Open Ph.D. position
Open Ph.D. position
Homogenized behavior and simulation of discontinuous thermoplastic laminates forming
CETIM develops a technology for manufacturing thermoplastic composite structures called QSP. It relies on the hot forming of a flat preform obtained by assembling discontinuous plies of thermoplastic prepreg positioned and oriented in an optimal manner. The forming can generate movements (rotation and translation) and deformations (transverse squeeze flow and bending of fibers) of the composites plies which gives rise to loss of straightness of the fibers and then mechanical weakening of parts. This happens because the individual discontinuous prepreg plies are free to move and deform in the mold during the forming step. It is important to know in advance where issues may occur during forming and how they can be solved.
The GeM investigated experimentally some of these mechanisms on flat samples. Owing to the complexity of the problem, the numerical simulation of the forming of complex blanks can be of great help. A detailed 3D computational model has been recently developed to investigate at the material scale the above-mentioned mechanisms. It describes both the interlaminar shear effects and the coupled intra-ply phenomena. While this model is helpful to understand the influence of
material parameters and processing conditions on the laminate deformation, it cannot be used to simulate the forming of a full part because of the current unaffordable computational cost.
The overall objective of the thesis is to reduce the existing 3D model to a 2D equivalent one to reach a suitable accuracy/computational cost trade-off, and implement it in commercial software package. First, an equivalent interfacial contact law, parameterized by the mechanical and kinematic response of adjacent prepreg plies will be developed and validated against lab-scale experiments. An 2D equivalent model for viscous prepreg will be proposed and validated agains lab-scale experiments. The 2D model developments will be achieved at the GeM laboratory (Nantes), in close relationship with a post-doc researcher in charge of the further development of
the 3D model. Material characterization methods will be proposed to identify input parameters. This reduced model will be then implemented by the PhD candidate in the Hyperform simulation software package (Altair) at the Altair facilities (Sophia Antipolis) in France. Comparison will be made with an industrial part in cooperation with CETIM.
Location: Nantes (France) & Sophia Antipolis (France)
Contract : CIFRE Scholarship (http://www.anrt.asso.fr/fr/espace_cifre/pdf/plaquette_cifre_en.pdf).
Expected starting date : November 2017
ECN/GeM : Christophe Binetruy