Analyse expérimental et modélisation du comportement thermomécanique d'un assemblage composite-polymère Experimental analysis and modelling of the thermomechanical behavior of composite-polymer joint

Ultra Deep offshore oil exploitation (down to 3000 meters depth) presents new challenges to offshore engineering and operating companies. Flow assurance and particularly the selection of insulation materials to be applied to pipe lines are of primary importance, and are the focus of much industry interest for deepwater applications. In this field, particular attention is now focused on the long term behavior of the assembly between coated field joints and parent coating material which appears to be critical for in-service durability. A field joint is the uncoated area that results when two pipe sections with coating cutbacks are assembled by welding. The in-service environmental conditions of the structure are severe and include high hydrostatic pressure up to 30 MPa and large thermal gradients through the thickness of the material (inner temperature up to 150°C and external temperature 4°C). This study aims to establish a model allowing the thermomechanical behavior of the assembly to be evaluated. First, the mechanical behavior of the parent coating (usually glass syntactic polypropylene material) and coated field joint material are analyzed using hydrostatic compression tests (static and creep) at different temperatures and Dynamic Mechanical Analysis (DMA). Then, a thermo-mechanical model of the parent material allowing hydrostatic creep deformation is developed and implemented in COMSOL Multiphysics ™ software. A global model of the structure under service conditions is then proposed to analyze the strain distribution in the structure. This distribution highlights the critical area of the assembly which is the bond between the parent coating material and the field joint coating. The final stage of this study focuses on the mechanical characterization of the interface between parent coating and field joint coating materials, which is addressed by using a modified ARCAN fixture allowing the determination of the failure envelope of a polymer-polymer joint.