Comsol Project # 2: Analysis of Bifold Structure

Introduction For this project your group is tasked with investigating the design space of active material composite structure which bends in response to a magnetic or electric field. The structure is composed of magnetically (MAE) and electrically (DE) active compliant materials bonded to a magnetically and electrically inert under layer of compliant material. The basic geometry of the composite is shown in the Figure at right. Two orthogonal fold lines are in place to facilitate bending.

The goal of this project is to better understand how the bulk geometry affects the ability of the material to bend, specifically to understand the trade-offs between the power required to promote bending and the bending angles formed. Expected results of applied electric (middle) and electric (bottom) fields are shown at right.

Theory The material in the MAE sections is a flexible magnet that is poled toward the y-axis fold line, i.e. horizontally in-plane. When a +z magnetic field is applied, the sections rotate about the y-axis in opposing directions to align with the field. The magnetic actuation in the MAE section is coupled to the elastic problem through the Maxwell Stress Tensor, which calculates the stresses on surface due to transitioning from a magnetic material to an non-magnetic material. Comsol will be used to solve the electromagnetics problem, which invovles Maxwells equations, which will not be discussed in detail.

The material in the DE section is a dielectric elastomer which is actuated when a voltage is applied across its top and bottom faces. The two opposing faces are attracted to each other and create a dielectric pressure equal to where V is the applied voltage, t is the thickness between the layers, and and and permittivity of space and the relative permittivity of the material.

Analysis To complete this work, your team must perform a parametric study that maps out the design space of variables and , charting their effect on both the bending angle resulting from each actuation mode with respect to power required and the mass of the composite. The ultimate goal is to maximize bending angle while minimizing both power and mass.

To calculate the mass assume . For material parameters, assume , . Deliverables You must submit a report that discusses the results of your query of the design space, i.e. how do the variables in question affect the desired metrics? The report should be structured similarly to the previous report with equivalent sections, length, and number of figures. You are not required to complete a convergence study, though you must explain how one would be conducted: what would you vary and what metric would you track. Label this as a subsection, “Convergence Study”, under the results section. Note, however, that you are in competition for other firms. Also, you must include a free body diagram showing reactions forces and moments, as well as applied pressures, body forces, and tractions.

The report will be due: 11/13/12