Question

Explain why bonding between carbon fibers and an epoxy matrix should be excellent, whereas bonding between silicon nitride fibers and a silicon carbide matrix should be poor? Q2- Explain briefly Ceramic-Matrix Composite?

Answer 1

if load is applied on the carbon fiber renforced epoxy matrix composit, the load should be transferred to the carbon fibers from the weak epoxy matrix. Thus , only if good bonding is present between carbon fibers and epoxy matrix, the composit will survive and show good strength.

In silicon nitride fiber reinforced silicon carbide matrix composite, fracture toughness is expected to be higher. Weak bonding between the matrix and fibers make the induced cracks (as a result of load application on the composite) to travel around fibers to make the composite fail Unbroken fibers thus formed join the cracks made, and thereby makes further opening of the crack tedious

If bonding is poor, the fibers will be pulled out from the matrix and as a cascading effect this process consumes energy which will lead to the increase in fracture toughness of the composite.

Therefore, unless pull-out of silicon nitride fibers from silicon fiber matrix does not occur, fibers will not get pulled out from the matrix of the composite, which eventually decreases the fracture toughness of the composite.

Ceramic matrix composites (CMCs) are a subgroup of composite materials as well as a subgroup of ceramics. They consist of ceramic fibers embedded in a ceramic matrix. Both the matrix and the fibers can consist of any ceramic material, whereby carbon and carbon fibers can also be considered a ceramic material.