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Open-Acces-Artikel über Prepreg Tack erschienen: A review of mechanisms, measurement, and manufacturing implication

The stickiness of prepregs (tack) is considered a decisive material property for the success of high‐quality composite manufacturing by automated lay‐up processes such as automated fiber placement (AFP) or automated tape laying (ATL). Adverse control of prepreg tack can easily result in laminate defects or machine breakdown, which are highly undesirable considering the tremendous machinery and material costs of these processes. Prepreg tack is governed by a complex interaction of adhesive and cohesive phenomena that are influenced by machine and environmental parameters of the production process as well as by intrinsic properties of the prepreg material itself. This review aims at providing a condensed insight into the current state of research on prepreg tack. Therefore, experimental studies including the discussion of utilized tack measurement methods as well as model approaches to prepreg tack are reviewed. The findings are discussed against the background of fundamental mechanisms, the strong interdependency of influencing parameters and the challenge of translating measured tack data into an enhanced AFP/ATL process stability by process adjustment. 

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Neuer Beitrag zum Thema Mischbauweisen auf LinkedIn: Our high performance Composite Joining Method #MULTILAYERINSERT has gotten even better:

The approach of scalable load introduction allows, due to the use of local metal inserts, increased strength and a calculable failure behavior. The HPCFK Multilayer-Insert is capable to withstand loads up to 20 kN in-plane. Compared to the load capacity of a pure carbon competitor with 5 kN the applicable load could be increased to 4 times. The investigated Multilayer-Insert samples failed to bearing stress in the metallic region without noteworthy impacting the surrounding composite structure. In contrast, the composite specimen show a massive damage of the fiber structure. Thus, this hybrid joining element helps to reduce the number of necessary joins and in this way prevents the composite structure from up to 75% less structural unfavorable drill holes.

Besides the here shown prepreg application, the Multilayer-Insert is also available for infusion processes and further fiber materials like glass fiber reinforced plastics. Find out more at https://2025.hpcfk.de/multi-layer-inserts-mli/ 

 

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DFG SPP1712 Multilayer-Inserts: Ergebnispräsentation auf der Hybrid 2020

Multilayer-Inserts bieten für Mischbauweisen von Faserverbundwerkstoffen mit metallischen Werkstoffen eine optimale Verbindungstechnologie mit hervorragenden mechanischen Eigenschaften. Eine deutlich gesteigerte Leistungsfähigkeit für das Einleiten von Kräften in dünnwandige Faserverbundstrukturen konnte im Rahmen des Schwerpunktprogramms 1712 „Intrinsische Hybridverbunde“ durch den Einsatz lokaler Hybridstrukturen, die in Form von metallischen Einzellagen im Bereich der Krafteinleitung vorliegen, erzielt und nachgewiesen werden. Dabei substituieren die metallischen Einzellagen örtlich Faserlagen in gleicher Dicke. Der schichtweise Aufbau bewirkt eine Vergrößerung der Überlappungsfügung zwischen den Metalllagen und dem umgebenden Laminat und realisiert eine Einleitung der angreifenden Kraft in alle Laminatlagen mit einem in Zentrum befindlichen reinmetallischen Kern.

Auf der vom 28.4. bis zum 29.4. stattfindenden Hybrid 2020 werden die in den vergangenen sechs Jahren erzielten Ergebnisse, wie zurzeit üblich über eine Web-Konferenz, präsentiert. Wir bedanken uns herzlich bei der Deutschen Forschungsgemeinschaft (DFG) für die Förderung dieses Schwerpunktprogramms 1712 “Intrinsische Hybridverbunde” und damit unserer interdisziplinären Forschung.

Mehr zum Thema und auch zu allen weiteren Projekten auf dem YouTube Kanal des SPP1712:

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Wir auf der K 2019

Vom 16.10. bis zum 21.10. präsentierten wir uns und unsere Ergebnisse im Bereich Faserverbund-Metall-Hybriden auf der K 2019 in Düsseldorf. Wir bedanken uns für alle konstruktiven Gespräche und neuen Kontakte, die wir auf der Messe knüpfen konnten. Wenn Sie Gelegenheit hatten, unsere Multilayer-Insert-Technologie anzuschauen oder Sie Interesse an weiterführenden Informationen haben, treten Sie gerne in Kontakt. 

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Therm-O-Plan

Automated Path Planing and Monitoring of Automated-Fiber-Placement-Processes

The Automated-Fiber-Placement (AFP) is one of the leading manufacturing technologies in the field of cost-effective, high-quality serial production of light-weight structures. Nevertheless, both the reliability of the automated production systems and the efficiency of the process planning still offer improvement potential. In addition to the aerospace industry, the automotive industry and other high-demanding lightweight construction industries are pushing further developments.

In the AFP process, pre-impregnated carbon fibers (tows) are placed automatically on a tool surface. Due to recent technological advances in the production technology, increasingly complex components can be realized. However, this progress also leads to a higher complexity of the tools and tool surfaces. Notwithstanding available CAD/CAM-applications, the additional high structural requirements for CFRP laminates require a manual, very time consuming adaptation of the laying path while adhering to strict design rules. In addition to the selected tow paths, the process parameters have a decisive influence on the laying quality. Inadequately pre-heated tool surfaces or deviating compaction pressure can lead to defects such as tows separating from the surface. If the occurring errors are not detected and corrected, deviations from the component’s design and structural requirements occur. In general, the machine operator is responsible for assuring the quality of the product. This is usually done by visually inspecting the individual layers. This approach not only restricts the productivity of the AFP process, but also entails high repair costs for undiscovered errors which need to be corrected at a later stage. In exceptional cases this can lead to the rejection of the entire component.

The „Therm-O-Plan“ project is a cooperation between the Institute of Production Engineering and Machine Tools of the Leibniz Universität Hannover, Automation Technology GmbH and Systemtechnik Ingenieurgesellschaft mbH (SMWS). The aim of the project is to reduce the planning effort for the production of light-weight structures by automated optimized path planning. In addition, the project aims to increase the process reliability of the AFP process by means of online thermographic process monitoring. The partial developments pursued in this process are integrated in a higher-level solution approach and can easily be implemented in conventional AFP process chains.

Funding: Central Innovation Program for SMEs (ZIM)

Duration: 2015-2017

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Multi-Matrix-Prepreg

Online-Production of Multi-Matrix-Prepreg in Automated-Fiber-Placement

3.MMPThis project pursues the establishment of an interdisciplinary research focus “individualized CFRP light-weight structures with the aid of flexible manufacturing technologies”. Overall, this research group is based on fundamental research projects as well as application-based research project with industrial partners. The Multi-Matrix-Prepreg (MMP) project is the first step of this local strategy and addresses the area of “material-side flexibility”.

Individualized structures made of fiber reinforced plastics (FRP), in particular carbon-fiber reinforced plastics (CFRP), present a great economic and manufacturing challenge in serial production, e.g. of aircraft (hull, wing, side guide). Future competitiveness of Lower Saxony CFRP industry requires the implementation of new, flexible material, construction and manufacturing concepts. This can lead to a reduction in production costs and enable the production of further function-integrated components using CFRP to an increasing extent. Production sites that are currently producing CFRP components, such as the fuselage of the Airbus A350XWB, can be technologically strengthened for future developments. Novel Material solutions are part of the measures to further exploit the potential of CRFP. The main idea behind the project is to influence component properties by combining different matrix materials in an online impregnation process. The matrix materials can either be duroplastic, thermoplastic or an elastomer. During the online imprenation process the chosen different matrix materials can be combined at a set ratio. By using different matrix materials for one component the impact resistance, crack propagation resistance, weldability, stiffness and strenght of the finished product con be improved severely.

The objective of the collaborative project is to develop, implement and verify methods for the automated and quality-monitored production of multi-matrix laminates with continuous fibers, as well as to demonstrate the resulting application potentials. An innovative interdisciplinary approach is being developed from existing material and production concepts in order to realize MMLs with continuous fiber strands and locally selectively applied thermoplastic, elastomeric or duroplastic matrix material. In this process, the rovings are impregnated and consolidated online and in an innovative AFP tooling module. This is done in accordance to the locally used matrix material, the overall component requirements and taking into account the material-dependent process parameters.

Funding: Niedersächsisches Vorab, Volkswagen Foundation

Duration: 2016-2019