[Varyon]

I'd be tempted to give ceramic inserts essentially 4 DR values. Let's call these MinDR, MaxDR, DR, and bDR. Damage below MinDR just bounces/splashes off with no (or minimal, use the rules for semi-ablative) effect on the armor itself. Damage at or above MinDR shatters the plate, but as long as MaxDR isn't exceeded, the plate does its job and the attack fails to injure the wearer (beyond possible blunt trauma). If MaxDR is exceeded, subtract the DR from the attack's damage to determine penetrating damage. Once a plate has been shattered, it continues to give semi-ablative DR equal to bDR.

A more simplistic, but perhaps less realistic, way to handle it is more-or-less the way I see Shardplate (from The Stormlight Archives) working, where armor has an HP-like stat (that exceeds the armor's weight-based HP, so should probably have a different name, but we'll use HP). Damage up to DR bounces/splashes off. Beyond DR, further damage reduces the armor's HP, but the armor continues to protect. If HP reaches 0, the armor shatters, either outright eliminating it or greatly reducing the DR. Optionally, allow the armor to actually absorb enough damage from a single attack to reduce it to -HP, or maybe even a multiple thereof. Note this is roughly the way most ablative enemy armor seems to work in games like Far Cry 5/New Dawn (non-ablative armor in games usually grants IT:DR rather than DR), and would actually be a useful paradigm for a lot of armor in a cinematic campaign.