Low Barcol Hardness Readings after switching materials (Phenolic Prepregs 270°F cure)

[Cisnerjo]

Hello everyone, I would like to request support from the experts on this matter. We are switching from certain phenolic prepreg to a different one available from same manufacturer which mentions both are the same. We perform Hardness test per our own specification which request an average of 68-75 we are testing this new material, and we are getting Hardness results as low as 50 and maximum of 70. We changed the recipe and increase the soak time up the maximum requested by the manufacturer, also performed different bagging methods in order to attempt to increase Barcol Hardness results without much good results. We also are checking ASTM D2583, which it calls for a Polyester Laminate and its average request is 55. Is there any other way to attempt to increase Barcol Hardness results on them or should we attempt to perform testings to come up with a base line and modify our own specification to reduce it to whatever the results we get?

Please advice ! Thanks a lot !

 

[SWComposites]

from same manufacturer which mentions both are the same.

LOL. I would never believe that statement from the manufacturer without actual data to back it up.
Is Hardness a test that the material supplier performs for batch certification? is it listed on their product datasheet.
Frankly, in 40+ years in the composites world, I've never heard of a hardness test being used to evaluate a composite material. Are there any other properties that you are testing?

 

[Compositepro]

Phenolics are condensation cure polymers, meaning that water is generated during cure. This water is usually trapped in the polymer after cure and acts as a plasticizer. An oven bake after cure should be done to allow this water to diffuse out of your part. This needs to be done with some care, as trying to dry too fast will blister or delaminate the part due to internal steam pressure.

Also consider that the hardness reading will be different if taken over a fiber bundle or in a weave opening between fiber bundles.