Member joining method

A method of joining comprising:

• providing a first outer member and a first inner member, wherein the first outer member has an end portion and the first inner member has an end portion;
• providing a second outer member and a second inner member, wherein the second outer member has an end portion and the second inner member has an end portion;
• arranging a first resin member on the first outer member, wherein the first resin member has an end portion;
• arranging a second resin member on the second outer member, wherein the second resin member has an end portion;
• performing a first joining step comprising joining the respective end portions of the first and second outer members to each other;
• performing a second joining step comprising joining the respective end portions of the first and second inner members to each other;
• performing a third joining step comprising joining the first outer member to the first inner member to define a first space therebetween, wherein the first resin member is covered by the first inner member and is located within the first space;
• performing a fourth joining step comprising joining the second outer member to the second inner member to define a second space therebetween, wherein the second resin member is covered by the second inner member and is located within the second space;
• wherein the combined first, second, third and fourth joining steps produce an assembly comprising the first and second inner members, the first and second outer members, and the first and second resin members respectively located within the first and second spaces;
• and
• heating the assembly to cause the first and second resin members to expand such that the respective end portions of the first and second resin members join to each other and mix with each other, the step of heating the assembly further causing the first and second resin members to cure.