Are aviation accident investigation reports always made public?
Unless there is some risk of national security to releasing a public report of the accident, the reports are released. You can search the public ones (almost all are public) at the BEA website. The same applies for the other aviation accident and incident reports and you can find the available reports on the websites of the group that has jurisdiction over the accident/incident; NTSB for the US, AAIB for the UK, and many other ones.