First, be aware that Apple generally does monitor or participate within the Apple Support Community. Contributors here are all end-users, just like you. As such, complaints made here are unlikely to be seen be Apple.
iPad models do not spontaneously "bend". Whilst mindful of your comments, damage of this nature is typically characteristic of physical/mechanical forces being applied...
In some situations, placing the iPad within some tightly fitting cases can require “some persuasion” - leading to unintended (and perhaps unnoticed) consequences - some models of iPad being more vulnerable than others to this type of damage. While defective/swelling batteries can cause screen deformation, bending of the chassis is not generally characteristic of a battery fault.
Damage due to bending is more often attributed to the iPad being transported/carried in an inappropriate container - such as a backpack - along with other items. Bags can be sat upon or squashed in crowded locations; unless an iPad is itself protected in a rigid case, damage can occur.
Damage from bending is unlikely to be accepted as a warranty issue. Apple’s flat-rate for repair is c.60% of the “as new” cost of the iPad. You can verify the repair cost for your country/region here:
iPad Repair & Service - Apple Support