Comparison of coupon tests, mean or B-Value? 2

[irq]

I need your advice in coupon or connections testing to produce material design values in composite field. I am comparing the new prepreg material to the existing one. The set of samples shows a high percentage difference between standard deviation and mean value of the new material and leads to the much lower B-Value as expected. Can I compare both materials using mean value, which is higher for the new material or is it necessary to compare B-values to comply with FAR 25.613?

 

[SWComposites]

If you are trying to show the new material is equivalent to the existing material (presumably so you can use the existing B-bass values for the new material), then you need to show that both the property mean and variations are equivalent. Sounds like this is not the case for your new material. And having a higher mean property for the new material is NOT better or necessarily acceptable. Your new material is different, and should not be treated as a second source. You should develop properties and allowables for the new material, and then perform stress analysis of your structures to determine if the new material is acceptable.

 

[vivekpdd]

Hi,

Can any one guide me on some literature which gives information on how to generate the material and design allowables ( A Basis and B basis ) and their usage to stress group.

Please share the literature if you have..

 

[Compositepro]

vivekpdd, look in MIL handbook 17, which you can find here:

http://www.abdmatrix.com/site/html/repository1.shtml