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Continuous assembly of aligned nanofibrils into a micro filament
KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.ORCID-id: 0000-0001-9976-8316
KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
Visa övriga samt affilieringar
(Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
Identifikatorer
URN: urn:nbn:se:kth:diva-150581OAI: oai:DiVA.org:kth-150581DiVA, id: diva2:744268
Anmärkning

QS 2014

Tillgänglig från: 2014-09-08 Skapad: 2014-09-08 Senast uppdaterad: 2014-09-08Bibliografiskt granskad
Ingår i avhandling
1. Orientation of elongated, macro and nano-sized particles in macroscopic flows
Öppna denna publikation i ny flik eller fönster >>Orientation of elongated, macro and nano-sized particles in macroscopic flows
2014 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Non-spherical particles are present all around us, in biological, industrial and environmental processes. Making predictions of their impact on us and systems in our vicinity can make life better for everyone here on earth. For example, the ash particles from a volcano eruption are non-spherical and their spreading in the atmosphere can hugely impact the air traffic, as was also proven in 2010. Furthermore, the orientation of the wood fibres in a paper sheet influences the final properties of the paper, and the cause of a specific fibre orientation can be traced back to the fluid flows during the manufacturing process of the paper.

In this thesis, experimental and numerical work is presented with the goal to understand and utilize the behavior of elongated particles in fluid flows. Two different experimental setups are used. The first one, a turbulent half channel flow, aims at increasing the understanding of how particles with non-zero inertia behave in turbulence. The second setup is an attempt to design a flow field with the purpose to align nanofibrils and create high performance cellulose filaments.

Experiments were performed in a turbulent half channel flow at different flow set- tings with dilute suspensions of cellulose acetate fibres having three different aspect ratios (length to width ratio). The two main results were firstly that the fibres agglom- erated in streamwise streaks, believed to be due to the turbulent velocity structures in the flow. Secondly, the orientation of the fibres was observed to be determined by the aspect ratio and the mean shear, not the turbulence. Short fibres were oriented in the spanwise direction while long fibres were oriented in the streamwise direction.

In order to utilize the impressive properties (stiffness comparable to Kevlar) of the cellulose nanofibril in a macroscopic material, the alignment of the fibrils must be controlled. Here, a flow focusing device (resulting in an extensional flow), designed to align the fibrils, is used to create a cellulose filament with aligned fibrils. The principle is based on a separation of the alignment and the assembly of the fibrils, i.e. first align the fibrils and then lock the aligned structure. With this process, continuous filaments were created, with properties similar to that of the wood fibre at the same fibril alignment. However, the highest alignment (lowest angle) of the fibrils in a filament created was only 31o from the filament axis, and the next step is to increase the alignment. This thesis includes modeling of the alignment process with the Smoluchowski equation and a rotary diffusion. Finding a model that correctly describes the alignment process should in the end make it possible to create a filament with fully aligned fibrils.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2014. s. xiii, 81
Serie
TRITA-MEK, ISSN 0348-467X ; 2014.19
Nyckelord
Orientation, fibre, fibril, turbulent channel flow, particle streaks, flow focusing, cellulose nanofibrils, extensional flow, Smoluchowski, rotary diffusion
Nationell ämneskategori
Teknisk mekanik
Identifikatorer
urn:nbn:se:kth:diva-150493 (URN)978-91-7595-254-3 (ISBN)
Disputation
2014-09-25, Kollegiesalen, Brinellvägen 8, KTKH, Stockholm, 10:15 (Engelska)
Opponent
Handledare
Forskningsfinansiär
Knut och Alice Wallenbergs Stiftelse
Anmärkning

QC 20140908

Tillgänglig från: 2014-09-08 Skapad: 2014-09-04 Senast uppdaterad: 2014-09-08Bibliografiskt granskad

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Prahl Wittberg, LisaSöderberg, DanielWågberg, Lars

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Av författaren/redaktören
Håkansson, KarlLundell, FredrikPrahl Wittberg, LisaFall, Andreas B.Söderberg, DanielWågberg, Lars
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MekanikWallenberg Wood Science CenterLinné Flow Center, FLOWFiberteknologi

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