In-plane Compressive Properties Research Articles

Predicting dynamic in-plane compressive properties of multi-axial multi-layer warp-knitted composites with a meso-model

Proper prediction of material microstructure from known processing conditions and constituent material properties is a critical step to determine the bulk properties of the composite. This paper reports a meso-structure model of multi-axial multi-layer warp-knitted (MMWK) composites from an elastic–plastic material model considering the strain rate effect for the components of the MMWK composite. The representative unit cell (RUC) of fiber tow is created to obtain the elastic–plastic parameters of the fiber tow. The 3D meso-structure model of the MMWK composite is based on an idealized geometrical model according to the preform structure of the MMWK fabric. The model is used to investigate the effect of the volume fraction of the knitting yarn on the dynamic in-plane compressive properties. The results show that the fiber tow failure at large extent is mainly caused by the micro cracking of the matrix, and the effects of the knitting yarn on the mechanical properties of MMWK composite are very limited. Particularly, MMWK composites could be considered as laminates when the volume fraction of the knitting yarn is low, such as below 1.5%. Experiments were also conducted to validate the results from the simplified meso-structure model of the MMWK composite. The material is found to be strain rate sensitive, and the experimental and predicted results agree well with respect to the compressive strength and modulus of the composite. This confirms that the meso-structure MMWK composite model proposed is capable of capturing the essential features for the response of the composite under different strain rate conditions at the meso-level.

Influence of Cell Filling Pattern and Position on Dynamic In-plane Compression Properties of Aluminum Honeycombs

Influence of Cell Filling Pattern and Position on Dynamic In-plane Compression Properties of Aluminum Honeycombs

High-Temperature Thermal Stability and In-Plane Compressive Properties of a Graphene and a Boron-Nitride Nanosheet

The structural performance of graphene and boron-nitride nanosheet (BNNS) with zigzag and armchair types, when subjected to high temperatures, is investigated through molecular dynamics simulations. It is found that the degree of structure distortion is related to chirality; materials at high temperature of 3500 K, the zigzag nanosheet always exhibits less distortion than the armchair for the same material, and the BNNS exhibits less distortion than graphene for the same chirality. Graphene and BNNS with different in-plane compressive strains are optimized by using the Universal Force Field (UFF) method. It is found that there are two entirely different buckling modes, i.e., the lateral buckling of graphene begins to occur at the middle part, whereas buckling of BNNS begins to occur at near both ends and shows lateral deformation in two opposite directions. The coefficient of elasticity of graphene is slightly smaller than that of BNNS for the same chirality, the coefficient of elasticity of zigzag is slightly bigger than that of armchair for the same material, buckling strain of zigzag nanosheet is larger than that of armchair for the same material, and buckling strains of graphene are always larger than those of BNNS. These phenomena are also analyzed on the basis of radial distribution function (RDF) and system energy. The results indicate that there are thermal expansion anisotropy and planar stress anisotropy in a graphene and a BNNS. Among these materials, zigzag graphene has the highest resistance to compressive buckling but zigzag BNNS can have the highest resistance to distortion at high-temperature distortion and have high compression elasticity.

753 セル充填位置がアルミニウムハニカムの面内衝撃圧縮特性に与える影響(OS7-3 衝撃工学,OS7 先進材料および構造の力学特性評価)

753 セル充填位置がアルミニウムハニカムの面内衝撃圧縮特性に与える影響(OS7-3 衝撃工学,OS7 先進材料および構造の力学特性評価)

Compression properties of z-pinned composite laminates

The effect of z-pinning on the in-plane compression properties and failure mechanisms of polymer laminates is experimentally studied in this paper. The reduction to the compression modulus, strength and fatigue performance of carbon/epoxy laminates with increasing volume content and diameter of pins is determined. The elastic modulus decreases at a quasi-linear rate with increasing pin content and pin diameter. Softening is caused by fiber waviness around the pins and reduced fiber volume content due to volumetric swelling of the laminate from the pins. A simple model is presented for calculating the compression modulus of pinned laminates that considers the softening effects of fiber waviness and fiber dilution. The compression strength and fatigue life also decrease with increasing volume content and diameter of the pins. The strength and fatigue properties are reduced by fiber kinking caused by fiber waviness around the pins and the reduced fiber content caused by swelling. The deterioration to the compression properties is also dependent on the fiber lay-up pattern of the laminate, with the magnitude of the loss in properties increasing with the percentage of 0° (load bearing) fibers in the laminate. The paper gives suggestions for minimizing the loss to the compression properties to laminates due to pinning.

Thickness effects on the compressive stiffness and strength of stitched composite laminates

A finite element unit cell model for predicting the 3-D mechanical properties of laminates with through-thickness reinforcement has been developed using a unique voxel mesh approach. As part of its development, the model is being verified to other models and validated with experimental data. The model has been validated to tensile experimental data with much success. For further validation of the model and its assumptions, an experimental program was conducted to investigate the compressive properties of stitched laminates for three different thicknesses. It was found that the unstitched modulus remained independent of thickness, while the stitched modulus increased with thickness due to spreading and kinking of the outer surface plies during the stitch formation process. The model predicted the change in modulus well, however did not capture the thickness effect observed in the experimental results. While it was found that stitching did have an influence on the in-plane compressive properties of the test specimens, the known damage tolerance and manufacturing advantages of stitched laminates are considered to outweigh any penalties for certain critical applications.

Fabrication of SUS304 Regularly Cell-Structured Material and Their Mechanical Properties

The quasi-static flexural and in-plane compressive properties of SUS304 stainless steel with circular close-packed cells are studied. Microstainless steel tubes coated with Ni3P were selected for constructing hexagonal close-packed arrays, which are subsequently joined together to form a cellular structure. The fabrication technique developed, involves the diffusion bonding of stacked metal tubes under the compressive stress state during heat treatment. SUS304 cell-structured materials can achieve the high specific flexural stiffness and specific flexural yield strength nearly equal to those for the dense materials. In-plane compressive properties as well as deformation behavior are also observed and discussed in this paper.