Projects / Programmes
Behaviour of disipative systems under extreme termo-mechanical loading
| Code |
Science |
Field |
Subfield |
| 2.05.02 |
Engineering sciences and technologies |
Mechanics |
Experimental mechanics |
| Code |
Science |
Field |
| T000 |
Technological sciences |
|
| Code |
Science |
Field |
| 2.03 |
Engineering and Technology |
Mechanical engineering |
mechanics of dissipative systems, time-dependent behavior of materials, behavior of materials under high-rate loading, behavior of materials under cycling loading
Researchers (15)
Organisations (3)
Abstract
The ultimate goal of the project is development of technology which utilizes extreme thermo-mechanical boundary conditions to induce non-linear processes of polymer structure formation which lead to material structural forms that exhibit orders of magnitude different mechanical and other physical properties. Such technology, for example, allows manufacturing of products with gradient functionality.
The efficiency of developed technology will be validated through manufactured prototype cylindrical polymeric samples with different levels of gradiency.
Gradient functionality is important both, for medical applications such as orthopaedic and dental implants, and engineering applications such as bearings and other applications where gradient functionality plays important role, such as newly emerging technologies, e.g., MEMS and NEMS technologies.
From the scientific stand point development of such technology requires understanding of multi-scale interaction between the macroscopic boundary conditions and nanoscale molecular re-arrangement in the material. Materials that are more sensitive to small variation in boundary conditions are therefore more preferable for such kind of applications.
The starting point of the proposed project is the new generation multimodal polyamide material, which is founded on the patent-protected technological breakthrough, achieved in the course of several years’ cooperation of the Centre for Experimental Mechanics with the German corporation BASF Aktiengesellschaft. These materials exhibit extremely nonlinear behaviour, and at certain thermo-mechanical boundary conditions (high pressures and rapid changes in temperature and pressure) they are able to form very different structures exhibiting orders of magnitude different properties and even gradient functionality.
Proposed project is subdivided into three work packages of activities:
1) Work package 1 (WP1): Theoretical predictions
2) Work package 2 (WP2): Processing of gradient materials under extreme conditions
3) Work package 3 (WP3): Characterization of gradient materials
In theoretical part of the project (WP1) we will start from the existing internal clock based non-linear viscoelastic models enabling mathematical description of the effect of thermo-mechanical boundary conditions on the time-dependent behaviour of polymer in melt and in solid state. These constitutive models, as well as experimental and numerical techniques, developed by the team in the previous period represent a unique tool for the study of understanding the influence of extreme thermo-mechanical boundary conditions on the long-term behaviour of structural polymers in solid state.
By applying proper thermo-mechanical boundary conditions (technology) we can therefore modify the material structure, which is the result of nonlinear interactions of the polymer chain reorganization processes at different space-time scales from nano- to macro-scale, thus modifying physical properties of the material by several orders of magnitude! Processing of polymeric materials under extreme thermo-mechanical boundary conditions will be implemented within WP2, whereas evaluation of the achieved levels of gradiency and characterization of several physical properties within WP3.
By modifying the material structure by different thermo-mechanical loading histories we can change and improve the functionality and durability of products, which presents the basis for increasing the added value of each product.
Therefore, within the proposed project we want to bring basic knowledge in the field of mechanics of dissipative systems or in particular, non-linear mechanics of time-dependent materials closer to the application by developing technology that will allow production of products and structural elements with gradient mechanical properties and gradient functionality.
Significance for science
Project addressed polymers as dissipative system. Dissipative systems can be defined as “open systems” that operate far from thermodynamic equilibrium state. Prigogine offered this definition and it means that dissipative systems require certain amount of energy for maintaining their structural forms. He observed that at any given scale of observation a single physical body cannot dissipate energy. Hence, dissipation results from interaction between bodies or processes that run simultaneously and interact between each other. Polymers consisting of molecules (i.e. multiple bodies) with different mass/length, which interact with each other may be considered as explicit representatives of dissipative systems. In line with this, inherent structural forms of polymers will depend on their molecular weight distribution & boundary conditions to which materials are exposed during solidification and later on in exploitation. Using different “technological paths” during solidification may lead to very different material structural forms that exhibit orders of magnitude different physical properties, which however will change over time. Hence, polymers are “time-dependent materials”. Within this project we have developed & elaborated analytical, technological & experimental tools needed to produce polymeric parts & products with extremely different inherent structures, which can exhibit orders of magnitude different physical properties. By modifying physical properties of materials we will modify functionality of the end products. This is particularly important for applications in medicine, say, for producing dental implants with gradient structure, which at one end mimic properties of bones & are extremely stiff at the other end. An example of such product is a dental implant that at the distance of 4mm exhibits properties that differ more that 400% in deformability and more than 200% in stiffness. Within the first part of the project we have upgraded the Knauss-Emri (KE) model into the Knauss-Emri-Licehtie (KEL) model, which enables more precise prediction of nonlinear time-dependant behavior of polymers & their nano-, micro- and macro- composites. This part of the research was conducted in close collaboration with the group of prof. Liechtie from University of Texas at Austin. The nonlinear viskoelastic constitutive model (KEL) was then incorporated as a subroutine into the ABAQUS software package. At present KEL is the first non-linear viscoelastic model that is incorporated into ABAQUS, which we consider as the first important scientific contribution of the project. Developed computational tool was used to predict extreme thermo-mechanical boundary conditions to which materials were exposed during solidification in order to achieve extreme variations in their mechanical properties in solid state. Using these boundary conditions we have prepared samples from polyamide and thermopolastic polyurethane with different gradient properties. Developed technology for manufacturing engineering structural elements, such as gears, and dental implants with desired mechanical time-dependant (gradient) properties is the second achievement of this project. Prepared samples with different gradient structure were finally characterized for their time-dependent mechanical and other physical properties. It was found that developed technology allows production of implants which at the distance of 4mm exhibit completely different properties (deformability and stiffness). To our knowledge these are worldwide first polymeric dental implants with gradient structure. In addition, it was shown that by changing the gradiency of the implant it is possible to control the rate of absorption and desorption of medicaments deposited into the material free volume. These findings led to establishment of the new research direction, which goal is to develop solid-state drug delivery system for local deposition of medicaments made from biodegradable polymers.
Significance for the country
The analytical, technological and experimental tools developed within this project represent intellectual potential, which may lead to technological breakthrough in different areas of engineering where polymers are becoming dominant structural materials. Examples of such products are non-lubricated gears, which are widely used in pharmaceutical industry, food industry, and production of kitchen appliances. Most promising market niche are dental and orthopedic implants and the new generation solid-state drug delivery system for delivery of chemotherapeutic drugs directly into the malignant tumors. With such approach we overcome the problem of too low concentration of the drug in the tumor and at the same time too high concentration in healthy tissues. Solid-state drug delivery system (SDD) utilizes material free-volume as drug delivery containers. By controlling the inherent material structure we can control the rate of drug delivery. SDD allows implanting of small polymeric containers directly into the soft tissues- and/or bone-tumors, as well as into the healthy tissues. Any chemotherapy or targeted therapy drug can be used as an active substance. Moreover, poly-chemotherapy principle that utilizes chemotherapy drug combination may be applied locally as well. As a follow up of this project we started to from an interdisciplinary innovation community consisting of leading Slovenian experts in all areas of expertise required to bring dental and orthopedic implants, and solid-state drug delivery system to the world market. This initiative could result in a major technological breakthrough.
Most important scientific results
Annual report
2011,
2012,
2013,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2011,
2012,
2013,
final report,
complete report on dLib.si
