FEDER - URN - FARM - INVEST/FONCT
Kohesio
UNIVERSITE DE ROUEN-NORMANDIE
The problems associated with the microstructures of semi-crystalline thermoplastic polymers appear today as major challenges, in terms of fundamental knowledge but also for application questions. It has been shown, in particular by partner 1, that semi-crystalline polymers must be described not by a simple two-phase model, but by a three-phase model where the 3rd phase (the rigid amorphous fraction, RAF) is a nano-phase located between crystalline phase and mobile amorphous phase. Taking RAF into account is essential to understand the physical and chemical properties of many materials very common in regional industry, both in the packaging sector (Sidel, Aptar) and in the aeronautics sector (Zodiac, Safran). Indeed, the presence of a rigid amorphous nano-phase is to be expected not only in the case of semi-crystalline polymers, where the amorphous chains are "blocked by the development of more or less regular crystalline domains, but also in the case of composite materials with a polymer matrix, a specialty of partner 2, where the action of is exerted by the reinforcements at the interface with the matrix. If thermosetting polymers have been almost exclusively used for decades in the field aeronautics, recent advances in terms of synthesis and implementation have allowed the emergence of thermostable semi-crystalline polymers with very promising thermomechanical properties. However, technological obstacles persist and a better understanding of the complex microstructure of these materials seems necessary. For example, the analysis of these materials in terms of a three-phase model has never been done. However, the microstructural understanding of composite materials with a thermoplastic polymer matrix requires the description of the matrix/fiber interfacial zone, but also the characterization of the local domains of stiffening of the amorphous phase very close to the interface (if the matrix remains amorphous) or close to the crystalline domains (if the matrix can crystallize), subjects not currently addressed on such complex materials. Also, having academic expertise in this field could make it possible to develop, in the medium term future, collaborations with the industrialists concerned. The detailed study of such complex materials (multiphase composites) is a real challenge, it is therefore necessary to model and try to understand the microstructure-mechanical properties links by analyzing model materials. One of the big pitfalls of such work by physicists is not investigating the chemical aspect. Indeed, polymers are complex materials in every respect (distribution of molecular masses, degradation by different mechanisms, presence of impurities and adjuvants, sensitivity to aging) and not being interested in this aspect limits the relevance of this work. Partner 3, through its skills in polymer chemistry, will significantly strengthen this project and for the first time, Norman researchers in mechanics, chemistry and physics of polymers are offering a multidisciplinary approach to characterize polymers and their composites. The mechanical behavior of these materials is closely linked to the solid state structuring of the macromolecules that constitute them: crystallinity, RAF, etc. The temperature and shear conditions required for shaping composite materials degrade chemically these macromolecules and are therefore likely to induce modifications in their structuring and their final properties. This project therefore aims to establish links between nanoscale structuring and the macroscopic behavior of semi-crystalline polymers used to produce composites for the aeronautics sector.
Smarter Europe / Research and innovation / Research and innovation activities in public research centres and centres of competence including networking