Dislocations and Strengthening Mechanisms PDF

Dislocations and Strengthening Mechanisms Multiple Choices Questionnaire (2pts each) 1. What is a dislocation in the context of materials science? A. A type of atom that causes material strength B. A linear crystalline defect in the atomic structure C. A defect caused by heat t...

Dislocations and Strengthening Mechanisms Multiple Choices Questionnaire (2pts each) 1. What is a dislocation in the context of materials science? A. A type of atom that causes material strength B. A linear crystalline defect in the atomic structure C. A defect caused by heat treatment D. A type of grain boundary ANSWER: B 2. When was the existence of dislocations directly observed? A. 1920s B. 1940s C. 1950s D. 1970s ANSWER: C 3. What are the two primary types of dislocations? A. Point and line dislocations B. Edge and screw dislocations C. Edge and surface dislocations D. Twinning and screw dislocation ANSWER: B 4. Which of the following best describes an edge dislocation? A. A dislocation where atoms move in parallel to the stress direction B. A dislocation where an extra half-plane of atoms is inserted C. A dislocation with no atomic bond distortions D. A dislocation with no associated stress fields ANSWER: B 5. What is the motion of a screw dislocation? A. The dislocation moves in the direction of the applied stress B. The dislocation moves perpendicular to the applied stress C. The dislocation does not move under stress D. The dislocation causes atom displacement in only one plane ANSWER: B 6. What is the term used to describe permanent deformation of materials by dislocation motion? A. Creep B. Elastic deformation C. Slip D. Strain hardening ANSWER: C 7. Which of the following is true about a slip system? A. The slip system consists of only one dislocation direction B. The slip system involves the movement of dislocations along a slip plane and direction C. The slip system only occurs in materials with cubic crystal structures D. The slip system involves only edge dislocations ANSWER: B 8. What is a slip plane? A. A plane where slip occurs least easily B. The plane with the lowest density of atoms C. The plane with the highest density of atoms D. The plane where atoms are compressed together ANSWER: C 9. What is slip direction? A. The direction in which atoms are displaced B. The plane where the dislocation line is located C. The direction in which dislocations move within the slip plane D. The direction of applied stress ANSWER: C 10. What does grain size reduction do to a material's strength? A. Decreases strength by reducing dislocation movement B. Increases strength by increasing grain boundaries C. Has no effect on strength D. Decreases ductility without changing strength ANSWER: B 11. According to the Hall-Petch Equation, what happens as grain size decreases? A. Yield strength increases B. Yield strength decreases C. Ductility increases D. Ductility decreases ANSWER: A 12. Which of the following strengthening mechanisms involves adding alloying elements to a metal? A. Grain size reduction B. Solid solution strengthening C. Strain hardening D. Recovery ANSWER: B 13. What type of impurity atom replaces a host atom in solid solution strengthening? A. Interstitial impurity B. Substitutional impurity C. Both interstitial and substitutional impurities D. None of the above ANSWER: B 14. What type of impurity atoms fill the gaps between atoms in solid solution strengthening? A. Substitutional impurities B. Interstitial impurities C. Both substitutional and interstitial impurities D. Alloying impurities ANSWER: B 15. Which strengthening mechanism involves the metal becoming stronger after plastic deformation? A. Strain hardening B. Grain size reduction C. Recovery D. Solid solution strengthening ANSWER: A 16. What is the effect of strain hardening on a metal? A. It makes the metal more ductile B. It makes the metal more brittle C. It decreases the yield strength D. It decreases the hardness of the material ANSWER: B 17. What is percent cold work (PCW) a measure of? A. The amount of strain applied during heat treatment B. The amount of deformation in a material expressed as a percentage C. The number of dislocations in a material D. The yield strength of a material ANSWER: B 18. Which of the following is the formula for percent cold work? A0− Ad A. %CW = ( ) x 100 Ad− Ao B. %CW = ( ) x 100 A0 A0 C. %CW = ( ) x 100 A d A D. %CW = ( d) x 100 A0 ANSWER: A 19. What is recovery in the context of metal deformation? A. The process of restoring strength through cold work B. Mild heating to allow dislocations to rearrange without affecting hardness C. High-temperature heating to create new grain structures D. The process of adding impurity atoms to increase strength ANSWER: B 20. What occurs during recrystallization? A. Dislocation density increases B. New, strain-free grains form, reducing dislocation density C. The material becomes more brittle D. The material retains its original grain structure ANSWER: B 21. What happens during grain growth? A. Grain boundaries increase, which increases strength B. The grains shrink, making the material more ductile C. The new grains grow larger, reducing the number of grain boundaries and strength D. The material becomes harder and more brittle ANSWER: C 22. What is the primary role of grain boundaries in strengthening metals? A. They act as obstacles to dislocation motion B. They increase the ductility of the material C. They promote the movement of dislocations D. They reduce the yield strength of the material ANSWER: A 23. Which technique is most effective for strengthening polycrystalline materials? A. Solid solution strengthening B. Grain size reduction C. Strain hardening D. Recovery ANSWER: B 24. What happens when metals undergo extensive plastic deformation at low temperatures? A. They recover their ductility B. They become softer C. They experience strain hardening D. Their crystal structure becomes more ordered ANSWER: C 25. Which of the following is NOT a stage in the recovery, recrystallization, and grain growth process? A. Recovery B. Recrystallization C. Precipitation hardening D. Grain growth ANSWER: C 1. Why is it important to study failure? a) To increase production speed b) To understand the mechanics of various failure modes – fracture, fatigue, and creep. c) To decrease material costs d) To improve aesthetic design of components ANSWER: b 2. What is one of the three usual causes of failure? a) Excessive use of lubricants b) Improper material selection and processing c) Frequent maintenance d) Excessive safety margins ANSWER: b 3. Which type of fracture is usually preferred? a) Brittle fracture b) Ductile fracture c) Complex fracture d) Instantaneous fracture ANSWER: b 4. Why is ductile fracture preferred over brittle fracture? a) It occurs with no prior deformation b) It provides a warning before failure due to plastic deformation c) It is less energy-intensive to induce d) It has a smoother fracture surface ANSWER: b 5. Which type of environment-assisted fatigue failure involves fluctuating thermal stresses? a) Chemical fatigue b) Thermal fatigue c) Mechanical fatigue d) Electrical fatigue ANSWER: b 6. What are the three usual causes of failure? a) Improper material selection and processing, inadequate component design, component misuse b) Excessive use, environmental factors, poor design c) High temperatures, high pressures, corrosive environments d) Mechanical overload, thermal expansion, vibration ANSWER: a 7. Which type of fracture occurs with very little accompanying plastic deformation? a) Ductile fracture b) Brittle fracture c) Fatigue fracture d) Creep fracture ANSWER: b 8. What is the main characteristic of brittle fracture? a) It occurs with extensive plastic deformation b) It spreads rapidly and is perpendicular to the tensile load c) It requires high energy to propagate d) It forms a cup-and-cone profile ANSWER: b 9. What type of failure is the single largest cause of failure in metals? a) Creep b) Fatigue c) Fracture d) Corrosion ANSWER: b 10. Which testing techniques are used to measure impact energy? a) Tensile and compression tests b) Charpy and Izod tests c) Hardness and toughness tests d) Bending and shear tests ANSWER: b 11. What is fatigue? a) Failure due to static stress b) Failure that occurs after repeated stress or strain cycling c) Failure caused by thermal expansion d) Failure due to corrosion ANSWER: b 12. What is the definition of creep? a) Time dependent and permanent deformation of materials when subjected to a constant load or stress b) Sudden failure under static load c) Temporary deformation under cyclic load d) Instantaneous failure due to thermal stress ANSWER: a 13. Which phase of creep involves a constant creep rate? a) Primary creep b) Secondary creep c) Tertiary creep d) Initial creep ANSWER: b 14. What type of creep occurs at elevated temperatures due to fluctuating stresses? a) Thermal creep b) Chemical creep c) Static creep d) Dynamic creep ANSWER: a 15. Which type of crack is more stable, requiring an increase in applied stress to propagate? a) Brittle crack b) Ductile crack c) Micro crack d) Macro crack ANSWER: b 16. What does the stress concentration factor depend on? a) Material hardness b) Temperature c) Crack tip radius and crack length d) Load frequency ANSWER: c 17. In which type of fracture do cracks spread extremely rapidly? a) Ductile fracture b) Brittle fracture c) Fatigue fracture d) Creep fracture ANSWER: b 18. What is the primary cause of thermal fatigue? a) Chemical attack b) High mechanical loads c) Fluctuating thermal stresses d) Constant static load ANSWER: c 19. What is the main focus of fracture mechanics? a) Designing components for aesthetic purposes b) Understanding the formation and propagation of cracks c) Increasing the speed of production processes d) Reducing the cost of materials ANSWER: b 20. Which phase of creep occurs first and involves a continuously decreasing creep rate? a) Primary creep b) Secondary creep c) Tertiary creep d) Final creep ANSWER: a 21. What does the Charpy test measure? a) Material hardness b) Impact energy c) Tensile strength d) Creep resistance ANSWER: b 22. Which factor can significantly increase the maximum stress at the crack tip? a) Temperature increase b) Small tip radius of curvature c) Large component size d) Reduced load frequency ANSWER: b 23. What type of fracture is characterized by a cup-and-cone profile? a) Brittle fracture b) Ductile fracture c) Fatigue fracture d) Creep fracture ANSWER: b 24. Which environment-assisted fatigue failure involves chemical attack during cyclic stress? a) Thermal fatigue b) Corrosion fatigue c) Mechanical fatigue d) Electrical fatigue ANSWER: b 25. In the context of creep, what does tertiary creep signify? a) Decrease in creep rate b) Constant creep rate c) Acceleration of the creep rate leading to failure d) Initial stage of creep ANSWER: c Multiple Choice (1 point each) 1. What are polymers? a) Small molecules b) Large molecules made up of repeating units c) Mixtures of different substances d) Single atoms Answer: b 2. What are the repeating units in polymers called? a) Monomers b) Isomers c) Dimers d) Atoms Answer: a 3. Which of the following is a natural polymer? a) Nylon b) Teflon c) Rubber d) Polystyrene Answer: c 4. Which polymer is used to make plastic bags? a) Polyethylene b) Polystyrene c) Polypropylene d) Polyvinyl chloride Answer: a 5. Which polymer is known for its elasticity? a) Nylon b) Rubber c) Polyethylene d) PVC Answer: b 6. Which polymer is commonly used to make pipes? a) PVC b) Nylon c) Polystyrene d) Bakelite Answer: a 7. Which polymer is lightweight, strong, and used in packaging? a) Polyethylene b) Nylon  c) Bakelite d) Teflon Answer: a 8. Which of the following is a synthetic polymer? a) Silk b) Wool c) Teflon d) Starch Answer: c 9. What is the main monomer used to make polystyrene? a) Ethylene b) Styrene c) Propylene d) Vinyl chloride Answer: b 10. What is cross-linking in polymers? a) Joining of monomers b) Formation of covalent bonds between polymer chains c) Breaking of polymer chains d) Mixing two polymers Answer: b 11. What is the main feature of biodegradable polymers? a) High durability b) Break down into harmless substances in the environment c) Resistance to chemicals d) High melting point Answer: b 12. Which polymer is used for making bottles? a) PVC b) PET c) Bakelite d) Nylon Answer: b 13. What is Bakelite used for? a) Packaging b) Electrical insulators c) Clothing d) Food containers Answer: b 14. What is the process called when monomers join without producing any byproduct?  a) Addition polymerization b) Condensation polymerization c) Crystallization d) Vulcanization Answer: a 15. What property allows polymers to stretch and return to their original shape? a) Rigidity b) Elasticity c) Plasticity d) Compressibility Answer: b 16. Which polymer is used for making bulletproof vests? a) Polypropylene b) Kevlar c) Nylon-6 d) Polystyrene Answer: b 17. What property of polymers makes them suitable for use as insulators in electrical applications? a) High conductivity b) Low density c) Poor thermal and electrical conductivity d) High flexibility Answer: c 18. What is a key factor affecting the strength of a polymer? a) The size of the polymer b) The number of impurities in the polymer c) The arrangement of molecular chains (degree of crystallinity) d) The color of the polymer Answer: c 19. Which property of polymers is enhanced by cross-linking? a) Solubility in water b) Flexibility c) Thermal and chemical resistance d) Transparency Answer: c 20. Why are polymers like polystyrene used for insulation? a) High toughness b) Low thermal conductivity c) High biodegradability  d) High electrical conductivity Answer: b 21. What does the molecular mass of a polymer represent? a) The mass of a single polymer chain b) The total mass of monomers used c) The average mass of polymer molecules in a sample d) The mass of a single repeating unit Answer: c 22. Which term is used to describe the average molecular mass of polymers weighted by the number of molecules? a) Weight-average molecular mass b) Number-average molecular mass c) Polydispersity index d) Relative molecular mass Answer: b 23. The Polydispersity index (PDI) is calculated using which formula? a) PDI=Mn + Mw b) PDI=Mw - Mn c) PDI=Mw / Mn d) PDI=Mn / Mw Answer: c 24. What is the value of the Polydispersity index (PDI) of natural polymers? a) 0 b) ½ c) 1 d) 2 Answer: c 25. Which of the following accurately describes weight-average molecular mass (Mw)? a) The molecular mass averaged by the number of molecules b) The molecular mass averaged by the weight of molecules c) The molecular mass of the longest chain in the polymer sample d) The molecular mass of the lightest chain in the polymer sample Answer: b (25 points) 1. A polymer sample contains chains with varying molecular weights. The sample has 5 chains with a molecular weight of 10,500 g/mol, 10 chains with a molecular weight of 21,000 g/mol, and 15 chains with a molecular weight of 38,500 g/mol. Calculate the number average molecular weight and weight average molecular weight of the polymer sample. Given: Molecular Weight (g/mol) Number of Chains 10,500 5 21,000 10 38,500 15 Solution: Number Average Molecular Weight ∑(𝑁𝑖 ∗ 𝑀𝑖 ) = 10500(5) + 21000(10) + 38500(15) ∑(𝑁𝑖 ∗ 𝑀𝑖 ) = 840000𝑔 ∑(𝑁𝑖 ) = 5 + 10 + 15 = 30 𝑚𝑜𝑙 ∑(𝑁𝑖 ∗ 𝑀𝑖 ) 840000 𝑀𝑛 = = = 𝟐𝟖𝟎𝟎𝟎. 𝟎𝟎𝒈/𝒎𝒐𝒍 ∑ 𝑁𝐼 30 Solution: Weight Average Molecular Weight ∑(𝑁𝑖 ∗ 𝑀𝑖 2 ) 𝑀𝑤 = ∑(𝑁𝑖 ∗ 𝑀𝑖 ) ∑(𝑁𝑖 ∗ 𝑀𝑖 2 ) = 5(10,500)2 + 10(21,000)2 + 15(38,500)2 ∑(𝑁𝑖 ∗ 𝑀𝑖 2 ) = 2.7195𝑥1010 𝑔2 /𝑚𝑜𝑙 ∑(𝑁𝑖 ∗ 𝑀𝑖 ) = 5(10,500) + 10(21000) + 15(38,500) ∑(𝑁𝑖 ∗ 𝑀𝑖 ) = 840,000𝑔 ∑(𝑁𝑖 ∗ 𝑀𝑖 2 ) 2.7195𝑥1010 𝑀𝑤 = = = 𝟑𝟐𝟑𝟕𝟓. 𝟎𝟎𝒈/𝒎𝒐𝒍 ∑(𝑁𝑖 ∗ 𝑀𝑖 ) 840,000 NANO AND BIOMATERIALS What is the size range of nanomaterials? a) 1-10 nm b) 10-100 nm c) 1-100 nm d) 100-1000 nm Answer: c) 1-100 nm Which of the following is an example of a nanomaterial? a) Hydroxyapatite b) Graphene c) Collagen d) PLA Answer: b) Graphene What property of nanomaterials enhances their reactivity? a) High surface-to-volume ratio b) High density c) Low reactivity d) High cost Answer: a) High surface-to-volume ratio Which of the following is a primary application of nanomaterials? a) Energy storage b) Drug delivery c) Pollution cleanup d) All of the above Answer: d) All of the above What is a major use of nanomaterials in electronics? a) Strengthening materials b) Energy conversion c) Miniaturization of components d) Water filtration Answer: c) Miniaturization of components Which biomaterial is commonly used in bone implants? a) Hydroxyapatite b) Carbon nanotubes c) Quantum dots d) Graphene Answer: a) Hydroxyapatite What is a characteristic of biomaterials used in medical applications? a) High electrical conductivity b) Biocompatibility c) Ability to conduct heat d) High opacity Answer: b) Biocompatibility What is the function of biomaterial scaffolds in tissue engineering? a) To degrade slowly b) To support tissue growth and regeneration c) To protect tissue from toxins d) To enhance mechanical strength Answer: b) To support tissue growth and regeneration Which of the following is an example of a biodegradable polymer used in biomaterials? a) PLA (Polylactic Acid) b) Graphene c) Collagen d) Quantum dots Answer: a) PLA (Polylactic Acid) Which property of nanomaterials is particularly useful for drug delivery systems? a) Lightweight b) High surface area c) High melting point d) Low conductivity Answer: b) High surface area What is a common application of nanomaterials in medicine? a) Drug delivery b) Bone implants c) Heart bypass surgery d) Blood pressure regulation Answer: a) Drug delivery What does biocompatibility in biomaterials refer to? a) The ability to conduct electricity b) The ability to break down in the body without harm c) The ability to resist corrosion d) The ability to integrate with living tissue without causing immune rejection Answer: d) The ability to integrate with living tissue without causing immune rejection What is a potential negative effect of nanomaterials? a) Increased strength b) Improved durability c) Toxicity to ecosystems d) Reduced conductivity Answer: c) Toxicity to ecosystems Which of the following biomaterials is commonly used for surgical implants? a) Graphene b) Hydroxyapatite c) Quantum dots d) Nanotubes Answer: b) Hydroxyapatite What is one advantage of biodegradable biomaterials? a) They do not need to be removed after use b) They are more expensive than non-biodegradable materials c) They enhance mechanical properties d) They increase risk of infection Answer: a) They do not need to be removed after use Which of the following is an effect of using nanomaterials in energy systems? a) Decreased efficiency b) Increased energy conversion efficiency c) Increased energy consumption d) Decreased lifespan of energy components Answer: b) Increased energy conversion efficiency How are biomaterials typically used in wound healing? a) To kill bacteria b) To provide structural support and promote tissue regeneration c) To cool the wound d) To prevent blood clotting Answer: b) To provide structural support and promote tissue regeneration Which of the following is a challenge associated with the use of nanomaterials? a) High electrical conductivity b) Environmental accumulation and toxicity c) Low cost of production d) High durability Answer: b) Environmental accumulation and toxicity What is a primary property of nanomaterials that makes them effective in drug delivery? a) High electrical conductivity b) High surface area-to-volume ratio c) High opacity d) Resistance to degradation Answer: b) High surface area-to-volume ratio What is a common use of biomaterials in tissue engineering? a) Temporary scaffolds for tissue regeneration b) Enhancing bone strength c) Conducting electrical impulses d) Filtering toxins from the body Answer: a) Temporary scaffolds for tissue regeneration Which of the following nanomaterials is often used in electronics due to its electrical properties? a) Graphene b) Collagen c) Hydroxyapatite d) PLA Answer: a) Graphene What is a key benefit of using biomaterials for implants and prosthetics? a) They are electrically conductive b) They support tissue healing and integration with the body c) They improve heat resistance d) They are more cost-effective than traditional materials Answer: b) They support tissue healing and integration with the body What is the role of quantum dots in nanotechnology? a) Structural reinforcement b) Drug delivery c) Optical applications (e.g., fluorescence) d) Biodegradable material for implants Answer: c) Optical applications (e.g., fluorescence) What is the impact of size-dependent properties in nanomaterials? a) They increase electrical resistance b) They cause nanomaterials to behave differently from bulk materials c) They make nanomaterials less reactive d) They increase their weight Answer: b) They cause nanomaterials to behave differently from bulk materials What is a key factor in choosing biomaterials for medical implants? a) High surface-to-volume ratio b) Biocompatibility and ability to integrate with body tissue c) Ability to conduct electricity d) Strength in extreme temperatures Answer: b) Biocompatibility and ability to integrate with body tissue Composite Materials Multiple-Choice Questionnaire 1. What is the defining characteristic of a composite material? A. It is formed by mixing multiple phases without a distinct interface B. It consists of multiple chemically distinct phases separated by an interface C. It has a single-phase microstructure D. It is naturally occurring without engineering modifications Answer: B 2. Why are composites considered advantageous for aerospace applications? A. High density and brittleness B. Low density and resistance to corrosion C. Ability to conduct electricity D. High temperature conductivity Answer: B 3. Which of the following industries is NOT a primary user of composite materials? A. Aerospace B. Bioengineering C. Textile manufacturing D. Underwater engineering Answer: C 4. What is the primary role of the matrix in a composite? A. It provides strength and stiffness B. It protects the dispersed phase and transfers stress C. It reacts chemically with the environment D. It reduces the weight of the material Answer: B 5. The dispersed phase in composites is responsible for: A. Providing elasticity B. Transferring stress C. Providing strength and stiffness D. Encasing the matrix Answer: C 6. Which of the following is NOT a classification of composites? A. Particle-reinforced B. Fiber-reinforced C. Natural composites D. Nanocomposites  Answer: C 7. In large-particle composites, the particulate phase typically: A. Provides corrosion resistance B. Enhances thermal insulation C. Restrains movement of the matrix phase D. Acts as the sole load-bearing component Answer: C 8. Which composite subclass relies on atomic or molecular-level strengthening? A. Large-particle composites B. Dispersion-strengthened composites C. Fiber-reinforced composites D. Structural composites Answer: B 9. What distinguishes continuous fibers in fiber-reinforced composites? A. Random orientation B. Short lengths C. High strength along their length D. Low manufacturing cost Answer: C 10. Which of the following is a common fiber material used in composites? A. Wood B. Nylon C. Glass D. Steel Answer: C 11. The rule-of-mixtures predicts which property in composites? A. Color B. Density C. Elastic modulus D. Electrical conductivity Answer: C 12. What type of composite is reinforced concrete? A. Fiber-reinforced B. Particle-reinforced C. Nanocomposite D. Natural composite Answer: B 13. The strength of a composite increases significantly with: A. Lower volume fraction of the dispersed phase B. Uniform distribution of particles or fibers C. Large void spaces within the matrix D. Use of brittle dispersed phases Answer: B 14. What is the most common application of cemented carbide composites? A. Aerospace structures B. Cutting tools C. Automotive panels D. Electrical circuits Answer: B 15. Which property is most improved by nanocomposites? A. Electrical insulation B. Gas permeability C. Tensile strength D. Optical clarity Answer: C 16. Why is carbon black commonly used in rubber composites? A. Increases stiffness B. Reduces cost C. Enhances tensile strength and toughness D. Improves heat resistance Answer: C 17. What is the primary feature of structural composites? A. High temperature resistance B. Multi-layered design with high structural integrity C. Molecular-level reinforcements D. Naturally occurring fibers Answer: B 18. The most common matrix material in polymer composites is: A. Epoxy resin B. Concrete C. Metal alloys D. Glass Answer: A 19. Kevlar is primarily valued for its: A. High cost B. Strength-to-weight ratio C. Brittleness under tension D. Susceptibility to acids Answer: B 20. Carbon fiber-reinforced composites are commonly used in: A. Food packaging B. Sporting equipment C. Fireproof insulation D. Road surfaces Answer: B 21. What is the critical fiber length required for effective reinforcement in fiber composites? A. 10 times the fiber diameter B. Equal to the fiber diameter C. Approximately 20–150 times the fiber diameter D. Independent of fiber diameter Answer: C 22. What is the primary benefit of aligned fibers in composites? A. Strength is uniform in all directions B. Maximum strength along the direction of alignment C. Reduced production cost D. Increased thermal expansion Answer: B 23. The effectiveness of load transfer between the matrix and fiber phases depends on: A. The length of the fibers B. The fiber–matrix bond strength C. The type of matrix material used D. All of the above Answer: D 24. Discontinuous fibers provide significant reinforcement only if: A. The fiber length is much shorter than the critical length B. The fiber length exceeds the critical length C. The fibers are aligned randomly D. The matrix is metallic Answer: B 25. Randomly oriented short fibers are typically used for applications requiring: A. Maximum tensile strength B. Isotropic properties C. High thermal conductivity D. Extreme corrosion resistance Answer: B 26. Large-particle composites typically involve: A. A molecular-level interaction between phases B. Particles significantly smaller than the matrix C. Reinforcing particles that are stiffer than the matrix D. Fibers as the dispersed phase Answer: C 27. Dispersion-strengthened composites derive their strength from: A. The plastic deformation of the matrix B. Hindered motion of dislocations C. Fiber alignment in the matrix D. Increased porosity of the matrix Answer: B 28. The most common material for dispersion strengthening in nickel alloys is: A. Carbon fibers B. Thoria (ThO₂) C. Silica nanoparticles D. Aluminum oxide Answer: B 29. The primary application of cemented carbides (e.g., WC-Co) is: A. Abrasion-resistant coatings B. Cutting tools C. High-temperature insulation D. Lightweight components Answer: B 30. Which type of particle reinforcement enhances tire durability? A. Silica particles B. Carbon black C. Ceramic particles D. Metallic powders Answer: B 31. Which polymer-matrix composite is the most widely produced? A. Carbon fiber–reinforced plastics B. Glass fiber–reinforced plastics (GFRP) C. Aramid fiber–reinforced plastics D. Boron fiber–reinforced plastics Answer: B 32. A limitation of glass fiber–reinforced composites is their: A. Low cost B. Rigidity C. High-temperature resistance D. Chemical reactivity Answer: B 33. Carbon fiber–reinforced composites are preferred in aerospace due to: A. Low thermal expansion and high specific modulus B. High reactivity and cost efficiency C. Ease of manufacturing D. Low specific strength Answer: A 34. Aramid fibers are best suited for: A. Electrical insulation B. Ballistic protection applications C. High-temperature resistance D. Abrasive tools Answer: B 35. The most commonly used matrix materials in polymer composites are: A. Concrete and epoxy B. Epoxy and polyester C. Nylon and carbon fibers D. Silicon and polycarbonate Answer: B 36. Ceramic-matrix composites primarily aim to improve: A. Electrical conductivity B. Fracture toughness C. Thermal expansion D. Cost efficiency Answer: B 37. Metal-matrix composites are commonly used for: A. Lightweight armor B. High-temperature structural applications C. Electrical insulators D. Water-resistant coatings Answer: B 38. The matrix material in metal-matrix composites must be: A. Brittle and strong B. Ductile and tough C. Lightweight and soft D. Corrosive and reactive Answer: B 39. An advantage of ceramic-matrix composites is their: A. Resistance to corrosion B. Ease of manufacturing C. Low density D. Improved ductility Answer: A 40. A limitation of metal-matrix composites is: A. High brittleness B. Difficulty in manufacturing C. Low thermal stability D. Susceptibility to moisture Answer: B 41. Which property is typically enhanced in composites used in marine applications? A. Electrical conductivity B. Corrosion resistance C. Thermal conductivity D. Magnetic properties Answer: B 42. What is the key advantage of sandwich composites? A. High density B. Lightweight design with high stiffness C. Uniform electrical conductivity D. Enhanced brittleness Answer: B 43. Portland cement concrete is reinforced with steel primarily to: A. Reduce weight B. Increase tensile strength C. Improve thermal insulation D. Reduce thermal expansion Answer: B 44. A common application of prestressed concrete is: A. Electrical transformers B. Highway bridges C. Lightweight vehicle panels D. Sporting goods Answer: B 45. The primary advantage of fiber reinforcement in composite applications is: A. Enhanced thermal conductivity B. High strength-to-weight ratio C. Lower cost compared to monolithic materials D. Uniform distribution of properties Answer: B 46. The primary disadvantage of composites is their: A. High strength B. High cost and recyclability challenges C. Poor corrosion resistance D. Limited design flexibility Answer: B 47. The strength of a composite under longitudinal loading is primarily determined by: A. Matrix strength B. Fiber strength and alignment C. Thermal properties D. Chemical reactivity Answer: B 48. Reinforcement efficiency in randomly oriented composites is generally: A. Zero B. Equal to continuous fibers C. Lower than aligned composites D. Higher than aligned composites Answer: C 49. The modulus of elasticity in the transverse direction for aligned composites is typically: A. Higher than in the longitudinal direction B. Lower than in the longitudinal direction C. Equal in all directions D. Independent of fiber orientation Answer: B 50. Composites achieve superior properties due to: A. Homogeneity of materials B. Combined action of multiple phases C. Use of single-phase materials D. Higher density than traditional materials Answer: B TOPIC: Selection / Re-use & Recycling of Materials PART I Instructions: Choose the letter with the correct answer. (2pts per number) 1. Its purpose is to recycle waste products by giving it to other people for free a. Freecycling b. Deconstruction c. Open handed reuse d. Upcycling Answer: A 2. It is a material that is not biodegradable, but it can be recycled repeatedly without diminishing its quality. a. Porcelain b. Glass c. Clay d. Metal Answer: B 3. Which represents a process in the total materials cycle: a. Earth → Raw Materials → Synthesis and Processing → Manufacture, Assembly → Engineered Materials → Product Design → Application → Waste → Earth b. Earth → Raw Materials → Synthesis and Processing → Engineered Materials → Product Design, Manufacture, Assembly → Application → Waste c. Earth → Raw Materials → Synthesis and Processing → Engineered Materials → Product Design, Manufacture, Assembly → Application → Waste → Earth d. Earth → Recycle / Reuse → Synthesis and Processing → Engineered Materials → Product Design, Manufacture, Assembly → Application → Waste → Earth Answer: C 4. The following are compositions of glass EXCEPT: a. soda–lime b. leaded c. borosilicate d. Alkaline Answer: D 5. Its purpose is to recycle used waste products. a. Open handed reuse b. Recycling c. Creative Reuse d. Uphill cycling Answer: C 6. Is technically a form of reusing, but it refers more specifically to items that are discarded and broken down into their raw materials. a. Freecycling b. Deconstruction c. Open handed reuse d. Recycling Answer: D 7. The materials reused in recycling serve as substitutes for raw materials obtained from such increasingly scarce natural resources as the following EXCEPT: a. Natural Gas b. Trees c. Mineral Ores d. Geothermal Heat Answer: D 8. Which is a type of reuse: a. Destruction b. Downcycling c. Recycling d. Construction Answer: B 9. What is the number on the recycle code of polypropylene? a. 6 b. 4 c. 5 d. 1 Answer: C 10. Its main goals include preserving architectural and cultural heritage, transforming urban blight, and igniting social change. a. Recycling b. Adaptive Reuse c. Adoptive Reuse d. Uphill Cycling Answer: B 11. It can help reduce the quantities of solid waste deposited in landfills, which have become increasingly expensive. a. Recycling b. Reuse c. Recovery d. Reduce Answer: A 12. Can be defined as using a waste product without further transformation and without changing its shape or original nature. a. Reduce b. Recycling c. Recovery d. Reuse Answer: D 13. Which of the following is NOT a part of the process in recycling metals: a. Collection b. Testing c. Transportation d. Processing Answer: B 14. This is the second option in the waste hierarchy. a. Recovery b. Reuse c. Recycling d. Reduce Answer: B 15. It is a closed system, in that its materials resources are finite. a. Factory b. Environment c. Earth d. Landfill Answer: C 16. Typical materials that are recycled include the following EXCEPT: a. Iron and Steel Scrap b. Aluminum Cans c. Appelation d. Glass Bottles Answer: C 17. Which of the following is an application on the total materials cycle. a. Exploration b. Energy c. Cooling d. Adventure Answer: B 18. Different types of solid wastes can be reused, such as the following EXCEPT: a. Bottles b. Detergents c. Old Clothes d. Books Answer: B 19. It is the repurposing of buildings that have outlived their original purpose. a. Adaptive Reuse b. Breakdown Reuse c. Recycling d. Adoptive Reuse Answer: A 20. Major sources of waste are from packaging, junked automobiles, automobile tires, and domestic durable goods. a. Plastics b. Rubber c. Styrofoam d. Cellophane Answer: A 21. This is a process from the total material cycle: a. Earth → Raw Materials → Synthesis and Processing → Engineered Materials → Product Design, Manufacture, Assembly → Application → Waste b. Raw Materials → Synthesis and Processing → Engineered Materials → Product Design, Manufacture, Assembly → Application → Waste → Earth c. Waste → Recycle/Reuse → Raw Materials → Synthesis and Processing → Engineered Materials → Manufacture & Assembly → Application d. Waste → Recycle/Reuse → Raw Materials → Synthesis and Processing → Engineered Materials → Product Design, Manufacture, Assembly → Application → Waste Answer: D 22. The purpose of this is to recycle things that have been previously used by giving them away to other people for free. a. Up Down Funk b. Freecycling c. Up Cycling d. Down Cycling Answer: B 23. It can help reduce the quantities of solid waste deposited in landfills, which have become increasingly expensive. a. Reuse b. Recovery c. Reduce d. Recycling Answer: D 24. What is the number on the recycle code of High-density polyethylene? a. 2 b. 1 c. 4 d. 3 Answer: A 25. What is the number on the recycle code of Polysterene? a. 3 b. 4 c. 5 d. 6 Answer: D