Paper Number
AM14 

Session
Additive Manufacturing and Composites

Title
The role of rheology in laser sintering of polymer particles

Presentation Date and Time
October 23, 2019 (Wednesday) 5:25

Track / Room
Track 1 / Room 305A

Authors (Click on name to view author profile)

1. Anderson, Patrick D. (Eindhoven University of Technology, Mechanical Engineering, Polymer Technology Group)
2. Hejmady, Prakhyat (Eindhoven University)
3. Balemans, Caroline (Eindhoven Univserisity of Technology)
4. van Breemen, Lambert (Eindhoven Univerisity of Technology)
5. Hulsen, Martien (Eindhoven Univerisity of Technology)
6. Cardinaels, Ruth (Eindhoven University of Technology, Mechanical Engineering, Polymer Technology Group)

Author and Affiliation Lines (in printed abstract book)
Patrick D. Anderson, Prakhyat Hejmady, Caroline Balemans, Lambert van Breemen, Martien Hulsen, and Ruth Cardinaels
Mechanical Engineering, Polymer Technology Group, Eindhoven University of Technology, Eindhoven, Noord-Brabant 5600 MB, The Netherlands

Speaker / Presenter 
Anderson, Patrick D.

Text of Abstract
Merging of particle pairs during selective laser sintering (SLS) of polymers is vital in defining final part properties. Depending on the sintering conditions, polymers can undergo full or partial sintering whereby incomplete sintering results in poor mechanical properties. In the present work, a novel in-house developed experimental setup is used to perform laser sintering experiments on polymer particle doublets while performing in-situ visualisation of the sintering dynamics. Sintering conditions such as heating chamber temperature, laser pulse energy and duration, laser spot size and particle size are precisely controlled and systematically varied. A non-isothermal viscous sintering model, extending the Frenkel model, is developed to qualitatively predict the observed effects of the various parameters. It is shown that the sintering kinetics is determined by a complex interplay between the transient rheology caused by the finite relaxation times of the polymer and the time-dependent temperature profile which also affects the polymer viscosity. The combination of a full material characterisation with sintering experiments under well-defined conditions has resulted in a general understanding of the effects of material and process parameters on laser sintering. Results are compared with a computational model using the finite element method. Firstly, we analysed the viscoelastic flow problem of the sintering process using both the Giesekus model and the eXtended Pom-Pom model to describe the complex behaviour of the polymer. Secondly, we included the temperature-dependent flow behaviour of the system to study the effect of process and material parameters. Finally, we discuss the crystallisation kinetics to predict and tune the morphology of the products.