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The joint must work in shear in its plane
Tensile stresses in the joint must be avoided
The following diagram portrays ideal geometries that we should emulate
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Solar Car/ DIY fastening methods used around the world for carbon fiber/composites:
Fastener Solutions for Composites
The first solution that this article mentioned were embedded fasteners, this means that we would actually include fasteners into the mfg process but there are some complications that arise some including:
If the fastener isn’t designed to be embedded can lead to “design compromises and process inefficiencies”.
These “compromises” may lead to the weakening of the composite or in turn making it thicker and therefore heavier.
Below is the cross-section of a traditional embedded bolt
As you can see, to fully embed it into the material, requires significant compromises.
There are some bolts that are designed for this, one example is a bonding fastener such as a bigHead®, this fastener is designed to be embedded into composites specifically, it’s pictured below.
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As you can see, it doesn’t need nearly as much material to anchor it into the panel.
The article outlined how it can save on cost and weight and since it’s designed for composites, it has been optimized to do so
https://pdf.directindustry.com/pdf/bighead-bonding-fasteners/bighead-catalogue/15331-22544-_3.html
^^This link is to a bunch of the fasteners which is what I think is what we’re supposed to be looking at, they look the same as the picture in the article, in general, bigHead® makes panel fasteners so I could look for more if needed but, I’d like to look for different possible solutions before I go all-in on one company.
The second solution given is using bonded fasteners, the way these work is that you simply stick the fastener onto your composite and boom, you’re done. Below is a picture of what I mean.
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These fasteners are handy when we don’t have enough material to embed our fastener into the composite.
In general, I like these two methods much more than a traditional fastener because it doesn’t require drilling into the CF panel to use them. Drilling results in a compromise in the strength of the panel and using one of the above two methods will give a good solution to that issue.