Threaded joint design for composites. Supplemental report.

摘要

This report summarizes work on the design of a composite threaded joint. Although the project was for a year, it was placed on hold about half way through the program at the stage of model refinement. Thus, the report provides only partial results on the design of a threaded joint. Composite joining is one of the major obstacles preventing composites from side usage. The difficulties in joining composite structures arise from factors associated with the anisotropic nature of these materials which are strong and stiff in the fiber direction and very weak in the transverse direction. One well known type of joints is the threaded joint which is used extensively in metallic structures. Among the common thread types is the buttress thread which has advantages when loading is in one direction only. The flank of the thread which almost takes all the thrust is referred to as the pressure flank. It is nearly perpendicular to the thread axis so that the radial component of the thrust is almost zero. Therefore, this form of thread is particularly applicable where tubular members are screwed together as in the case of breech mechanisms of large guns and airplane propeller hubs. In this report, we use a buttress type thread in a composite laminate. The following sections will define the problem and describe the finite element model proposed to solve the problem. Some preliminary results are also included in the report.