https://popups.uliege.be/esaform21/index.php?id=620 Publications of Auteurs Vincent Sobotka 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=2067 Mitigation of cure-induced defects in thermoset composite parts has always been a challenging problem for manufacturers especially when it comes to high dimensional accuracy of components. Thus, it is crucial to understand the evolution of the thermo-chemical properties of these materials during the totality of the curing cycle. In this paper, a new methodology is presented to characterize the process-induced strains throughout the cure. The investigation is based on the development of an existing laboratory bench named as PvT-HADDOC. The tests were performed on an interlayer toughened aerospace carbon/epoxy prepreg. Unidirectional laminate samples (105x105 mm2) of almost 6 mm of thickness were manufactured by hand lay-up then debulked at room temperature under full vacuum. The PvT-HADDOC device allows a manufacturing process following the recommended cure cycle of epoxy composites under 7 bars pressure and a temperature up to 180°C. It enables the measurements of the process-induced strains, simultaneously, along two directions: through-thickness and in-plane. Results show a complex behavior of an assumed unidirectional composite. It exhibits a temperature and time dependent compaction behavior through the thickness only. The measured thermal expansion coefficients are proved to be higher in the thickness direction for the uncured as well as for the cured state of the material. Most of the chemical shrinkage occurs along the thickness direction. This unexpected complexity is mainly attributed to the presence of interleaf layers of resin in the laminate structure. Thus, the investigated M21/IMA material is considered fully orthotropic. Tue, 23 Mar 2021 12:39:08 +0100 Mon, 12 Apr 2021 10:29:06 +0200 https://popups.uliege.be/esaform21/index.php?id=2067