The influence of charge heterogeneity in nanoparticles such as montmorillonite layered silicates (MLS) and hybrid systems of MLS + carbon nanotubes was investigated in cured and uncured epoxy. Epoxy nanocomposites made with cation-exchanged montmorillonite clay were found to form agglomerates near a critical concentration. Using differential scanning calorimetry it was determined that the mixing temperature of the epoxy + MLS mixture prior to the addition of the curing agent critically influenced the formation of the agglomerate. Cured epoxy samples showed evidence of the agglomerate being residual charge driven by maxima and minima in the concentration profiles of thermal conductivity and dielectric permittivity respectively. A hybrid nanocomposite of MLS and aniline functionalized multi walled nanotubes indicated no agglomerates. The influence of environmentally and process driven properties on the nanocomposites was investigated by examination of moisture, ultrasound, microwaves and mechanical fatigue on the properties of the hybrid systems. The results point to the importance of charge screening by adsorbed or reacted water and on nanoparticulates.

Ceramic Matrix Composites (CMC) are attractive material systems for structural applications where resistance to intermediate (700 0C-950 0C) and high temperatures (900 0C-1400 0C) is required and low density is desired. There are currently barriers to a more widespread adoption of CMCs which include less robust simulation tools, which this dissertation seeks to address. A novel unified reduced order homogenization model for initial quasi-static, creep, and fatigue loading of SiC/SiC CMCs at intermediate and high temperatures is proposed. Driven by a single set of parameters, the model can seamlessly transition between initial quasi-static, creep, and fatigue regimes while capturing the complex material response of SiC/SiC CMCs. The reduced order homogenization approach provides a robust and efficient computational platform for analyzing composite behavior. Continuum damage mechanics provides the basis for the initial brittle CMC behavior while a hybrid damage-viscoplasticity model combined with an oxidation driven crack sealing effect drives the time-dependent brittle-ductile material behavior at high temperatures. A temporal multiscale approach extends the spatial multiscale model into fatigue regime at high temperatures, avoiding the computational complexity of modeling each cycle individually. At intermediate temperatures, a one-dimensional model based on the slow crack growth model originally proposed by Iyengar and Curtin is generalized to three dimensions focusing on a woven composite architecture. For this oxidation-assisted rupture model, the constitutive equation in the axial tow direction is governed by the continuum damage mechanics variant of the slow crack-growth model and the availability of oxygen to fibers, which in turn depends on the initial matrix pores and subsequent matrix cracking. The model is verified on two SiC/SiC material systems, S200H and GEA SMI, in both initial quasi-static and time-dependent loading regimes at both high and intermediate temperatures.

Indiana University-Purdue University Indianapolis (IUPUI) / This study proposes and evaluates a multi-functional carbon fiber reinforced composite with embedded Lithium-ion battery for its structural integrity concept. The comparison of versatile composite structures manufactured conventionally, air-sprayed and electrospun multi walled carbon nano tubes in order to discover a better packaging method for incorporating lithium-ion batteries at its core is determined. In the electrospinning process recognized globally as a flexible and cost-effective method for generating continuous Nano filaments. It was incorporated exactly on the prepreg surface to obtain effective inter-facial bonding and adhesion between the layers. The mechanical and physical properties of carbon fiber reinforced polymers (CFRP) with electrospun multi walled carbon nano tubes (CNTs) have evidenced to possess higher mechanical strength incorporated between the layers of the composite prepreg than the traditional CFRP prepreg composite, At the same time the air sprayed CFRP with CNTs offers mechanical strength more than the traditional CFRP prepreg but lesser than the electrospun. This can be a design consideration from the economic feasibility viewpoint. They also contribute to efficient load transfer and structural load bearing implementation without compromising the chemistry of battery. The design validation, manufacture methods, and experimental characterization (mechano-electrical) of Multi-functional energy storage composites (MESCs) are examined. Experimental results on the electrochemical characterization reveal that the MESCs show comparable performance to the standard lithium-ion pouch cells without any external packaging and not under any loading requirements. The mechanical performance of the MESC cells especially electrospun CFRP is evaluated from three-point bending tests with the results demonstrating significant mechanical strength and stiffness compared to traditional pouch cells and conventional, air-sprayed CFRP and at lowered packaging weight and thickness. This mechanical robustness of the MESCs enable them to be manufactured as energy-storage devices for electric vehicles.

This diploma thesis deals with machining of rotating components made of composite material. Components of the two manufacturing technologies are compared. The aim of the thesis was to analyze and calculate the costs of the given technologies for different production batches. At the end of the diploma thesis there is a technological-economic evaluation and decision on which production technology will be used.

This master thesis represents a step forward in vehicle dynamics of TU Brno Racing Formula Student team from Brno University of Technology monoposts. A detailed research focused on light automotive wheels. Its main part is to design and make a composite wheel for a formula monopost Dragon 9. The wheel design was formed from the rules side, car packaging, forces acting and limits of composite parts production. There’s a collection of CAD documentation of wheel designs, moulds and connected fixtures. The designed moulds for hollow carbon fiber wheels were manufactured. The technology in making of composite wheels is described in detail. Also, the ways of testing the wheel before a straight use on a race car were designed. There are several wheel prototypes made as an outcome of this thesis. The wheel design is reviewed in terms of functionality and manufacturing side of things.

Buildings construction and realization of public infrastructures have always been a primary need in the human society, developing low cost and user-friendly materials which also encounter safety and durability requirements. Portland cement is the most used material in construction industry from the industrial revolution up to date, but the raising concerns related to the climate change are pushing the governments worldwide to replace it with more eco-friendly and greener materials. Geopolymers are considered to be best alternatives to Portland cement in construction industry, but issues related to cost and mechanical properties are still hindering the commercialization of this material. Geopolymer incorporating wastes is one of the solutions. Fly ash, a thermal power plant by-product, and borosilicate glass, a recycled glass from pharmaceutical vials, are suitable candidates in geopolymers activation. NMR and FTIR spectroscopies demonstrated that borates from borosilicate glass are active compounds in geopolymerization, substituting the alumina is its role, composing a B-Al-Si network never observed before. Various fly ash and borosilicate glass weight contents were studied in terms of mechanical properties (compression test, 3-point bending test). It was found that fly ash 55 wt.% and borosilicate 45 wt.% composition activated in 13 M NaOH solution holds the best compressive and flexural strength (45 and 4 MPa respectively), 25% stronger than similar counterparts found in literature. Cellulose fibres in different weight contents were dispersed into the geopolymeric paste to produce geopolymer composites, with the aim to render the material more suitable for structural applications. 3-point bending test showed an improvement of the flexural strength of about 165% (12 MPa), while the chevron notch method displayed a fracture toughness of 0.7 MPam1/2, in line with the results of geopolymer composites found in literature. In this thesis work, fly ash was also successfully densified in 3 M NaOH solution and distilled water through a new method based on hydraulic pressure, called hydro-pressure sintering. This innovative technology involves a drastic reduction of NaOH utilization in geopolymerization, rendering the material more eco-friendly. XRD spectroscopy conducted on produced samples revealed a higher formation of crystals, most likely induced by the application of hydraulic pressure (450 MPa).

Syntactic foams are hollow particles-filled lightweight composites that are widely used in areas that require high strength while maintaining low weight and density. These foams are highly tailorable materials whose properties can be altered during the manufacturing process by changing various parameters like matrix and microballoon material type, size, distribution, as well as the volume fraction and wall thickness of microballoons. Therefore, understanding the effect of these parameter changes in the behavior of syntactic foams is very important to manufacture the foam for different applications. In the present study, syntactic foams of various volume fractions of microballoons were fabricated and different mechanical testing was conducted to study their elastic and viscoelastic behavior. Moreover, density, void content, and microstructure of the syntactic foam with varying volume fractions of microballoons were also studied to better characterize these foams. Results show that changes in the volume fraction of the microballoons had a significant impact on the elastic and viscoelastic behavior of the foams. The introduction of the microballoons into the epoxy resin decreased the density of the epoxy resin by up to 43.36% and at the same time increasing the specific modulus by up to 21.059%. In addition, representative 3D models of these syntactic foams were also developed to further study the elastic behavior of these materials which were found to be in good agreement with the experimental results. These findings will help in designing and optimizing the material properties of the syntactic foam required for different applications.

This work is focused on optimalisation of coposite materials for civil engineering. In the theoretical part of the project is introduction of the composite materials and materials which are used for their production. There are also concerned their properties and possible application areas. In conclusion of theoretical part this project is a summary of the possible use of composite materials. The practical part compares the characteristics of the different types of composites made in terms of conductivity and the rate of corrosion.

Diplomová práce pojednává o návrhu kapotáže vozidla Formula Student. Vozy této kategorie se každoročně učástní série mezinárodních závodů všech zůčastněných studentských týmů. Úroveň návrhu se posuzuje jak v dynamických tak ve statických disciplínách. Tato práce popisuje proces návrhu tří koncepčních variant společně s rozpracováním finální varianty pro fázi výroby. Navíc je zde prezentován koncept obsahující aerodynamický paket, který slouží jako výhledová studie možného vývoje vozidla.

The work is aimed to propose a methodology for creating an equivalent of composite materials used for construction of small aircraft. Such equivalent should enable to create numerical models of small aircraft in the simulation of precertication EMC tests for aircraft resistance against the lightning. Eliminating situations threatening the aircraft and passengers in the initial steps of the design will allow savings in production costs and contribute to the safety of air transport. In order to nd the equivalent of composite materials, global optimization methods will be used.