2 A what is creeping Why is this not desirable in engineerin

2) A) what is creeping? Why is this not desirable in engineering structures? B) Explain one way which the flammability of polymer matrix can be measured? C) Compute the thickness of fiber in a CSM mat made out of 800 g/mA2 of E-glass fibers having a density of 2.5 g/cmA3

Solution

(A) Answer:- Creeping is tendency of material to move slowly or deform permanently under the influence of mechanical stresses.

Creeping is not desirable in structure because it is harmful for structure. Creep is harmful for dams. Loss of prestress due to creep of concrete in prestressed concrete structure. In eccentrically loaded column, creep increases the defection and can load to buckling.

(B) Answer:-A pyrolysis combustion flow calorimeter is used for measuring of flammability of polymer.

5 mg of the cured resin sample is taken. It is Heated at 1 degree celsius to 900 degree Celsius under nitrogen. The volatile thermal decomposition product products are purged from the sample chamber and combined with oxygen at 900 degree Celsius to affect complete oxidation . Water is scrubbed from the combustion gas stream and heat release rate is calculated from the oxygen and the flow rate measurement. Heat release capacity is calculated as HRR divided by sample mass and heating rate.

(C) Solution:-

Given

Density = 2.5 g/cm³ = 2.5 *10⁶ g/m³       , weight = 800 g/m²

Thickness of fiber =Weight /Density

                                      = 800/(2.5*10⁶)

                                     = 0.32 mm Answer