Joint strength measurements of individual fiber-fiber bonds: An atomic force microscopy based method

Schmied, Franz; Teichert, Christian; Kappel, Lisbeth; Hirn, Ulrich; Schennach, Robert

doi:10.1063/1.4731010

Cited by 30 publications

(21 citation statements)

References 26 publications

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“…In this mode, so called Mode I, the force is acting perpendicular to the joint surface while in shearing, the force acts parallel to the joint. Peeling tests yield lower values than shearing (Schmied et al 2012;Magnusson et al 2013b). Secondly, led by the findings of Stratton (1991), Koubaa and Koran (1995) assumed that the measure of RBA is the relation between the apparent sheet density and fibre wall density, therefore, calculating the values for the entire bonded area and not for individual fibre to fibre joints.…”

Section: Optically Bonded Area Of Hardwood and Softwood Fibresmentioning

confidence: 94%

Strength of individual hardwood fibres and fibre to fibre joints

et al. 2016

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In the present study hardwood fibre strength and fibre to fibre joint strength measurements using bleached, industrial eucalyptus kraft pulp have been performed. The device used for the measurements was a micro bond tester developed at Graz University of Technology. Results were compared to those obtained in previous studies dealing with both, hardwood and softwood. The mean force to break individual hardwood joints (1:82 AE 0:48 mN) was found to be 72 % smaller than that of unbleached softwood joints and is mainly governed by the bonded area of the joints. Furthermore, the optically bonded area (OBA) of hardwood fibre to fibre joints was investigated. OBA of hardwood joints is about 81 % smaller than those of softwood and the reduction is attributed to smaller width and lower collapsibility of the fibres. Compared to softwood, the force per unit OBA of hardwood is 1.72 times higher (5:32 AE 1:46 MPa). This difference is believed to be due to the well known size effect. Single fibre tensile testing resulted in a mean breaking load of 38:81 AE 16:31 mN and show a 76 % reduction when compared to softwood. The reduction is attributed to the smaller cross sectional area and the effect of bleaching.

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Section: Optically Bonded Area Of Hardwood and Softwood Fibresmentioning

confidence: 94%

Strength of individual hardwood fibres and fibre to fibre joints

et al. 2016

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“…Fibre bonds are formed due to several mechanisms e.g., mechanical interlocking, hydrogen bonds, electrostatic interactions, interdiffusion, and induced dipoles; however, the discussion in this area is still open [8]. Mechanical behaviour of paper is indisputably affected by the properties of microstructure components.…”

Section: Motivationmentioning

confidence: 99%

“…[16] which may itself cause premature partial damage of the interfibre joint. Conventional atomic force microscopy (AFM) technique has also been used to measure fibre bonding force in peeling mode [8]. A microrobotic platform was developed for making, manipulating and measuring the strength of individual paper fibre bonds in shear mode [14], which has been the first effort to use microrobotics to obtain strength properties of individual fibre bonds.…”

Section: State-of-the-art Bond Strength Measurementmentioning

confidence: 99%

Microrobotic system for multi-rate measurement of bio-based fibres Z-directional bond strength

2015

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The core content of this study is micro-testing of microscale objects -an emerging application area for microrobotics -where microrobotics has been used in paper industry for measuring properties at the single fibre level. Pulp and paper scientists are interested to have experimental data of single fibre-fibre bond strength distribution of paper/board products in different loading modes and rates. Meeting this demand is quite challenging since the system should be able to measure the bond strength i) in the individual fibre level, ii) in different loading modes, and iii) in different loading rates. The current methods of measurement do not satisfy all these three requirements. Among the four different loading modes, the Z-directional behaviour of paper/board products is a matter of high significance for papermaking and paper converting companies. The Z-directional properties influence compressive properties, and accordingly the performance of structural paper/board products. According to the literature, there is not any reported method to facilitate the measurement of Z-directional strength at the single fibre level in different loading rates. This paper reports an in-depth study of a measurement method for experimental evaluation of Z-directional individual fibre-fibre bond strength in multiple loading rates using microrobotics and a Polyvinylidene fluoride (PVDF) film microforce sensor. The results from the measurement system are promising. In summary, the first concept for multi-rate measurement of Z-directional bond strength at the individual fibre level is developed during this work which has a high practical impact on the fibre characterization research field.

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“…2. The details for the experimental procedure for mode 1 are described by Schmied et al (2012) and for modes 2 and 3 by Fischer et al (2012). In short the setups are as follows.…”

Section: Methodsmentioning

confidence: 99%

“…fiber length, fiber tensile strength, paper density, and straining during drying of the sheet. Therefore, fiber-fiber bond strength is usually investigated by measuring the bond strength of individual fiber-fiber joints (Schniewind et al 1964;Saketi and Kallio 2011;Fischer et al 2012;Schmied et al 2012;Saketi et al 2012;Magnusson et al 2013b). It might be intuitive to think that the breaking load (in N) of a fiber-fiber joint is composed of a specific bond strength (bonding force per unit area, N/m 2 ) times the bonded area (in m 2 ) of the fiber-fiber joint.…”

Section: Introductionmentioning

confidence: 99%

A Proposed Failure Mechanism for Pulp Fiber-Fiber Joints

et al. 2016

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Due to stress concentration at the edges, fiber-fiber bonds under load are known to fail gradually inwards from the edges. In this paper, we propose a failure mechanism for fiber-fiber joints under load, based on the peak stresses occurring at the bond edges. We have modeled the mechanical testing of individual fiberfiber joints using a finite element method (FEM) framework. The model is based on experimental results of fiber-fiber joint strength tests designed to induce each of the three modes in fracture mechanics: opening, sliding, and tearing. A parametric study of the peak load at the edges of the fibers was carried out in order to identify a failure mechanism. The peak stresses were not directly taken from the FEM models, as these values are highly discretization-dependent. Instead, the peak stresses were estimated from resultant forces and moments in the bond and an idealized geometry of the bonding region. The literature has, up to now, focused on shear load as a failure mechanism for fiber-fiber bonds. However, our findings indicate that pulp fiber joints are sensitive to normal stresses and insensitive to shear stresses. Hence, we suggest utilizing failure criteria related to normal stress in future work.

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Joint strength measurements of individual fiber-fiber bonds: An atomic force microscopy based method

Cited by 30 publications

References 26 publications

Strength of individual hardwood fibres and fibre to fibre joints

Strength of individual hardwood fibres and fibre to fibre joints

Microrobotic system for multi-rate measurement of bio-based fibres Z-directional bond strength

A Proposed Failure Mechanism for Pulp Fiber-Fiber Joints

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