After letting the epoxy splice sit for a week we pressure tested the spliced-pair to destruction today. At around 120 psi a small leak developed. We kept increasing the pressure until the splice failed at ~150psi.
This time it was the PET bottle that failed rather than the splice. It fairly cleanly tore itself off from around the edge of the sleeve. The epoxy glue though separated cleanly from the bottle that flew off. This means that the epoxy did not do as good a job of holding onto the PET, even though the 1cm x 1cm tests showed promising results.
The sleeve was glued on with PL premium.
We are now waiting for the sikaflex and PL to cure on the next splice test.
The reinforcing shells worked well and the bottles did not show any signs of stress in the neck area. We have taken them off again, and will use them on the next splice test.