The analysis of the bolted joint is performed using several established analytical techniques. When combined, these techniques represent an efficient means of performing the initial stress calculations required for sizing a composite joint.
- Load sharing calculations are performed to determine which bolt (if more than one is present) carries the greatest bearing load. This bolt is identified as the critical bolt.
- The 2-D stress field around the location of this critical bolt is determined using stress functions.
- The strength of the bolted joint is predicted using the characteristic length and the point-stress method in conjunction with the characteristic curve.
- The 2-D stress field is evaluated along the characteristic curve using the Yamada-Sun failure criterion and the predicted joint failure load.
Assumptions and Limitations
A number of assumptions are made to simplify the analytical procedure:
- Bolt is assumed to be a frictionless pin
- There is zero clearance between the bolt and bolt hole
- Bolt is assumed to be rigid and there is no clamping force considered
- The entire distributed edge load is reacted by the bolt as a concentrated force applied at its center
- Through-thickness effects are not considered
- The analysis takes place at the laminate level using orthotropic material properties of the laminate
- No lamina or constituent level stresses are considered
- The 2-D stress field around the critical bolt is calculated under the assumption that laminate plates are of infinite width
- A finite width correction factor is applied to the predicted strength of the joint to include the effects of the finite laminate width as proposed by Tan
The analysis will be stopped if:
- e/d < 0.5
- w/d < 2 (possible to get results, but unlikely to be reliable)
- Countersink depth is deeper than the laminate thickness
- Only isotropic plates are used in the joint