed using these fibers revealed a 6.75-fold increase in work of pull-out compared to pristine carbon fibers. Controlled laser irradiation is a route to modify the shape of continuous carbon fibers along their lengths, as well as to cut them into controlled lengths leaving tapered or cotton-bud shapes. KW - Composite KW - Irradiation KW - Pull-out tests KW - Pulsed laser treatment KW - Single carbon fibers PY - 2016 DO - https://doi.org/10.1021/acsami.6b05228 SN - 1944-8244 SN - 1944-8252 VL - 8 IS - 25 SP - 16351 EP - 16358 PB - ACS Publications CY - 1155 Sixteenth Street, NW, Washington, DC 20036, USA AN - OPUS4-37699 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - de Camp, N. V. A1 - Kalinka, Gerhard A1 - Bergeler, J. T1 - Light-cured polymer electrodes for non-invasive EEG recordings N2 - We invented the first non-metallic, self-adhesive and dry biosignalling electrode. The PEDOT polymer electrode changes its aggregate state and conductivity by a light curing procedure. The electrode can be applied as a gel underneath hair without shaving. With the aid of blue light, the electrode can be hardened within a few seconds at the desired location on the scalp. The cured polymer electrode is highly conductive and can be applied on a very small location. Unlike other EEG electrodes, our electrode does not lose conductivity upon drying. Furthermore, our electrode strongly bonds to Skin and does not require any additional adhesive. Short circuits due to an outflow of gel are prevented with this technique. Therefore, the PEDOT polymer electrode is extremely well suited for applications that, up to now, have been challenging, such as non-invasive EEG recordings from awake and freely moving animals, EEG recordings from preterm babies in the neonatal intensive care unit or long-term recordings in the case of sleep monitoring or epilepsy diagnostics. We addressed two technical questions in this work. First, is the EEG recorded with polymer electrodes comparable to a standard EEG? Second, is it possible to record full-band EEGs with our electrodes? KW - Light curing KW - Polymer KW - Electric conductivity PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-459803 UR - https://rdcu.be/7aPD DO - https://doi.org/10.1038/s41598-018-32304-6 SN - 2045-2322 VL - 8 IS - 14041 SP - 1 EP - 9 PB - Nature Publishing Group CY - London AN - OPUS4-45980 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhandarov, S. A1 - Mäder, E. A1 - Kalinka, Gerhard A1 - Scheffler, C. A1 - Poitzsch, C. A1 - Fliescher, S. T1 - Investigation of interfacial strength parameters in polymer matrix composites: Compatibility and reproducibility N2 - Effects of various geometrical and physical factors, as well as the method of data reduction (analysis of experimental forceedisplacement curves) on the values of local interfacial strength parameters (local IFSS, td, and critical energy release rate, Gic) determined by means of a single fiber pull-out test are discussed. Experimental results of our pull-out tests on several fiberepolymer matrix systems showed that td and Gic weakly depended on geometrical factors. However, the pull-out test appeared to be sensitive to the conditions of specimen formation and testing, such as changing the nature of the contacting surfaces (fiber sizing) and the fiber pull-out rate. Of several methods of td and Gic Determination from a forceedisplacement curve, the most reliable and reproducible one is the approach based on the values of the maximum force recorded in a pull-out test and the interfacial frictional force immediately after fiber debonding. KW - Interface KW - Interfacial shear strength KW - Pull-out composite materials KW - Polymer matrix composites KW - Critical energy release rate KW - Geometrical factors PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-460918 DO - https://doi.org/10.1016/j.aiepr.2018.06.002 SN - 2542-5048 VL - 1 IS - 1 SP - 82 EP - 92 PB - Elsevier CY - Amsterdam AN - OPUS4-46091 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kalinka, Gerhard A1 - Sahin, M. A1 - Schlögl, S. A1 - Wang, J. A1 - Kaynak, B. A1 - Mühlbacher, I. A1 - Ziegler, W. A1 - Kern, W. A1 - Grützmacher, H. T1 - Tailoring the interfaces in glass fiber-reinforced photopolymer composites N2 - The present work provides a comparative study on the interface and adhesion properties of surface modified single glass fibers embedded in an acrylate matrix. To facilitate a covalent bonding at the fibermatrix interface, the fibers are functionalized with selected organosilanes that comprise either passive (unsaturated C¼C bonds of methacrylate moieties) or photoactive functionalities (photocleavable bis(acyl)phosphane oxide groups). Immobilization of the functional silanes is carried out by a classic silanization reaction involving a condensation reaction across the surface hydroxyl groups of the inorganic glass fibers. The change of the physico-chemical properties of the fibers due to desizing and subsequent surface modification is monitored by X-ray photoelectron spectroscopy and zeta potential measurements. In addition, scanning electron microscopy is used to follow the changes in surface morphology. After the modification step, the desized and modified single fibers are embedded in a photocurable acrylate resin formulation. By performing single fiber pull-out tests, maximum pull-out force, friction strength and apparent interfacial shear strength are determined as a function of the coupled silanes. The results reveal that the attached organosilanes lead to a significant increase in adhesion strength, whilst the performance of the photo-cleavable organosilane is superior to the passive methacryl-functional derivative. KW - Photocleavable organosilanes KW - Fiber-matrix interface KW - Photopolymer composites KW - Single fiber pull-out test KW - Surface modification PY - 2018 DO - https://doi.org/10.1016/j.polymer.2018.03.020 SN - 0032-3861 VL - 141 SP - 221 EP - 231 PB - Elsevier Ltd. CY - New York AN - OPUS4-44784 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kaiser, T. M. A1 - Braune, C. A1 - Kalinka, Gerhard A1 - Schulz-Kornas, E. T1 - Nano-indentation of native phytoliths and dental tissues: implications for herbivore-plant combat and dental wear proxies N2 - Tooth wear induced by abrasive particles is a key process affecting dental function and life expectancy in mammals. Abrasive particles may be plant endogenous opal phytoliths, exogene wind-blown quartz dust or rain borne mineral particles ingested by mammals. Nano-indentation hardness of abrasive particles and dental tissues is a significant yet not fully established parameter of this tribological system. We provide consistent nano-indentation hardness data for some of the major antagonists in the dental tribosystem (tooth enamel, tooth dentine and opaline phytoliths from silica controlled cultivation). All indentation data were gathered from native tissues under stable and controlled conditions and thus maximize comparability to natural systems. Here we show that native (hydrated) wild boar enamel exceeds any hardness measures known for dry herbivore tooth enamel by at least 3 GPa. The native tooth enamel is not necessarily softer then environmental quartz grit, although there is little overlap. The native hardness of the tooth enamel exceeds that of any silica phytolith hardness recently published. Further, we find that native reed phytoliths equal native suine dentine in hardness, but does not exceed native suine enamel. We also find that native suine enamel is significantly harder than dry enamel and dry phytoliths are harder than native phytoliths. Our data challenge the claim that the culprit of tooth wear may be the food we chew, but suggest instead that wear may relates more to exogenous than endogenous abrasives. KW - Phytolith KW - Indentation hardness KW - Enamel KW - Dentine KW - Tooth wear PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-451417 UR - http://zoobank.org/5C7DBB2B-B27D-4CE6-9656-33C4A0DA0F39 DO - https://doi.org/10.3897/evolsyst.2.22678 VL - 2 SP - 55 EP - 63 PB - PENSOFT CY - USA AN - OPUS4-45141 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, Luman A1 - de Greef, Nils A1 - Kalinka, Gerhard A1 - Van Bilzen, Bart A1 - Locquet, Jean-Pierre A1 - Verpoest, Ignaas A1 - Won Seo, Jin T1 - Carbon nanotube-grafted carbon fiber polymer composites: Damage characterization on the micro scale N2 - Multiwall carbon nanotubes (CNTs) e carbon fibers (CFs)hybrid materials were produced by directly growing CNTs on CFs by means of chemical vapor deposition. For the latter, the oxidative dehydrogenation reaction of C2H2 and CO2 was applied, which allows growing CNTs without damaging the CF surface. Uni-directional nano-engineered carbon fiber reinforced composites (nFRCs) were fabricated by impregnating these hybrid materials with epoxy. The nFRCs subjected to single fiber push-out tests revealed a decrease of the interfacial shear strength (IFSS) of about 36% compared to the carbon fiber composites without CNTs. By means of transverse three-point bending tests performed on pre-notched composite beams inside a scanning electron microscope, the fracturing behavior parallel to the fibers was studied in-situ. The nFRCs showed significantly reduced fiber/matrix debonding while CNTs pull-out, CNTs bridging as well as matrix failure occurred. These results demonstrate that the presence of CNTs in nFRCs affects the stress distribution and consequently the damage Initiation as well as the damage propagation. The presence of CNTs suppresses the stress concentration at the fiber/Matrix interface and reduces the debonding of CFs from the matrix. However, our results indicate that the stress concentration shifts towards the CNTs' ends/matrix interface and causes promoted matrix failure leading to lower IFSS. KW - Carbon fibres nanotubes interface PY - 2017 DO - https://doi.org/10.1016/j.compositesb.2017.06.004 SN - 1359-8368 SN - 1879-1069 VL - 126 SP - 202 EP - 210 PB - Elsevier CY - Niederlande AN - OPUS4-42202 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 - CONF A1 - Kalinka, Gerhard T1 - Einzelfaserausdrück und -durchdrückversuche T2 - Wissenschaftskolloquium "Nanotechnologie für Kunststoffverbunde", Haus der Wissenschaft, Veranstalter: Virtuelles Institut Nanotechnologie in Polymer Composites CY - Braunschweig, Deutschland DA - 2014-09-30 PY - 2014 AN - OPUS4-32040 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -