Chapter 3 until Disadvantages Flashcards
What are composites?
Composites are materials made by combining two or more different materials to achieve unique properties. Each component retains its individual properties, but the combination creates a material with characteristics not achievable by the individual components alone.
What are the three main types of composites?
- Metal Matrix Composites (MMC): Uses metals, such as aluminum, as the matrix with fibers like silicon carbide for reinforcement.
- Ceramic Matrix Composites (CMC): Uses ceramics as the matrix, reinforced with short fibers or whiskers.
- Polymer Matrix Composites (PMC): Uses polymer-based resins as the matrix, reinforced with fibers like glass, carbon, or aramid.
What is the primary role of the matrix in composite materials?
The matrix in composite materials serves to bind the fibers together, transfer loads to the fibers, isolate them, provide surface finish quality, and protect the fibers from chemical and mechanical damage.
What are the main functions of reinforcing fibers in composites?
Reinforcing fibers in composites provide strength, stiffness, thermal stability, and, in some cases, electrical conductivity or insulation. They primarily carry the load within the composite material.
What are the key characteristics of Metal Matrix Composites (MMC)?
Metal Matrix Composites use a metal, like aluminum, as the matrix material, reinforced with fibers such as silicon carbide. They are commonly used in the automotive industry due to their durability and strength.
Why are Ceramic Matrix Composites (CMC) suitable for high-temperature environments?
Ceramic Matrix Composites are ideal for high-temperature applications because they utilize ceramics as the matrix material, which can withstand extreme temperatures. They are often reinforced with heat-resistant fibers like silicon carbide and boron nitride.
What are Polymer Matrix Composites (PMC), and why are they common?
Polymer Matrix Composites are composites that use a polymer-based resin as the matrix, reinforced with fibers like glass, carbon, or aramid. They are common because they offer flexibility, ease of processing, and good performance-to-weight ratios.
What is the advantage of composites in terms of specific stiffness and strength?
Composites offer high specific stiffness (stiffness-to-density ratio) and high specific strength (strength-to-density ratio), making them lightweight yet strong compared to traditional materials like metals.
How do composites contribute to design flexibility?
Composites allow for design flexibility by enabling complex shapes, special contours, and near-net-shape parts to be fabricated. This is due to their adaptable nature during processing.
What are some advantages of composites over traditional materials?
Advantages of composites include high performance with low weight, higher fatigue strength, excellent corrosion resistance, better noise and vibration characteristics, and the ability to embed sensors for in-service monitoring.
What makes composites desirable for the automotive industry?
In the automotive industry, composites are desirable due to their ability to reduce weight, enhance fuel efficiency, provide greater design flexibility, and improve impact properties.
What are some disadvantages of using composites?
High material costs, making them more expensive than traditional materials.
Temperature resistance is often limited by the matrix material.
Susceptibility to solvent resistance, chemical resistance, and environmental stress cracking, which depend on the polymer used.
Composites tend to absorb moisture, which can affect performance and durability.
Why do composites have high material costs?
The high material cost of composites is mainly due to the specialized materials used, such as advanced fibers and high-performance resins, which are more expensive to produce and process than conventional materials.
How does temperature resistance in composites depend on the matrix?
The temperature resistance of a composite is directly related to the type of matrix material used. If the matrix material has a low thermal stability, the overall temperature resistance of the composite will be limited.
What environmental factors can affect the durability of composite materials?
Composite materials can be affected by factors like moisture absorption, chemical exposure, and environmental stress cracking. These factors can degrade the performance of the composites over time, depending on the type of polymer matrix.
