Thermographical Analysis of Paper During Tensile Testing and Comparison to Digital Image Correlation

Abstract

The thermal response in paper has been studied by thermography. It was observed that an inhomogeneous deformation pattern arose in the paper samples during tensile testing. In the plastic regime a pattern of warmer streaks could be observed in the samples. On the same samples digital image correlation (DIC) was used to study local strain fields. It was concluded that the heat patterns observed by thermography coincided with the deformation patterns observed by DIC. Because of its fibrous network structure, paper has an inhomogeneous micro-structure, which is called formation. It could be shown that the formation was the cause of the inhomogeneous deformations in paper. Finite element simulations was used to show how papers with different degrees of heterogeneity would deform. Creped papers, where the strain at break has been increased, were analysed. For these paper it was seen that an overlaid compaction of the paper was created during the creping process. During tensile testing this was recovered as the paper network structure was strained.

Identifying the weak spots in packaging paper: local variations in grammage, fiber orientation and density and the resulting local strain and failure under load

“…6b, that the temperature decreased first in the elastic region of the stress-strain curve and then increased considerably after reaching the plastic region. This behavior is well in line with previous studies and can be explained with thermoelastic effect (Dumbleton et al 1973;Hagman and Nygårds 2017). The increase of the temperature at 0.7% strain (red line) indicates the onset of fiber-fiber bond failure, which, as discussed above, is caused by the heat dissipation of the strain energy in the fibers when the bonds break.…”

“…The local deformation was investigated microscopically and the local basis weight by gravimetrically measuring the local regions of fibrous networks. Korteoja et al (1998) as well as Hagman and Nygårds (2017) concluded that locally high tensile strain and tensile damage occurred in the regions with low basis weight. Besides, Wong et al (1996) found that the rupture of paper initiated from the region with low basis weight and high strain.…”

“…Korteoja et al (1998) studied local tensile damage optically with the aid of silicon impregnation which improved the visibility of the damaged regions. Hagman and Nygårds (2017) as well as Yamauchi and Murakami (1994) utilized in turn infrared thermography (IRT) to investigate the damage distribution. This method is based on the fact that thermal energy is dissipated (temperature increases) in the regions with plastic deformation, i.e.…”

“…Korteoja et al (1998) and Wong et al (1996) measured local basis weight with a b-radiographic transmission method (described in ''Local basis weight'' section). Yamauchi and Murakami (1994) utilized a soft X-ray method and Hagman and Nygårds (2017) optical method to estimate the basis weight variations within paper.…”

Non-invasive methods in diagnosis of wall dampness degree in sacral buildings

“…The causes of dampness may be [4]:  Precipitation;  capillarity of groundwater;  condensation of steam or sanitary installation breakdowns;  technological processes connected with erecting buildings.…”