Damping behavior of polymeric composites with nano structured phases is significantly different from usual
polymer composites. Viscoelastic homopolymers exhibit high material damping over a relatively narrow range of
temperature and frequencies. In many practical situations a polymeric structure is required to possess better
strength and stiffness properties together with a reasonable damping behavior. Viscoelastic polymers show
higher loss factor beyond the glassy region which comes with a significant drop in the specific modulus.
Addition of nano alumina particles to epoxy leads to improved strength and stiffness properties with an increase
in glass transition temperature while retaining its damping capabilities. Experimental investigations are carried
out on composite beam specimen fabricated with different volume fractions of alumina nano particles in epoxy to
determine loss factor, tan δ. Impact damping method is used for time response analysis. A single point Laser is
used to record the transverse displacement of a point on the composite beam specimen. Experimental results are
compared with theoretical estimation of loss factor using Voigt estimation. The effect of interphase is included in
theoretical estimation of loss factor. Passive vibration suppression may be introduced in the polymeric structures
along with improved structural properties by tailored dynamic characteristics using nano alumina particle filled
epoxy composites.
The present work has proposed a 2-D triangular high precision finite element (HPFE) based on Classical Laminated
Plate Theory (CLPT). This high precision plate element with 38 degrees of freedom is used to obtain fundamental
frequencies and the mode shapes of a passive composite plate. A standard FEM package-ABAQUS is used to verify the
FEM code and to validate the results. The same element is subsequently used with piezoelectric sensory network to
develop an active damping matrix that tends to suppress vibration. Control algorithm based on classical negative
velocity feedback is used. Simulations are carried out on smart composite plates in time domain for effective vibration
suppression. The effect of size and location of PVDF film on settling time and damping ratio at different control gains is
studied. The high precision piezoelectric finite element is later used to identify damage signals in a ribbon-reinforced
composite. In order to identify the damage, voltage profile is obtained for healthy and delaminated composite plates. A
change in sensing voltage is observed at simulated damage locations in comparison to the healthy laminate for two
different configurations used in the numerical analysis.
Fundamental research and development in smart materials and structures have shown great potential for enhancing the
functionality, serviceability and increased life span of civil and mechanical infrastructure systems. Researchers from
diverse disciplines have been drawn into vigorous efforts to develop smart and intelligent structures that can monitor
their own conditions, detect impending failure, control damage and adapt to changing environments. Smart structures are
generally created through synthesis by combining sensing, processing and actuating elements integrated with
conventional structural materials. The conventional non-destructive evaluation techniques are not very effective in
monitoring the structural integrity of composite structures due to their micro-mechanical complexities. With the
commercial availability of the magnetostrictive (MS) material Terfenol-D in particulate form, it is now feasible to
develop particulate sensors to detect damage with minimum effect on structural integrity. In present investigation, the
electromagnetic response in the MS layer at the onset of delamination in one of the weakest ply of the composite
laminate has been analyzed. For the numerical analysis symmetric and asymmetric carbon epoxy laminates with one of
its layers embedded with Terfenol-D particles have been taken. Terfenol-D layer experiences a change in stress due to
onset of delamination causing a change in its magnetic state, which can be sensed as induced open circuit voltage in the
sensing coil enclosing the laminate beam. The effect of material properties, lamination schemes and placement of MS
layer on the sensing capabilities has been analyzed.
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