By philiplardner - 11/11/2013 11:12:42 PM
Hi,
I have been vacuum infusing using IN2 infusion resin for some months now with great success. I regularly check the quality of an infusion batch by load testing sample parts to destruction so that I can verify my strength calculations. All my parts are cured at around 20-25C for 24hrs (under an electric blanket and duvet cover, monitored by a digital thermometer) followed by post-curing in an oven to 80C. So far, so good.
I recently infused a flat plate 20" x 13" x 17 layers of CF cloth. The finished plate seemed to turn out and 'feel' ok. However, when I cut up the plate into 1" wide strips using a table saw I discovered that the strips could be bent quite easily, as if the resin had not fully cured. The strips bend as if they were made from a very stiff plastic or rubber and do not return to being flat/straight once you stop bending them. The table saw did not overheat the part while being cut.
I always measure both resin and hardener (slow set) to 0.1g on a digital scales and ensure a thorough mix. This is the first time I have encountered this problem and I would be interested to know what you think may be the cause.
These strips of carbon are designed to take very high loads in both tension and compression (in an aircraft wing.) This infusion run clearly failed and can not be used. I really want to avoid wasting more CF cloth until I understand the problem.
Any help appreciated.
Philip.
PS - I can send a physical sample by post if that's any help.
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By philiplardner - 11/14/2013 10:40:29 AM
Thanks Dravis - that's pretty much the conclusion I was coming to also. I'll try to verify this by calculating the ideal weight of one of my resin starved pieces and comparing that to the actual measured weight.
I considered the possibility of the resin having gone off during the summer but other, thinner parts made recently turned out just fine.
I'll chalk this one up as an expensive lesson... and remake the part using a wet lay-up before vac-baging it.
Phil.
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