Submitted by Renata Lopes (renatasil82@gmail.com) on 2015-12-04T14:43:43Z No. of bitstreams: 1 thaianadamacenocunha.pdf: 1265962 bytes, checksum: 6d8fb90304d78d671faf48a4a00e64e5 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2015-12-07T03:22:42Z (GMT) No. of bitstreams: 1 thaianadamacenocunha.pdf: 1265962 bytes, checksum: 6d8fb90304d78d671faf48a4a00e64e5 (MD5) / Made available in DSpace on 2015-12-07T03:22:42Z (GMT). No. of bitstreams: 1 thaianadamacenocunha.pdf: 1265962 bytes, checksum: 6d8fb90304d78d671faf48a4a00e64e5 (MD5) Previous issue date: 2015-04-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O objetivo deste estudo foi mensurar a alteração dimensional de uma silicona por condensação através de um paquímetro digital (Mitutuyo), de um estéreo microscópio (Olympus) e de uma máquina de medição tridimensional por coordenadas (Mitutuyo). Foram realizadas 4 moldagens através de um dispositivo específico com a silicona por condensação pesada e leve Speedex (Coltene/Vigodent). Em cada um dos 4 moldes 4 distâncias foram mensuradas pelos 3 instrumentos, em 4 tempos distintos: no momento da remoção do molde e após 30min, 1h e 7 dias. As médias das mensurações foram submetidas ao teste estatístico Kruskal-Wallis com nível de significância de 5%. Os resultados mostraram diferenças significantes entre as alterações dimensionais verificadas por cada um dos instrumentos de medição, as mensurações realizadas pelo paquímetro digital e pela máquina de medição tridimensional por coordenadas apresentaram alterações dimensionais significantes nos 4 tempos testados, enquanto as pelo estéreo microscópio não apresentaram diferença significante nos 4 tempos. Concluiu-se que as alterações dimensionais verificadas nos moldes da silicona por condensação testada obtidas através de cada instrumento de medição utilizado nesta pesquisa foram diferentes entre si, evidenciando que os diferentes métodos de medição utilizados podem fornecer resultados distintos, e consequentemente, indicações equivocadas. / The aim of this study was to measure the dimensional changes of a silicone condensation using a digital paquimeter (Mitutuyo), an estereomicroscope (Olympus) and a three-dimensional coordinate measuring machine (Mitutuyo). Were made 4 impressions trhough a specif device using the putty and light silicone condensation Speedex (Coltene/Vigodent). Four distances were measured at each impression through the 3 instruments at 4 different times: in the moment of removal of the die and after 30min, 1h e 7 days. The avarage of the measurements were subimitted to the statistical test Kruskal-Wallis with level of significance of 5%. The results shows significant diferences between the dimensional changes verified by each one of the measuring instruments, the measurements through the digital paquimeter and the measurements trhough the three-dimensional coordinate measuring machine showed significant dimensional changes in the 4 tested times, while the measurements through the estereomicroscope did not show significant difference in the 4 tested times. It concludes that the dimensional changes verified in the tested silicone condensation by each measurement instrument used in this study were diferente, indicating that the different measuring methods used can provide wrong results, and consequently, wrong indications.

The diploma thesis deals with computational modelling of stress-strain states in elastomeric components of a flexible coupling. The first part of the thesis is dedicated to research about usage and designs of flexible coupling and about fatigue of elastomers. The second part of the thesis concerns creation of the computational model. The model of material is determined based on uniaxial tension test of a specimen produced from a real elastomer component. The results are presented in the form of comparison of two designs of elastomer component with respect to fatigue behaviour based on a maximum principal strain range. The results of computational modelling in the viewpoint of crack initiation site are in good agreement with the results from the component used in operation and dif-ferences between the two designs are negligible. The quantitative difference of the two designs is 15 %.

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Indiana University-Purdue University Indianapolis (IUPUI) / Background: VST-50 (a room temperature-vulcanizing silicone (RTV) by Factor II Inc.) has long been proposed as a potential alternative material for MDX4-4210, another RTV by Dow Corning Corp. and the current material of choice for maxillofacial prosthesis. Though VST-50 has similar chemistry and flexibility as MDX4-4210, its mechanical properties is still too low for it to be used in the clinic. An improvement in the mechanical property of VST-50 is a critical step to bring the material to clinical application. Objective: To investigate the effect of AEROSIL® R 812S (colloid silica) addition on the mechanical properties of VST-50 and compared to that of MDX4-4210. Methods: The VST-50 was mixed with AEROSIL® R 812S at 2 or 4 parts per hundred parts of rubber. That material was mixed with the catalyst under vacuum. The mixture was poured onto a machined plastic mold to produce a silicone sheet 3.0 ± 0.2 mm thick. All samples were prepared by manufacturer recommended method. Testing samples were prepared and tested following ISO 37 for tensile strength, ASTM D624 for tear strength and ASTM D2240 for shore A hardness test. One way ANOVA was used to compare the groups (Alpha=0.05). Result: Significant differences (P<0.001) were found between MDX4-4210 and modified VST-50 groups. The mean value of tensile strength, tear strength and hardness of VST-50 (4phr colloid silica) were 7.43(MPa), 34.82(N/mm) and 40.4 respectively, compared to MDX4-4210 were 3.67(MPa), 5.48(N/mm) and 31.5, respectively. Conclusion: Modified VST-50 with 4phr silica revealed improved mechanical properties to use as a maxillofacial prosthetic silicone elastomer.

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Indiana University-Purdue University Indianapolis (IUPUI) / The purpose of this study was to investigate the effect of nano ceramic fiber fillers on the physical properties of VST-50HD silicone maxillofacial prosthesis. Nano alumina fibers at 2 percent, 4-percent, and 6-percent wt were mixed into the VST-50HD silicone elastomer (Factor II Inc., Lakeside, AZ), a commercially-available poly(dimethylsiloxanes). Ten dumb-bell-shaped specimens were used to determine the tensile strength according to ISO 37:2005 and elongation at fracture. Ten trouser-shaped test pieces were used to determine the tear resistance according to ISO 34-1:2004. Shore A test method was used to measure the hardness of the material. The data collected from all quantitative studies of the modified silicones were analyzed using one-way ANOVA with concentration of nano ceramic fiber as the main variable. Specimens from VST- 50HD were also made and tested as control. Results: The mean values for tensile strength (MPa) of control group, 2-percent, 4-percent, and 6-percent reinforced nano ceramic fiber fillers were from 3.43 ± 0.12 to 5.48 ± 0.71. Tear strength (MPa) were from 2.34 ± 0.37 to 5.01 ± 0.39. Elongations at fracture were from 699.66 ± 43.69 to 793.51 ± 57.27. Shore A hardness were from 25.76 ± 2.18 to 38.76 ± 1.83. Conclusion: There was a significant difference (p < 0.001) in the mean tensile, tear and Shore A hardness strengths between the control group and 2-percent, 4-percent, and 6-percent percent reinforced nano ceramic fiber fillers; however, there was not a significant difference (p > 0.05) between 2-percent, 4-percent, and 6-percent reinforced nano ceramic fiber fillers. There was a significant difference (p < 0.001) in the mean elongation at fracture between the 2-percent and control group, 4-percent, and 6-percent reinforced nano ceramic fiber fillers; however, there was not a significant difference (p > 0.05) between control group, 4-percent, and 6-percent reinforced nano ceramic fiber fillers. The properties of the experiment were all lower than the control. Further research is needed to determine the appropriate material and amount of dispersing agent, coupling agent, and determination of the hydprophilicity of the nano ceramic fiber fillers with great emphasis on the dispersing agent.

Multi-component soft materials offer innovative solutions for traditional and emerging technologies by possessing unique combinations of tunable functionality and adaptive mechanical response. These materials often incorporate functional inclusions such as metals or ceramics in elastomers to create deformable composite structures with high thermal or electrical conductivities, magnetic material response, or stimuli-responsive shape and rigidity tuning. In recent years, these materials have become enabling for wearable electronics and soft machines which has led to the development of new material architectures that provide advanced functionalities while maintaining a low mechanical modulus and high extensibility. In this work, we develop methods for the fabrication and utilization of advanced material architectures which integrate room temperature liquid metals (LM), low melting point alloys (LMPA), and magnetic powders and fluids with soft elastomers to introduce multifunctionality to electronic and machine systems. LM-elastomer composites which have high thermal and electrical conductivities are enabling for heat transfer applications and soft, extensible wiring for wearable electronics and soft robots. These materials have been utilized to create emerging devices such as electronics that are capable of improving human health and efficiency, as well as robots capable of adapting their functions based on environmental need. One possible area where LM composites could be applied is in marine environments, where wearable electronics can improve safety for divers, and soft machines could be utilized for underwater exploration. In Chapter 2, we provide the first study to quantify the effects of underwater aging in freshwater and saltwater environments on the important mechanical and functional properties of LM composites for long-term underwater use. It is found that LM composites are largely resistant to changes in their mechanical properties, as well as both thermal and electrical functionality due to long-term underwater aging. In Chapter 3, we introduce a new chemical approach for the tough bonding of LM composites to diverse substrates, which increases adhesion by up to 100x, improving the integration of these materials with rigid electronics. It is shown that the fracture energy and thermal conductivity of these materials can be tuned by controlling the size and volume loading of the LM inclusions. The utility of this method is then shown through the permanent bonding of LM composites to rigid electronics for use as thermal interface materials. \\ Chapter 4 introduces a multi-component shape morphing material that leverages an LMPA endoskeleton and soft LM resistive heaters to produce rapid (< 0.1 s) and reversible shape change. The morphing material utilizes a unique 'reversible plasticity' mechanism enabled by patterned kirigami cuts that allows for instantaneous shape fixing into load bearing shapes without the need for sustained power. The material properties are enabling for the creation of shape morphing robots, which we show through by integration of on board power and control to create a multi-modal morphing drone capable of land and air transport as well as through an underwater machine that can be reversibly deployed to obtain cargo. For magnetic elastomers, the magneto-mechanical properties of state-of-the-art magnetorheological elastomers (MREs) with diverse structures are studied. These materials have long been studied for their ability to rapidly tune stiffness in the presence of a magnetic field. Chapter 5 introduces a new form of hybrid MRE material architecture which utilizes a combination of magnetic powders and fluids to achieve high magnetic permeability and low stiffness for wearable electronic applications. The zero-field magneto-mechanical properties of MREs with rigid particles, magnetic fluids, and a combination of the two are studied. The inclusions are modeled through an Eshelby analysis which demonstrates magnetic fluids can be utilized to increase magnetic response while decreasing the stiffness of the composite material. The stiffness tuning capabilities of these material architectures are then explored in Chapter 6, where we introduce a predictive model that captures the stiffness tuning response of MREs across diverse microstructures and compositions. This model guides the creation of materials with rapid (~ 20 ms) and extreme stiffness tuning (70x) which we utilize to create a soft adaptive gripper capable of handling objects of diverse geometries. / Doctor of Philosophy / Multi-component soft materials offer innovative solutions for traditional and emerging technologies by possessing unique combinations of tunable functionality and adaptive mechanical properties. These materials often incorporate functional inclusions such as metals or ceramics in elastomers in order to create deformable composite structures with high thermal or electrical conductivities, magnetic material response, or user-controlled shape morphing and stiffness change. In recent years, these materials have become enabling for wearable electronics and soft machines which has led to the development of new materials that provide advanced functionalities while maintaining a low stiffness and high extensibility. In this work, we develop methods for the fabrication and utilization of advanced materials that integrate room temperature liquid metals (LM), low melting point alloys (LMPA), and magnetic powders and fluids with soft elastomers to introduce multifunctionality to electronic and machine systems. LM-elastomer composites which have high thermal and electrical conductivities are enabling for heat transfer and stretchable electronic applications for wearable electronics and soft robots. These materials have been utilized to create emerging devices such as electronics that are capable of improving human health and efficiency, as well as robots capable of adapting their functions based on environmental need. One possible area where LM composites could be applied is in marine environments, where wearable electronics can improve safety for divers, and soft robots could be utilized for underwater exploration. In Chapter 2, we provide the first study to quantify the effects of underwater aging in freshwater and saltwater environments on the important mechanical and functional properties of LM composites for long-term underwater use. It is found that LM composites are largely resistant to changes in their mechanical properties, as well as both thermal and electrical functionality due to long-term underwater aging. In Chapter 3, we introduce a new chemical approach for the tough bonding of LM composites to diverse substrates, which increases adhesion by up to 100x, improving the integration of these materials with rigid electronics. It is shown that the adhesion and thermal conductivity of these materials can be tuned by controlling the size and volume loading of the LM inclusions. The utility of this method is then shown through the permanent bonding of LM composites to rigid electronics for use as thermal interface materials. Chapter 4 introduces a multi-component shape morphing material that leverages an LMPA endoskeleton and soft LM resistive heaters to produce rapid (< 0.1 s) and reversible shape change. The morphing material utilizes a unique 'reversible plasticity' mechanism enabled by patterned kirigami cuts that allows for instantaneous shape fixing into load bearing shapes without the need for sustained power. The material properties are enabling for the creation of shape morphing robots, which we show through by integration of on board power and control to create a multi-modal morphing drone capable of land and air transport as well as through an underwater machine that can be reversibly deployed to obtain cargo. For magnetic elastomers, the magnetic and mechanical properties of state-of-the-art magnetorheological elastomers (MREs) with diverse structures are studied. These materials have long been studied for their ability to rapidly change stiffness in the presence of a magnetic field. Chapter 5 introduces a new form of hybrid MRE material architecture which utilizes a combination of magnetic powders and fluids to achieve exceptional magnetic properties and low stiffness for wearable electronic applications. The mechanical properties of MREs with rigid particles, magnetic fluids, and a combination of the two are studied. The inclusions are modeled through a mechanical analysis which demonstrates magnetic fluids can be utilized to increase magnetic character while decreasing the stiffness of the composite material. The stiffness tuning capabilities of these material architectures are then explored in Chapter 6, where we introduce a predictive model that captures the stiffness tuning response of MREs across diverse microstructures and compositions. This model guides the creation of materials with rapid (~ 20 ms) and extreme stiffness tuning (70x) which we utilize to create a soft adaptive gripper capable of handling objects of diverse geometries.

No description available.