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Transparent plywood as a load-bearing and luminescent biocomposite
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
KTH, School of Engineering Sciences (SCI), Applied Physics, Photonics.ORCID iD: 0000-0002-3368-9786
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
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2018 (English)In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 164, p. 296-303Article in journal (Refereed) Published
Abstract [en]

Transparent wood (TW) structures in research studies were either thin and highly anisotropic or thick and isotropic but weak. Here, transparent plywood (TPW) laminates are investigated as load-bearing biocomposites with tunable mechanical and optical performances. Structure-property relationships are analyzed. The plies of TPW were laminated with controlled fiber directions and predetermined stacking sequence in order to control the directional dependence of modulus and strength, which would give improved properties in the weakest direction. Also, the angular dependent light scattering intensities were investigated and showed more uniform distribution. Luminescent TPW was prepared by incorporation of quantum dots (QDs) for potential lighting applications. TPW can be designed for large-scale use where multiaxial load-bearing performance is combined with new optical functionalities.

Place, publisher, year, edition, pages
Elsevier, 2018. Vol. 164, p. 296-303
Keywords [en]
Transparent Wood, Nanotechnology, Biocomposite, Photonics
National Category
Composite Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-233274DOI: 10.1016/j.compscitech.2018.06.001ISI: 000440121700036Scopus ID: 2-s2.0-85048381154OAI: oai:DiVA.org:kth-233274DiVA, id: diva2:1240335
Funder
EU, European Research Council, 742733
Note

QC 20180821

Available from: 2018-08-21 Created: 2018-08-21 Last updated: 2024-03-18Bibliographically approved
In thesis
1. Deformation and Fracture Behavior of Transparent Wood-Polymer Biocomposites
Open this publication in new window or tab >>Deformation and Fracture Behavior of Transparent Wood-Polymer Biocomposites
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Transparent wood-polymer biocomposites (TWPBs) are interesting wood-based materials with a unique combination of optical transmittance and mechanical properties. The wood substrate is delignified (removal of lignin) while the wood microstructure is preserved. In this thesis, the deformation and fracture behavior of TWPBs are investigated, and material properties are determined. In addition, a method is presented for identifying orthotropic and fracture properties from single small and thin specimen geometries of wood composites by minimizing the discrepancy between experimentally measured and numerically generated strain fields. Material model parameters in the finite element method (FEM) are updated by optimization routines (FEMU). The focus of the thesis is on TWPBs, but wood fiber biocomposites are included to develop the FEMU approach. In

Paper I and II, the mechanical and optical behavior of laminated and single lamina of TWPBs are investigated. Orthotropic mechanical properties, such as elastic stiffness parameters and tensile strength, are determined along and across the fiber direction, and the deformation mechanisms are characterized. Reducedanisotropic ratio (e.g., a ratio of in-plane elastic stiffness parameters), increased wood cell wall effective properties, and improved stress transfer by a more homogeneous strain field are found for TWPBs compared to native wood. Lamination moderates the weakest properties and allows structural tailoring, making it more suitable as a load-bearing material.

In Paper III and IV, fracture and deformation mechanisms are investigated, and the fracture properties are determined using cohesive zone models (CZM) along and across the fiber direction. This approach made it possible to explain 90° crack deflection phenomenon. Large fracture process zones (FPZ) dominated by the cell wall properties are observed, involving fiber pull-out with large cohesive strength in the fiber direction. Also, cross-over bridging mechanisms by cell wall peeling in the transverse fiber direction, with low cohesive strength properties. Longitudinal fracture properties of native wood are improved with a polymer matrix, while the transverse fracture properties are reduced as well as the size of the FPZ.

In Paper V, random and oriented wood-fiber biocomposites are investigated, relating nano- and microscale structures to macroscopic mechanical properties. Orthotropic elastic-plastic material parameters are identified from off-axis tensile tests by using FEMU. Fracture mechanisms are related to microstructural features by the use of supporting in situ tensile tests in a scanning electron microscope.

Abstract [sv]

Genomskinliga träpolymer biokompositer (TWPB) är intressanta träbaserade material med unik kombination av optiska och mekaniska egenskaper. Träsubstraten är delignifierat och trämikrostrukturen är bevarad. I denna avhandling studeras deformation- och brottmekanismer hos TWPB, och deras mekaniska egenskaper bestäms. Utöver detta utvecklas en metod för att bestämma ortotropa material- och brottparametrar från enstaka små och tunna provstavsgeometrier av träkompositer genom att jämföra töjningsfält från experiment och numeriska modeller med optimerade modellparametrar i finita elementmetoden (FEMU). Fokus i avhandlingen är på TWPB men även generella träfiberkomopositer är av intresse för att utveckla en metod för FEMU.

I artiklarna I and II undersöks de mekaniska och optiska egenskaperna för laminerade och enriktade TWPBs. Materialparametrar bestäms och deformationsmekanismer identifieras. För TWPB visade resultaten minskade förhållandet av anisotropi mellan elastiska parametrar, cellväggens effektiva egenskaper ökade och jämfört med rent trä så uppmättes betydligt mer homogena töjningsfält. De svaga mekaniska egenskaperna i transversell fiberriktning får mindre betydelse genom lamineringen, vilket gör materialen bättre lämpade för lastbärande konstruktioner.

I artiklarna III och IV undersöks deformations- och brottmekanismer och brottegenskaperna tas fram med hjälp av kohesiva zon modeller längs de två materialriktningarna i planet. Stora brottprocesszoner (FPZ) observerades, och de domineras av cellväggens egenskaper, med fiberbrott för longitudinell belastning. För transversell belastning dominerar längsgående gående sprickor i cellväggen på grund av svag kohesiv hållfasthet. Brottegenskaperna i fiberriktningen förbättras på grund av polymermatrisen, medan transversella brottegenskaperna försämrades och storleken på FPZ minskade jämfört med rent trä.

I artikel V undersöks träfiberbiokompositer med riktad och slumpmässig fiberorientering samt effekten av olika fiberstrukturer från nano- till mikroskala på materialparametrarna. Ortotropa elastiskt-plastiska materialparametrar är framtagna med FEMU för de riktade träfiberbiokompositerna från dragprover lastad med en vinkel från fiberriktningen. Mikromekanismerna är observerade från töjningsfält och brottmekanismerna är relaterade till materialens struktur med hjälp dragprover på plats under ett svepelektronmikroskop.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2022
Series
TRITA-SCI-FOU ; 2022:38
Keywords
biocomposites, fracture mechanics, strain field measurement, cohesive zone modeling, mechanical properties
National Category
Composite Science and Engineering
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:kth:diva-316995 (URN)978-91-8040-323-8 (ISBN)
Public defence
2022-09-29, Kollegiesalen, also on zoom: https://kth-se.zoom.us/j/65216494216, Brinellvägen 8, Stockholm, 10:00 (English)
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Supervisors
Note

QC220905

Available from: 2022-09-05 Created: 2022-09-02 Last updated: 2023-06-30Bibliographically approved

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Fu, QiliangYan, MaxJungstedt, ErikYang, XuanLi, YuanyuanBerglund, Lars A.

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