Influence of Structure and Geometry on the Compressive Deformation Behavior of Macadamia Integrifolia and Bertholletia Excelsa Shells: A Validated Finite Element Simulation Study

Macadamia (Macadamia integrifolia) and Brazil nuts (Bertholletia excelsa) have an impressive mechanical resistance. To better understand the key structural features and foam-like deformation behavior, mechanical compression tests coupled with numerical finite element simulations are performed. Models with different degrees of structural complexity highlight the effects of geometry where even small changes strongly influence the stress distribution and deformation behavior. Circumferential tensile stresses play a vital role in the failure process. Voids or vascular bundles in the shell wall redistribute stresses and bolster the overall strength of structures by preventing early crack propagation. The void arrangement has the potential to inspire the design of lightweight materials with strategically incorporated porosity, leading to improved mechanical performance. Linear elastic models, despite their oversimplification, are valuable for gaining crucial insights about the influence of geometry. The mechanical behavior is further influenced to different extents by isotropy and orthotropy. The distinctive architecture of nutshells offers valuable insights into the design of composite structures with controlled failure, capable of withstanding high compression loads combining foam-like behavior and fibrous layers.