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Carbon fibres and their surface modification for aluminium alloy matrix composites

Rafał Kozera

Abstract

Nowadays, lightweight structural materials with high load capacity and improved thermal properties are extremely high demand in transportation, as well as mechanical engineering. These requirements can only be fulfilled by high strength, low density materials. Aluminium alloys reinforced with continuous carbon fibres are among the composites of great interest. However, problems concerning the high reactivity of carbon fibres with the liquid aluminium alloy, their very poor wettability and unsatisfactory mechanical properties of the composites still remain despite many years of investigation. Therefore, the aim of the present studies was the preparation and characterization of the carbon fibres’ surface for application in aluminium alloy matrix composites, as well as characterization of the interface between the carbon fibres and the matrix depending on the fabrication methods used. The following thesis was assumed: deposition of the Ni-P coating on the surface of carbon fibres leads to the improvement of their wettability by liquid aluminium alloy and provides protection against their degradation during the infiltration process. The investigations were carried out using commercially available high strength HTA40 carbon fibres manufactured by Toho Tenax. The fibres were characterized by 7 m diameter and they were covered by the manufacturer with 1.3 mass% epoxy based sizing. The preparation of carbon fibres’ surface for aluminium alloy composites consisted of two main stages: sizing removal and electroless metallization of carbon fibres with Ni-P coatings with 2.5 mass% of phosphorous. The studies were focused on the assurance of the fibres’ highest mechanical properties before infiltration at the stage of sizing removal, metallization as well as after pre-heating, during the process of infiltration with liquid aluminium alloy. The mechanical tests of single carbon fibres before and after thermal treatment, as well as after the Ni-P deposition process were conducted using an especially developed methodology. The microstructure of the processed carbon fibres was analysed by high resolution SEM and XRD techniques. Further, evaluation of the influence of Ni-P coatings and infiltration parameters on the microstructure of composites fabricated with gas pressure infiltration and high pressure die casting was carried out using HRSEM and TEM. Moreover, for better characterization of the fabricated composites a methodology for an interfacial strength measurements between the carbon fibres and matrix using push out tests was developed. A special shape of the micro intender was designed and developed using ion microscope.
Record ID
WUT471eebb620f1407f9fec6939ae70e875
Diploma type
Doctor of Philosophy
Author
Title in Polish
Włókna węglowe i modyfikacja ich powierzchni do zastosowań w kompozytach o osnowie stopów aluminium
Title in English
Carbon fibres and their surface modification for aluminium alloy matrix composites
Language
(en) English
Certifying Unit
Faculty of Materials Science and Engineering (FMSE)
Discipline
material sciences and engineering / (technology domain) / (technological sciences)
Status
Finished
Start date
23-03-2012
Defense Date
24-10-2014
Title date
24-10-2014
Supervisor
Internal reviewers
External reviewers
Anita Zofia Olszówka-Myalska Anita Zofia Olszówka-Myalska,, External affiliation of publication: Silesian University of Technology
Pages
161
Keywords in English
xxx
Abstract in English
Nowadays, lightweight structural materials with high load capacity and improved thermal properties are extremely high demand in transportation, as well as mechanical engineering. These requirements can only be fulfilled by high strength, low density materials. Aluminium alloys reinforced with continuous carbon fibres are among the composites of great interest. However, problems concerning the high reactivity of carbon fibres with the liquid aluminium alloy, their very poor wettability and unsatisfactory mechanical properties of the composites still remain despite many years of investigation. Therefore, the aim of the present studies was the preparation and characterization of the carbon fibres’ surface for application in aluminium alloy matrix composites, as well as characterization of the interface between the carbon fibres and the matrix depending on the fabrication methods used. The following thesis was assumed: deposition of the Ni-P coating on the surface of carbon fibres leads to the improvement of their wettability by liquid aluminium alloy and provides protection against their degradation during the infiltration process. The investigations were carried out using commercially available high strength HTA40 carbon fibres manufactured by Toho Tenax. The fibres were characterized by 7 m diameter and they were covered by the manufacturer with 1.3 mass% epoxy based sizing. The preparation of carbon fibres’ surface for aluminium alloy composites consisted of two main stages: sizing removal and electroless metallization of carbon fibres with Ni-P coatings with 2.5 mass% of phosphorous. The studies were focused on the assurance of the fibres’ highest mechanical properties before infiltration at the stage of sizing removal, metallization as well as after pre-heating, during the process of infiltration with liquid aluminium alloy. The mechanical tests of single carbon fibres before and after thermal treatment, as well as after the Ni-P deposition process were conducted using an especially developed methodology. The microstructure of the processed carbon fibres was analysed by high resolution SEM and XRD techniques. Further, evaluation of the influence of Ni-P coatings and infiltration parameters on the microstructure of composites fabricated with gas pressure infiltration and high pressure die casting was carried out using HRSEM and TEM. Moreover, for better characterization of the fabricated composites a methodology for an interfacial strength measurements between the carbon fibres and matrix using push out tests was developed. A special shape of the micro intender was designed and developed using ion microscope.
Thesis file
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    Kozera.pdf
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Uniform Resource Identifier
https://repo.pw.edu.pl/info/phd/WUT471eebb620f1407f9fec6939ae70e875/
URN
urn:pw-repo:WUT471eebb620f1407f9fec6939ae70e875

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