Compression testing of additively manufactured continuous carbon fiber-reinforced sandwich structures

Patrick Striemann; Martin Eichenhofer; Daniel Schupp; Michael Niedermeier; Daniel Huelsbusch; Frank Walther

doi:10.3139/120.111216

Published by De Gruyter November 15, 2018

Compression testing of additively manufactured continuous carbon fiber-reinforced sandwich structures

Druckversuch von additiv gefertigten und kontinuierlich kohlenstofffaserverstärkten Sandwichstrukturen

Patrick Striemann , Martin Eichenhofer , Daniel Schupp , Michael Niedermeier , Daniel Huelsbusch and Frank Walther

From the journal Materials Testing

https://doi.org/10.3139/120.111216

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Abstract

The novel, additive manufacturing technique, continuous lattice fabrication, combines the advantages of continuous fiber-reinforcement with those of additive manufacturing. This enables the generation of fiber-reinforcement within a single layer and especially along an out-of-plane load path inside all spatial dimensions. This study is a test-related evaluation of sandwich panels with lattice core structures modifying a compression test. The specimens were manufactured differentially via plug and bond and automatically using continuous lattice fabrication. Additionally, the spatial arrangement of the rods within the lattice core structure varied in terms of base area. The ultra-lightweight sandwich panels have lattice core structures with core densities < 10 mg × cm⁻³. The material testing was performed by a modified compression test at room temperature. The damage analysis of the single rods shows current deficits and future potentials for optimization of lattice core structures. It could be shown that sandwich panels exhibit a compression strength of up to 0.30 MPa at a core density of 6.57 mg × cm⁻³. Using a dimensionless lightweight index demonstrates a mechanical performance on a level comparable with that of selected core materials.

Kurzfassung

Das neuartige Verfahren Continuous Lattice Fabrication kombiniert die Vorteile einer kontinuierlichen Faserverstärkung und der additiven Fertigung. Dabei kann die Faserverstärkung nicht nur innerhalb einzelner Schichten, sondern auch kraftflussgerecht (out-of-plane) im dreidimensionalen Raum generiert werden. Ziel dieses Beitrags ist eine testbasierte Bewertung von Sandwichstrukturen mit fachwerkähnlichen Kernstrukturen durch die Modifikation eines Druckversuchs. Dafür wurden Proben differentiell mit Steck- und Klebeverbindungen sowie automatisch mittels continuous lattice fabrication gefertigt. Zusätzlich wurde die räumliche Anordnung der Fachwerkstäbe, durch verschiedene Grundflächen und Stabwinkel, variiert. Ultraleichtbau-Strukturen mit fachwerkähnlichen Kernstrukturen haben Kerndichten kleiner 10 mg × cm⁻³. Die grundlegende werkstoffmechanische Untersuchung wurde mit Hilfe eines modifizierten einachsigen Druckversuchs bei Raumtemperatur durchgeführt. Die erarbeitete Systematik zur Schadensanalyse legt zukünftiges Optimierungspotential des noch jungen Verfahrens offen. Es konnte gezeigt werden, dass die Sandwichelemente mit einer Kernstrukturdichte von 6.57 mg × cm⁻³ eine Druckfestigkeit von bis zu 0.30 MPa aufweisen. Durch Auswertung einer dimensionslosen Leichtbaukennzahl konnte gezeigt werden, dass die Kennwerte der entwickelten Strukturen auf einem ähnlichen Niveau mit ausgewählten technischen Kernmaterialien liegen.

Keywords: Additive manufacturing; continuous fiber-reinforcement; sandwich; core material; compression strength

*Correspondence Address, Patrick Striemann, M.Eng., Laboratory of Material Testing, University of Applied Sciences, Ravensburg-Weingarten, Doggenriedstraße, D-88250 Weingarten, Germany, E-mail: patrick.striemann@hs-weingarten.de

Patrick Striemann, born in 1990, studied Mechanical Engineering with a specialization in development and engineering design at the University of Applied Sciences (UAS) Ravensburg-Weingarten, Germany and received his Bachelor's degree in 2015. In 2017 he successfully completed a Master's degree in Technology Management & Optimization at UAS Ravensburg-Weingarten. Since then he has been working as a research assistant at the Laboratory of Material Testing at UAS Ravensburg-Weingarten. In the past years, he has focused on the additive manufacturing of continuous fiber-reinforcements.

Martin Eichenhofer, born in 1988, obtained his Bachelor's degree in Mechanical Engineering at the University of Applied Sciences Ravensburg-Weingarten, Germany followed by a Master's degree in Mechanical Engineering at ETH Zurich, Switzerland and a post-graduate Master's degree in Economics at the Collège des Ingénieurs, Paris, France. He specializes in functional design, processing and mechanics of composite materials. While working on his Master's thesis, he developed a new processing route for the continuous fabrication of composite materials (CLF). He is particularly interested in the symbiosis of digital fabrication and load tailored design.

Daniel Schupp, born in 1991, studied Mechanical Engineering with an emphasis on designing and developing at the University of Applied Sciences (UAS) Ravensburg-Weingarten, Germany. He received his Bachelor's degree in 2015, focusing on the development of new products for Bosch Power Tools. After that, he studied Technical Management at the UAS Ravensburg-Weingarten and received his Master's degree in 2017. Since 2015, he has been working for the Laboratory of Material Testing at UAS Ravensburg-Weingarten. His research mainly focuses on quasi-static testing of fiber-reinforced materials and the development and manufacturing of ultra-lightweight parts for aircrafts.

Prof. Dr.-Ing. Michael Niedermeier, born in 1962, studied Mechanical Engineering at the TU Munich, Germany from 1983 to 1988. After that, he worked as a scientific assistant at IKB at ETH Zurich, Switzerland. The topic of his PhD thesis was the investigation and characterization of the diaphragm forming of advanced thermoplastic composites. From 1995 to 1997 he was employed as R&D engineer in the field of new technologies/composites at Schindler Waggon AG, Altenrhein, Switzerland. Subsequently, he headed the department Joining and Forming with the additional function Program Manager Lightweight Structures at Alusuisse (later ALCAN) in Neuhausen, Switzerland, until 2003. Since 2003 he has been Professor at UAS Ravensburg-Weingarten University, Germany, Faculty of Mechanical Engineering, for lightweight design and composite materials and is head of the Laboratory of Material Testing.

Daniel Huelsbusch, born in 1986, studied Mechanical Engineering with an emphasis on technical management and materials science at the TU Dortmund University, Germany, where he received his diploma degree in February 2013 after focusing on joining techniques for fiber-reinforced polymers at BMW group. Since then he has been working as a scientific assistant and group leader for “Composites” at the Department of Materials Test Engineering (WPT) at the TU Dortmund University, Germany, and was appointed general Senior Engineer in 2015. His research is mainly focused on the fatigue properties of fiber-reinforced polymers, including the determination of deformation behavior, by advanced hysteresis measurements, and the corresponding damage propagation by in situ computed tomography.

Prof. Dr.-Ing. Frank Walther, born in 1970, studied Mechanical Engineering majoring in Materials Science and Engineering at the TU Kaiserslautern University, Germany. There, he finished his PhD on the fatigue assessment of railway wheel steels in 2002 and his habilitation on physical measurement techniques for microstructural-based fatigue assessment and lifetime calculation of metals in 2007. At Schaeffler AG in Herzogenaurach, Germany, he headed the Public Private Partnership within Corporate Development from 2008 to 2010. Since 2010 he has been Professor for Materials Test Engineering (WPT) at the TU Dortmund University, Germany. His research portfolio includes the determination of structure-property relationships of metal- and polymer-based materials and components under fatigue loading from LCF to the VHCF range, taking the influence of manufacturing and joining processes as well as service loading and corrosion deterioration into account. Prof. Walther has published more than 200 research papers and conference proceedings and maintains close scientific contact with institutions and industries in materials science and engineering field worldwide.

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Published Online: 2018-11-15

Published in Print: 2018-09-30

Compression testing of additively manufactured continuous carbon fiber-reinforced sandwich structures

Abstract

Kurzfassung

References

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