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Hybrid Composites Combining Short Deformable Fibers and Particulate Fillers in Polymeric Matrix
Smrčková, Markéta ; Pavelka,, Vladimír (referee) ; Poláček, Petr (advisor)
In this work, the effect of adding short deformable polyvinylalcohol fibers into dimethacrylate resins on mechanical properties of composite materials was investigated. Furthermore, micro- or nano-fillers were added into the matrix. The effect of filler/short fibers combination on mechanical properties of so-called hybrid composites was studied. Composites were characterized by differential compensation photocalorimetry (DPC), termogravimetric (TGA) and dynamic mechanical (DMA) analysis. The fracture surfaces were examined using scanning electron (SEM) and confocal laser (CLSM) microscopy. Elastic modulus and strength, the critical value of stress intensity factor and strain energy release rate and the viscoelastic properties of composite materials were measured. The mechanical properties of composite materials are affected not only by the type of filler/reinforcement, but also by properties of the matrix. These properties also depend on the way of network formation during photo-initiated polymerization. For this reason, heat of polymerization, degree of conversion and the maximum polymerization rate of mixture of dimethacrylate monomers were determined.
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Ceramic nanofiber-reinforced composites
Bocian, Luboš ; Přikryl, Radek (referee) ; Poláček, Petr (advisor)
This thesis investigated how the addition of unsilanized and silanized ceramic SiO2 nanofibers into particle reinforced composite affects flexural strength, fracture toughness, total fracture work and temperature dependence of viscoelastic properties. Fracture surfaces were analyzed with SEM. Flexural strength always decreased with addition of nanofibers. Composites with silanized nanofibers showed higher flexural strength than those with unsilanized nanofibers. Fracture toughness was higher with addition of nanofibers. Fracture toughness of composites with silanized nanofibers was always lower than that of systems with unsilanized nanofibers. Total fracture work was lower with addition of nanofibers, but sharply increased in composites with 5 % of nanofibers. Glass transition temperature almost always increased with addition of nanofibers. Storage modulus increased with addition of nanofibers. Storage modulus was always lower in composites with silanized nanofibers.
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Short Fibers Reinforced Particulate Filled Composites
Kročová, Blanka ; Pavelka, Vladimír (referee) ; Poláček, Petr (advisor)
This diploma thesis examines the effect of short fiber reinforcement in particle composite with a polymer matrix and the effect of its structure on the mechanical properties. It studies the refraction toughness depending on the addition of short polyvinylalcohol fibers (PVAL), nanosilica and pulverized polymethylacrylate (PMMA) to a dimethylacrylate matrix. Matrix strengthening was characterised with the help of differential compensation photocalorimetry. The inner structure of the composite and the morphology of fracture were studied using a scanning electron microscope. For the tested samples, the modules of elasticity and toughness were measured, the critical values of stress intensity factor and the energy release rate were determined. The findings suggest that the limit value of short fibers content is 4 vol. %. This content of fibers significantly increases the tenacity of the material but at the same time the uniform distribution of fibers and the ease of preparation of the material decrease. Within the possible applications, the manipulation of this material worsens as well. The fibers content of 2 ± 0.5 vol. % is an acceptable compromise between good treatability, uniform distribution of fibers and the required mechanical properties. During the study of the fracture surfaces of the material, different types of fibers disruption were witnessed (extraction from the matrix, plastic deformation, fibrillation on the surface of the fibers, fracture) depending on the type of used matrix and filling.
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Ceramic nanofiber-reinforced composites
Bocian, Luboš ; Přikryl, Radek (referee) ; Poláček, Petr (advisor)
This thesis investigated how the addition of unsilanized and silanized ceramic SiO2 nanofibers into particle reinforced composite affects flexural strength, fracture toughness, total fracture work and temperature dependence of viscoelastic properties. Fracture surfaces were analyzed with SEM. Flexural strength always decreased with addition of nanofibers. Composites with silanized nanofibers showed higher flexural strength than those with unsilanized nanofibers. Fracture toughness was higher with addition of nanofibers. Fracture toughness of composites with silanized nanofibers was always lower than that of systems with unsilanized nanofibers. Total fracture work was lower with addition of nanofibers, but sharply increased in composites with 5 % of nanofibers. Glass transition temperature almost always increased with addition of nanofibers. Storage modulus increased with addition of nanofibers. Storage modulus was always lower in composites with silanized nanofibers.
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Short Fibers Reinforced Particulate Filled Composites
Kročová, Blanka ; Pavelka, Vladimír (referee) ; Poláček, Petr (advisor)
This diploma thesis examines the effect of short fiber reinforcement in particle composite with a polymer matrix and the effect of its structure on the mechanical properties. It studies the refraction toughness depending on the addition of short polyvinylalcohol fibers (PVAL), nanosilica and pulverized polymethylacrylate (PMMA) to a dimethylacrylate matrix. Matrix strengthening was characterised with the help of differential compensation photocalorimetry. The inner structure of the composite and the morphology of fracture were studied using a scanning electron microscope. For the tested samples, the modules of elasticity and toughness were measured, the critical values of stress intensity factor and the energy release rate were determined. The findings suggest that the limit value of short fibers content is 4 vol. %. This content of fibers significantly increases the tenacity of the material but at the same time the uniform distribution of fibers and the ease of preparation of the material decrease. Within the possible applications, the manipulation of this material worsens as well. The fibers content of 2 ± 0.5 vol. % is an acceptable compromise between good treatability, uniform distribution of fibers and the required mechanical properties. During the study of the fracture surfaces of the material, different types of fibers disruption were witnessed (extraction from the matrix, plastic deformation, fibrillation on the surface of the fibers, fracture) depending on the type of used matrix and filling.
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Hybrid Composites Combining Short Deformable Fibers and Particulate Fillers in Polymeric Matrix
Smrčková, Markéta ; Pavelka,, Vladimír (referee) ; Poláček, Petr (advisor)
In this work, the effect of adding short deformable polyvinylalcohol fibers into dimethacrylate resins on mechanical properties of composite materials was investigated. Furthermore, micro- or nano-fillers were added into the matrix. The effect of filler/short fibers combination on mechanical properties of so-called hybrid composites was studied. Composites were characterized by differential compensation photocalorimetry (DPC), termogravimetric (TGA) and dynamic mechanical (DMA) analysis. The fracture surfaces were examined using scanning electron (SEM) and confocal laser (CLSM) microscopy. Elastic modulus and strength, the critical value of stress intensity factor and strain energy release rate and the viscoelastic properties of composite materials were measured. The mechanical properties of composite materials are affected not only by the type of filler/reinforcement, but also by properties of the matrix. These properties also depend on the way of network formation during photo-initiated polymerization. For this reason, heat of polymerization, degree of conversion and the maximum polymerization rate of mixture of dimethacrylate monomers were determined.
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