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Relation between Structural Non-Uniformity and Strength of Paper

Researchers: Petri Hirvonen and Kimmo Kaski


In this project we studied experimentally how formation type disorder affects damage accumulation and final fracture pattern of a paper specimen. SC base paper specimens were dog bone shaped and silicon impregnated to enhance damage area visibility. After digital image processing 33 damage accumulation in the middle section of paper tensile specimen was determined in two ways: first by calculating standard deviation of gray levels and second by calculating microscale. These results suggest that formation does not affect on damage accumulation in paper specimen.

 
Figure 33
Figure 33:   Image enhancement steps. Second image from left was used to calculate damage accumulation. The image on the farthest right is the one from which fracture path was determined.

We used Far Infra Red (FIR) technique for determining spatial relation between basis weight and fiber orientation. Results show that no relation is to be found. Earlier results in our project suggest that non-uniform structure lead to an effective concentration of strain and damage into low grammage areas of paper so that high grammage areas are left practically intact. We used the FFT method to calculate flock size distribution of a specimen and fracture path wavelength distribution of the same specimen. Results suggest that flock size is bigger for poor formation samples than for good formation samples. Fracture path roughness was also calculated from which it can be said that poor formation specimen have rougher fracture path than that from good formation specimen.


next up previous contents
Next: Studies on Microelectromechanical Systems Up: Computational Materials Research Previous: Electro- and Magneto-rheological Fluids
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