Joining method

1. A joining method for joining together a first member in which fiber material including fibers is mixed into a first resin, and a second member that includes at least a second resin, the joining method comprising:

providing a stirring member including a pin member and a shoulder portion in which the pin member is inserted such that the shoulder portion surrounds the pin member, the stirring member configured such that the pin member and the shoulder portion rotate together as a single unit around an axis and are able to move relative to one another in a direction of the axis;

arranging the first member and the second member such that the first member and the second member abut together;

softening or melting the first resin of the first member and the second resin of the second member that are adjacent to abutting surfaces of the first member and the second member, inserting the stirring member into a joint forming portion formed by the softened or melted first resin of the first member, the softened or melted second resin of the second member, and the fiber material included in the softened or melted first resin of the first member, and stirring the joint forming portion in a direction orthogonal to the abutting surfaces to orient the fibers included in the joint forming portion in the direction orthogonal to the abutting surfaces, by moving the shoulder portion in a direction toward the abutting surfaces along the direction orthogonal to the abutting surfaces and moving the pin member in a direction away from the abutting surfaces along the direction orthogonal to the abutting surfaces while rotating the pin member and the shoulder portion of the inserted stirring member together as a single unit around the axis;

stirring the joint forming portion in the direction orthogonal to the abutting surfaces to orient the fibers included in the joint forming portion in the direction orthogonal to the abutting surfaces, by moving the shoulder portion of the stirring member in the direction away from the abutting surfaces along the direction orthogonal to the abutting surfaces and moving the pin member in the direction toward the abutting surfaces along the direction orthogonal to the abutting surfaces, and removing the stirring member from the joint forming portion; and

hardening the first resin of the first member and the second resin of the second member included in the joint forming portion.

2. The joining method according to claim 1 , wherein

the stirring member is made to contact a facing surface of the first member that faces the abutting surfaces or a facing surface of the second member that faces the abutting surfaces, the first resin of the first member and the second resin of the second member are softened or melted from the facing surface of the first member or the facing surface of the second member by the stirring member, and the stirring member is inserted into the joint forming portion.

3. The joining method according to claim 2 , wherein

when softening or melting the first resin of the first member and the second resin of the second member, the stirring member is rotated around a rotational axis that is parallel to the direction orthogonal to the abutting surfaces, and friction heat generated between the first member or the second member, and the stirring member is used.

4. The joining method according to claim 3 , wherein

the first resin of the first member and the second resin of the second member are softened or melted and the stirring member is inserted into the joint forming portion, while moving the stirring member into the first member and the second member from the facing surface of the first member or the facing surface of the second member.

5. The joining method according to claim 1 , wherein

the second member also includes fiber material.