Help with reinforcing a weak 3D print

[MonitorChakas]

Hi there! I have a big 3D print of Guilty Spark in PLA material. Im trying to rescue this print that unfortunately was not printed using much material so it suffers from brittleness. Any advice on how to reinforce?

My ideas are first filling all the holes that are accessible to me with insulation foam
Then coating it with UV Resin once I glue all the pieces together.
Is this a good plan or do I need to use something stronger as coating? Is the foam filling a good idea or is it too much risk of cracking?
Also before adding UV resin do I need to sand the print or will the resin sooth over the ridges well?

Thanks for the help!

Notes:
I don't own a 3d printer so reprintimg is not an option for me unfortunately.

 

[PlanetAlexander]

This will be interesting to see done! Those walls do look pretty solid so unless you still feel they're pretty weak, you probably needn't worry so much. Instead of insulation foam, have a look at expanding foam for filling the gaps in the infill - it's pretty strong, lightweight, and will expand to fill all the gaps.

I'm not sure what sort of resin would work best for this purpose - Smooth On does make a resin designed to smooth prints called XTC 3D, which I've heard works well for smoothing (and sands well), not sure how durable it is. I would recommend sanding the print down first before applying resin, just to rough it up and give the resin a better surface to grip on to.

 

[MonitorChakas]

Thanks for the reply!
Ill look into the expanding foam. Any brands you recommend or doesn't matter?
It feels solid in most parts but it has cracked in a few parts.
My only fear with a 2 part epoxy is I seem to only get the mixture right 50% of the time even when I measure with a scale. Maybe its the brand I used though it was a cheaper brand.
Ill try to research its durability as I would like to keep this prop for as long as possible.

 

[PlanetAlexander]

I come from a land down under, so the only expanding foam I have used is by Parfix from Bunnings. If there's a few areas that have cracked, you may want to go over those cracks with some superglue first, or if you happen to have some spare filament and a soldering iron, you can weld those cracks too (though now that I look at the picture, those methods won't work for a hole of that size). In relation to the epoxy issue, make sure you double check if it's measured by weight or volume (it can vary), and make sure you always mix it very, very well.

 

[MonitorChakas]

I bought a 3d printer pen from cyber monday as some of the cracked pieces are missing Hopefully that will help to fill it. I also wanted it for any extra detailing
Ill use superglue to attach any of the pieces I do have thanks for the tip!
Oh didnt know the weight/volume thing Ill make sure I pay attention to this.
I appreciate all the advice!!

 

[Off Earth]

Expanding foam and the old faithful, fiberglass + resin