Thanks Steve - Let's say we have a 3 row joint. Is it possible to forgo the load share analysis and and to use a fitting factor to account for load peaking that may be present if the end fasteners still see more load than the middle? or is the fastener load share too uncertain to set an...
Is it common to assume load distributes evenly amongst all fasteners for a multi row, single shear joint where one plate is carbon fiber and the other plate is a ductile metal? Is this a valid assumption if the metal plate thickness is sized such that bearing yield in the metal plate has the...
Ok copy, that makes sense. Is tension bypass something you would check for a single row joint? or is bearing forced to be the critical failure mode by using >5D spacing? I imagine a net-section check would have to be rooted in test data?
I'm glad I asked. To confirm - the 5-6D spacing applies to single row joints? I was under the impression tighter spacing could be used since there is no bearing-bypass interaction.
I would love to read through the CMH-17 update once it's available.
I've typically used 4D fastener pitch for single row CFRP joints. The following reference discusses 3D pitch as optimal to maximize the joint strength.
"Critical Joints in Large Composite Aircraft Structure"
https://ntrs.nasa.gov/api/citations/19870001540/downloads/19870001540.pdf
What is...
The load concentration is mechanical in nature due to a geometric discontinuity near the joint. It's a joint between two tubes for a launch vehicle application - I attached a sketch. I have positive bearing yield margins at limit load at the fasteners away from the load concentration, but not...
Hey All,
Is there a good way to increase the bearing capability local to a few fasteners for a single row (double shear)joint with many bolts? The applied line load is concentrated at a few fastener locations, causing them to transfer additional load than the rest.
Current ideas:
1) Use bigger...
Awesome - that's super helpful. It sounds like there is a good chance some of our coupons are buckling if we are measuring 20-30% knockdowns. I'll circle back with our M&P team to try to confirm that.
The sandwich panel facesheets would be cocured to either honeycomb or foam.
What is the typical % difference between tensile/compressive modulus for the widely used carbon fiber material systems?
I've seen values ranging from 0 to 30% from literature and internal M&P test efforts. I understand it can be a difficult parameter to measure and want to understand what is...
Hey all,
Does anyone have a literature source discussing how rapidly composite (carbon fiber) joint capability deteriorates as a function of edge distance? I understand anything less than 2.5D runs the risk of undesirable failure modes occurring. I'm being asked to look at joint with e/D = 1.75...
Are there situations where it is acceptable to forgo a BVID knockdown when calculating ply strength or laminate strength margins? The startup I am employed at (expendable launch vehicle industry) has historically not accounted for a strength knockdown due to impact damage. I understand it is...
