In this study, the effect of different void sizes with different void contents are investigated on all coefficients of constitutive coefficients for unidirectional composites. The unidirectional composite can be assumed as a periodic structure. To fulfill this requirement, unit cells with different void contents and different void sizes are simulated. To capture the real effect of void sizes, the unit cells are modeled with different uniform void sizes with a fixed percentage of void content. To quantify all coefficients of material properties in presence of voids, the periodic boundary conditions are applied to the unit cells. The average stresses and strains are obtained using ANSYS interface. The results showed that in the fixed percentage of void content, constitutive coefficients degraded more with the smaller void sizes.
With developments in software and micro-measurement technology and finite element analysis software, a threedimensional Basilar membrane finite element (BMFE) model can now be further straightforwardly created to investigate the physics and sound transfer function of basilar membrane. Numerous FE studies of the middle ear have been investigated to date, and each has its own specific advantages and shortcomings. In this conference paper, the latest PVDF-based development of the Basilar membrane and its FE modeling technology in both COMSOL Multiphysics and ANSYS software has been investigated and verified. The output responses versus the sound frequency is recorded and caparisoned.
In spite of many studies concerning the potential of auditory nerve actions, the timing of neural excitation in relation to basilar membrane motion is still not well understood. In this study, therefore, a Piezoelectric Artificial Basilar Membrane (PABM) is fabricated using Denton Explorer evaporator. The proposed dynamical system is made of polyvinylidene fluoride membrane on which 40 chromium electrodes were deposited with thickness close to 104 Å. The PABM sensor was tested with variable engineering parameters that contribute to its frequency selection capabilities. To characterize the frequency selectivity of the PABM, mechanical displacements were measured using a very precise high-resolution data acquisition board. When electrical and acoustic stimuli were applied, the measured resonance frequencies were in the ranges of 600to2000. These results demonstrate that the mechanical frequency selectivity of this PABM is close to the human communication frequency range (300–3000 Hz), which is a vital feature of potential auditory prostheses.
The objective of this study is to investigate the effect of nonlocal precursor damages through modulated constative properties on the Guided wave propagation in composite materials. To understand the effect of lower scale damage on the interaction of wave propagation in composite materials, all the constitutive coefficients need to be evaluated. Hence, a method is developed to investigate the effective material properties of damaged composite materials using the representative volume element (RVE) model. To calculate the full matrix of constitutive coefficients, periodic boundary conditions were applied on the RVE and average stresses and strains were evaluated using a finite element model. In this study, the effect of different percentages of void contents on effective material properties is presented. Further, the effect of modified material properties on the Guided wave propagation in a transversely isotropic composite plate was investigated.
Energy harvesters primarily depend on on a groups of unit cells to harvest energy at broadband frequencies so that each unit cell is responsible to harvest energy at a distinct frequency. Other design complexity, space, and financial profusion are required for transferring from unit-frequency to multi-frequency energy scavenging. Also, it is very unlikely to obtain expected power output if the available vibration source doesn’t match the designed loading condition (usually, unidirectional) of the device and requires rearrangement of the base structure to have projected output. In this paper we model the unique feature of acoustic metamaterial (AM), which is not only able to harvest energy at multiple frequencies using only a unit cell device, but also able to harvest energy under a variety of uncoupled (unidirectional) and coupled (multi-directional) vibration environments with an identical base structure arrangement.