In 2019, commercial flights worldwide produced approximately 915 million tons of CO₂. In response to this critical situation, the European Commission (EC) has recently set a target to achieve climate neutrality by 2050. One way to achieve this goal is to develop greener (e.g. hybrid electric aircraft, fuel cells powering electric motors) propulsion systems in lighter and more sustainable aircraft.

The team, led by Sergio Amancio, aims to develop innovative and novel engineering approaches to produce lightweight and high performance light metals, composites, and metal-composite hybrid structures. The team focuses on sustainable materials with improved recyclability to support the circular economy. Examples include carbon and glass fiber reinforced thermoplastic composites - a class of recyclable and repairable composites - that can be combined with lightweight and high strength alloys, such as aluminum and titanium and stainless steel, to reduce aircraft weight without compromising passenger safety. More recently, wood-thermoplastic composite and wood-metal hybrid structures have been investigated with a focus on secondary and tertiary structural applications (e.g. interior, cabin and cargo applications).

The manufacturing of hybrid structures is challenging due to the incompatibility of physicochemical material properties. The professorship's R&D approach aims to mitigate these challenges by integrating materials science knowledge, joining and additive manufacturing (AM) processes. The R&D methodology combines materials science knowledge, advanced friction-based joining and new additive manufacturing routes supported by process optimization, modeling and simulation tools. The scientific-engineering approach is shown schematically in Figure 1. In this methodology, innovative friction-based joining techniques are used together with additive manufacturing of metals (powder bed and directed energy deposition processes) and engineering thermoplastics composites (e.g. via FFF/FDM) to produce hybrid structures.

Two innovative manufacturing routes have been followed:

1. Friction-based joining (FB-J) and 2. additive manufacturing (AM).

In the friction-based joining (FB-J) route, both the metal and polymer/composite parts are manufactured separately using additive, subtractive, or formative manufacturing. Subsequently, an FB-J technique is used to join the hybrid structure.

In the AM route, the metal part is preferably fabricated by AM processes (state-of-the-art metal fabrication processes can also be used) and then hybridized by polymer or composite by polymer/composite 3D printing (or automated fiber/taple placement). Process optimization methods, such as design of experiments (DoE) and analysis of variance (ANOVA), and machine learning (e.g., supervised learning regression) are combined with process modeling and simulation (e.g., FEA, CFD, topology optimization) to better understand and optimize the manufacturing processes and properties of the hybrid structure.

Joining of hybrid metal-polymer and polymer composite structures is a hot topic that will be addressed extensively in the coming decades. Although encouraging, the transition from similar to hybrid lightweight structures usually requires new joining concepts since traditional welding and joining techniques are not directly applicable to such material combinations. This is mainly due to their physical and chemical material dissimilarities, which hinder miscibility during joining.

FB-J processes for metal-thermoplastic composite hybrid structures (MTC-HS) are known to be highly energy efficient, typically converting over 90% of the input electrical energy into frictional heat for the joining process. Compared to laser joining with an energy efficiency of 30-70%, the FB-J process can be considered a greener manufacturing process. The FB-J processes for MTC-HS use rotation (or ultrasonic vibration) and pressure to generate frictional heat, which plastically deforms the metal part to induce geometric interlocking with the polymer; simultaneously, the polymer part is softened or melted by heat transfer from the metal. Thus, a combination of macro- or micro-mechanical interlocking together with strong adhesive forces is typically present in the FB-joined MTC-HS. Due to the lower process temperatures and short joining cycles (only a few seconds instead of many minutes or hours observed in actual mechanical fastening and adhesive bonding), the polymer composite matrix does not degrade and retains its structural integrity.

In addition, the fiber reinforcement of the composite part is only slightly disturbed or damaged, leaving the original polymer composite properties virtually intact. No pre-drilling of through-holes is required in the parts, which reduces stresses in the composite. A friction joined MTC-HS with high quasi-static, dynamic and impact strength, damage tolerance and durability (i.e. resistance to natural and artificial aging) can thus be achieved in a simpler, faster and more environmentally friendly way without emissions or chemical disposal. Furthermore, the reconsolidated polymer at the metal-composite interface creates a barrier to the development of corrosion, a common problem associated with galvanic coupling between metal and carbon fiber composites. 

Three novel friction-based joining technologies patented by Amancio’s team, are being investigated and further developed at TU Graz: Friction Spot Joining (FSpJ), Ultrasonic Joining (U-Joining) and Friction Riveting (FricRiveting). These techniques complement each other and find specific application niches for different material thicknesses and structural applications. Figures 2 through 7 show schematics of the processes and the microstructural characteristics of typical hybrid joints.

The manufacturing of engineering metal-polymer laminates is currently a challenging process, typically requiring long processing cycles to cure thermoset-based resin composites and the use of expensive molds, such as those used to produce epoxy-based fiber-metal laminates (FMLs).

Thermoplastic-based FMLs (T-FMLs), such as carbon-fiber-reinforced PEEK/Ti, can be produced with shorter thermoforming cycles. However, there are challenges to automation and the ability to produce complex 3D T-FML parts. AddJoining is a novel method for manufacturing layered MTC-HS based on the principles of joining and polymer AM. AddJoining uses fused filament fabrication, FFF (for unreinforced and short-reinforced polymers), to hybridize metals - i.e. to form the polymer/composite part around the metal parts. Automated fiber/layer placement can also be used to create continuous fiber-reinforced hybrid structures. Thus, parts with complex 3D geometries can be produced by depositing extruded or tape material layer by layer on a metal substrate (e.g., extruded, rolled, machined, or additively manufactured metals). AddJoining is shown in (Figure 8). Production times for AddJoining are on the order of minutes, compared to the typical several hours for state-of-the-art composite lamination processes. No tooling is required and robotic application is possible. Figure 9 shows examples of two different metal-composite add-joints. Figures 10 and 11 show examples of additively manufactured and joined MTC-HS produced at TU Graz.

Wood is a renewable natural material that is climate-neutral, light and strong, making it an attractive material for different industrial applications. One challenge to date has been the robust joining of wood to other materials in the vehicle, such as metals and polymer composites. We have have successfully tested two novel approaches to achieve such extremely strong hybrid joints without adhesives or screws, one based on AddJoining (a) and the other on Ultrasonic Joining (b). The application of these techniques to wood is patent pending and could be used in the aircraft, automotive and furniture industries. Beech and oak wood, carbon fiber-reinforced polyamide, and polyphenylene sulfide, and 316L stainless steel and Ti-64 alloys were used as test materials. With the new manufacturing processes, the renewable wood raw material could replace components made from energy-intensive or difficult-to-recycle materials.

AddJoining route

With AddJoining technology, a component made of polymer composites or metal is applied directly to the surface of the wood using a polymer additive manufacturing process. The printed material penetrates into the open wood pores and vessels at the surface induciing micromechanical anchoring after polymer consolidation. Strong chemical bonds may form, similar to the chemical reactions of adhesive with wood. The resulting hybrid joints are strong. Fracture analysis indicate that failure takes place in the surface of the wood, whereby brokein wood fibers remain attached to the surface of the polymer. These successful initial tests were carried out on the untreated wood surface. Even more durable bonds could be created if a micro- or nano-structure is engineed onto the wood surface in advance by chemical etching or laser structuring by ablation. This technology works particularly well with complicated 3D geometries because the polymeric components are printed directly onto the wood surface.

U-Joining route

Ultrasonic energy is used to join wood to a thermoplastic or thermoplastic fiber reinforced composite to form a hybrid structure. In this way, a very strong spot joint can be achieved, combining mechanical interlocking and adhesive forces. The U-joints have been successfully subjected to mechanical testing. The hybrid spot joints could also be strengthened by prior treatment of the surface and costumization of the surface texture.This technique is particularly suitable for large components and 2D structures, where spot joints are preferred. Figure shows examples of joints before and after mechanical testing.

Development of metal powders for Laser Powder Bed Fusion (L-PBF) by in situ alloying.

Preliminary work has shown potential to reduce L-PBF costs for different metal. An example are NiTi alloys. While 10 kg of NiTi pre-alloyed costs an average of 8500 euros (TLS Technik Spezialpulver, Germany), the same in situ alloyed powder (i.e., powder is mechanically mixed) has a cost of only 840 euros, while displaying comparable printability and mechanical properties. Figure 12 shows the morphology of the produced powder. The AM feasibility of this alloy has been performed with the aid of design of experiments (DoE) and statistical analysis. Crack-free specimens have been produced. A deeper understanding of the correlations between in situ alloying, L-PBF parameters, microstructure and printed part mechanical properties will be a focus of the research in the coming years.

Wire-Based Electron Beam Additive Manufacturing (w-EBAM) of shape-memory alloys (SMA)

Alloys displaying shape memory – i.e., these alloys can be trained to react to external stimuli, such as temperature - these are generally high-strength alloys difficult to be processed by conventional subtractive and formative processes due to their superlastic behaviour. An example of a potential application in aircraft for SMAs is the combination to polymer composites to form smart lightweight hybrid structures, such as in smart metallic hinge connectors for thermoplastic composite wing ailerons. The first wire-Based Electron Beam Additive Manufacturing (w-EBAM), NiTi shape memory alloy (Figure 13a and 13b) has been recently demonstrated in two publications:
https://doi.org/10.1177/1464420720975059 and https://doi.org/10.1177/14644207231184787

Solid-state welding of AM metals to wrought alloys

Various small to medium-sized aircraft parts with complex geometries are machined from larger billets. Using L-PBF to enable printing of these parts with complex geometries and welding them into larger machined or formed parts can reduce material waste and thus improve the buy-to-fly ratio of the final part. However, there are unknown challenges associated with welding AM materials to conventional materials due to their different properties, such as different textures and residual stresses. We have investigated for the first time the refill friction stir welding (RFSSW) of laser powder bed fusion (L-PBF) AlSi10Mg - rolled AA7075 dissimilar welds. The main objective of this R&D work, carried out in collaboration with the University of Strathclyde in Scotland, is to investigate the influence of process parameters on the microstructure, mechanical behavior of these welds. Published preliminary results show that RFSSW is capable of producing strong spot welds between AM and wrought aluminum alloys (https://doi.org/10.1016/j.mfglet.2022.09.01). Figures show the microstructural characteristics. Figure 15 shows the mechanical strength
and fracture surface of exemplary RFSSW dissimilar welds.

2024

“Halil Kaya Gedik Award 2024”
Winner: Univ.-Prof. Dr.-Ing. Sergio Amancio, International Institute of Welding (IIW), 7^th July 2024, Rhodes, Greece.

2023

“Yoshiaki Arata Award 2023”
Winner: Univ.-Prof. Dr.-Ing. Sergio Amancio, International Institute of Welding (IIW), 16^th July 2023, Singapore.

European Materials Day 2023
Winner: Bettina Rauchdobler. 2^nd Place for the work entitled “The Effect of Heat Treatments on the Transfor-mation Temperature and Superelastic Response of Ni-rich NiTi Parts Manufactured by Electron Beam Freeform Fabrication“, German Materials Society (DGM), November 10, 2023, on-line event, Germany.

Bernhard Gross Award
Winner: Dr.techn. Brenda Juliet Martins Freitas. 1^st Place Best Poster of Symposium Q for the work entitled “Wear and corrosion behavior of a boron-modified duplex stainless steel produced by laser powder bed fusion”, XI B-MRS Meeting of Brazilian Materials Research Society, October 1-5, 2023, Maceió-AL, Brazil.

ACS Publication Prizes Award of American Chemical Society
Winner: Dr.techn. Brenda Juliet Martins Freitas. 1^st Place Best Poster for the work entitled “Wear and corrosion behavior of a boron-modified duplex stainless steel produced by laser powder bed fusion”, XI B-MRS Meeting of Brazilian Materials Research Society, October 1-5, 2023, Maceió-AL, Brazil.

Best Poster Presentation at 10^th KMM-VIN Industrial Workshop
Winner: Dr.techn. Gean Marcatto. 2^nd Place, Politecnico di Torino, Torino, Italy, 2023

2022

“DGM-Preis 2022”
Winner: Univ.-Prof. Dr.-Ing. Sergio Amancio, German Society for Materials Science (Deutsche Gesellschaft für Materialkunde –DGM), DGM-Forum 2022, 26^th September 2022, Darmstadt, Germany

“Energy Globe STYRIA AWARD 2022” Category “Research”
Auszeichnung in der Kategorie “Forschung”. Project GreENJOINable - Enabling advanced aircraft lightweight structures to reduce CO₂ emissions. Sponsored by State of Styria and Energie Steiermark, 6^th July 2022, Graz Austria.

2^nd Place - Best Paper Award 2022 of the "Joining of Plastics and Composites Technical Interest Group"
for the paper: Ultrasonic joining of additively manufactured metal-polymer lightweight hybrid structures W.S. Carvalho, S.T. Amancio-Filho. ANTEC 2022, Society of Plastics Engineers, 15 June 2022, Charlotte, NC, USA.

2021

Karl H. Ditze Prize 2021
Winner: Dr.-Ing. Natascha Zocoller Borba. Best PhD thesis award, sponsored by Karl H. Ditze Stiftung, Hamburg, Germany.

2017

Best Paper Award 2017 of the "Joining of Plastics and Composites Special Interest Group"
for the paper: “ULTRASONIC JOINING OF THROUGH-THE-THICKNESS REINFORCED TI-4AL-6V AND POLYETHERIMIDE HYBRID JOINTS, E. Feistauer, T. Ebel, J.F. dos Santos, S.T. Amancio-Filho, at ANTEC 2017 - Annual Technical Conference of the Society of Plastics Engineers (SPE), Anaheim, USA, 9^th May 2017.

4^th International Conference on Structural Adhesive Bonding.
Winner: Dr.-Ing. Natália Manente André. Best oral presentation, sponsored by Springer, Porto, Portugal, 2017.

2016

Henry Granjon Prize 2016 of the International Institute of Welding.
Winner: Dr.-Ing. Seyed M. Goushegir. Category A: Joining and Fabrication Technology (Friction Spot Joining), Melbourne, Australia.

Best Paper Award 2016 of the "Joining of Plastics and Composites Special Interest Group"
for the paper: “PRELIMINARY ANALYTICAL MODELING OF HEAT INPUT IN FRICTION RIVETING, Sergio T. Amancio Filho, Jorge F. dos Santos, at ANTEC 2016 - Annual Technical Conference of the Society of Plastics Engineers (SPE), Indianapolis, USA, 23^rd May 2016.

2015

“2015 GHTC AlumNI in Dallas”
Winner: Univ.-Prof. Dr.-Ing. Sergio Amancio, award in Lightweight Design, prize of Germany Trade & Invest (GTAI) for GHTC® Alumni to present the Friction Spot Joining (http://www.research-in-germany.org/en/campaigns-and-activities/ghtc-award/2015-ghtc-meets-gtai/Amancio.html) at CAMX 2015, 29^th October 2015, Dallas, USA.

“Rising Star, Category Joining Techniques”
Winner: Univ.-Prof. Dr.-Ing. Sergio Amancio, Automotive Circle International, Automotive Engineering Expo 2015, Nürnberg, 9^th June 2015.

2014

“Georg-Sachs-Preis 2013”
Winner: Univ.-Prof. Dr.-Ing. Sergio Amancio. German Society for Materials Science (Deutsche Gesellschaft für Materialkunde –DGM), DGM-Forum 2014, Darmstadt, Germany, 22^nd September 2014.

Best Paper Award 2014 of the “Joining of Plastics and Composites Special Interest Group”
for the paper: “FRICTION STAKING: A NOVEL STAKING JOINING METHOD FOR HYBRID STRUCTURES, André B. Abibe, Jorge F. dos Santos, Sergio T. Amancio Filho, at ANTEC 2014 -Annual Technical Conference of the Society of Plastics Engineers (SPE), Las Vegas, USA, 29^th May 2014.

2013

“German High Tech Champions 2013 in Lightweight Design”
Winner: Univ.-Prof. Dr.-Ing. Sergio Amancio award in the category joining technology. Federal Ministry of Education and Research (BMBF) and Fraunhofer Institut, Munich, Germany, 2013.

2010

2^nd Place - Best Poster Award at the 26th Polymer Processing Society Annual Meeting
with the work entitled “A. Abibe, S. Amancio, J.F. dos Santos, E. Hage, Jr., Processing and analysis of a new joining method for polymer-metal hybrid structures”, Banff Centre, Calgary, Canada, 4^th July 2010.

2009

Henry Granjon Prize 2009, Category A: Joining and Fabrication Technology (Friction Riveting)
Winner: Univ.-Prof. Dr.-Ing. Sergio Amancio International Institute of Welding, 12^th July, 2009. Singapore.

2008

Nordmetall Prize 2008 of the Northern German Association of Metal and Electric Industry
Winner: Univ.-Prof. Dr.-Ing. Sergio Amancio, for the best PhD thesis in 2007 of the state of Hamburg, Hamburg, Germany.

Hannes Oberlercher, MSc

Rafael Paiotti Marcondes Guimaraes, Eng. Mestr.

Matija Avbar, MSc

Awais Awan, M.Sc.

Dr.techn. Nicolas Rojas Arias, Eng.
Dr.techn. Carlos Alberto Belei Feliciano, Bach. Mestr.
Dr.techn. Brenda Juliet Martins Freitas, MSc
Dr.techn. Willian Sales de Carvalho
Dr. Gonçalo Pina Cipriano
Dr. Mateusz Skalon
Dr.-Ing. Natascha Zocoller Borba
Dr.-Ing. Natalia Manente André
Dr.-Ing. Rielson Falck
Maura Vioreanu
Maxime Lutz

pure ...

orcid ...

google scholar ...

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S. Salunkhe, S.T. Amancio-Filho, J. Paulo Davim, Advances in Metal Additive Manufacturing, Elsevier-Woodhead Publishing, England.
250p, paperback ISBN: 9780323912303 https://www.elsevier.com/books/advances-in-metal-additive-manufacturing/salunkhe/978-0-323-91230-3 1^st edition publication in October 2022.

S.T. Amancio-Filho, L. Blaga, Joining of Polymer-Metal Hybrid Structures: Principles and Applications, John Wiley & Sons Inc, USA.
416p, ISBN-10: 1118177630, ISBN-13: 978-1118177631, Feb 2018 (USA) / March 2018 (Europe), https://www.wiley.com/en-us/Joining+of+Polymer+Metal+Hybrid+Structures%3A+Principles+and+Applications-p-9781118177631

S.T. Amancio-Filho, Metal-Polymer Multi-Material Structures and Manufacturing Techniques in Transportation, MDPI Books, Switzerland,186p, ISBN: 978-3-03936-150-2 (Hbk), ISBN 978-3-03936-151-9 (PDF), August 2020 https://doi.org/10.3390/books978-3-03936-151-9