While taxiing the rental airplane for departure, the pilot felt the right brake fail which initiated a left turn. The pilot attempted to correct the turn by applying right rudder pedal, but the airplane veered off onto the grass. The airplane then pivoted 180 degrees, came back onto the taxiway surface and came to rest. Examination of the airplane showed a portion of the right main landing gear composite strut had separated, and the right wing was buckled. The composite fracture surface showed discoloration consistent with a previous crack to that area of the strut. The airplane underwent a 100-hour inspection on August 21, 2012.