Thermal spike test

[CompoMan]

Hi,
Can anyone offer advice on the heating/cooling rate use in thermal spike testing of composites, for both civil and military applications??

 

[SWComposites]

What kind of real world "thermal spike" are you trying to simulate?

 

[CompoMan]

Hi SWComposites,

I need to investigate if my composites are prone to matrix cracking or other failure mode when subject to thermal shock during flights.

 

[SWComposites]

Thermal shock due to:
- cold ambient conditions at altitude,
- aero heating due to supersonic flight,
-??

What FAR/customer requirement is driving this need?

SW

 

[CompoMan]

Hi SW, I have no particular customer requirement. I just want to find out how my composite material performance under thermal shock condition. I was thinking of plunging the test samples into a chamber set at, say -50C, leave for 5-10 minutes and move them to hot chamber, say 100C, leave for 5-10 minutes and back to -50C and repeating the cycles number of times. These would mean a quite severe heating/cooling rate. Is there a recommended rate of cooling/heating??

 

[Compositepro]

One of the most severe tests is dipping in liquid nitrogen. It survives that it will likely pass any test.

The test should be somewhat more severe than the worst case expected exposure to be realistic. There are different thermo-cycles used in different industries. I'm not aware of any standard cycle in aerospace.

Just as important as the cycle is the lay-up of the laminate. Thick plies are far more likely to micro-crack than thinner ones. If I recall, a common lay-up is a 0-90 symmetric, with each ply made from three layers of prepreg, so you have six layers together in the center.

 

[CompoMan]

Thanks for all your info