Simple Implementation of Asymptotic Homogenization Method for Periodic Composite Materials

In this paper, a simple implementation method of Asymptotic homogenization (AH) method is developed with the aid of commercial FEM software as a tool box. Then, abundant structural elements (like beam, shell and solid elements) in commercial software can be used to model unit cell with various complex substructures of periodic materials, while simultaneously reducing the model to a small scale with less amount of calculation. During the implementation, a set of simple displacement boundary conditions are assumed for unit cell, and final effective elastic constant can be directly calculated after several static analysis. Two representative examples of applications are chosen and discussed to verify the validity and applicability of the new implementation method by comparing with other methods. The proposed method is expected to become an effective benchmark for assessing other homogenization theories and extended to other homogenization problems (such as thermal expansion coefficient) in the future.

Highly Sensitive Pressure Sensor Using Two-Dimensionally Aligned Carbon Nanotube Bundles

A highly sensitive two-dimensional tactile sensor has been developed by applying the stain-induced change of the electronic resistance of MWCNTs (Multi-Wall Carbon Nano-Tubes). The elastic deformation of a bundle of MWCNTs was confirmed under the axial compressive strain from 0% to 60%, and the sensitivity of compressive force was 1 mN. The maximum gauge factor of the bundle under the compressive strain was about 100, and it was obtained from the buckling deformation of the bundle. Since the effective elastic constant of the bundle was about 140 kPa, it was important to use a very soft dielectric material for electrical isolation among area-arrayed fine bundles in the tactile sensor. The application of polydimethylsiloxane (PDMS) was found to be effective for assuring the flexible deformation of each bundle in the sensor under the application of a distributed load.

Sound Transmission Loss of Adhesively Bonded Sandwich Panels with Pyramidal Truss Core: Theory and Experiment

In this paper, an analytical model is developed to investigate sound transmission loss characteristic of adhesively bonded metal sandwich panels with pyramidal lattice truss cores based on 3D elasticity theory. Meanwhile, practical specimen is fabricated to conduct corresponding sound insulation experiment test via a standing wave tube method. The effective elastic constant of truss cores is derived using one homogenization theory on account of equivalent strain energy. It is found that satisfactory agreement is achieved between theoretical solutions and experiment results, and damping effect of adhesive bonding interface between facesheets and core has a great impact on transmission loss. Further parameter investigations demonstrate the significant effect of the elevation and azimuth angles of the pyramidal cores, which can be conveniently changed to tailor the acoustic performance of the sandwich panels in the whole frequency range.

Study on Effective Elastic Constants of Homogenization Tube Sheet

The expressions of the effective elastic constants of composite material with cylindrical inclusions are derived based on M-T method, and it can be used in discussing the approximate range of effective elastic constant of air. Moreover, it is possible to homogenize tube-sheet by making use of the expression. The numerical result obtained is in good agreement with effective elastic constant adopted by the ASME code. It demonstrates that the approach is effective and accurate. At the last, the relationship between effective elastic and thickness of the tube-sheet is discussed.