What was found
1R COCKPIT WINDSHIELD CRACKED. FIRST OFFICERS WINDSHIELD STARTED ARCING IN LOWER CORNER AND PROGRESSED INTO THE WINDOW UNTIL THE WINDOW SHATTERED. FOD DAMAGED OUTER LAYER OF FIRST OFFICER'S NR 1 WINDSHIELD NEAR CENTER OF WINDSHIELD. THIS DAMAGE RESULTED IN STRESS CONCENTRATION THAT CAUSED OUTER PLY TO FAIL (CRACKED). SUBSEQUENT TO THIS FAILURE, ARCING OCCURRED AT THE BUS-BAR FOLLOWED BY SHATTERING OF OUTER WINDSHIELD PLY AND "R FWD WINDOW HEAT" EICAS MESSAGE. REPLACED FIRST OFFICER'S NR 1 WINDSHIELD ASSEMBLY. NO VISIBLE SIGNS OF MOISTURE INGRESSION WERE PRESENT THAT MAY HAVE CAUSED WINDOW FAILURE.