Identification of current material state in composites using a dielectric state variable

Vadlamudi, Vamsee; Shaik, Rauhon Ahmed; Raihan, Rassel; Reifsnider, Kenneth; Iarve, Endel V.

doi:10.1016/j.compositesa.2019.105494

Cited by 18 publications

(15 citation statements)

References 24 publications

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“…It can be observed that impedance increases initially, followed by a decrease and sudden jumps close to failure when the fiber splitting starts. This trend is contrary to what was observed in multi directional laminates in [14] where in the impedance initially decreased followed by an increase when delamination initiated. This could be because of the longitudinal matrix cracks that develop in the laminate that lead to debonding (matrix fiber interface) which hinders the charge flow and hence leads to increase in impedance.…”

Section: Virgin Samplescontrasting

confidence: 99%

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Performance Enhancement and Prediction of Composite Materials with Embedded Electrospun Piezoelectric Sensors

Mazed¹,

Elenchezhian²,

Vadlamudi³

et al. 2020

SAMPE 2020 | Virtual Series

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In today's world, continuous fiber reinforced composite materials are extensively used in the aerospace, automotive and other structural industries. Since the applications of such fibers demand for a high safety rating, it is of utmost importance for engineers who design such materials to analyze its safety. When cracks are developed in such materials, the mechanical, electrical, and thermal properties also get altered as a function of the cracks. Previous studies have shown that changes in electrical properties can be directly correlated with the development of cracks in the material which can then be used to predict the remaining life of such materials. In this study we propose to introduce an additional layer of Electrospun Polyvinylidene Fluoride (PVDF) nanofiber in the CFRP matrix. PVDF is a piezoelectric material, meaning it will generate electricity on encountering vibrations. Therefore, when PVDF nanofibers are introduced in the matrix, the stress on the matrix will be translated onto the nanofibers which in turn will output electrical signals. In this study, 3 types of glass fiber composites (embedded with PVDF, embedded with PVDF with Multiwalled Carbon nanotube, and no additional material) are subjected to quasi static tensile tests while the impedance across the material is continuously measured. The change in impedance was then related to the stress the material was subjected to and predict the remaining life of the material.

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Section: Virgin Samplescontrasting

confidence: 99%

“…The ends of the coupons were attached to tabs using 0.051m×0.013m tabs made from 8 plies of woven glass fiber. The tab material was manufactured using compression molding technique recommended by the manufacturer [14].…”

Section: Nanofiber Matmentioning

confidence: 99%

Performance Enhancement and Prediction of Composite Materials with Embedded Electrospun Piezoelectric Sensors

Mazed¹,

Elenchezhian²,

Vadlamudi³

et al. 2020

SAMPE 2020 | Virtual Series

View full text Add to dashboard Cite

show abstract

“…The resistivity-based technique can be also applied to glass fiber composites, provided that the matrix is filled with conductive particles, usually made of carbon. As an alternative, the measurement of the dielectric response in composite laminates has been recently proposed by Vadlamudi et al [ 99 ]. The technique intends to observe and model the variation in the dielectric response as a function of the damage evolution in order to characterize the current material state.…”

Section: Resistivity-based Measurementsmentioning

confidence: 99%

Residual Properties in Damaged Laminated Composites through Nondestructive Testing: A Review

et al. 2021

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The development of damage tolerance strategies in the design of composite structures constitutes a major challenge for the widespread application of composite materials. Damage tolerance approaches require a proper combination of material behavior description and nondestructive techniques. In contrast to metals, strength degradation approaches, i.e., the residual strength in presence of cracks, are not straightforwardly enforceable in composites. The nonhomogeneous nature of such materials gives rise to several failure mechanisms and, therefore, the definition of an ultimate load carrying capacity is ambiguous. Nondestructive techniques are thus increasingly required, where the damage severity is quantified not only in terms of damage extension, but also in terms of material response of the damaged region. Based on different approaches, many nondestructive techniques have been proposed in the literature, which are able to provide a quantitative description of the material state. In the present paper, a review of such nondestructive techniques for laminated composites is presented. The main objective is to analyze the damage indexes related to each method and to point out their significance with respect to the residual mechanical performances, as a result of the working principle of each retained technique. A possible guide for future research on this subject is thus outlined.

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“…where ε r * is complex permittivity, and ε r and ε r " represent real and imaginary parts of measured ε r *. The permittivity of the free space is presented by ε 0 F m −1 and the capacitance of the free space is presented by C 0 (F) [26].…”

Section: Broadband Dielectric Spectroscopy (Bbds)mentioning

confidence: 99%

“…The dielectric properties, such as the dielectric relaxation strength (DRS), were calculated from real permittivity values for both the TIMs. Dielectric relaxation strength (DRS) is the difference between real permittivity at higher frequency and real permittivity at lower frequency (static permittivity) [26]. DRS values of TIM A and TIM B are shown in Figure 20.…”

Section: Dielectric Propertiesmentioning

confidence: 99%

A Comparative Study of Thermal Aging Effect on the Properties of Silicone-Based and Silicone-Free Thermal Gap Filler Materials

et al. 2021

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Thermal conductive gap filler materials are used as thermal interface materials (TIMs) in electronic devices due their numerous advantages, such as higher thermal conductivity, ease of use, and conformity. Silicone is a class of synthetic materials based on a polymeric siloxane backbone which is widely used in thermal gap filler materials. In electronic packages, silicone-based thermal gap filler materials are widely used in industries, whereas silicone-free thermal gap filler materials are emerging as new alternatives for numerous electronics applications. Certainly, characterization of these TIMs is of immense importance since it plays a critical role in heat dissipation and long-term reliability of the electronic packages. Insubstantial studies on the effects of various chemical compounds on the properties of silicone-based and silicone-free TIMs has led to this study, which focuses on the effect of thermal aging on the mechanical, thermal, and dielectric properties of silicone-based and silicone-free TIMs and the chemical compounds that cause the changes in properties of these materials. Characterization techniques such as dynamic mechanical analysis (DMA), thermomechanical analysis (TMA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and broadband dielectric spectroscopy (BbDS) are used to study the mechanical, thermal, and dielectric characteristics of these TIMs, which will guide towards a better understanding of the applicability and reliability of these TIMs. The experiments demonstrate that upon thermal aging at 125 °C, the silicone-free TIM becomes hard, while silicone-based TIM remains viscoelastic, which indicates its wide applicability to higher temperature applications for a long time. Though silicone-based TIM displays better mechanical and thermal properties at elevated temperatures, dielectric properties indicate low conductivity for silicone-free TIM, which makes it a better candidate for silicone-sensitive applications where higher electric insulation is desired.

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Identification of current material state in composites using a dielectric state variable

Cited by 18 publications

References 24 publications

Performance Enhancement and Prediction of Composite Materials with Embedded Electrospun Piezoelectric Sensors

Performance Enhancement and Prediction of Composite Materials with Embedded Electrospun Piezoelectric Sensors

Residual Properties in Damaged Laminated Composites through Nondestructive Testing: A Review

A Comparative Study of Thermal Aging Effect on the Properties of Silicone-Based and Silicone-Free Thermal Gap Filler Materials

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