In Situ Characterization of Damage Development in Cottonid Due to Quasi-Static Tensile Loading.

Ronja Scholz,Frank Walther,Alexander Delp

doi:10.3390/ma13092180

Abstract

Cottonid is a layered material based 100% on cellulose that holds excellent material properties by being completely sustainable. The finite nature of petroleum-based resources nowadays makes these properties significant for technical applications again. To understand how Cottonid reacts to application-oriented mechanical loads and how it fails, development of microstructural damage on the surface and in the volume of Cottonid was studied using innovative in situ testing techniques for the first time. Quasi-static tensile tests were comparatively performed in a scanning electron microscope as well as a microfocus computer tomograph, and the development of defects present in the initial condition of the material was investigated. In the elastic region, no visible damage initiation on the surface and a decrease of overall void volume within the gauge length could be detected. When reaching the yield strength, crack initiation on the surface starts at critical areas, like pores and microcracks, which propagation and assembly could be visualized via scanning electron micrographs. In the plastic region, an increase in void volume could be shown in the gauge length until final failure of the specimen. Innovative material testing techniques presented in this study support lifetime estimation in technical applications and understanding of process–structure–property relations. Particularly, characterization of microstructural damage development due to a mechanical load, which leads to final failure of the specimen, is essential to be able to create material models for lifetime prediction in respect to variable manufacturing or application parameters.

Highlights

Cottonid is a cellulose-based polymer, which was developed in 1844 by J
In the beginning of the 20th century, Cottonid was replaced by synthetic plastics in most technical applications and, despite the long awareness of the material, research activities have remained static over a long time
Damage development on Cottonid’s surface due to quasi-static tensile loading is range and how the carbon coating on the surface for avoidance of charging effects of the noncharacterized by crack initiations on microstructural characteristics, like pores and microcracks, conductive material influences the mechanical behavior has to be verified over ongoing studies

Summary

Introduction

Cottonid is a cellulose-based polymer, which was developed in 1844 by J. The material shows a direction-dependent deformation behavior due to a preferred orientation of the cellulose fibrils in manufacturing direction of the raw paper, i.e., highest mechanical strength (ultimate tensile strength, UTS) can be obtained in manufacturing direction and is comparable to common technical plastics, like polyamide (PA) or polyvinyl chloride (PVC), and wood-based materials [7]. Depending on the material thickness tmat (amount of paper layers), Cottonid shows a more or less pronounced and directed swelling and shrinking behavior in reaction to varying relative humidity, similar to wood. These properties were investigated with respect to the chosen manufacturing parameters, with the aim to use Cottonid as a functional material in terms of climate-adaptive architectural applications [8,9,10]. To assess the microstructural changes during loading, qualitative and advanced optical surface and volume analyses via in situ SEM and μCT techniques were performed

Sample Preparation

Test Setup for Microstructural In Situ Investigations

30 MPaduring and σTthold

Results

In Situ Quasi-Static Tensile Tests in μCT

Conclusions and Outlook