Glasses have many applications such as containers, substrates of displays, high strength fibers and portable electronic display panels. Their excellent mechanical properties such as high hardness, good forming ability and scratch resistance make glasses ideal for these applications. Many factors affect the selection of one glass over another for a given purpose such as cost, ingredients, scalability of manufacturing, etc. Typically, silicate based glasses are often selected because they satisfy most of the selection criteria. However, with the recent abundant use of these glasses in touch-based applications, understanding their abilities to dissipate energy due to surface contact loads has become increasingly desirable. The most common silicate glasses worldwide are glassy silica and soda lime. Calcium aluminosilicates are also gaining popularity due to their importance as substrates for display screens in electronic devices. The surface energy dissipation and strength of these glasses are based on several factors, but predominantly rely on ingredient composition and the so-called Indentation Size Effect (ISE), where the strength depends on the maximum surface force. Both the composition and ISE alter the strength and favored energy dissipation mechanisms of the glass. Unlocking the contribution of these mechanisms and elucidating their dependence on composition and force is the underlining goal of this thesis.Prior to cracking, silicate glasses can inelastically deform by shear and densification. However, the link between the mechanical properties, strength, glass structure and maximum force and the propensity by which either of these mechanisms are favored still remains unclear. In this study, the first aim is to elucidate the causes of the ISE and i explore the relationships between the ISE and the dissipation mechanisms, and identify what feature(s) of the glass can be used to infer their behavior. All glasses have shown a strong link between the ISE and shear flow and densification. Second, the link between composition and the dissipation mechanisms will be elucidated. This is accomplished by performing indentation tests coupled with an annealing method to independently quantify the amount of volume associated with each dissipation mechanism and elucidate relationships with ingredients and structure of the glasses. Some conclusions will then be presented that link all these behaviors together.

The preceding paper analyzes the effects of UV radiation in plastic reinforcement and its effects on the fracture properties of cement-based materials. Three point tests were performed on notched beams, which called for the consideration of the Type II Size Effect. A comparison of the ductility of beams with and without polyethylene plastic powder reinforcement was done through the calculation of the fracture parameters Gf and cf, which represent the initial fracture energy and the characteristic length respectively. Although there was an observed increase in ductile behavior and properties in beams with polyethylene reinforcement, there did not seem to be a significant effect caused by the UV radiation. The hydrophilicity of the polyethylene powder was successfully increased through UV radiation and validated through water retention tests, which showed that the UV-treated polyethylene was retaining more water than the non-treated polyethylene, yet there was no extra increase in ductility of the cement beams compared to using non-treated polyethylene. The Type II Size Effect analysis was performed and compared to the stress analysis results of the experiment. For future research, it is recommended that a higher volume of polyethylene per 1000 grams of cement powder be used, as well as increasing the strength of the UV chamber to achieve a larger increase in the hydrophilicity of the polyethylene. Also, perhaps using more precise equipment to cut the notches in the beams would be helpful in ensuring that all specimens are identical and there is no error in notch depth caused by inaccurate use of the hacksaw or radial saw. Further experiments will be conducted.