Mechanics of paper deformation
During the manufacturing of paper, wood fibers are dispersed in water and this pulp is spread onto a moving sieve. The water is then extracted and the remaining fiber mat is then turned into paper by drying it.
Nowadays this process has been industrialized and engineered to a high degree, enabling paper manufacturers to produce paper at very high speeds (typically up to 1200 m / min), over large widths of the paper machine (typically up to 12 m).
The speed of this process is so high that the fibers get, more or less, aligned and therefore the fiber orientation in the resulting paper sheet is not random.
The fiber network is, therefore, more stiff in the machine direction than it is in the cross direction (figure 1).
The mechanical behaviour of a paper sheet can be described by the orthotropic material model : elastic constants are different for different directions of measurement, see figure 2.
Fig. 1. The three reference directions for the Fig. 2. Directions for measurement of the
mechanical properties of paper : in-plane elastic properties of paper
In this assignment we use the orthotropic material model for the description of the deformation behaviour of paper. Using a modern DIC measurement technique the in-
plane elastic constants of various types of paper will be measured. In literature several publications are available that explore relations between these elastic constants.
Most of these relations have been derived using special boundary conditions. The goal of this assignment is to explore the limits of the application ranges for these relations.
Focus will be on the measurement of the in-plane elastic constants, but the assignment can be extended with measurements of out-
of-plane properties (Ezz, Exz, Eyz).
You will be mainly challenged on your experimental skills. The DIC set up and tensile testing equipment is available for this research.
You will use an existing (Matlab) software module to analyse the measurement results. Some literature research will be necessary to find appropriate publications on the topic and to design and implement postprocessing of the results.
If the assignment will be extended to the determination of properties in the Z-direction, the design of the experiment must be developed, the setup built and the method must be tested.
For this assignment you are
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