Laboratory-based Imaging of Microstructure in Polymers

Project Information

LIMP

Grant agreement ID: 101113532

DOI

10.3030/101113532

Project closed

EC signature date 13 March 2023

Start date 1 April 2023

End date 30 September 2024

Funded under

• European Research Council (ERC)

Total cost

No data

EU contribution

€ 150 000,00

Coordinated by

DANMARKS TEKNISKE UNIVERSITET
Denmark

Periodic Reporting for period 1 - LIMP (Laboratory-based Imaging of Microstructure in Polymers)

Reporting period: 2023-04-01 to 2024-09-30

Summary of the context and overall objectives of the project

Polymers are increasingly used as a lightweight and more sustainable alternative to traditional materials like metals in e.g. the aviation and automotive industries. However product developers are not using the polymer materials to their full potential since they don’t fully trust their models of strength and longevity. Having information about the material properties in the bulk of the components during the product development and production stage will provide this trust.
Based on decades of experience from x-ray characterization and instrumentation, our team has developed an x-ray diffraction method to efficiently generate this bulk data for semicrystalline polymers and provide it for intuitive utilization for high performance manufacturers of polymers and composites components.
During the LIMP POC project we pursue the following objectives to enable this technology:
1. Extend the functionality of the technique from 2D maps to 3D maps
2. Engage with key actors in the market to disseminate demonstration cases
3. Increase the portfolio of material the technique has been tested on.
4. Increase speed of acquisitions
Polymers experience a phase transition during production and will generally go through a thermal cycle. Both aspects have a high impact and the final properties of the material. The geometry of the components influences both temperature and the magnitude and direction of imposed forces a volume has been subjected to. This means that mechanical properties vary for different volumes in the component. Extending functionality of the technique from 2D to 3D means the distribution in all three spatial dimensions can be measured. Furthermore, having 3D measurements means that the results are aligned with the simulations manufacturers rely on at this moment. Familiarity with the format of the information means a higher adaptation rate.
Diffraction has been used many years to reveal microstructure of materials, but manufacturers have not had an efficient method use this technique. This means that this type of data is new to potential customers even if they in rare cases evaluate material properties in the final product it is not done consistently and for the complete geometry. Providing potential users with examples and demonstrating use cases will accelerate the adaptation from end-users. In order to make the examples feel relevant a need for both production challenges and materials that are known and similar to the approached end-users are needed.
The project aims to provide full maps of the microstructure and thus a map of variations in mechanical properties for polymers manufacturers. For this information to be available and relevant the measurements need to be efficiently conducted. The measurement needs to be made shortly after the order is made and to be finished quickly. From experience with industrial CT measurements, we have aimed for 1 week of lead time and a full day of measuring.
The impact of having this technique efficiently available would be substantial in terms of giving a more sustainable manufacturing. In polymer production the critical components that are produced are typically overengineered 50% which would be a significant reduction in material use. Furthermore, will the waste be reduced when fewer components are scrapped.
An even more significant impact will be the potential to drive the change in material use away from traditional materials like metal to lightweight and low CO2 emitting polymers. Lighter materials save emissions both during transportation and when the product is in use in e.g. the transportation sector for planes and automobiles.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

As a part of the activities in the showcases we have developed a method for reconstructing three-dimensional information of the parts we are measuring. We were able to reconstruct with a spatial resolution of approximately 200 micrometre, which have been sufficient for the two showcases and corresponds to the spatial resolution we use for the two other dimensions. Simulations show we can resolve even smaller features if needed at the cost of additional acquisitions. At the moment the method has both a high manual preparation resource cost and computational cost and we will work to decrease the time required to perform the reconstruction.
During the project we have made two show cases. In one case we measured the residual strain in a part meant for implant and this could directly be compared with finite element simulations. This work has after the PoC project led to a new project to measure additional parts to track changes in strain as a function of changes in the thermal cycle used in the production. In the second showcase we measured the anisotropy in an injection molded part. During use this type of part has shown unreliable performance and failure. We expect that this work also will lead to new measurements with the developed technique that can track the level of anisotropy as the production parameters are adjusted.
We have made substantial progress in terms of acquisition speed. We have designed a poly-capillary optics that covers the most suitable part of the energy spectrum from the x-ray source extending from 9 to 22 keV and provides an average flux increase of 17 times for the relevant beam size of 400µm. Another substantial factor that increase speed is to tailor the acquisition for the material property that need to be measured and the needed resolution. For features such as anisotropy we are able to reduce acquisition times a factor 20.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The main achievements described above are summarized here.
1. A method based on instrument design and algorithm development for reconstructing 3D maps of microstructure properties.
2. Development of two showcases to demonstrate both residual stress maps and anisotropy maps.
3. Inclusion of thermosets in addition to thermoplastics as materials that can be mapped by the developed technique.
4. Implementation of optics to directly reduce acquisition times down to 6% and additionally optimization for specific use cases for additional reduction up to a factor 20.
The method for reconstructing 3D maps are instrumental for exploiting the technique fully in a commercial market. For commercial utilization the algorithm needs to be implemented more efficiently.
Based on market research such as dialogue with potential customers and attending tradeshows, we see composites based on either a matrix of thermoset or of thermoplastic, as an important market to operate in, since a number of high performance industries such as Aviation and automobile are transitioning to composites from traditional materials such as metals. Besides mapping stresses, crystallinity and anisotropy in composites we will seek to include the degree of cure in the portfolio of properties we can map the distribution of.
The needed acquisition speed will depend on the implementation, at the moment a higher speed translates directly to lower costs but for example in the case of quality assurance application the speed needs to be aligned with the speed of production e.g. the pultrusion speed. The polycapillary optics we have designed improves the acquisition speed but other components giving a higher yield of registered photons such as sources and detectors can also be procured. We will continuously seek to improve speed while balancing the cost of these components.

Example of map performed during the project