PROCESSES AND STRUCTURES
1. Analysis and modelling of shape defects generated during the manufacturing of composite structures
During the manufacturing of laminated composite structures, many physicochemical and thermomechanical phenomena are at work and can produce unwanted deformations of the parts produced. Thermochemical modelling of the polymerization process has been carried out, making it possible to predict, among other things, overshoots during the polymerization of a thermoset resin of a thick composite. On another level, a semi-empirical model of thermomechanical spring-back has been developed and recently applied to a large part: the A350 rib, in the framework of CORAC, these two studies are used to predict the spring-back of bonded stiffeners
2. Analysis of links between manufacturing/machining parameters and mechanical strengths
During machining of composite materials, the major problem that arises today is the choice of criteria for the qualification of machined surfaces. The industrial criteria currently imposed (for example: the average roughness Ra, Rp, etc.), do not appear to be relevant for composites. In this context, we are interested in studying the influence of the microstructure (such as the presence of thermoplastic nodules between the plies) and the conditions in which the composite is manufactured and cured on the quality of machining. In particular, the surface defects and the extent of delamination during machining (both conventional and non-conventional process) are analysed. In addition, the influence of the machining process (laser, abrasive water jet…) on the nature of the defects and its impact on the structural integrity in static or fatigue is studied. New machining quality criteria based on new parameters such as: crater volume, bearing surface, depth of damage are proposed for establishing a better correlation to the structural integrity.
3. Machining of composite and wood
The anisotropic and highly abrasive nature of the reinforcements, associated with the heterogeneity of the composite structures, make their machining a challenging task. This task becomes even more complex when hybrid materials (CFRP/Ti, CFRP/Al…) are considered specifically for one-shot drilling. As a result, the studies carried out at the ICA concerning the machining of composite materials (including wood and eco-materials) and multi-materials largely relate to:
- – the understanding of surface creation mechanisms in relation to material removal processes (orthogonal cutting, drill, bit and orbital drilling, and high pressure abrasive water jet);
- – in situ measurement of the drilling temperature by introducing instrumentation in the core of the cutting tools using Optical Fibers with Bragg grating;
- – the multi-scale analysis of machined surfaces to predict the damage initiation and propagation to improve the service life of the structures;
- – analytical and numerical modelling of the machining process (drilling, trimming) taking into account the thermomechanical phenomena to predict the critical process parameters (tool geometry, machining parameters…) to improve the machining quality;
- – multiscale modelling of material removal mechanisms and induced defects;
- – Machining of eco-composites (wood, flax, cork…).