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316 || AWSAR Awarded Popular Science Stories - 2019
beam of rectangular cross-section, which is made of two different homogeneous-isotropic materials. The interface of these materials is on the mid-horizontal plane. It is assumed that
there is no slip at the interface. Now we apply the same force on both materials, as shown in Fig.1 below.
Fig.1 Schematic of bi-metallic beam
Although the individual material is homogeneous-isotropic, but as a whole, the beam material is non-homogeneous-isotropic. As the cross-section of both materials is the same, and applied load is also the same, the stress (force per unit area) generated will be same for both materials. But due to the different young modulus, the extension of
both materials will be different.
This difference of extension
results in the compression of
one material while extension
of the other at the interface.
This produces the deformation
gradient along the thickness
of the whole beam as a result
of this, there is significant
difference in the extension
of the extreme surface.
This extension difference
produces the bending of this non-homogeneous beam.
This case of extension-
bending coupling is easier to
explain, but for general non- homogeneous-isotropic is
complicated to explain in a similar fashion. We need a complex mathematical formulation to describe the other coupling in general non- homogeneous-isotropic materials. Similarly,
coupling behaviour in general anisotropic- homogeneous material is a very complex phenomenon that cannot be explained by taking such an example, but can be described using mathematical formulation. So it suffices to believe that coupling occurs along with extension, bending and twisting, which is
collectively called non-classical effect in the general non- homogeneous and anisotropic materials.
The composite materials, due to their distinct properties over conventional materials and non- classical effects, have proved useful in different applications, such as in Micro Aerial Vehicles (MAVs), wind turbines, aircraft, and helicopter. MAVs are broadly classified as fixed-wing, rotary wing, and flapping wing type. Flapping wing type MAVs are inspired by the flapping insects. The wing of these insects performs bending and
twisting motion simultaneously in a particular fashion during flight. This type of motion can be achieved by exploiting the coupling effect of the composite materials.
The composite materials, due to their distinct properties over conventional materials and non- classical effects, have proved useful in different applications, such as in Micro Aerial Vehicles (MAVs), wind turbines, aircraft, and helicopter. MAVs are broadly classified as fixed-wing, rotary wing, and flapping wing type.