(20 pts) Most commercial aircraft have side windows that are covered on the outs
ID: 698691 • Letter: #
Question
(20 pts) Most commercial aircraft have side windows that are covered on the outside by PMMA. You have been asked to solve a mystery: the occurrence of numerous crazes on the windows. You suspect the crazes are caused bya combination of scratches caused by the airline's diligent efforts to keep the outsides of their planes very clean by vigorous scrubbing, and one among half a dozen of the strong cleaning solutions specified by the aircraft manufacturer Someone else suggests that it is due to exposure to ultra-violet (UV) radiation The cleaning agents contain various amounts of kerosene and other chemicals. Write a brief report to the airline that contains the following The two necessary and sufficient external conditions that cause crazing in a. PMMA. (3 pts.) b. The possible role of UV. (3 pts.) c. The possible role of the scratches. (3 pts.) d. How to distinguish between scratches and crazes. (3 pts.) e. A method to rank the order of the half dozen cleaning solutions. (4 pts.) f. An overall recommendation for minimizing the future occurrence of crazes without changing the PMMA to another plastic. (4 pts.)Explanation / Answer
THE above situation clearly states that NON-MODIFIED PMMA is being used by the airline company.
A. Two of the common reasons for crazing in non-modified PMMA is the loss of tensile strength due to cleaning techniques used to scrub the outer surface of the planes. Another would be due to impact force of the UV radiations.
B. Although modified PMMA is UV- resistent and has good tensile strength, the use of non-modified PMMA can lead to widening of the scratches/ crazes cause by the impact force during cleaning.
C. Scratches have been caused by the impact force of cleaning the outer surface of the plane and may further add to the degradation of the PMMA surface. Also, the use of flammable liquids in the cleaning agents could also lead to heating up of the PMMA layer when exposed to UV RAYS.
D. Scratches have been manually causes by the impact force of cleaning, whereas the crazes have been formed to the degradation of the polymer PMMA caused by the harmful UV- Radiation.
E. The various cleaning agents can be classified by placing the non flammable ones first and keep the cleaning agents with flammable liquids as the last resort.
F. An overall and very strong recommendation for minimising the future occurence of crazes with out changing the PMMA to another plastic, is the use of (MODIFIED PMMA) which is UV resistent, has tensile and flexural strength. is chemical and heat resistent, has polishability and also possesses impact strength.
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