5.The ratio of length (L)to diameter (D)of a reinforcing fiber is known as 11) 6.The four basic types of hybrid composites include 12) 13) 14) and superhybrid. 7.The term used to describe the crystallinity of polymers is 15) s餐yk the statemen.write the lelter产 Chemical resistance will decrease in plastics as temperature increase. 2.Amorphous structure in a material decreases its degree of transparency. 3.Most plastics lose their strength at relatively low temperature. 4.The creep resistance of thermosets is better than that of thermoplastics 5. Thermosetting plastics are generally better than thermoplastic plastics in foughness and impact resistance. 6.There is a chemical cross-linking in the network of thermoplastic rubbers. 7.Carbon/carbon composites have good resistance to oxidation at high temperature. Since larger repeat units,bulkier side groups,chain branches,and polar side groups each tend to inhibit mole ular motion,they also tend to increase the glass transition temperature. 9.Acrylonitrile-butadiene rubber (NBR)and Fluoroelastomers have excellent resistance to oil,kerosene,and gasoline. 10.Butyl rubber (IIR)has little resistance to gas permeating. rheol gical (ER)and )fluids change with variations in the application of either current or magnetic fields. 12.Usually in brittle materials,the larger the flaw,the less the ability to withstand any degree of load. 13.Use landfilling method to treat MSW is the least desirable but the most common method. -of-solvent adhesives 15.As the wind angle increases,the hoop tensile strength decreases and the axial tensile strength increases in filament winding processing. 16.The disadvantage of polymer matrix composites such as residual stresses, electrochemical effec reater environmental degradation are resulted from the two-phase structures in the composit tes 17.Resin Transfer Molding,Injection Molding,and Spay up are closed molding processes. 18.Boron fiber is a composite fiber. 19.Both strength and stiffness of materials in fiber form are over the same materials in bulk form 20.Plywood is one type of laminate composites with isotropic properties. 6 6 5. The ratio of length (L) to diameter (D) of a reinforcing fiber is known as 11) . 6. The four basic types of hybrid composites include 12) 13) 14) , and superhybrid. 7. The term used to describe the crystallinity of polymers is 15) IV. True or false questions. If you think the statement is true, write the letter “T”; otherwise, write the letter “F” (10pts) 1. Chemical resistance will decrease in plastics as temperature increase. 2. Amorphous structure in a material decreases its degree of transparency. 3. Most plastics lose their strength at relatively low temperature. 4. The creep resistance of thermosets is better than that of thermoplastics. 5. Thermosetting plastics are generally better than thermoplastic plastics in toughness and impact resistance. 6. There is a chemical cross-linking in the network of thermoplastic rubbers. 7. Carbon/carbon composites have good resistance to oxidation at high temperature. 8. Since larger repeat units, bulkier side groups, chain branches, and polar side groups each tend to inhibit molecular motion, they also tend to increase the glass transition temperature. 9. Acrylonitrile-butadiene rubber (NBR) and Fluoroelastomers have excellent resistance to oil, kerosene, and gasoline. 10. Butyl rubber (IIR) has little resistance to gas permeating. 11. The viscosity, plasticity or elasticity of Electrorheological (ER) and magnetorheological (MR) fluids change with variations in the application of either current or magnetic fields. 12. Usually in brittle materials, the larger the flaw, the less the ability to withstand any degree of load. 13. Use landfilling method to treat MSW is the least desirable but the most common method. 14. Hot-melt adhesives usually have longer curing time than loss-of-solvent adhesives. 15. As the wind angle increases, the hoop tensile strength decreases and the axial tensile strength increases in filament winding processing. 16. The disadvantage of polymer matrix composites such as residual stresses, electrochemical effects and greater environmental degradation are resulted from the two-phase structures in the composites. 17. Resin Transfer Molding, Injection Molding, and Spay up are closed molding processes. 18. Boron fiber is a composite fiber. 19. Both strength and stiffness of materials in fiber form are over the same materials in bulk form. 20. Plywood is one type of laminate composites with isotropic properties