https://popups.uliege.be/esaform21/index.php?id=3684 Publications of Auteurs Jean-Luc Bailleul fr 0 https://popups.uliege.be/esaform21/index.php?id=3677 Thermal analysis plays a key role in the design of hybrid manufacturing processes of High-Performance Thermoplastic Composites (HP-TPC) parts. Indeed, an inadequate temperature distribution, during the transformation of these materials, could not only lead to mechanical and surface defects but also to inefficient energy consumption. These problems become difficult to avoid with the interaction of different materials within the part, and also with the influence of subsequent stages on the process. To overcome this challenge, the methodology proposed in this work aims to determine the spatial and temporal distribution of the heat sources that must be applied at each sequential stage of a process to reach a thermal objective within the part. The methodology is based on the concept of conformal cooling [1]. A surface enveloping the part is created [2]. Once a computational model is set up, the optimization problem is treated as an inverse problem subjected to constraints that depend on the process response in terms of temperature cycles. Thus, it requires the calculation of the direct problem, the adjoint-state solution, and the development of the sensitivity equations to implement a first-order gradient-based algorithm. As an application example, a thermo-stamping of HP-TPC with a metal insert followed by an over-molding process has been chosen because of the different stages and materials involved. The first results show a reduction of temperature gradients on the part surface at each stage while arriving at the established temperature level. Further analysis will include a constraint problem taking into account adhesion and/or energy criteria. Mon, 29 Mar 2021 14:09:33 +0200 Thu, 08 Apr 2021 19:15:44 +0200 https://popups.uliege.be/esaform21/index.php?id=3677 https://popups.uliege.be/esaform21/index.php?id=409 Thermoplastic composites offer new manufacturing prospects, thanks to the ability to melt the matrix. Welding, tape placement, 3D printing, overmoulding, or even stamping involve adhesion of the thermoplastic polymer at high temperature. First, under heat and pressure, contact at the microscopic scale is ensured by the deformation of surface roughness, this is the intimate contact step. Then, the development of the mechanical strength of the assembly is controlled by the diffusion of macromolecules at the interface which is defined as the healing step. Nowadays, continuous manufacturing processes tend to be faster and present very short residence time which could limit the adhesion development. A good understanding of these mechanisms is therefore very important to control and predict such industrial processes. Welding tests at different temperatures and contact pressures were carried out over a large range of residence times using a controlled welding bench enabling very short welding times (down to 1 second). The mechanical adhesion between PEKK-carbon composite samples was characterized using double cantilever beam fracture tests. Adhesion was found to develop in two steps which could be described as an intimate contact-healing coupled step and a pure healing step. From this, the healing kinetics was identified and an empirical model was developed to account for the effect of pressure on adhesion build-up. This model could then be compared with existing models to describe the establishment of intimate contact between the coupons. Fri, 19 Mar 2021 18:40:55 +0100 Fri, 02 Apr 2021 14:47:41 +0200 https://popups.uliege.be/esaform21/index.php?id=409