The pilot reported that he was conducting a local pattern flight and performing touch and goes when during his second landing when he applied the brakes to slow down, the brakes did not respond. The pilot used the emergency break handle to stop but got no response. The pilot then steered the airplane into the grass adjacent to the runway to slow down. During the excursion, the left main landing gear struck a hole in the grass causing the aircraft to stop abruptly and nose over coming to rest inverted. The airplane sustained substantial damage to the forward fuselage and wings. A postaccident examination of the airplane revealed a small hole in left brake line and the line in that area was chaffed. The line transitioned from the airplane fuselage to the landing gear and brakes through a jagged hole in a metal support bulkhead. The hole did not possess a barrier or material to prevent rubbing of the break line. A review of the airplane’s maintenance logs did not show any entries regarding the brakes or any damage to the left brake line area. It is likely that the hole in the brake line existed for some time before it leaked enough fluid to cause the brakes to malfunction during the accident flight. According to a manufacturer’s engineering diagram, there should have been a grommet installed (Part Number: AN331-6-10) in the bulkhead hole that the brake line passed through. The part was designed to protect the brake line from chaffing. The pilot reported that there were no indications of a brake issue when he did his preflight.