Pottery and ceramics. Download FREE 3D Models! Related information.

It has been a long-standing effort to create materials with low density but high strength. Technical foams are very light, but compared with bulk materials, their strength is quite low because of their random structure. Natural lightweight materials, such as bone, are cellular solids with optimized architecture. They are structured hierarchically and actually consist of nanometer-size building blocks, providing a benefit from mechanical size effects. In this paper, we demonstrate that materials with a designed microarchitecture, which provides both structural advantages and size-dependent strengthening effects, may be fabricated.

Kondicioner-lj-instrukciya kondicioner-mdv-instrukciya kondicioner-midea-instrukciya-k-pultu kondicioner-vestel-instrukciya kondicioner-vs-instrukciya konfigurator-1s-82-samouchitel konkurs-po-pojarnoy-bezopasnosti-2014 instrukciya-po-ekspluatacii-ij-planeta instrukciya-po-ekspluatacii-jabra instrukciya-po-ekspluatacii-janome-423s instrukciya.

Using 3D laser lithography, we produced micro-truss and -shell structures from ceramic–polymer composites that exceed the strength-to-weight ratio of all engineering materials, with a density below 1,000 kg/m 3. To enhance the strength-to-weight ratio of a material, one may try to either improve the strength or lower the density, or both. The lightest solid materials have a density in the range of 1,000 kg/m 3; only cellular materials, such as technical foams, can reach considerably lower values. However, compared with corresponding bulk materials, their specific strength generally is significantly lower. Cellular topologies may be divided into bending- and stretching-dominated ones.

Technical foams are structured randomly and behave in a bending-dominated way, which is less weight efficient, with respect to strength, than stretching-dominated behavior, such as in regular braced frameworks. Cancellous bone and other natural cellular solids have an optimized architecture. Their basic material is structured hierarchically and consists of nanometer-size elements, providing a benefit from size effects in the material strength. Designing cellular materials with a specific microarchitecture would allow one to exploit the structural advantages of stretching-dominated constructions as well as size-dependent strengthening effects. In this paper, we demonstrate that such materials may be fabricated. Applying 3D laser lithography, we produced and characterized micro-truss and -shell structures made from alumina–polymer composite.

Size-dependent strengthening of alumina shells has been observed, particularly when applied with a characteristic thickness below 100 nm. The presented artificial cellular materials reach compressive strengths up to 280 MPa with densities well below 1,000 kg/m 3. The suitability of a material for lightweight applications is determined mainly by two properties: the specific strength and the specific stiffness, here defined as the strength and stiffness of a material divided by its density.

In the past century, major advancements have been made in optimizing classical lightweight materials, such as aluminum alloys or composite materials, with respect to these properties. However, the lightest solid materials have a density in the range of 1,000 kg/m 3 (). Natural lightweight materials, such as bone and wood, are not fully dense and may exhibit considerably lower values (). They contain several levels of hierarchical structuring down to the nanometer scale (–), leading to remarkable specific mechanical properties (–). For instance, cancellous bone is built of truss- or shell-like framework architectures grown adaptively to the loading situation (, ). The material thickness and the orientation of the individual structural elements depend on the magnitude and orientation of loading. This leads to an optimized topology, in which each structural element is aligned with the principal stress trajectories (, ).