I wanted to see how they stacked up against macadamia's and came across this paper:

"Topological Interlocking and Geometric Stiffening as Complementary Strategies for Strong Plant Shells" [1]

also contributed to by the scientist mentioned in the article. It has pictures, graphs, cross sections and other data for all you nutcracking enthusiasts out there.

[1] https://onlinelibrary.wiley.com/doi/epdf/10.1002/adma.202004...