SASCOM Seminar Series - Thin-Ply Composites: Towards Lighter and Multifunctional Aerospace Composite Structures

In recent years, important progress has been made in the development of composite laminates using thinner pre-impregnated plies down to about 20 micrometers instead of ~200 micrometers for traditional composites. The motivation for this trend towards the development of thin-ply composites is not only to allow the production of thinner and lighter laminates for lightweight structures, but also to provide enhanced effective design space for laminate optimization as well as improved strength and damage resistance thanks to positive size effects.

The first prime benefit of using thinner plies is the ability to optimize among a larger number of ply orientations for a given laminate thickness or to allow the manufacturing of ultra-thin laminate for example for flexible structures or skins for lightweight sandwich panels. The second benefit is that thin-ply composites present a very significant performance advantage over traditional composites due to delayed delamination and transverse cracking. Indeed, it has been shown that multi-axial laminates made of thin-ply composites can reach an ultimate strength and first ply failure close to the ultimate strain of the fiber. Thirdly, as it will be presented in this talk, thin-ply composites are also ideally suited to develop multifunctional structures that integrate electronic circuits to interconnect active components such as radio communication, sensors for IoT.

In this seminar, an overview of the mechanics of thin-ply composites will be presented to highlight the main performance advantages and drawbacks of this new class of composites [1,2]. To explain those mechanisms, a multiscale model of transverse cracking in thin-ply laminates has been developed and provides important insight on the cause of the observed experimental scaling of in-situ strength and apparent toughness of thin-ply quasi-isotropic laminates [3,4].

Applications examples on the use of thin-ply composites in aeronautic structures will be presented where a potential weight reduction up to 30% has been demonstrated compared to standard composites while reaching a similar or better production rate by using automation and optimized design for manufacturing. Finally, the use of thin-ply composites in the manufacturing of smart multifunctional structures will be presented.

Acknowledgements: the work presented in this paper is the result of several research projects funded by the Swiss Commission for Technology and Innovation (CTI/Innosuisse), Swiss National Science foundation and HES-SO. The author would like to acknowledge the major contributions of the following people: Robin Amacher, Guillaume Frossard, Sébastien Kohler, Miguel Herraez (EPFL) & B. Giuntoli (HEIG-VD)

About the Speaker

After graduating in 2000 as a mechanical engineer with a specialty in solid mechanics, Joël Cugnoni obtained is PhD from EPFL, Switzerland in 2004 in the field of dynamic identification of the elastic properties of composite laminates. After a post-doc in the field of experimental characterization and finite element modeling of micro-electronic solder joints under the supervision of Prof. John Botsis, he became senior researcher and lecturer at the EPFL in 2008, were he focused his research on fracture mechanics of composites and multi-scale modeling of complex materials. In 2018, he was appointed associate professor at the University of Applied Sciences of Yverdon-les-Bains (HEIG-VD), Switzerland where he continues his research in composites structure and additive manufacturing.

By Professor Joël Cugnoni

  • Associate Professor, HEIG-VD, Switzerland
  • PhD in Solid Mechanics from EPHL, Switzerland

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Recordings link

SASCOM Courses - Introduction to Composite Materials

st lecture, Nov 2, 2021

  • Constituent materials, manufacturing processes and semi-products.
  • Matrices, fibers and interfaces. Role and selection of the constituents.
  • Properties of the constituents; effects of fiber sizing.
  • Semi-products: short-fiber, SMC, NCF, textiles and pre-pregs.
  • Examples of applications of different types of composite materials.
  • Processes for thermoset-based composites: RTM, autoclave, resin infusion, pultrusion, filament winding.
  • Processes for thermoplastic-based composites: automatic tape laying, stamp forming.
  • Additive manufacturing of composite materials.
  • Effects of manufacturing defects.

nd lecture, Nov 9, 2021

  • Mechanical behavior and characterization.
  • Properties of composite systems and how to measure them. Characterization of the mechanical properties of the constituents, fiber, matrix and interface. Mechanical tests from coupon to sub-component. Building-block approach.

rd lecture, Nov 16, 2021

  • Classical lamination theory.
  • Lamina stiffness, stiffness of symmetric laminates, stiffness of general laminates, warpage. Invariant-based approach to stiffness.

th lecture, Nov 23, 2021

  • Designing with composite materials.
  • Failure mechanisms. Ply-based failure criteria. Last-ply failure of multidirectional laminates. Omni-envelope approach. Effects of stress concentrations. Point- and average-stress methods. Finite Fracture Mechanics. Damage tolerance design

About the Speakers

Albertino Arteiro received a Master’s Degree in Mechanical Engineering – Specialisation in Structural Engineering and Machine Design – from the Faculty of Engineering – University of Porto in 2012, and a Doctoral Degree in Mechanical Engineering (cum Laude) from the same University in 2016, during which he was a Visiting Student Researcher at the Department of Aeronautics and Astronautics of Stanford University. He was awarded the Best PhD Thesis by the Portuguese Association of Theoretical, Applied and Computational Mechanics (APMTAC).

Albertino Arteiro was appointed Assistant Professor at the Materials and Technological Processes Group of the Department of Mechanical Engineering (DEMec) of the Faculty of Engineering – University of Porto in 2019. He is currently a member of the ECCOMAS Young Investigators Committee.

His research interests include material modelling at different length-scales, design and analysis of composite systems based on new concepts, and composites manufacturing.

Pedro Camanho (MSc in Mechanical Engineering, UPorto, 1995) received his PhD in Composite Materials from the Department of Aeronautics, Imperial College London, UK, in 1999. In the same year he joined the Institute of Mechanical Engineering and Industrial Management (INEGI – www.inegi.up.pt) as Director of the Structural Integrity Unit and the Department of Mechanical Engineering of the University of Porto as Assistant Professor. Since 2014 he has been Full Professor at the Department of Mechanical Engineering of the University of Porto. Pedro Camanho is currently the President of the Associated Laboratory in Energy, Transportation and Aeronautics (LAETA), and the Vice-President of INEGI.

The main research interests of Pedro Camanho are the mechanics of deformation and fracture of advanced polymer composite materials, and new concepts for lightweight composite materials and structures for aerospace applications such as hybrid, nano-structured, multi-functional, variable-stiffness, energy-storage and ultra-thin composites.

By Prof. Albertino Arteiro & Prof. Pedro Camanho

  • INEGI, University of Porto