- How is the stress intensity factor K influenced by the acting stress σ, defect size a and form factor f? By rearranging this formula, how is the critical defect size a_c depending on the fracture toughness K_c of a specific material, assuming that a constant stress σ is acting? How much larger is the critical defect size for a part made of steel (K_c = 100MPa m^1/2) in comparison to the same part made of glass (K_c = 1MPa m^1/2), asumming that the form factor as well as stress are the same in both cases?
- How can materials be categorized in terms (a) of types of bonds which act between the atoms and (b) in terms of crystal structure. Give one example for each category
- When asking Copilot the following question, “How can the toughness of dental composites be increased?”, it gives this answer, “The toughness of dental composites is increased primarily by optimizing filler content and morphology, strengthening the filler-matrix interface, toughening the resin matrix, and introducing extrinsic mechanisms such as crack deflection, crack bridging, and controlled stress relaxation.” How does that relate to the general 4 toughening mechanism which we learned? Is there something missing?
- Define the terms “biodegradation” and “bioerosion”. Name two applications where biodegradable polymers are used in medicine. Name at least two classes of biodegradable polymers.
- What are the differences between chain growth and step growth polymerization? Provide the molecular weight-conversion diagram for both types to explain how they differ in reaching their final molecular weights.
- What are the benefits of using Nitinol in cardiovascular stents? How does a stress-strain diagram of Nitinol look like? Explain the different stages of such a stress-strain diagram and the underlying metal physical phenomena.
- What are the key components of photocurable dental composites? Which chemical mechanisms occur on a molecular level when such a composite is photopolymerized using radical polymerization?
- What is the Materials Biocompatibility Matrix (related to ISO 10993)? Explain one test in detail to assess biocompatibility?
- Describe what occurs in the body upon implantation of a medical device (mention approximate time-scale and cell and molecular players). What materials characteristics might influence the body’s response to the medical device, and what can be done to tune it?
- There are many sterilization methods, how would you choose the most suitable one for your medical device?
*Answers to these questions to follow. I am waiting for my grades.