Name: Dr. Kishor Shingare
Department: Aerospace Engineering
Program: Post-Doctoral Fellow (1st Year)
Name of supervisor: Prof. Susmita Naskar
Topic of research: Comprehensive study on piezoelastic properties of graphene-based composite: analytical and numerical approaches
Description of research work:
Probing the prediction of piezoelastic properties for graphene-based composites
Introduction and applications of the research:
In the twenty-first century, graphene is considered as one of the most striking 2D material to form next generation micro- and nano-electromechanical systems due to its unique multifunctional properties with size-dependent physical structure. Owing to its remarkable electro-thermo-mechanical properties such as high Young’s modulus (~1.1 TPa), electrical conductivity (~6000 S/cm), thermal conductivity (~5000 W/m/K) and scale-dependent electronic properties, graphene fascinated rigorous research interests. Hence, with the rapid use of graphene in nanocomposite structures, it becomes important to investigate its effective piezoelastic properties and its use in different energy harvesters for illustrating various global responses in future. Therefore, it is imperative to account the effect of influence of graphene as fiber or nanofillers to ensure the desired sustainable and robust system performance. From this, we can provide computational model to set up a benchmark for the researchers to investigate the validation of experimental results and novel graphene-based composite for various structures such as actuators, sensors, etc.
Novelty and methodologies:
On careful examining the available literature, it shows that there is no single study available on piezoelectric composite decorated or incorporated with graphene interphase to improve its electromechanical properties. This novel graphene-reinforced piezoelectric compositesaccounting the different shapes and several inclusions has not been conveyed yet which can act as a replacement for the traditional piezoelectric nanostructure applications. In addition to this, we also compared our all set of results with existing conventional piezoelectric composite (without introduction of graphene nanofillers) made of high modulus matrix as compared to presentcomposite considering different combination of percentage of piezoelectric fiber and graphene nanofillers in composite. This is an undeniable encouragement behind this research. The novelty of present research comprises the consideration of graphene nanofillers in effective properties of composite following the different finite element (FE) models via representative volume element (RVE) based approach. Due to the absence of structural simplicity of continuous fiber composite, the FE numerical techniques are frequently used as compared to analytical modeling for multiphase materials. Therefore, the different micromechanical modelling techniques based on analytical and numerical approaches such as: rules-of-mixture (ROM), modified rules-of-mixture (mROM), shear-lag and Halpin-Tsai (HT), two and three-phase mechanics of materials (MOM) and FE models with different shape of fibers including continuous fiber, cylindrical and ellipsoidal inclusions are studied to determine the effective elastic and piezoelectric properties of graphene-based composites.In this, the various form of graphene fiber such as continuous/aligned, multiple inclusions with different shapes including 2D and 3D RVE applying periodic boundary conditions have also been considered.
Results and discussions:
Wehave predicted the effective properties of graphene-based composite with and without the considering strong covalent bond which provides interaction and in-plane stability of 2D crystalline graphene or strong van der Wall forces formed between graphene layers and the matrix. It isobserved that the large surface area of graphene helps in strong interaction with fiber and matrix which results in improved effective properties.From these observations, we have concluded that the random orientation of fiber reinforcement gives noteworthy results as uniform dispersion of nanofillers in matrix is difficult to achieve and resembles with experimental estimates.
Summary and conclusions:
It has been observed from our study, that in case of mROM, different factors including Krenchel orientation, critical length efficiency and agglomeration factors play significant role while evaluating the effective properties of graphene-based composites while the geometrical parameters in HT model.We have also concluded that the axial, transverse and shear effective piezoelastic properties of graphene-based compositesshow significant enrichment due to the incorporation of graphene into the epoxy matrix as compared to conventional/existing piezoelectric composite (For Ex. Axial effective elastic property of graphene-based composite shows near about ~400% enhancement when we consider content of graphene equals to 0.25% of piezoelectric fiberas compared to the existing material). In addition to this, the significant results from this work, for effective elastic and shear effective properties of the composite are also observed in case of cylindrical and ellipsoidal shaped nanofillers. Therefore, one can use these present novel composites with different geometrical aspects for different structural MEMS/NEMS applications over conventional existing materials.