tailieunhanh - Composites Manufacturing - Materials, Product, and Process Engineering Part 2

Tham khảo tài liệu 'composites manufacturing - materials, product, and process engineering part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | utilized to monitor the resin flow in an RTM resin transfer molding process. Materials with embedded sensors are known as smart materials. 3. Composite materials have a high specific stiffness stiffness-to-den-sity ratio as shown in Table . Composites offer the stiffness of steel at one fifth the weight and equal the stiffness of aluminum at one half the weight. 4. The specific strength strength-to-density ratio of a composite material is very high. Due to this airplanes and automobiles move faster and with better fuel efficiency. The specific strength is typically in the range of 3 to 5 times that of steel and aluminum alloys. Due to this higher specific stiffness and strength composite parts are lighter than their counterparts. 5. The fatigue strength endurance limit is much higher for composite materials. Steel and aluminum alloys exhibit good fatigue strength up to about 50 of their static strength. Unidirectional carbon epoxy composites have good fatigue strength up to almost 90 of their static strength. 6. Composite materials offer high corrosion resistance. Iron and aluminum corrode in the presence of water and air and require special coatings and alloying. Because the outer surface of composites is formed by plastics corrosion and chemical resistance are very good. 7. Composite materials offer increased amounts of design flexibility. For example the coefficient of thermal expansion CTE of composite structures can be made zero by selecting suitable materials and lay-up sequence. Because the CTE for composites is much lower than for metals composite structures provide good dimensional stability. 8. Net-shape or near-net-shape parts can be produced with composite materials. This feature eliminates several machining operations and thus reduces process cycle time and cost. 9. Complex parts appearance and special contours which are sometimes not possible with metals can be fabricated using composite materials without welding or riveting the separate pieces. .