The use of polymers in home appliances for parts and products is continuously increasing over the years. This is an obvious result of the facts that polymers are easy to process, they have excellent strength to weight ratio with favorable chemical and electrical properties.
Though polymers have long been used in home appliances, their integration in complex products and parts, especially in the light of increased durability demand, is still challenging. One of the main characteristics of polymeric materials is that their mechanical properties (i.e. the properties that define their structural integrity) can significantly change with time, load and environmental conditions. In practice, this means that the functionality and the durability of the products manufactured from polymers can substantially change during their life cycle, leading to premature functional or structural failure of the product.
Another critical issue during the use of polymer products is that most polymers are still prepared from natural resources. Their increased use already shows some severe effects on people and the environment. EU's goal in next years outlined in the European Green Deal is dedicated, among others, to product sustainability in the way that products placed on the EU market will have to be designed to last longer, they should be easy to reuse, repair and recycle, and they should incorporate as much recycled material as possible. Additionally, it is expected that in following years the sustainability principles and the ways to regulate various aspects related to products will be accepted and will require:
- improved durability, reusability, upgradability and reparability of the product,
- increased content of recycled components in final products and
- restrictions on single-use and countering premature obsolescence of products.
Obviously, the benefits of using polymers in home appliances will have to be balanced with demands for increased durability, which is related to the ability of reliable prediction of long-term behavior of polymer products, that are exposed to different environmental conditions during their use.
In line with this, the proposed applicative project's main objective is to develop a methodology for predicting time-dependent stress-strain behavior of polymer products at low to medium stress levels, at various temperature and humidity conditions. The results will enable the production of home appliances with new design solutions and extended durability with less impact on the environment.
The methodology will be based on the exact characterization of the material's time-dependent properties and the prediction of long-term material behavior coupled with the validated FEM material model. The methodology will cover non-linear time-dependent processes and will be limited to constant stress loading conditions and applicable to strong material nonlinearities or material failure. Even though polymers' viscoelastic non-linear behavior has already been investigated, non-linear models have not been used to predict long-term material behavior, which is one of this project's primary goals. Thus, within the project, we address the possibility of applying the time-temperature superposition principle in the non-linear domain, the exact characterization of material in non-linear regime, modeling and implementation of the material model into FEM code. And finally, the accuracy of durability predictions of polymeric products will be validated.
The three project partners Laboratory for Experimental Mechanics, Laboratory for numerical modeling and simulation and co-financer of the project, BSH Home Appliances, Nazarje have the necessary knowledge, experiences and experimental equipment for successful implementation of the proposed project which will result in new and improved way of designing polymer parts and products.
