Epoxy bonding

[Ron B.]

A friend today,pulled the window trimmings out of the garbage and once started with his knife he was easily able to seperate the two layers . The doors have been glued (epoxy) for over two weeks. The 3/4" trimmings might not have had perfict prepwork and good epoxy coverage but I'm surprised how easily they seperated. Does this sound correct?
Ron

 

[Ramendala]

I am not familiar with the -10's window trimmings but it is very easy to pull fiberglass apart like you describe. Similar to how you can "hurt" a glass plane with point pressure. Two different loads but the bottom line is structures are built for load distribution. There is very little bonded area to take the load when peeling apart the glass as your friend did. As an illustration, you could take some other trimmings and hold an end in each hand as you make a "U" as you bring your hands together. The glass structure will stay intact for a great distance due to the load being applied across all the fibers. This is in contrast to the peeling apart of the two layers.

Kinda long winded simple answer...

Ryan

 

[Rick S.]

Ron,

Are the trimmings the ones you prepped and bonded? If so as long as you cleaned them before sanding and just prior to gluing you should be OK. You should have sanded the edges to be bonded until all the shine was gone and with no more 150 paper..too fine of a grit and you loose some tooth. The epoxy seems to cure for quite awhile especially if it's located in a cool damp climate. Take a few pieces inside for a week and see if it's the same. Small pieces can be pryed apart because of the small surface area you are dealing with. A knife blade can cut through the epoxy between the two parts as well. Tell your friend he was lucky he didn't slice his hand!! when thos piecs pop, not only the knife is sharp but so is the scrap.

 

[Ivan Kristensen]

Ron,

I had the very same problem and interestingly enough it was discovered in a similar way by a friend of mine who was twisting and bending the scarp pieces.

As you, I was quite concerned about this at first until I called the Epoxy Mfg. in California (AeroPoxy) there I spoke to a very knowledgeable guy who explained to me that epoxy actually has quite a poor "peel strength" whereas in tension or in sheer it is great. Being able to peel apart small flexible scrap parts does not indicate poor adhesion of the door as a whole.

I used 50 grit paper to sand the door parts to be glued together to give the epoxy as good a "mechanical grip" as possible, even then the scrap pieces peeled apart quite easily.

The door halves also have the hinge bolts in the top as well as bolts holding the latch pin guides in place in both bottom corners which all contribute to the integrity of the door structure .

Hope this helps put your mind as ease.

 

[Ron B.]

I work with polyester resin everyday, mind you not on such a small layup. For taring apart, I would say poly would hold better. When you peel the layers you will expose fibers. I know we can't use poly on epoxy, I'm refering to poly on poly. I hope the epoxy holds as I sealed down the overhead console yesterday and run a full bead around the full inside perimeter today. I used a turkey baster and put a 1/4" poly tube on the needle end to extend into the hollows of the console. I wanted to help out in the bonding and make sure it was sealed.
Thanks for the responces, glad to hear we are not off coarse.
Ron

 

[Ron B.]

Another question, other than heat is there anything that can speed up the cure process for epoxy and 410 filler so one can proceed to the fun task of sanding sooner?
Ron