Structure-Function Relationships in Macadamia integrifolia Seed Coats – Fundamentals of the Hierarchical Microstructure

Schüler, Paul; Speck, Thomas; Bührig–Polaczek, Andreas; Fleck, Claudia

doi:10.1371/journal.pone.0102913

Cited by 51 publications

(72 citation statements)

References 20 publications

(54 reference statements)

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“…Petrechen [8], incorporated Brazil nut mesocarp particles (NLF) with different polypropylene (PP) matrices and the biocomposites obtained showed significant improvements in several mechanical properties, compared with the PP matrix and with other similar particulate NLF biocomposites [24]. In that way, as already stated for the case of Macadamia seed shell [22,25,26], the Brazil nut fruit mesocarp, due its outstanding mechanical characteristics, could well serve as NFL for biocomposites, or as a hierarchical architecture model for biomimetics materials.…”

Section: Resultsmentioning

confidence: 85%

“…Schüler et al [22] compared the crack resistance of different nuts shells/coats and found a much higher strength for the Macadamia (Macadamia integrifolia) seed coat. Unlike others nuts shells/coats, formed by compact arrangements of sclereid cells [23], the cell arrangement found in the Macadamia seed coat was similar as the found in the Brazil nut fruit mesocarp, where fiber cell bundles and sclereids are acting together as a composite structure, as shown in the Fig.…”

Section: Resultsmentioning

confidence: 99%

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Morphological Characterization of Brazil Nut Tree (Bertholletia excelsa) Fruit Pericarp

Petrechen¹,

Arduin²,

Ambr髎io³

2019

Journal of Renewable Materials

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This article presents the overall morphological structure of the Brazil nut tree (Bertholletia excelsa) fruit pericarp, from macro to nano scale. The acquired knowledge would be used for the development of new applications, like using the materials as fillers for biocomposites, or as a hierarchical architecture model for biomimetics. This research was performed using stereo and light microscopy and conventional and force field emission scanning electron microscopy. The pericarp presents three layers: the exocarp, a dark gray, brittle and fragile outer layer; the mesocarp, a beige, dry, rigid, impermeable and fibrous intermediate layer; and the endocarp, an inner layer with similar characteristic as the exocarp, but formed next to the seeds. Morphologically, the exocarp and the endocarp presented minor regions of sclereids, fibers and vascular cell bundles, inside major regions of parenchyma cells. The mesocarp presents a structure of fiber cells regions alternating with sclereids and vascular cells regions, arranged in a composite like arrangement, with the fibers cells bundles acting as randomly oriented disperse phases in a sclereid cells matrix. This arrangement was associated with the mesocarp relative superior proprieties, indicating a great material for using as fillers for biocomposites or in biomimetics applications.

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Section: Resultsmentioning

confidence: 85%

Section: Resultsmentioning

confidence: 99%

Morphological Characterization of Brazil Nut Tree (Bertholletia excelsa) Fruit Pericarp

Petrechen¹,

Arduin²,

Ambr髎io³

2019

Journal of Renewable Materials

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“…The tracheid cells are usually surrounded by fibers, that provide mechanical stability to the structure. This kind of cell is common among other nutshells, like in macadamia and coconut 12,13 . Phloem cells are responsible for transporting nutrients through the plant and are formed by sieve elements, as shown in Fig.…”

Section: Resultsmentioning

confidence: 97%

“…However, an interesting feature in the mesocarp of Brazil nut is how the sclereids are arranged, filling the gaps between the fiber bundles 1 . This arrangement is uncommon in other nutshells such as macadamia 12 , coconut 25 and babassu 22 , where fibers and sclereids are present in different layers of the structure. The cell arrangement in the Brazil nut mesocarp reminds of a foam-filled sandwich structure, as used in the aerospace industry where there is a skin made of a stiff material and the core is filled with foam 16 .…”

Section: Discussionmentioning

confidence: 96%

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Hierarchical levels of organization of the Brazil nut mesocarp

Sônego

Fleck

Pessan

2020

Sci Rep

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Aiming to understand Nature´s strategies that inspire new composite materials, the hierarchical levels of organization of the Brazil nut (Bertholletia excelsa) mesocarp were investigated. Optical microscopy, scanning electron microscopy (SEM), microtomography (MicroCT) and small-angle X-ray scattering (SAXS) were used to deeply describe the cellular and fibrillary levels of organization. The mesocarp is the middle layer of the fruit which has developed several strategies to avoid its opening and protect its seed. Fibers have a different orientation in the three layers of the mesocarp, what reduces the anisotropy of the structure. Sclereids cells with thick cell walls fill the spaces between the fibers resembling a foam-filled structural composite. The mesocarp has several tubular channels and fractured surfaces which may work as sites for crack trapping and increase toughness. The thick and lignified cell wall of sclereids and fibers and the weak interface between cells can promote a longer and tortuous intercellular crack path. Additionally, fibers with high strength and stiffness due to microfibrils oriented along the main cell axis (µ = 0° to 17°) were identified in the innermost layer of the mesocarp. Such an understanding of each hierarchical level can inspire the development of new cellular composites with improved mechanical behaviorThe mesocarp layer of Bertholletia excelsa fruit, the seed of which is known as brazil nut, is an impressive structure. It is a shell capable to resist falls as high as 50 m and compression forces higher than 10 kN 1 . Such a strong natural structure has great potential as a source for bioinspiration to produce new high performance composites 1,2 . The impressive properties of the mesocarp arise from its hierarchical structure, which emerged from millions of years of evolution.This hierarchy is the main factor to explain how relatively weak components organized in a complex way can result in a system with outstanding properties 3 . Four hierarchical levels of structuring have been described for plants: macroscopic, cellular, fibrillar, and molecular 3 . Each hierarchical level has its own contribution to the overall properties of the natural composite.On the largest length-scale, the "macroscopic" level, trunk, leaves, roots, flowers, and fruit are distinguished, and it is analyzed how the association of different tissues leads to different geometries and functions in the plant. At this level, the mesocarp is described as a spherical or elliptical shell of 10-12 cm diameter with a wall thickness of approximately 1 cm. Its function is to protect the seeds against predators and impact on the ground when the fruit falls from the tree 1,4,5 . The mesocarp has a rough surface with a peduncle and an opercular opening on opposite sides of the fruit. The opening is a hole with a diameter of approximately 2 cm, which is, however, not large enough to allow the dispersion of the seeds, as it was millions of years ago.On the cellular hierarchical level, the cells and vegetable tissues are ...

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

Ali,

Sonego,

Salavati

et al. 2023

Adv Eng Mater

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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, we performed mechanical compression tests coupled with numerical finite element simulations. 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 over‐simplification, 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 foamlike behavior and fibrous layers.This article is protected by copyright. All rights reserved.

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Structure-Function Relationships in Macadamia integrifolia Seed Coats – Fundamentals of the Hierarchical Microstructure

Cited by 51 publications

References 20 publications

Morphological Characterization of Brazil Nut Tree (Bertholletia excelsa) Fruit Pericarp

Morphological Characterization of Brazil Nut Tree (Bertholletia excelsa) Fruit Pericarp

Hierarchical levels of organization of the Brazil nut mesocarp

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

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