Is it normal for an oak tree to slough off its thick bark without it growing back?

To me, this looks like normal growth, these trees will go through the natural "shedding" process as they grow. Those trees do not appear to be even close to full-grown yet and if there are not small brown fungal spores that turn grey or black then that's good if you notice that they do contract the disease, unfortunately, the best thing to do is burn it and cut it out of the area. If there is any dark smelly fluid draining from the cracks in the bark The bark will usually fall right off then you could be dealing with something known as slime flux the recommended thing to do is drill a 1/4" hole into the tree and put a copper tube in to let it drain. I think you should be fine the new bark looks healthy

There seems to be new bark growing where the old has come off.

If the bald area extends right round the tree and there is no new bark growing underneath, the tree will not live long, but you don't mention any other visible problems with your trees so that seems unlikely. Your picture only shows half the circumference of the tree trunk, of course.

If there is new bark developing, there is nothing to worry about. The cause is probably that the trees have had exceptionally good growing conditions for a year or two, and the trunk is growing faster than the old bark can expand.

There are some fungus and virus diseases which cause this, but they are likely to produce either liquid oozing from cracks in the bark, or discoloured wood (e.g. bright reddish brown) on the bald patches. If that is the case, the only "cure" is to remove the tree before others nearby become infected as well.

Another option which has been observed is damage caused by squirrels - though why they do this isn't very obvious!