In this work, we propose a constitutive model to describe the behavior of Piezoelectric Fiber Reinforced Composite
(PFRC) material consisting of elasto-plastic matrix reinforced by strong elastic piezoelectric fibers. Computational
efficiency is achieved using analytical solutions for elastic stifness matrix derived from Variational
Asymptotic Methods (VAM). This is extended to provide Structural Health Monitoring (SHM) based on plasticity
induced degradation of flapping frequency of PFRC. Overall this work provides an effective mathematical
tool that can be used for structural self-health monitoring of plasticity induced flapping degradation of PFRC
flapping wing MAVs. The developed tool can be re-calibrated to also provide SHM for other forms of failures
like fatigue, matrix cracking etc.
Asymptotically accurate nonlinear analysis of electro elastomer membrane structures is carried out using Variational
Asymptotic Method (VAM) with moderate strains and very small thickness-to-wavelength ratio as small
parameters. Present work incorporates large deformations (displacements and rotations), material nonlinearity
(hyper elasticity), and electrical effects. It begins with 3-D electro-elastic energy and mathematically splits the
analysis into a 1-D through-the-thickness analysis and a 2-D membrane analysis. 1-D analysis provides asymptotically
equivalent of 3-D energy which in turn 2-D constitutive law is input to membrane analysis and a set
of recovery relations to approximately express the 3-D mechanical field variables in terms of two-dimensional
variables determined from solving the equations of the membrane analysis. Numerical examples are presented
to compare with existing analytical, semi-analytical and finite element solutions. Results based on this model
will be demonstrated for specific inflatable structures of aerospace and bio-mechanics applications.
KEYWORDS: Composites, Atrial fibrillation, Microsoft Foundation Class Library, Aerospace engineering, Epoxies, 3D modeling, Sensors, Homogenization, Actuators, Ferroelectric materials
An asymptotically correct analysis is developed for Macro Fiber Composite unit cell using Variational Asymptotic
Method (VAM). VAM splits the 3D nonlinear problem into two parts: A 1D nonlinear problem along the length
of the fiber and a linear 2D cross-sectional problem. Closed form solutions are obtained for the 2D problem
which are in terms of 1D parameters.
Active Fiber Composites (AFC) possess desirable characteristics over a wide range of smart structure applications,
such as vibration, shape and flow control as well as structural health monitoring. This type of material,
capable of collocated actuation and sensing, can be used in smart structures with self-sensing circuits. This paper
proposes four novel applications of AFC structures undergoing torsion: sensors and actuators shaped as strips
and tubes; and concludes with a preliminary failure analysis. To enable this, a powerful mathematical technique,
the Variational Asymptotic Method (VAM) was used to perform cross-sectional analyses of thin generally
anisotropic AFC beams. The resulting closed form expressions have been utilized in the applications presented
herein.
KEYWORDS: Microsoft Foundation Class Library, Sensors, Composites, Ultrasonics, Testing and analysis, Ferroelectric materials, Acoustic emission, 3D modeling, Wave plates, Finite element methods
The change in extension-twist coupling due to delamination in antisymmetric laminates is experimentally measured.
Experimental results are compared with the results from analytical expression existing in literature and finite
element analysis. The application of the Macro-Fiber Composite (MFC) developed at the NASA Langley Research
Center for sensing the delamination in the laminates is investigated. While many applications have been reported in
the literature using the MFC as an actuator, here its use as a twist sensor has been studied. The real-life application
envisaged is structural health monitoring of laminated composite flexbeams taking advantage of the symmetry in
the structure. Apart from the defect detection under symmetric conditions, other methods of health monitoring for
the same structure are reported for further validation. Results show that MFC works well as a sensor.
In order to demonstrate the feasibility of Active Fiber Composites (AFC) as sensors for detecting damage, a
pretwisted strip made of AFC with symmetric free-edge delamination is considered in this paper. The strain
developed on the top/bottom of the strip is measured to detect and assess delamination. Variational Asymptotic
Method (VAM) is used in the development of a non-classical non-linear cross sectional model of the strip. The
original three dimensional (3D) problem is simplified by the decomposition into two simpler problems: a two-dimensional
(2D) problem, which provides in a compact form the cross-sectional properties using VAM, and a
non-linear one-dimensional (1D) problem along the length of the beam. This procedure gives the non-linear
stiffnesses, which are very sensitive to damage, at any given cross-section of the strip. The developed model is
used to study a special case of cantilevered laminated strip with antisymmetric layup, loaded only by an axial
force at the tip. The charge generated in the AFC lamina is derived in closed form in terms of the 1D strain
measures. It is observed that delamination length and location have a definite influence on the charge developed
in the AFC lamina. Also, sensor voltage output distribution along the length of the beam is obtained using
evenly distributed electrode strip. These data could in turn be used to detect the presence of damage.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.