Mechanical Properties Of Shell Research Articles

Rapid and Application-Tailored Assessment Tool for Biogenic Powders from Crustacean Shell Waste: Fourier Transform-Infrared Spectroscopy Complemented with X-ray Diffraction, Scanning Electron Microscopy, and Nuclear Magnetic Resonance Spectroscopy.

Due to their chemical composition, richness in calcium carbonate, chitin, proteins, and pigments, and nanoporous structure, crustacean shell waste shows great potential for a wide variety of applications. Large quantities of waste shells are produced annually, meaning that they can be considered a renewable source of ecofriendly biogenic materials, which can be turned into value-added byproducts. In this paper, an IR-based technique is developed to differentiate various biogenic powders originated from crude or food-processed crustacean shells. The validity of the method is supported by cross-checking with XRD, NMR, and SEM–EDX analyses. Our goal was to determine changes in properties of waste crab shells after the two most common treatments, deproteinization and milling. We discovered that deproteinization with NaOH could be tracked from the IR absorbance intensity ratio of the υ(CH2,3) and υasym(CO32–) bands while milling time less influenced this ratio but induced changes in powder particle size distribution and morphology. The relative organic/inorganic ratio was different for different colored shells. Unexpectedly, waste shells stored for an average of 6 months or more were found to contain hydrated calcium carbonate (monohydrocalcite), which was absent in equivalent fresh shell composition. Deproteinization caused changes in mechanical properties of shells, making them more brittle, which resulted in a larger fraction of fine particles after powdering.

An Ingenious Microstructure Arrangement in Deep-Sea Nautilus Shell against the Harsh Environment.

Mollusk shells generally consist of several macro-layers with different microstructures. To explore the specific role that different macro-layers play in the overall mechanical properties of shells, the microstructures, hardness distribution, and three-point bending behavior in the deep-sea Nautilus shell were investigated. It is found that the shell presents a hierarchical structure comprising three layers in thickness, that is, the outer, middle, and inner layers, which exhibit homogeneous, prismatic, and nacreous structures, respectively. Among them, the homogeneous structure in the outer layer is harder, which is beneficial for the shell to enhance resistance to wear and perforation. Furthermore, both the bending strength and fracture energy for group Up (loading from outer to inner surfaces) are far higher than those for group Down (loading from inner to outer surfaces), indicating that the inner nacreous layer is not only stronger but also tougher. Cracks tend to deflect at the interfaces in nacreous structure, and nacreous structure is thereby more resistant to breakage. Hence, the nacreous structure in the inner layer could protect the shell from breaking catastrophically in the deep sea with high pressure. In brief, the combination of a harder outside layer and a tougher inside layer provides an effective protective structure for the deep-sea shell, and the excellent environment adaptability of Nautilus shell can thus be interpreted in terms of its ingenious microstructure arrangement.

Structural and mechanical evolution of Tridacna gigas during permineralization

Mollusk shells have highly complex hierarchical structures and unique mechanical properties, which have been widely studied, especially in fresh shells. However, few studies have revealed differences in the structure-property correlations of shells during the permineralization process, which occurs after organism death. To better understand the effect of permineralization on the microstructure and mechanical properties of shells, this study investigated and compared the compositions, microstructures, and mechanical properties of Tridacna gigas and permineralized J-Tridacna gigas. The results showed that permineralized J-Tridacna gigas possessed coarsened aragonite minerals, less anisotropy and organic matter, and higher hardness and strength than Tridacna gigas. The toughening mechanisms of Tridacna gigas, including crack deflection, aragonite platelet pull-out, and mineral bridges, were discovered during Vickers hardness tests. Moreover, the permineralization mechanism comprised three main steps: organic matter dissolution, aragonite plate compaction, and recrystallization. This work further elaborates the permineralization mechanism, which can help increase the crystal size and improve the strength and hardness of materials. Moreover, this study provides valuable insights into the design of bioinspired advanced materials with outstanding hardness and strength.

Influence of Microstructure on Mechanical Properties of Limaria basilnica

Shell was the simplest biological mineral material protecting the soft tissue. In this paper, the effects of the cross bedded structure of Limaria basilanica shell and organic matter on the three-point bending behavior of Limaria basilanica shell were studied. Experimental results showed that the mechanical properties of shell were closely related to its microstructure, and both of them had anisotropy. The mechanical properties and density of the shell decreased evidently with the increase of temperature. It was indicated that the organic matter in the shell decreased with the increase of heating temperature, which lead to a marked decrease in mechanical properties of Limaria basilanica. The bearing capacity of the shell in the vertical direction was higher than that of the shell in the horizontal direction. When the organic matter in the shell was removed, the three-point bending strength of the shell was only one- twenty or one-thirty of its original strength. The main toughening mechanisms of Limaria basilanica shell were crack deflection, fiber pull out, and viscoelastic properties of organic matter. The bionic study on the toughening mechanism of shell material provided important information about design of the composite materials.

Effect of Water Content on Mechanical Properties of Shell

Effect of Water Content on Mechanical Properties of Shell

Testing and simulation of the three point bending anisotropic behaviour of hazelnut shells

In order to improve the performance of shelling machines, and to enhance the numerical modelling of anisotropic behaviour of hazelnuts shells, the mechanical properties of shells are useful experimental data. A procedure to obtain an effective numerical model and to calibrate anisotropic material properties by means of experimental testing is described. The procedure was applied to a commercial variety of Italian hazelnuts and the mechanical properties were experimentally obtained for shell on specimens obtained from conform hazelnuts. The numerical finite element model investigates single and double curvature geometry simulation performance of the shell specimens.

Shell Hardness and Compressive Strength of the Eastern Oyster, Crassostrea virginica, and the Asian Oyster, Crassostrea ariakensis

The valves of oysters act as a physical barrier between tissues and the external environment, thereby protecting the oyster from environmental stress and predation. To better understand differences in shell properties and predation susceptibilities of two physiologically and morphologically similar oysters, Crassostrea virginica and Crassostrea ariakensis, we quantified and compared two mechanical properties of shells: hardness (resistance to irreversible deformation; GPa) and compressive strength (force necessary to produce a crack; N). We found no differences in the hardness values between foliated layers (innermost and outermost foliated layers), age class (C. virginica: 1, 4, 6, 9 years; C. ariakensis: 4, 6 years), or species. This suggests that the foliated layers have similar properties and are likely composed of the same material. The compressive force required to break wet and dry shells was also not different. However, the shells of both six- and nine-year-old C. virginica withstood higher compressive force than C. virginica shells aged either one or four, and the shells of C. ariakensis at both ages studied (4- and 6-years-old). Differences in ability to withstand compressive force are likely explained by differences in thickness and density between age classes and species. Further, we compared the compressive strength of differing ages of these two species to the crushing force of common oyster predators in the Chesapeake Bay. By studying the physical properties of shells, this work may contribute to a better understanding of the mechanical defenses of oysters as well as of their predation vulnerabilities.

Mechanical characterization of kernel and shell of hazelnuts: Proposal of an experimental procedure

In order to improve the performance of selecting machines for non-conform and damaged hazelnuts and to enhance the numerical modelling of anisotropic behaviour of hazelnuts, the mechanical properties of shells and kernels are useful experimental data. A procedure to experimentally obtain physical and mechanical properties of hazelnuts is described and the optimized specimen shapes to obtain stress to failure and elastic modulus values for kernel and shell are also defined. The procedure is applied to a commercial variety of Italian hazelnuts and the mechanical properties are experimentally obtained both for kernel and shell on specimens made from conform and damaged hazelnuts.

Effect of incorporation of zirconia layer upon physical and mechanical properties of investment casting ceramic shell

Post-heat treatment recrystallisation is a significant cause of scrap in single crystal component production. This defect could be prevented by a reduction in the mechanical strength of the shell after the metal has solidified. Addition of a zirconia layer, to produce large cracks around grain boundaries and among the large grains during phase transformations, was considered as a method of reducing sintered strength. In this study, two types of zirconia stucco, monoclinic and partially stabilised, were introduced into the shell. The effect of the incorporation of a zirconia layer on the microstructure and mechanical properties of the shell were investigated. Shell with a monoclinic zirconia additional layer showed no reduction in the green strength but a better performance in high temperature deformation tolerance, maintaining shell performance during wax removal and metal casting. The shell strength after alloy solidification is reduced, suggesting that a reduction in recrystallisation may be possible with this method.

Structure and mechanical properties of Saxidomus purpuratus biological shells

The strength and fracture behavior of Saxidomus purpuratus shells were investigated and correlated with the structure. The shells show a crossed lamellar structure in the inner and middle layers and a fibrous/blocky and porous structure composed of nanoscaled particulates (∼100 nm diameter) in the outer layer. It was found that the flexure strength and fracture mode are a function of lamellar organization and orientation. The crossed lamellar structure of this shell is composed of domains of parallel lamellae with approximate thickness of 200–600 nm. These domains have approximate lateral dimensions of 10–70 μm with a minimum of two orientations of lamellae in the inner and middle layers. Neighboring domains are oriented at specific angles and thus the structure forms a crossed lamellar pattern. The microhardness across the thickness was lower in the outer layer because of the porosity and the absence of lamellae. The tensile (from flexure tests) and compressive strengths were analyzed by means of Weibull statistics. The mean tensile (flexure) strength at probability of 50%, 80–105 MPa, is on the same order as the compressive strength (∼50–150 MPa) and the Weibull moduli vary from 3.0 to 7.6. These values are significantly lower than abalone nacre, in spite of having the same aragonite structure. The lower strength can be attributed to a smaller fraction of the organic interlayer. The fracture path in the specimens is dominated by the orientation of the domains and proceeds preferentially along lamella boundaries. It also correlates with the color changes in the cross section of the shell. The cracks tend to undergo a considerable change in orientation when the color changes abruptly. The distributions of strengths, cracking paths, and fracture surfaces indicate that the mechanical properties of the shell are anisotropic with a hierarchical nature.

Fabrication and Mechanical Properties of Double-Shell Thermal Energy Storage Microcapsules Applied as Environmental Temperature-Controlling Materials in Building

The aim of the present work was to fabricate heat energy storage microcapsules, which could be used in indoor-wall materials as environmental temperature-controller. Melamine formaldehyde resin (MF) double-shell structure microcapsules were fabricated and the mechanical properties of shell were investigated. The average diameter of microcapsules was in the range of 5-10 μm, and the globular surface was smooth and compact. The mechanical properties of shell were evaluated through observing the surface morphological structure change after pressure by means of scanning electron microscopy (SEM). The results showed that a yield point was found both on single and double shell, and when the press was beyond the point the microcapsules showed plastic behavior. In addition, the mechanical intensity of double-shell microcapsules was better than that of single shell. Analysis of DSC indicated that the phase change temperature was not affected by the double –shell structure.

Fundamental study on microstructure and physical properties of fluidised bed and rainfall sanding ceramic shells

The investment casting technique has advantages in the production of quality components and key benefits of accuracy, versatility and integrity. The mechanical performance of the ceramic shell is fundamental to the quality of the finished component. Two main techniques are used in the casting industry for the application of stucco material: rainfall sanding and fluidised bed. Work was carried out to characterise the fundamental difference in physical structure and mechanical properties of shells produced by both techniques. Stucco application within samples prepared by fluidised bed showed a tendency for the particles to be parallel to the ceramic surface, while in samples prepared by rainfall sanding the particles were more random and embedded into the slurry layer resulting in a thinner total shell build. Stress–strain curves generated form fired samples prepared by fluidised bed demonstrated a certain degree of non-brittle fracture, where this is not the case for rainfall sanding produced material. It is suggested that this is related to the manner in which cracks propagate through in the fluidised bed structure during testing. A relatively larger proportion of through stucco fracture was found in rainfall sanding produced samples in comparison to that in fluidised bed produced samples.