Guillaume Broggi
Project description
Over the last years, several studies have brought evidences that overall mechanical properties in fiber-reinforced laminates are significantly improved when using thin-ply – about 20-150 μm ply thickness – instead of thick-ply – typically 300 μm. These better performances ensure a broaden design space. For a given load, the designer can achieve a lighter structure and vice versa. While expected to reduce energy consumption in the transport sector – by weight loss – this technology remains underused in this field due to lack of toughness.
The key challenge of this project is to characterize and understand the fracture processes in hybrid carbon-carbon thin-ply composites at micro and macro scale, resulting in a reliable prediction model for the phenomenon. We aim to use this model to further optimize thin-ply laminates for improved notched strength and translaminar toughness, thanks to fiber hybridization. In this way, thin-ply composites will be brought to new commercial applications, including aircraft and automotive industries.
This research is being conducted in the Laboratory for Processing of Advanced Composites (LPAC), at École Polytechnique Fédérale de Lausanne (EPFL), under the supervision of Prof. Véronique Michaud and Prof. Joël Cugnoni and in close relationship with North Thin Ply Technology (NTPT), a thin-ply manufacturer. The scope of this project includes three secondments, one at NTPT, one at KU Leuven and one at University of Bristol.
Education
PhD candidate, École Polytechnique Fédérale de Lausanne, Switzerland (2018 - present)
M.Sc in Mechanical Engineering, Georgia Institute of Technology, United States (2016 - 2018)
Arts et Métiers Engineer, Arts et Métiers ParisTech (2014 - 2018)
Research interests
Pseudo-Ductility, Hybrid Composites, Numerical modeling of damage and failure in composites, Composites testing, Hybrid composites, Fracture mechanics.
Personal note
On a serious but personal note, I am deeply interested in programming, data science, machine learning and microtechnology. I enjoy to train myself in these skills and to achieve small projects like building a 3D printer.
Outside of academia, I enjoy to share the good things in life with friends or my family. I always try to make the most of the beautiful Alps mountains by going hiking or skiing. I also love to growth vegetables in my garden and to cook them.
Latest publications by this author
Improving the performance of pseudo-ductile hybrid composites by film-interleaving [OPEN ACCESS]
Salvatore GiacomoMarino, GergelyCzél
Improvement of the interfacial fracture toughness of the layer interfaces is one way to increase the performance of interlayer hybrid laminates containing standard thickness carbon/epoxy plies and make them fail in a stable, progressive way. The layer interfaces were interleaved with thermoset 913 type epoxy or thermoplastic acrylonitrile–butadienestyrene (ABS) films to introduce beneficial energy absorption mechanisms and promote the fragmentation of the relatively thick carbon layer under tensile loads. Carbon layer fragmentation and dispersed delamination around the carbon layer fractures characterised the damage modes of the epoxy film interleaved hybrid laminates, which showed pseudo-ductility in some cases. In the ABS film interleaved laminates, a unique phase-separated ABS/epoxy inter-locking structure was discovered at the boundary of the two resin systems, which resulted in a strong adhesion between the fibre-reinforced and the thermoplastic layers. As a result, the delamination cracks were contained within the ABS interleaf films.
Effect of Plasma-Treatment of Interleaved Thermoplastic Films on Delamination in Interlayer Fibre Hybrid Composite Laminates [OPEN ACCESS]
Salvatore Giacomo Marino, Florian Mayer, Alexander Bismarck and Gergely Czél
Safe, light, and high-performance engineering structures may be generated by adopting composite materials with stable damage process (i.e., without catastrophic delamination). Interlayer hybrid composites may fail stably by suppressing catastrophic interlayer delamination. This paper provides a detailed analysis of delamination occurring in poly(acrylonitrile-butadiene-styrene) (ABS) or polystyrene (PS) film interleaved carbon-glass/epoxy hybrid composites. The ABS films toughened the interfaces of the hybrid laminates, generating materials with higher mode II interlaminar fracture toughness (GIIC), delamination stress (σdel), and eliminating the stress drops observed in the reference baseline material, i.e., without interleaf films, during tensile tests. Furthermore, stable behaviour was achieved by treating the ABS films in oxygen plasma. The mechanical performance (GIIC and σdel) of hybrid composites containing PS films, were initially reduced but increased after oxygen plasma treatment. The plasma treatment introduced O-C=O and O-C-O-O functional groups on the PS surfaces, enabling better epoxy/PS interactions. Microscopy analysis provided evidence of the toughening mechanisms, i.e., crack deflection, leading plasma-treated PS to stabilise delamination.
Understanding the mechanical response of glass and carbon fibres: stress-strain analysis and modulus determination
Rajnish Kumar, Lars P Mikkelsen, Hans Lilholt and Bo Madsen
Accurate characterization of fibres is crucial for the understanding the properties and behaviour of fibre-reinforced composite materials. Fibre properties are key parameters for composite design, modelling and analysis. In this study, characterization of mechanical properties of glass and carbon fibres has been performed using a semi-automated single-fibre testing machine. Based on a sample set of 150 glass and carbon fibers fibres, engineering and true stress-strain curves are analyzed. Different modulus determination methods are discussed based on true stress-strain and tangent modulus-strain relationships. For glass fibres, the true stress-strain based tangent modulus is found to be independent of applied strain, whereas for carbon fibres, a tendency of tangent modulus to increase with applied strain is observed. The modulus of glass fibres is found to be independent of fibre diameter, whereas carbon fibres with smaller diameter show higher modulus compared with carbon fibres with larger diameters.