At 1407 mountain time, a Cessna 172L suffered a propeller blade failure during departure from Bullhead City/Laughlin International Airport. The student pilot landed on the remaining runway and overrun area. Neither the pilot nor his passenger was injured. Control tower personnel said the airplane had climbed to about 800 feet when the airplane experienced the failure. Preliminary examination revealed a disintegrated propeller hub with loss of propeller blades and a severed crankshaft aft of the shaft flange. The pilot reported that about 1 year prior to the accident, he and his instructor struck a bird during cruise flight. They made a dead stick landing into an airport, where they found the engine had shifted in the cowling. The pilot reported the cowling was repaired but no repairs were made to the propeller or engine.