Goal 
The aim of this thesis is to develop knowledge of how fiber dimensions such as fiber length, wall thickness and diameter affect mechanical properties of papers. 

Background 
At Billerud, we are convinced that working together with other companies, universities and research institutes is the best way to tap into new thinking concerning improved packaging materials in a circular approach. The purpose of the department Innovation, Product and Application Development (IPAD) is to create new materials that can replace fossil-based materials with more sustainable alternatives based on forest raw materials. The major challenge for cellulosic materials is to improve certain properties, such as extensibility, strength or barriers to water vapor and other gases and to produce these materials in a resource and energy efficient way.  

Within the area of Package Performance, it is of utmost importance to be able to do predictions of paperboard performance in relation the properties of the fibers that are used in the papermaking process. In previous work1, a first attempt was made to correlate papermaking parameters to paper properties, it was shown that strength can be expressed as a function of density, fiber length and the degree of anisotropy.

Project 
Pulp fibers are made from different tree species, and the fiber dimensions are different depending on the species. However, the fiber dimensions, such as wall thickness and diameter, should affect strength. The purpose of this work is to develop models addressing this dependency. 

The work that will be carried out involves the following activities: 

• Literature study of in-plane and out-of-plane strength properties made of different fiber types.  
• Study of production data and data of paperboard and free-laid plies from Billerud. 
• Formulation of hypotheses on how the fiber dimensions will enter the relation needs to be developed, where knowledge will be sought in the literature. This includes formulation of inertia and collapse loads for fibers. This also includes building an understanding of how the yield (e.g. the amount of lignin that is maintained) affects properties. We know that increased yield gives stiffer fibers, in addition we can see that is affects strength differently,  
• Numerical implementation of models and verification by comparing with literature and productions data. 
• Writing of MSc thesis and reporting at Billerud and academia. 

Timetable 
The project preferably starts in January 2025. A detailed schedule will be defined together with the candidate. 

Location 
Preferably a location at KTH can be arranged, alternatively at our mills in Frövi or Gävle. 

To be able to successfully contribute to this degree project, we believe that you are a master student in materials science, solid mechanics or equivalent. To be able to carry out the practical part of the degree project, you be able to do numerical analysis using e.g Matlab, Python etc.

Our values are central in our business and we believe that you recognize yourself in: we care for each other and we do what we say.

For any questions, please contact Mikael Nygårds, Mikael.Nygards@billerud.com

Candidates apply with the Billerud application system by submitting a resume, cover letter and grades. Please note that our system only allows 2 document uploads, therefore we kindly ask you to combine 2 of the 3 requested documents.

The deadline for applications is 2024-12-15.