A door assembly for a washing machine appliance includes an outer door frame, an inner door frame, and two reinforcement brackets positioned between the outer door frame and the inner door frame on opposite sides of the door assembly. The outer door frame defines a boss and the reinforcement bracket defines an expandable sleeve received within the boss. A mechanical fastener passes through the inner door frame and into the expandable sleeve to increase a diameter of the expandable sleeve to engage the boss and join the inner door frame, the reinforcement brackets, and the outer door frame.