Axial Tensile Testing of Single Fibres

The mechanical and damage properties of single fibres used in fibrous composite have gained tremendous importance in recent years. These properties are used in determination of effective properties of composites by micromechanics. These are also used in the micromechanical damage modeling. Further, these properties are used as an indicator of the excellence of product by manufacturers. In the present study the axial tensile modulus, ultimate strength and failure strain of single fibres are determined for carbon and glass fibres. ASTM D3379-75 standard is followed and a number of fibers are tested for statistical analysis. The axial tensile moduli measured are 246.7 GPa and 93.3 GPa, respectively and strength are 3031.6 MPa and 2035.9 MPa, respectively for carbon and glass fibres. Further, the respective axial tensile failure strains are 0.0137 and 0.0224. The error in the measurement of axial modulus is below 8% while for axial tensile strength is below 1%.

Dragonfly Inspired Nanocomposite Flapping Wing for Micro Air Vehicles

The current research is aimed towards the development of dragonfly inspired nanocomposite flapping wing for micro air vehicles(MAVs).The wing is designed by taking inspiration from the hind wing of dragonfly(Anax Parthenope Julius).Carbon nanotubes(CNTs)/polypropylene nanocomposite and low-density polyethylene are used as the wing materials.The nanocomposites are developed with varying CNTs'weight percentage(0%-1%)and characterized for dynamic mechanical properties,which revealed that the 0.1 weight percentage case produces highest storage modulus values throughout the frequency range(1 Hz一90 Hz).It is also observed that the storage modulus values are in the range ofYoung^modulus of veins and membrane of natural insect wings.This is useful to achieve true biomimicking.Advanced manufacturing technique such as photolithography is used for wing fabrication.The length,weight and average thickness of the fabricated wing are^44 mm,26.22 mg and 187 pm,respectively.The structural dynamic properties of the fa bricated wing are obtained experimentally and computationally using DIC and ANSYS,respectively.The developed dragonfly inspired wing showed a natural frequency of 29.4 Hz with a bending mode shape which is close to the characteristic frequency of its natural counterpart.

Biomimicking and evaluation of dragonfly wing morphology with polypropylene nanocomposites

Dragonfly hindwing inspired two different flapping wing morphologies are investigated for flexible flapping wing micro air vehicles(FWMAV)applications.The wing skin is developed using 1%functionalized carbon nanotubes reinforced polypropylene nanocomposites with carbon fiber epoxy composite strands as venation pattern.The resonance frequencies are the fundamental information for biomimicking and were calculated theoretically from stiffness data.Bending dominated first natural frequency was obtained from flexural stiffness data and found close to the flapping frequency of natural dragonfly hindwing.Twisting dominated second natural frequency was obtained from torsional stiffness,which revealed that the artificial wings can be fabricated thinner.The flapping frequency of artificial wings is unaffected by the twisting deformation.The bending and twisting dominated mode shapes are also studied using the digital image correlation(DIC)system.To verify the static and dynamic results,finite element simulations are performed that agree with experimental findings.It was found that the proposed flexible nanocomposite wing skin can control the bending and twisting dominated frequencies by tailoring the wing morphology without affecting the mode shapes of deformation.