A thermo-mechanically coupled constitutive model for semi-crystalline polymers at finite strains: Mechanical and thermal characterization of polyamide 6 blends

Continuum Mechanics and Thermodynamics, vol. 36, pp. 657–698

Abstract

Abstract In the field of material modeling, thermoplastic polymers are often studied because of their complex material behavior and their prevalence in industry applications due to their low cost and wide range of applications. Nowadays, where reusability becomes more and more important, materials which can undergo reversible thermomechanical deformations are appealing for, e.g., the construction of car body components. To predict such complex forming processes with multiple influencing factors, such as temperature, strain rate or underlying material morphology, model formulations are needed that account for these influences simultaneously and are validated against experimental data. Unfortunately, up to now only a few contributions are available which consider all these phenomena. In addition, the range of process parameters considered is often narrow due to the experimental effort required for testing. This usually results in limited predictive capabilities of the model. To overcome these limitations, in this work, a thermo-mechanically coupled material model is developed that accounts for the underlying morphology in terms of the degree of crystallinity (DOC). The model formulation is derived in a thermodynamically consistent manner, incorporating coupled nonlinear visco-elastic and elasto-plastic material behavior at finite strains. To characterize and further validate the model, mechanical as well as thermal experiments are conducted for polyamide 6 (PA6). Here, a blending strategy of PA6 together with an amorphous co-polymer is introduced during specimen production to achieve a wider range of stable DOCs(approximately 15%). The model formulation is successfully applied to experimental results and its predictions are in good agreement with experimental observations.

Authors 9

1. Marie‐Christine Reuvers corresponding Aachen Institute of Applied Mechanics

   RWTH Aachen University

   Affiliation as printed

   Institute of Applied Mechanics, RWTH Aachen University, Mies-van-der-Rohe-Str. 1, 52074, Aachen, Germany

2. S. K. Kulkarni

   Universität der Bundeswehr München

   Affiliation as printed

   Institute of Mechanics, University of the German Federal Armed Forces Munich, Werner-Heisenberg-Weg 39, 85577, Neubiberg, Germany

3. Birte Boes

   University of Wuppertal

   Affiliation as printed

   Chair of Computational Applied Mechanics, University of Wuppertal, Pauluskirchstr. 7, 42285, Wuppertal, Germany

4. Sebastian Felder Aachen Institute of Applied Mechanics

   RWTH Aachen University

   Affiliation as printed

   Institute of Applied Mechanics, RWTH Aachen University, Mies-van-der-Rohe-Str. 1, 52074, Aachen, Germany

5. André Wutzler
   Affiliation as printed

   Polymer Service GmbH, Geusaer Straße 81f, 06217, Merseburg, Germany

6. Michael Johlitz

   Universität der Bundeswehr München

   Affiliation as printed

   Institute of Mechanics, University of the German Federal Armed Forces Munich, Werner-Heisenberg-Weg 39, 85577, Neubiberg, Germany

7. Alexander Lion

   Universität der Bundeswehr München

   Affiliation as printed

   Institute of Mechanics, University of the German Federal Armed Forces Munich, Werner-Heisenberg-Weg 39, 85577, Neubiberg, Germany

8. Tim Brepols Aachen Institute of Applied Mechanics

   RWTH Aachen University

   Affiliation as printed

   Institute of Applied Mechanics, RWTH Aachen University, Mies-van-der-Rohe-Str. 1, 52074, Aachen, Germany

9. Stefanie Reese Aachen Institute of Applied Mechanics

   RWTH Aachen University

   Affiliation as printed

   Institute of Applied Mechanics, RWTH Aachen University, Mies-van-der-Rohe-Str. 1, 52074, Aachen, Germany