Hedi Nouri

Microstructural and Mechanical Implications of Microscaled Assembly in Droplet-based Multi-Material Additive Manufacturing

To reveal the potential and limits of multi-material three-dimensional (3D) printed parts in droplet-based additive manufacturing, a study combining tensile experiments and 3D imaging technique is proposed. A polymeric composite structure made of acrylonitrile butadiene styrene and thermoplastic polyurethane is manufactured using a two extrusion head printer. The quality of the interface between the two thermoplastics is quantified by adjusting the number of intertwining droplets at the interface. Tensile experiments assisted with digital image correlation are performed with two-interface orientation to discriminate shearing and traction at the interface. The 3D imaging results, which are based on X-ray micro-tomography, show the distinct features of droplet-based additive manufacturing in terms of porosity content and connectivity. Interface properties are found to control, in an incomparable way, the mechanical response. It is found that the interface quality is determinant for enhancing the ultimate performance whereas the interface orientation is found to be the perfect leverage for varying the slope of the linear part.

Experimental Parameters Identification of Fatigue Damage Model for Short Glass Fiber Reinforced Thermoplastics GFRP

In the present work, a new polycyclic fatigue damage model is formulated and applied for short glass fibre reinforced thermoplastics. The model is able to capture experimental trends observed for the considered composites. The damage growth description involves a set of 20 parameters in the case of a complete 3D –structure. In the current paper, it is considered the particular case of a displacement controlled fatigue tensile test involving 4 damage parameters. The present contribution is a first approach of parameter identification. It is considered a least squares sense based cost function and homogeneous fatigue tests performed on a short glass fibre reinforced polyamide. The identified set of parameters appears to be not depending on the adopted initial values. The model as the parameters determined by the minimisation algorithm, are validated on a fatigue test performed with a different loading condition.