Impact of Sample Size and Deformation Measurement Techniques on Uniaxial Tensile Testing of Fiber-Based Materials

TL;DR

This paper examines how sample size and measurement techniques affect tensile testing of fibrous materials like paper and paperboard.

Contribution

The study provides insights into optimal specimen geometry and deformation measurement methods for accurate tensile testing of fiber-based materials.

Findings

Sample size has a negligible effect on stress–strain curves but influences paperboard fracture.

Digital image correlation highlights the impact of paperboard inhomogeneity on mechanical properties.

Grip slip, not sample size, likely causes apparent variations in tensile test results.

Abstract

The uniaxial tensile test is a common and fundamental test in materials science and engineering, in which a specimen is subjected to controlled tension until failure. From this, the stress–strain curve and many property parameters of the material can be calculated, such as tensile strength, ultimate strength, maximum elongation, Young’s modulus, Poisson’s ratio, and yield strength. As fibrous materials, such as paper and paperboard, become more popular, accurately measuring their mechanical properties becomes essential for developing and applying these materials, especially in packaging. However, since they are anisotropic and inherently inhomogeneous due to the arrangement of the fibers, accurately determining their mechanical properties is not straightforward. This study investigated how several key factors influence the results of tensile tests on fiber-based materials: sample size and deformation measurement techniques using three fiber materials. This study also compared three different strain recording methods: digital image correlation (DIC), video extensometer, and conventional extensometer (Traverse). The DIC technique emphasized the effect of the inherent inhomogeneity of the paperboard on the overall mechanical properties obtained from tensile tests. The results indicated that sample size has a negligible effect on the stress–strain curve, and any apparent influence likely stems from slip at the grips during tensile testing. However, sample size does affect paperboard fracture to some extent. The study also provided recommendations for optimal specimen geometry and deformation recording methods to improve the accuracy and repeatability of tensile testing of fiber-based materials.

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