TY - JOUR A1 - Wagner, Jan A1 - Häfner, P. A1 - Reimann, H.-A. A1 - Schartel, Bernhard T1 - Valorization of Natural Fibers in Flame Retarded Poly(lactic acid) N2 - Extensive research has explored natural fiber reinforced composites, typically focusing on a single fiber within a polymer matrix. Comprehensive comparisons across different natural fibers in the same polymer, which are critical for industrial material selection, remain limited. This work presents a systematic comparison of untreated hemp, flax, and sisal fibers incorporated at varying fiber lengths and loadings into flame retarded poly(lactic acid) (PLA). Fire behavior, thermal, and mechanical responses were investigated through thermogravimetry, UL 94, and cone calorimetry, alongside crystallinity, molecular weight (MW), and microstructural analysis. Fiber incorporation reduced the peak heat release rate (pHRR) by up to 30 % in 30 wt% hemp, attributed to protective layer formation, but increased flammability in UL 94. A phytic acid melamine salt combined with expandable graphite and 20 wt% hemp produced incomplete combustion at 50 kW/m², raising char residue from 4 to 24 wt% and halving pHRR. Petrella plots revealed that fiber addition alone lowered fire load and flashover propensity as effectively as phytic acid melamine; with hemp, phytic acid and expendable graphite, the flashover hazard and fire load were halved. MW was preserved while crystallinity and modulus increased with fiber content. Hemp delivered the most consistent reinforcement, while optimized processing enabled flax and sisal to improve stiffness. Performance gains were strongest when individual fibers were dispersed via optimized processing, preventing bundle fracture under load. Plasma modification of the fibers improved the maximum tensile strength in the composites. A practical guide is provided for valorizing natural fibers in PLA composites, demonstrating routes to bio-based, compostable materials with improved fire safety and mechanical performance suitable for industrial processing. KW - Poly(lactic acid) KW - Hemp KW - Sisal KW - Flax KW - Flame retardant KW - Phytic acid PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-653038 DO - https://doi.org/10.1016/j.mtcomm.2025.114575 SN - 2352-4928 VL - 50 SP - 1 EP - 41 PB - Elsevier Ltd. AN - OPUS4-65303 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 - Rodricks, Carol T1 - Recyclable or One-Way Composites? Evaluating the Durability of Elium vs. Epoxy Glass Fibre Composites N2 - Fibre-reinforced polymers are widely used, particularly in lightweight construction, due to their high strength-to-weight ratio and versatility. The expansion of wind turbines calls for ever-lighter materials, and polymer matrix composites are well-positioned to meet this need, offering the necessary strength and long-term durability with reduced weight. However, conventional thermoset composites, such as epoxy-based systems, pose significant recycling challenges as they cannot be easily reprocessed or remoulded. A promising alternative is Elium, a novel thermoplastic resin that offers mechanical properties similar to thermoset polymers while providing the added benefit of chemical recyclability through solvolysis in acetone. This raises an important question: can a recyclable Elium composite match or even surpass the durability of a conventional epoxy composite, particularly in demanding structural applications? In our study, we compare the fatigue performance of Elium (191SA, 151-XO) glass fibre composites to conventional epoxy (RIMR 135, RIMH 137) glass fibre composites. Results indicate that Elium composites demonstrate superior fatigue resistance compared to their epoxy counterparts. The combination of enhanced fatigue durability and chemical recyclability highlights the potential of Elium composites as a sustainable alternative to conventional epoxy-based systems for long-term structural applications. T2 - Materials Week 2025 CY - Frankfurt am Main, Germany DA - 02.04.2025 KW - Polymer matrix composites KW - Recycling KW - Elium KW - Fatigue performance PY - 2025 AN - OPUS4-62936 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rodricks, Carol T1 - Advancing Sustainable Composites: Challenges and innovations N2 - With the increased use of carbon fibre polymer matrix composites comes the important question of their management at the end of their life cycle. Given the high costs associated with carbon fibre production, recycling carbon fibres from composite waste is a desirable source of reinforcing fibres for new applications. However, current recycling methods result in recycled carbon fibres that are short with little to no orientation which can only be used in applications requiring intermediate strength at a fraction of the potential of the continuous, aligned virgin fibres. Thus, a method to recycle fibres with their original length and orientation intact is vital to truly realising a circular economy for carbon fibre polymer composites. Our research introduces a novel hierarchical composite aimed at preserving the length and orientation of carbon fibres on recycling. Virgin carbon fibres are encapsulated in an insoluble epoxy matrix to form tapes that serve as the primary units of the hierarchical structure. The primary epoxy matrix protects the fibres from chemical and environmental elements while maintaining their permanent orientation. The primary tape units are subsequently embedded in a secondary recyclable matrix polymer to make larger composite structures. Elium, a thermoplastic that dissolves in acetone and has mechanical properties comparable to epoxy, was chosen as the secondary matrix of choice in this study. This approach aims to achieve a composite that is mechanical equivalent to thermoset composites while facilitating easy recycling with minimal impact on the fibres in the primary unit. T2 - Materials Week 2025 CY - Frankfurt am Main, Germany DA - 02.04.25 KW - Recycling KW - Carbon fibres KW - Mechanical testing KW - Polymer-matrix composites (PMCs), micromechanics KW - Elium PY - 2025 AN - OPUS4-63004 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 - 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 - Pavasarytė, Lina A1 - Azevedo do Nascimento, Allana A1 - Cysne Barbosa, Ana Paula A1 - Trappe, Volker A1 - Melo, Daniel T1 - Effects of particle size and particle concentration of poly (ethylene-co-methacrylic acid) on properties of epoxy resin N2 - Self-healing polymers have been developed to improve durability and reduce costs associated with maintenance during service. The addition of thermoplastics to thermosets to produce mendable polymers appears as a promising selfhealing technique. In this study, poly (ethylene-co-methacrylic acid) (EMAA) was added to epoxy resin and the effects of EMAA addition on epoxy properties were evaluated. Specimens with two different contents of thermoplastic and particles sizes were manufactured. A two-level full factorial experimental design was used to evaluate the effect of particle size and particle content on properties of epoxy modified with addition of EMAA. Tensile tests and dynamic mechanical analysis (DMA) were used and the evaluated responses were tensile strength, modulus of elasticity, and glass transition temperature (Tg). X-ray computed tomography (XCT) was used to investigate particle size and concentration after manufacturing. It was found that the particle concentration has greater effects on stress–strain behavior of epoxy while Tg was not significantly affected by neither of the analyzed entrance variables. KW - Fracture KW - Self-healing KW - Epoxy KW - Thermoplastic PY - 2024 DO - https://doi.org/10.1002/app.55677 SN - 0021-8995 SP - 1 EP - 14 PB - Wiley online library AN - OPUS4-60205 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 - CONF A1 - Trappe, Volker T1 - Advanced lightweight applications – recycling versus reliability and fossil energy footprint N2 - Advanced light weight applications like aircrafts and wind turbine blades are made of fibre reinforced plastics (FRP) with continuous fibre reinforcement and must withstand a high thermo-mechanical cyclic loading. The quality of the fibre matrix interface has a high impact on the fatigue life and was continuously improved over the years since the 50th. The fatigue life of glass fibre reinforced plastics (GFRP) used in aircraft industry is 10 to 100 times higher compared to glass fibre non crimp fabrics used for wind turbine blades. To assure a constant and reliable high quality and strength of reinforcement fibres, synthetic fibre production is state of the art (CF, GF). There is a need for recycling GFRP and CFRP waste due to the upcoming use. Pyrolysis and solvolysis are more expensive than the mechanical route however enable a more sustainable recycling. Natural fibres and recycled synthetic fibres have a high scatter in quality and strength. Hence it is a challenge to optimize the production / recycling processes to get a reliable quality for any demanding (second life) application. Chemical routes for using renewables resources and recycling, is going to be a good approach especially for polymer-matrix systems to get 100% quality (back) compared to the state of the art. Finally, a proper design, life-time extension and repair is preferable to recycling to keep the carbon footprint as low as possible. T2 - 27. INTERNATIONALES DRESDNER LEICHTBAUSYMPOSIUM CY - Dresden, Germany DA - 13.06.2024 KW - Polymer Matrix Composites KW - Carbon Fibre KW - Recycling KW - Circular Economy PY - 2024 UR - https://leichtbausymposium.de/deu/ AN - OPUS4-60683 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -