Hi Cameron - I think your variable set, range, and potential result is getting closer. I will suggest a slightly different way to view it which might be entirely wrong, but here it is anyway.
a) The first testing set
- Modeling is great, but obviously, we are getting to the point where the theoretical models need some baseline testing - if for no other reason, than to see if they are not just figments of our imagination.
- At this stage, we have so little experimental information on the "real" effects, that we should concentrate on getting a baseline on likely first order effects in the general mix range that is plausible.
- It should also be assumed that the first DOE experiment will be botched. That is not a criticism, it is just simple reality - science is messy, especially wet lab science. Keep it simple.
b) Phi - essentially void space as a variable in the DOE.
- My perception is that this is not a good item to select as a variable, even though it is a calculable variable and subject to some reasonable experimental control.
- Even if you have an extremely well controlled bulk value for Phi, locally, this will have wide variation no matter how well we are able to mechanically mix.
- The smaller the agr. size, the more difficult it will be to mix, making Phi even less reliable as an indicator.
- Once the minimum size agr takes on an (unknown) layer thickness of epoxy, the Phi value becomes almost lost in the noise.
b) Minimum agr size as a variable
- My suggestion is to use the presence or absence ( 0 - 100 %) of your smallest agr. as a variable and see if the needle moves enough to keep it in as a first order effect compared to other factors.
c) Epoxy concentration
- This one is more obvious 10 - 20 % range
- If the real need becomes 25 %, then the first DOE will tell us to go that direction anyway.
d) Hardener
- Type - I would guess there is an effect, but this is not a variable that can easily take on a 3 "level" effect for the DOE, especially the first round.
- Qty of hardener - this is more easily fit into a DOE.
e) Cure Temperature
- Likely first order effect
f) Cure Time
- Likely first order effect
Keep everything else steady.
That is more than enough variables for a a first trial. JMHO.