Reference: Abbott, Richard. Analysis and Design of Composite and Metallic Flight Vehicle Structures 3 Edition, 2019

‘Joint strength’ considers the failure of all the components and all failure modes within the joint. Joint strength is determined by the first critical failure mode of the joint.

Achieving full joint strength depends on good composition of the joint and selecting the correct hardware. Correct grip length, threaded portion length and use of washers will affect the static strength and durability of the joint.

The designer also must be aware of galvanic corrosion potential between all the items in the joint. The plates or components being fastened, the bolt, nut and washers should be chosen with care. Reference section 4.4.

In mechanical joints involving composite structure the torque applied during bolt installation can damage the components fastened by the joint. In the authors experience, up to ¼in diameter fasteners can be installed in carbon fiber composite structure with standard installation torque. Larger fasteners require mitigations such as a reduction in installation torque or large washers or plates. For more design guideline on mechanical joints in composite structure see section 12.2.4.1.