Research projects are (co)financed by the Slovenian Research and Innovation Agency
- Member of the University of Ljubljana: Faculty of Mechanical Engineering
- Project code: L2-3165
- Science: Engineering sciences and technologies
- SICRIS: Sustainable use of polymers in home appliances – Prediction of long-term viscoelastic behavior (cobiss.net)
The use of polymers in household appliances for individual components and end products has been increasing steadily over the years. This is understandable, as polymers are easy to process, have an excellent strength-to-weight ratio, are chemically resistant and have good electrical properties.
Although polymers have been used in household appliances for a relatively long time, their integration into complex products and components, especially due to the increased need for durability, is still a challenge. One of the main characteristics of polymer materials is that their mechanical properties (properties that determine the structural strength of the product) can change significantly with time, load and environmental conditions. In practice, this means that the functionality and durability of products made from polymers can change significantly during their life cycle, leading to premature functional or structural failure of polymer products.
Another important disadvantage of polymers is that most of them are still made from natural resources. Their increased use is already having a significant impact on people and the environment. The EU’s objectives in the coming years, also outlined in the European Green Deal, will be focused on product sustainability, so that products placed on the EU market will have to have a longer durability, will have to be easy to reuse, repair and recycle, and will have to include as much recycled material as possible. In addition, in the coming years, we can expect the adoption of the principle of sustainability and ways to regulate various aspects related to products, which will require:
- improved durability, reusability, upgradability and repairability of products,
- increased content of recycled components in finished products and
- restrictions on single-use products and prevention of premature aging of products.
It is obvious that the advantages of using polymers in household appliances will need to be balanced with the requirements for greater sustainability, which is linked to the ability to reliably predict the long-term behavior of polymer products exposed to different environmental conditions during use.
Accordingly, the main objective of the proposed application project is to develop a methodology for predicting the time-dependent stress-strain behavior of polymer products at low to medium stresses, at different temperatures and humidities. The methodology will enable the production of household appliances with new design solutions with longer lifespan and lower environmental impact.
The methodology will be based on the accurate characterization of time-dependent material properties and the prediction of long-term material behavior, together with a validated FEM material model. The methodology will include an inventory of nonlinear time-dependent processes and will be limited to constant stress loads, and will be valid up to the range of pronounced material nonlinearities or material failure. Although the field of nonlinear viscoelastic behavior of polymers is relatively well known, nonlinear models have not yet been used to predict long-term material behavior, which is one of the main goals of this project. Thus, within the framework of the project, we will discuss the possibility of using the principle of time-temperature superposition in the nonlinear range of material behavior, accurate characterization of the material in the nonlinear regime, modelling and implementation of the FEM material model in software code. In addition, we will also verify the accuracy of the predicted durability of polymer products.
The three project partners, the Laboratory for Experimental Mechanics, the Laboratory for Numerical Modelling and Simulation, and the project co-financier BSH Household Appliances, Nazarje, have the necessary knowledge, experience, and experimental equipment for the successful implementation of the project, so we expect that the project results will lead to a new and improved way of designing polymer elements and products for household appliances.
The research work is organized in four main work packages, where the fourth work package is intended for the management and dissemination of the project results. The mentioned work packages are:
Work package 1: Linear viscoelastic characterization and modeling
- Task 1.1: Sample preparation and analysis of the sample structure
- Task 1.2: Material characterization and determination of material properties
- Task 1.3: FEM analysis and model verification
Status: completed
Final documents (COBISS.SI-ID): 180456451 in 133516803 (Polypropylene-PP); 166330115 in 166320643 (Polycarbonate-PC); 166328323 in 166321923 (polioksi metilen-POM); 166325763 in 166321923 (Thermoplastic Polyurethane-TPU); 166315779 in 166324995 (Acrylonitrile Butadiene Styrene-ABS); 203016451 in 226656003 (Silicon Rubber-SR); 132934915 (Tensile properties of PC); 132932099 (implementation of linear viscoelastic model in FEM).
Work package 2: Nonlinear viscoelastic characterization and modeling
- Task 2.1: Material characterization and determination of nonlinear material properties
- Task 2.2: FEM implementation of nonlinear viscoelastic behavior
- Task 2.3: FEM validation of nonlinear viscoelastic model
Status: completed
Final documents (COBISS.SI-ID): 173721091 (PC); 183277315 (POM); 197335299 (TPU); 173723395 (ABS); 139657987 (syntetic materials for FEM analizo); 154221571 (implementation of nonlinear viscoelastic model).
Work package 3: Upgrading and generalizing the methodology
- Task 3.1: Influence of moisture
- Task 3.2: Generalizing the methodology
Status: completed
Final documents (COBISS.SI-ID): 203185923 (original scientific article with a generalized theory of nonlinear viscoelastic behavior),
Work package 4: Project management and dissemination
- Task 4.1: Management and dissemination
- Task 4.2: Seminars for BSH
Status: completed
The results of the research work were published in the form of original scientific publications and presented at several domestic and international conferences.
Original scientific publication
- OSELI, Alen, MIHELČIČ, Mohor, ŠOBAK, Matic, SLEMENIK PERŠE, Lidija. Nonlinear time-dependent behavior of rheodictic polymers : a theoretical and experimental investigation. Polymer testing. Aug. 2024, vol. 137 , [article no.] 108535, str. 1-11, ilustr. ISSN 1873-2348. https://www.sciencedirect.com/science/article/pii/S0142941824002125, Repozitorij Univerze v Ljubljani – RUL, DOI: 10.1016/j.polymertesting.2024.108535. [COBISS.SI-ID 203185923]
Published scientific paper at the conference
- OSELI, Alen, ŠOBAK, Matic, ZAFOŠNIK, Boštjan, SLEMENIK PERŠE, Lidija. Determination of complete constitutive viscoelastic description of polymers. V: GOLOBIČ, Iztok (ur.). Akademija strojništva 2022 : inženirstvo – inovativne rešitve za trajnostni razvoj in samooskrbo, Ljubljana, 23. november 2022 : [11. mednarodna konferenca]. Ljubljana: Zveza strojnih inženirjev Slovenije – ZSIS, 2022. Letn. 11, št. 3/6, str. 136-137, ilustr. Svet strojništva, letn. 11, št. 3/6. ISSN 1855-6493. https://www.zveza-zsis.si/2022/11/22/svet-strojnistva-akademija-strojnistva-2022/. [COBISS.SI-ID 133753603
Published abstract of scientific paper at conference
- SLEMENIK PERŠE, Lidija, OSELI, Alen. Non-linear time-dependent behavior of amorphous polymers : experimental and theoretical approach. V: AERC 2024 : Leeds : book of abstracts. [S. l.: s. n.], 2024. Str. 128. https://rheology-esr.org/index.php?rex_media_type=redactorImage&rex_media_file=aerc_abstracts_2024.pdf. [COBISS.SI-ID 196835331]
- OSELI, Alen, ZAFOŠNIK, Boštjan, SLEMENIK PERŠE, Lidija. Experimental and theoretical investigation on non-linear time-dependent behavior of amorphous polymers. V: Materials today conference 2023 : 2-5 August 2023, Singapore Expo, Singapore. [Amsterdam]: Elsevier, 2023. Str. 1. https://www.elsevier.com/events/conferences/materials-today-conference/program. [COBISS.SI-ID 162377219]
- MIHELČIČ, Mohor, OSELI, Alen, ZAFOŠNIK, Boštjan, SLEMENIK PERŠE, Lidija. Sample preparation and thermal conditioning of PC and PP on thermal and mechanical properties. V: PPS-38 : book of abstracts : 38th International Conference of the Polymer Processing Society, Olma Messen, St. Gallen, Switzerland, May 22 – 26, 2023. [S. l.: s. n., 2023]. Str. 20. https://www.pps-38.org/documents/7430410/0/Book+of+Abstracts.pdf/1c1488ea-b634-4069-acc7-2ee964680007. [COBISS.SI-ID 153697795]
An outstanding achievement of the research project is the A” type publication in the prestigious journal Polymer testing (Q1, IF=5) entitled: “Nonlinear time-dependent behavior of rheodictic polymers: a theoretical and experimental investigation” (DOI: 10.1016/j.polymertesting.2024.108535). The publication presents a generalized theory and experimental methodology for predicting behavior of polymers and their structures under extreme environmental and loading conditions.
With the developed analytical and numerical tools coupled with novel experimental methodologies for predicting such behavior fresh collaboration with new industrial partners were established in the form of research and development projects, such as:
- Behavior and simulation of orthotropic materials and structures, in collaboration with Hella Saturnus Slovenija, d.o.o (contract: 05/032-2023).
- Behavior and simulation of rheodictic materials and structures with complex thermo-mechanical history, in collaboration with Hella Saturnus Slovenija, d.o.o (contract: 05/034-2023).