Liaison structurale par collage de composite fibre carbone / PEEK : élaboration et analyse des propriétés physiques

L'objectif de ce travail de thèse est le développement d'une solution de collage structural de composite à matrice thermoplastique thermostable (Fibre Carbone / PolyEtherEtherKetone) avec une finalité aéronautique. Plusieurs mécanismes d'adhésion ont été combinés : ancrage physique, activation de surface par réduction et association avec un promoteur d'adhésion. L'influence des fonctionnalisations de surface sur le substrat de PEEK a été caractérisée par des techniques spectroscopiques de surface ; des analyses thermiques, mécaniques et diélectriques. La liaison structurale par collage de référence a été effectuée par un adhésif thermodurcissable. Un adhésif thermoplastique thermostable à base PolyEtherImide a été formulé et mis en œuvre afin de favoriser les phénomènes d'interdiffusion avec le PEEK puis créer une liaison structurale par collage thermoplastique. La spectroscopie diélectrique dynamique a été appliquée à l'analyse des modifications structurales dans les assemblages. L'efficacité des fonctionnalisations de surface développées a été évaluée par des essais de cisaillement simple recouvrement. Après optimisation des propriétés d'adhésion, la contrainte à la rupture a été multipliée par un facteur 5.The aim of this PhD work is the development of a structural bonding for thermostable thermoplastic composites (Carbon Fiber / PolyEtherEtherKetone) in view of aerospace applications. Several adhesion mechanisms have been combined : mechanical anchoring, surface activation by reduction and adhesion promoter association. The influence of PEEK surface functionalization was characterized by surface spectroscopies, thermal, mechanical and dielectric analyses. The reference structural bonding was created by a thermoset adhesive. A thermostable thermoplastic adhesive was formulated and developed to promote interdiffusion and create a thermoplastic structural bonding. Dynamic dielectric spectroscopy has been applied to the analysis of structural modifications in the assemblies. The surface functionalization efficiency was evaluated by single lap shear tests. The ultimate stress was multiplied by a factor five, upon optimization of adhesion properties

Influence of aging on the mechanical behavior of bonded assemblies

This work is a preliminary study to investigate the combiend effects of aging processes and dynamic response of adhesives. Specially, a specific accelerated hygro-thermal aging experimental method is used to characterize some adhesives dedicated to crash applications

Dielectric relaxations in PEEK by combined dynamic dielectric spectroscopy and thermally stimulated current

The molecular dynamics of a quenched poly (ether ether ketone) (PEEK) was studied over a broad frequency range from 10-3 to 106 Hz by combining dynamic dielectric spectroscopy (DDS) and thermo-stimulated current (TSC) analysis. The dielectric relaxation losses e00 KK has been determined from the real part e0 T(x) thanks to Kramers–Kronig transform. In this way, conduction and relaxation processes can be analyzed independently. Two secondary dipolar relaxations, the c and the b modes, corresponding to non-cooperative localized molecular mobility have been pointed out. The main a relaxation appeared close to the glass transition temperature as determined by DSC; it has been attributed to the delocalized cooperative mobility of the free amorphous phase. The relaxation times of dielectric relaxations determined with TSC at low frequency converge with relaxation times extracted from DDS at high frequency. This correlation emphasized continuity of mobility kinetics between vitreous and liquid state. The dielectric spectroscopy exhibits the ac relaxation, near 443 K, which has been associated with the rigid amorphous phase confined by crystallites. This present experiment demonstrates coherence of the dynamics of the PEEK heterogeneous amorphous phase between glassy and liquid state and significantly improve the knowledge of molecular/dynamic structure relationships

Influence of aging on the mechanical behavior of bonded assemblies

International audienceThis work is a preliminary study to investigate the combiend effects of aging processes and dynamic response of adhesives. Specially, a specific accelerated hygro-thermal aging experimental method is used to characterize some adhesives dedicated to crash applications