Aeroelastic flutter performance of shape memory alloy embedded 3D woven composite plate under subsonic flow
Recent advancements in the aeroelasticity of aircraft structures show an increasing trend in using smart materials with composite structures for improved aeroelastic performance. An example is using shape memory alloys (SMAs) to be combined with composite structures either as actuators or for...
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| Format: | Thesis |
| Language: | English |
| Published: |
2021
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/97781/1/FK%202021%2071%20UPMIR.pdf |
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| Summary: | Recent advancements in the aeroelasticity of aircraft structures show an
increasing trend in using smart materials with composite structures for
improved aeroelastic performance. An example is using shape memory alloys
(SMAs) to be combined with composite structures either as actuators or for
morphing capabilities. SMA has the ability to accommodate strain rather than
breakage by unfolding its lattice when a load is applied and also, it generates
stresses due to phase transformation from martensite to austenite at higher
temperatures. Due to this coupling effect of SMAs in response to load and
temperature, SMAs are embedded in laminated composites for improving
damping, stiffness and vibrational characteristics. However, SMA embedded
laminated composites are poor in through-the-thickness mechanical properties
and SMA-induced stresses and temperature can cause delamination of plies
that ultimately results in structural failures under high vibrations.
In this research, SMA wires are embedded in the glass-fibre reinforced
composites using 3D woven reinforcements to improve tensile and vibrational
characteristics. 3D woven reinforcements provides delamination resistance,
higher through-the-thickness mechanical properties and a strong grip to SMA
wire due to binding yarns of 3D structure in through-the-thickness direction.
Three different 3D woven orthogonal interlock configurations having different
interlocking pattern of yarns with SMA wire are analysed in terms of tensile,
dynamic and aeroelastic flutter properties. These 3D configurations are layer-to-layer (L2L), through-the-thickness (TT), and a modified interlock (MF)
structure that provides the strongest grip to SMA wire than L2L and TT. SMA
positioning was also evaluated for both dynamic and aeroelastic flutter
properties i.e. SMA at mid, near to trailing, and near to leading edge of
cantilevered composite plate. Tensile results showed that embedding SMA wires into structures have
significantly improved tensile properties due to the coupling effect of SMA. The
vibrational characteristics are also improved by embedding SMA wire and SMA
wire at mid has a higher impact on bending mode frequencies while torsional
mode frequencies are more affected for SMA wire at near to trailing and
leading edge. Interesting results are obtained from aeroelastic testing by wind
tunnel test. Activating SMA results in decrement of flutter speed and flutter
frequency due to increment in flexibility of the deflected plate in airflow by SMA-induced stresses. However, there is an improvement in post-flutter behavior as
the bending and twist limit cycle oscillation (LCO) amplitudes are reduced by
activating SMA wire.
Among 3D configurations, L2L displayed the highest increase of 34.9% in
Young’s modulus as L2L provides more freedom to SMA for generating
stresses due to loose grip of yarns to SMA. For dynamic properties, L2L with
SMA at mid showed the highest percentage increment of 17%, 11% and 4% in
natural frequencies of first three bending modes respectively. For post-flutter
behavior, L2L with SMA near to trailing edge showed a significant decrement of
22.2% in twist LCO amplitude while L2L with SMA at mid showed a decrement
of 9.5% for bending LCO amplitude. Hence, this work showed that embedding
SMA is beneficial for improving tensile and dynamic properties as well as
mitigating the post-flutter vibrations but as the consequence of reduced flutter
speed and frequency. |
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