Analysis of localized failure in low-basis-weight paper

Abstract

Continuum damage mechanics (CDM) is used to describe the post-elastic behavior of low-basis-weight paper. The relevance of undertaking studies of the mechanical behavior of low-basis-weight paper is that it enables characterization, optimization and quality control. In accordance with a CDM theory, an internal variable is introduced that represent the degree to which the material has degraded in a continuum sense and details inherent in a damage evolution law contain information about the rupture mechanism. To account for long ranging micro-structural effects, because of the fiber structure in the paper material, a non-local formulation of the constitutive law is considered. Of particular interest is the fracture toughness of the material, i.e. the ability to resist further crack propagation, as it is often a good measure of flaw tolerance and durability in the context of paper. The constitutive model discussed is verified against tensile tests on rectangular paper specimens containing pre-fabricated cracks. Acoustic emission was used to study the damage evolution in paper specimens during tensile loading. An orthotropic material description has been utilized. The model is contrasted with a purely isotropic formulation. It seems that for the type of problem analyzed in this work, an orthotropic material description does not significantly improve the predictive capability as compared to an isotropic formulation. It is concluded that the model can be used to evaluate the influence of arbitrary defect geometries, defect size and loading conditions and can easily be incorporated into a finite element code.

Prospects for Maintaining Strength of Paper and Paperboard Products While Using Less Forest Resources: A Review

“…Fundamental works and review articles have described key aspects (Linhart et al 1987;Deng and Dodson 1994;Niskanen and Leskela 1997;Niskanen and Kärenlampi 1998). Also, progress has been achieved in terms of mathematical models to bridge the gap between paper structure and the damage leading to breakage that occurs on a local level within the structure (Korteoja et al 1997;Niskanen and Leskela 1997;Kotik et al 2005;Hagglund and Isaksson 2006). Certain studies that set out to demonstrate benefits of dry-strength additives have shown, probably to the surprise of the researchers, that some effects of the additives could be accounted for based on changes in the uniformity of the resulting paper (Roberts et al 1986;Kim and Hubbe 2010).…”

Influence of fiber orientation on the ballistic performance of needlepunched nonwoven fabrics

“…The initial studies of the structural performance of nonwoven fabrics were focused on paper (Bronkhorst, 2003;Hägglund and Isaksson, 2006;Isaksson et al, 2006Isaksson et al, , 2004 but more recent analyses have dealt with glass (Ridruejo et al, 2010), polyamide (Silberstein et al, 2012), polypropylene (Farukh et al, 2013;Jubera et al, 2014;Ridruejo et al, 2011Ridruejo et al, , 2015 and polyethylene (Martínez-Hergueta et al, 2015;Raina and Linder, 2014;Raval et al, 2013) nonwoven fabrics. These investigations found that the micromechanisms of deformation and fracture depend on the interaction of a number of factors including fiber uncurling, bond failure and fiber reorientation as well as fiber sliding and fracture.…”

Strain energy distribution in a crack-tip region in random fiber networks

“…Hägglund and Isaksson 2006;Isaksson and Hägglund 2007a), it is reported that classical continuum mechanical descriptions of paper materials cannot fully describe deformations near macroscopic cracks. This is due to microstructural effects altering the strain field in the body if it is inhomogeneous; the fibers introduce long-ranging actions that limit the size of gradients in strain.…”

“…Heyden and Gustafsson 1998; Ritala and Huiku 1989;Åström and Niskanen 1993;Fig. 1 Fracture testing of tissue paper for two pre-fabricated slit lengths, 5 mm (a) and 70 mm (b) for a specimen size of 230 × 150 mm Hägglund and Isaksson 2007). It is observed in experiments on paper that for networks having anopen (sparse) structure, a relatively large macroscopic crack is required to localize macroscopic failure (Hägglund and Isaksson 2006). Figure 1 illustrates the difference in behavior between an initial crack length of 5 mm and 70 mm for a tissue paper material.…”