Experimental study on the actuation and fatigue behavior of the biopolymeric material Cottonid

Scholz, Ronja; Langhansl, Matthias; Zollfrank, Cordt; Walther, Frank

doi:10.1016/j.matpr.2018.11.112

Cited by 10 publications

(12 citation statements)

References 16 publications

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“…Cellulose as most abundant biopolymer on earth and therefore a very sustainable resource is an attractive material candidate for substitution of fossil products in specific, i.e. mostly functional, [32][33][34]. Furthermore, the impact of outdoor weathering conditions on the long-term actuation and fatigue behavior is characterized.…”

Section: Cottonid Materials Systemmentioning

confidence: 99%

“…The samples are then smoothed and dried in a calender (Sumet, Denklingen, Germany) under pressure and temperature. In order to prevent a dimensional change of the material due to water absorption from the environment, the samples are stored under weight in a dry atmosphere until further analysis [33]. Caused by the manufacturing process, the cellulose micro fibrils in the paper layers have a preferred orientation in manufacturing direction [30].…”

Section: Sample Preparationmentioning

confidence: 99%

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Impact of Solar Radiation on Chemical Structure and Micromechanical Properties of Cellulose-Based Humidity-Sensing Material Cottonid

Scholz

Langhansl

Hemmerich

et al. 2020

Preprint

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Renewable and environmentally responsive materials are an energy- and resource-efficient approach in terms of civil engineering applications, e.g. as so-called smart building skins. To evaluate the influence of different environmental stimuli, like humidity or solar radiation, on the long-term actuation behavior and mechanical robustness of these materials, it is necessary to precisely characterize the magnitude and range of stimuli that trigger reactions and the resulting kinetics of a material, respectively, with suitable testing equipment and techniques. The overall aim is to correlate actuation potential and mechanical properties with process- or application-oriented parameters in terms of demand-oriented stimuli-responsive element production. In this study, the impact of solar radiation as environmental trigger on the cellulose-based humidity-sensing material Cottonid, which is a promising candidate for adaptive and autonomously moving elements, was investigated. For simulating solar radiation in the lab, specimens were exposed to short-wavelength blue light as well as a standardized artificial solar irradiation (CIE Solar ID65) in long-term aging experiments. Photodegradation behavior was analyzed by Fourier-transform infrared as well as electron paramagnetic resonance spectroscopy measurements to assess changes in Cottonid’s chemical composition. Subsequently, changes in micromechanical properties on the respective specimens’ surface were investigated with roughness measurements and ultra-micro-hardness tests to characterize variations in stiffness distribution in comparison to the initial condition. Also, thermal effects during long-term aging were considered and contrasted to pure radiative effects. In addition, to investigate the influence of process-related parameters on Cottonid’s humidity-driven deformation behavior, actuation tests were performed in an alternating climate chamber using a customized specimen holder, instrumented with digital image correlation (DIC). DIC was used for precise actuation strain measurements to comparatively evaluate different influences on the material’s sorption behavior. The infrared absorbance spectra of different aging states of irradiated Cottonid show decreased absorption at 2,900 cm-1, i.e. the spectral region of C - H stretching vibrations, and increased absorption at 1,800-1,700 cm-1, i.e. the spectral region of C = O stretching vibrations, with respect to unaged samples and therefore indicate oxidative stress on the surface. These findings differ under pure thermal loads. EPR spectra could corroborate these findings as radicals were detected, which were attributed to oxidation processes. Instrumented actuation experiments revealed the influence of processing-related parameters on the sorption behavior of the tested and structurally optimized Cottonid variant. Experimental data supports the definition of an optimal process window for stimuli-responsive element production. Based on these results, tailor-made functional materials shall be generated in the future where stimuli-responsiveness can be adjusted through the manufacturing process.

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Section: Cottonid Materials Systemmentioning

confidence: 99%

Section: Sample Preparationmentioning

confidence: 99%

Impact of Solar Radiation on Chemical Structure and Micromechanical Properties of Cellulose-Based Humidity-Sensing Material Cottonid

Scholz

Langhansl

Hemmerich

et al. 2020

Preprint

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“…Programmable self-shaping materials are widely studied, e.g. at small scale in fields such as soft (or hard) actuated matter [1][2][3][4][5][6][7][8][9], or at medium and large scale mostly for adaptive structures in construction applications [10][11][12][13][14][15][16][17]. A commonly known principle of obtaining self-shaping systems is the bilayer-laminate.…”

Section: Introductionmentioning

confidence: 99%

Computational analysis of hygromorphic self-shaping wood gridshell structures

et al. 2020

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Bi-layered composites capable of self-shaping are of increasing relevance to science and engineering. They can be made out of anisotropic materials that are responsive to changes in a state variable, e.g. wood, which swells and shrinks by changes in moisture. When extensive bending is desired, such bilayers are usually designed as cross-ply structures. However, the nature of cross-ply laminates tends to prevent changes of the Gaussian curvature so that a plate-like geometry of the composite will be partly restricted from shaping. Therefore, an effective approach for maximizing bending is to keep the composite in a narrow strip configuration so that Gaussian curvature can remain constant during shaping. This represents a fundamental limitation for many applications where self-shaped double-curved structures could be beneficial, e.g. in timber architecture. In this study, we propose to achieve double-curvature by gridshell configurations of narrow self-shaping wood bilayer strips. Using numerical mechanical simulations, we investigate a parametric phase-space of shaping. Our results show that double curvature can be achieved and that the change in Gaussian curvature is dependent on the system’s geometry. Furthermore, we discuss a novel architectural application potential in the form of self-erecting timber gridshells.

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“…Depending on the material thickness t mat (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].…”

Section: Introductionmentioning

confidence: 99%

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

2020

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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.

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Experimental study on the actuation and fatigue behavior of the biopolymeric material Cottonid

Cited by 10 publications

References 16 publications

Impact of Solar Radiation on Chemical Structure and Micromechanical Properties of Cellulose-Based Humidity-Sensing Material Cottonid

Impact of Solar Radiation on Chemical Structure and Micromechanical Properties of Cellulose-Based Humidity-Sensing Material Cottonid

Computational analysis of hygromorphic self-shaping wood gridshell structures

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

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