Corentin Perderiset defends his PhD in Computational Mechanics and Materials on Oct. 14, 22.
Study of the adhesion mechanisms in a titanium / composite bonded joint with consideration of environmental aging
Corentin Perderiset conducted his PhD work under the supervision of Pierre Montmitonnet, Frédéric Georgi (PSF team) and Jean-Luc Bouvard (MPI team). He defends his PhD in "Computational Mechanics and Materials" on October 14, 22 (subject to the agreement of the reviewers) in front of the following jury:
– Mme Valérie Nassiet, ENIT
– M. Eric Paroissien, Isae-Supaero
– M. Romain Creachcadec, ENSTA Bretagne
– M. Maelënn Aufray, INPT-ENSIACET
– M. Anthony Grunenwald, SAFRAN
– M. Pierre Montmitonnet, Mines Paris – PSL
– M. Jean-Luc Bouvard, Mines Paris – PSL
– M. Frédéric Georgi, Mines Paris – PSL
Abstract:
Structural bonds today offer a convincing alternative to raw metals for the purpose of reducing the mass of structures in the aeronautical field. Also, titanium reinforcements are now bonded to composite matrices. However, metallic materials do not have good predispositions to bonding, which is why it is necessary to carry out a surface preparation to promote adhesion.
The objective of this thesis is to contribute to the understanding of the adhesion mechanisms after bonding a titanium alloy part with an organic matrix composite, involving a surface treatment and an adhesion primer. The main point of interest is in particular the study of titanium/primer and primer/adhesive interfaces. Their behavior over time is also studied. For this, they were subjected to accelerated aging in damp heat (70 °C, 80 % RH, up to 1000h).
Initially, a shifted-TAST test was chosen to stress the assembly at these interfaces and thus make it possible to identify key parameters of the surface treatment process. Thanks to the exploitation of mechanical tests in conjunction with the study of fracture facies at several scales, it was possible to determine that several adhesion mechanisms are involved in this assembly. The parameters that most influence the adhesion properties of the interface are the initial microstructure of the TA6V and the thickness of primer deposited. Too thick a primer degrades the adhesion properties after aging by limiting the mechanical anchoring of the adhesive on the titanium surface because it reduces its roughness. The absence of a primer also reduces the adhesion properties because the adhesive wets the surface less well than the primer. The latter also makes it possible to delay the degradation of the interface in humid conditions.
Regarding the initial microstructure of TA6V, the presence of α nodules allows the creation of a rough surface that serves to promote the mechanical anchoring of the adhesive. On the other hand, these areas are often poorly covered with primer and the latter has a better affinity with the adhesive, especially after aging. The presence of lamellar grains, of smaller dimensions (α lamellae of the order of 200 to 400 nm) offers better wettability for the primer and thus allows these areas to better resist environmental aging.
Keywords: Surface treatment, adhesion, titanium-composite bonding, TAST testing, interfaces, aging
