Study on the Fracture Toughness of Softwood and Hardwood Estimated by Boundary Effect Model.

The tensile strength and fracture toughness of softwood and hardwood are measured by the Boundary Effect Model (BEM). The experimental results of single-edge notched three-point bending tests indicate that the BEM is an appropriate method to estimate the fracture toughness of the present fibrous and porous woods. In softwood with alternating earlywood and latewood layers, the variation in the volume percentage of different layers in a small range has no obvious influence on the mechanical properties of the materials.

Distinctive Impact of Heat Treatment on the Mechanical Behavior of Nacreous and Crossed-Lamellar Structures in Biological Shells: Critical Role of Organic Matrix.

As biological ceramic composites, mollusk shells exhibit an excellent strength-toughness combination that should be dependent on aragonite/organic matrix interfaces. The mechanical properties and fracture mechanisms of the nacreous structure in the () shell and crossed-lamellar structures in the () shell were investigated, focusing on the critical role of the organic matrix/aragonite interface bonding that can be adjusted by heat treatments. It is found that heat treatments have a negative impact on the fracture behavior of the nacreous structure in the shell, and both the bending and shear properties decrease with increasing heat-treatment temperature because of the loss of water and organic matrix.

An Ingenious Microstructure Arrangement in Deep-Sea 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 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.

Three-Point Bending Fracture Behavior of Single Oriented Crossed-Lamellar Structure in Shell.

The three-point bending strength and fracture behavior of single oriented crossed-lamellar structure in shell were investigated. The samples for bending tests were prepared with two different orientations perpendicular and parallel to the radial ribs of the shell, which corresponds to the tiled and stacked directions of the first-order lamellae, respectively. The bending strength in the tiled direction is approximately 60% higher than that in the stacked direction, primarily because the regularly staggered arrangement of the second-order lamellae in the tiled direction can effectively hinder the crack propagation, whereas the cracks can easily propagate along the interfaces between lamellae in the stacked direction.

The nanocomposite of polyaniline and nitrogen-doped layered HTiNbO5 with excellent visible-light photocatalytic performance.

An effective approach has been used to synthesize N-doped HTiNbO5 (denoted as N-HTiNbO5) with a better intercalation property. The synthesis of polyaniline (PANI) with N-HTiNbO5 to form PANI-N-HTiNbO5 lamellar nanocomposites by in situ polymerization using the aniline (ANI) intercalation compound ANI/N-HTiNbO5 as the intermediate has been investigated. The resulting PANI-N-HTiNbO5 nanocomposite showed a better crystallinity with a monolayer of PANI within the interlayers of N-HTiNbO5, because nitrogen doping can affect the surface charge distribution of [TiNbO5](-) layers.