iPhone dead despite battery and charger port change

I received a phone today which is dead, non responsive. It is fairly battered (broken screen and bent frame). I was told it had 'an argument with the pavement'. I have tried a new battery, charger port and screen (all parts that are known to be working) but there is still no life even when plugged into a laptop. Does anyone have any other ideas? Does it sound like a chip fault or am I missing something more obvious? The phone is not water damaged as all sensors are clear and I was told by owner it has never been near water. Could the hard fall have broken the motherboard despite there not being an obvious aesthetic damage?

Cheers for your help