P u b l i c a t i o n s
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2024
19. Fast and accurate prediction of cure quality and mechanical performance in fiber-reinforced polymer composite using dielectric variables and machine learning
Monjur Morshed Rabby, Partha Pratim Das, Minhazur Rahman, Vamsee Vadlamudi, Rassel Raihan
Conference: Polymer Composites, Volume: 45, Issue: 2, Pages: 1810-1825, John Wiley & Sons, Inc.
Abstract:
Fiber-reinforced polymer (FRP) composites are widely used in the aerospace and automotive industries due to their high strength-to-weight ratio. However, the manufacturing process of FRP composites is intricate, requiring precise control over multiple parameters, which can be challenging. To ensure top-notch product quality and bolster confidence in the durability of composite materials, it requires a uniform curing evaluation technique and a predictive strength model. This study presents a rapid nondestructive quality inspection technique for composites, involving three distinct studies that employ machine learning techniques in combination with the frequency-dependent dielectric response of materials. The first study introduces a nondestructive method for swiftly inspecting the cure state (degree of cure) of composite samples. This technique combines broadband dielectric spectroscopy with supervised machine learning algorithms, particularly support vector machines. The second study employs advanced artificial neural networks like multi-layer perceptron to predict the tensile strength, a measure of mechanical performance, of composite materials. The results demonstrate an accurate classification of the curing state with 96.7% accuracy and a prediction of tensile strength with 87.5% accuracy. The final study explores the application of machine learning in quality monitoring of prepreg (raw materials for FRP) aging at room temperature.
Follow here for more info: https://doi.org/10.1002/pc.27891
18. Physics Informed Neural Network (PINN) Utilization in Discovery of Diffusion–Electrical Cross–property Relation in Polymer Composites
Partha Pratim Das, Vamsee Vadlamudi, Minhazur Rahman, Sharmin Akter, Monjur Morshed Rabby and Rassel Raihan
Conference: AIAA SCITECH 2024 Forum, 8-12 January 2024
Abstract:
This research work investigates the relationship between moisture absorption and changes in electrical properties in polymer and polymer matrix composites. The dielectric properties of the matrix are altered due to induced polarization mechanisms by water molecules. Fick's law of diffusion can be used to model moisture absorption, and Maxwell's equations of electromagnetism can be used to model the electrical response of the material. However, computationally coupling diffusion and Maxwell's equations in hygrothermal loading of polymers remain unexplored. A novel approach using physics-informed neural networks (PINN) is proposed to address this. The proposed methodology explores the coupling between diffusion and evolving electrical properties through the development of a physics informed deep neural network framework. The proposed method has the potential to estimate moisture diffusion based on electrical properties, and vice-versa, providing insights for composite structure design and durability assessment in a non-conservatism manner.
Follow here for more info: https://doi.org/10.2514/6.2024-0774
2023
17. A Neural Network Framework for Predicting Durability and Damage Tolerance of Polymer Composites under Combined Hygrothermal-mechanical Loading
Partha Pratim Das
Conference: Doctoral Symposium, Proceedings of the Annual Conference of the PHM Society 2023, Vol. 15 No. 1 (2023)
Abstract:
Fiber-reinforced polymer (FRP) composites are used in crucial structures which are susceptible to a combination of mechanical (static/dynamic) and hygrothermal (moisture absorption and temperature) loads. This research presents a novel artificial neural network (ANN) framework that employs the dielectric permittivity response of FRP composites under combined mechanical-hygrothermal loading to predict the extent of moisture absorption, fatigue life, and remaining useful life. The proposed framework is based on the phenomenological and data-driven study of the effects of static and dynamic mechanical loads along with moisture absorption in the dielectric characteristics of these composites.
Follow here for more info: https://papers.phmsociety.org/index.php/phmconf/article/view/3800
Poster Link: Click Here
16. Carbon Fibers Recycling from Degraded Prepregs and Mechanical Properties or Recycled Composite
Monjur Morshed Rabby, Minhazur Rahman, Partha Pratim Das, Vamsee Vadlamudi, Rassel Raihan
Conference: Society of the Advancement of Material and Process Engineering. SAMPE Conference Proceedings. Seattle, WA, April 17-20, 2023
Abstract:
The size of the global composites market is anticipated to grow more than previously. Due to the rapidly rising volume of CFRP production, the waste from this material poses numerous problems and has significantly increased the socio-technological pressure to find sustainable composite recycling solutions. The problem is that recycling the composite part is challenging once its service life has expired. The same problem is true for the raw materials (prepregs) used in composite manufacturing. When the prepreg out-life/shelf-life is over, prepregs are abandoned, resulting in a loss of millions of dollars and an adverse environmental effect. In this study, the prepreg matrix and fiber were separated by a chemical process using acetone as the primary solvent and other oxidants as a secondary treatment. The retrieved fibers were analyzed for surface morphologies and functional groups on the surface and compared with the fiber recovered using the pyrolysis process. Due to the loss of the sizing agent, plasma treatment has been performed to increase the wettability and adhesion between fiber and matrix. This recycled fiber is then used in manufacturing composite panels via the Vacuum Assisted Resin Transfer Molding (VARTM) process. The mechanical properties of the recovered fiber have been studied to ensure that it can be repurposed for other applications. The proposed method can be used to recover carbon fiber, and then the fiber can be used to reinforce the polymer matrix, reducing sociotechnical pressure while remaining cost-effective and environmentally friendly.
Follow here for more info: https://rc.library.uta.edu/uta-ir/handle/10106/31204
15. Artificial Intelligence Assisted Residual Strength and Life Prediction of Fiber Reinforced Polymer Composites
Partha Pratim Das, Muthu Elenchezhian, Vamsee Vadlamudi, Rassel Raihan
Conference: AIAA Scitech Forum 2023, MD
Abstract:
With the increased use of composite materials, researchers have developed many approaches for structural and prognostic health monitoring. Broadband Dielectric Spectroscopy (BbDS)/Impedance Spectroscopy (IS) is a state-of-the-art technology that can be used to identify and monitor the minute changes in damage initiation, accumulation, interactions, and the degree of damage in a composite under static and dynamic loading. This work presents a novel artificial neural network (ANN) framework for fiber-reinforced polymer (FRP) composites under fatigue loading, which incorporates dielectric state variables to predict the life (durability) and residual strength (damage tolerance) from real-time acquired dielectric permittivity of the material. The findings of this study indicate that this robust ANN-based prognostic framework can be implemented in FRP composite structures, thereby assisting in preventing unforeseeable failure.
View Video Presentation: https://www.youtube.com/watch?v=Z6z1Jm8WBk8&ab
Follow here for more info: https://rc.library.uta.edu/uta-ir/handle/10106/31086
2022
14. Prepreg age monitoring and qualitative prediction of mechanical performance of composite using dielectric state variables
Monjur Morshed Rabby, Partha Pratim Das, Minhazur Rahman, Vamsee Vadlamudi, Rassel Raihan
Journal: Polymers and Polymer Composites
Abstract:
The aviation and automobile industries have recently depended on thermoset epoxy-based prepreg as a raw material for manufacturing composites. Since prepregs have a limited out-life (i.e., the maximum storing time allowed at room temperature), they must be stored in refrigerators at low temperatures. If not maintained, they can often adversely affect the desired quality of the final product. Prepregs are often discarded once the prepreg out-life ends, leading to a loss of millions of dollars and a detrimental impact on the environment. Therefore, it is necessary to develop a simple method to monitor prepreg aging/degradation in order to ensure its usability or repurpose prepreg usage. In this study, we used broadband dielectric spectroscopy to monitor the degradation state of the glass fiber/epoxy prepreg sample stored at room temperature, and the data has been used to predict the mechanical performance of the final manufactured composite part. The frequency-based nondestructive dielectric measuring technique was used to calculate the dielectric strength and relaxation time of the prepregs. The dielectric strength decreased and relaxation time increased with aging, allowing the aging progression to be captured. Furthermore, with aging, the real permittivity value changes to a lower value and the relaxation peak in imaginary permittivity with respect to frequency shifts to a lower frequency. The physics behind this dielectric measurement method has been understood in the context of analyzing the prepreg’s cure kinetics parameters, which has been investigated using differential scanning calorimetry. Overall, this simple dielectric-based monitoring technology will provide confidence in the future use of degraded or out-of-life raw material systems for manufacturing.
Follow here for more info: https://doi.org/10.1177/09673911221145053
13. Moisture Content Prediction in Polymer Composites Using Machine Learning Techniques
Partha Pratim Das, Monjur Morshed Rabby, Vamsee Vadlamudi, Rassel Raihan
Journal: Polymers
Abstract:
The principal objective of this study is to employ non-destructive broadband dielectric spectroscopy/impedance spectroscopy and machine learning techniques to estimate the moisture content in FRP composites under hygrothermal aging. Here, classification and regression machine learning models that can accurately predict the current moisture saturation state are developed using the frequency domain dielectric response of the composite, in conjunction with the time domain hygrothermal aging effect. First, to categorize the composites based on the present state of the absorbed moisture supervised classification learning models (i.e., quadratic discriminant analysis (QDA), support vector machine (SVM), and artificial neural network-based multilayer perceptron (MLP) classifier) have been developed. Later, to accurately estimate the relative moisture absorption from the dielectric data, supervised regression models (i.e., multiple linear regression (MLR), decision tree regression (DTR), and multi-layer perceptron (MLP) regression) have been developed, which can effectively estimate the relative moisture absorption from the dielectric response of the material with an R2 value greater than 0.95. The physics behind the hygrothermal aging of the composites has then been interpreted by comparing the model attributes to see which characteristics most strongly influence the predictions.
Follow here for more info: https://www.mdpi.com/2073-4360/14/20/4403/htm
12. Dielectric Analysis to Predict Moisture Absorption in Structural Composites: A Data-driven Approach
Partha Pratim Das, Monjur Morshed Rabby, Vamsee Vadlamudi, Rassel Raihan
Conference: 37th American Society for Composites (ASC) Technical Conference, Tucson, AZ
Abstract:
Due to continual exposure to moist environment, environmental degradation is a major threat to structural composites throughout their service life. Impedance Spectroscopy (IS)/Broadband Dielectric Spectroscopy (BbDS) is a reliable non-destructive method that has been used in polymer industries for dielectric characterization of material. While moisture absorption causes irreversible changes in the polymer matrix composites, it also alters the electrical properties of the system which is detectable using BbDS. Since the physics that drives the change in electrical characteristics is driven by the modifications imposed by water molecules (whether free or bound), both events can be linked. A dielectric spectrum over a broad frequency range can give an accurate estimation of moisture absorption in structural composites. In this work, machine learning (ML) models (Discriminant Analysis (DA) and Support Vector Machine (SVM) with Principal Component Analysis (PCA)) were developed that incorporate the dielectric data from BbDS to predict the current material state due to hygrothermal ageing. The models not only can detect the presence of moisture in composites, but also can predict the current saturation state of the material based on their dielectric properties. It uses the dielectric spectra and composite’s geometry as features to train supervised learning classification algorithms. The ML models developed in this study shows high accuracy and efficiency in predicting the current moisture state of the composite test samples due to hygrothermal ageing.
Follow here for more info: https://rc.library.uta.edu/uta-ir/handle/10106/30998
11. Dielectric State Variables as Qualitative Indicators of Moisture Absorption-caused Mechanical Property Degradation in GFRP Composite Structures
Partha Pratim Das, Vamsee Vadlamudi, Rassel Raihan
Journal: Composites Part C: Open Access
Abstract:
Fiber reinforced polymer (FRP) composites are being used in numerous fields owing to their intrinsic strength to weight ratio and various design benefits. However, these materials are prone to environmental aging, particularly moisture absorption. In essence, absorbed moisture infiltrates the polymer matrix and induces changes in the polymer network through chain scission, plasticization, and other bonding interactions. This causes irreversible damages to the material and significantly decreases mechanical strength. In this study, Broadband Dielectric Spectroscopy (BbDS) has been used to identify the absorption mechanisms in glass fiber reinforced polymer (GFRP) composites by detecting the related polarization mechanisms. Here, results show an increase in the real permittivity and dielectric relaxation strength of the material with moisture absorption and attaining a steady-state once absorption approaches saturation. In this work, moisture-induced degradation of tensile and flexural properties of the material have also been studied and a correlation has been found to exist between the dielectric state variables, absorbed moisture, and the mechanical properties of the material. The correlation resolves the integration of the different material physics involved here and can be used to empirically predict the residual strength of a composite structure using the non-destructive broadband dielectric characterization technique.
Follow here for more info: https://doi.org/10.1016/j.jcomc.2022.100295
10. Coupled Effects in Dielectric and Thermal Properties of Polymer Matrix Composite Structures due to Moisture Absorption
Partha Pratim Das, Monjur Morshed Rabby, Vamsee Vadlamudi, Kenneth Reifsnider, Rassel Raihan
Conference: SAMPE 2022, Charlotte, NC
Abstract:
Fiber reinforced polymer (FRP) composites are being used in number of fields including aerospace, marine, sports, medical, power sectors, etc. due to their lightweight nature while retaining high mechanical performance in terms of high specific strength, stiffness, and great fatigue properties. However, the applicability of these materials is restricted by their stability up to a certain temperature (i.e. glass transition temperature) and environmental degradation (i.e. moisture, UV light, etc.). Moisture ingression greatly reduces their mechanical properties altering material structure by causing polymer plasticization, chain scission and fiber-polymer interface deterioration. These changes instantaneously affect the thermal properties of the materials which in turn reduces its applicability in real life applications. Broadband dielectric spectroscopy (BbDS) is a robust non-destructive characterization technique that can directly assess the impact of moisture on material properties. In this current work, BbDS has been used to correlate the changes in thermal properties (glass transition temperature, enthalpy change) of glass fiber reinforced polymer composites due to moisture absorption. This work investigated the extent of these effects in conjunction with the dielectric property changes which can be utilized to help understand the material state and reliability in hygrothermal conditions, as well as for structural health monitoring.
Follow here for more info: https://rc.library.uta.edu/uta-ir/handle/10106/30341
9. The Effect of Plasma Treatment on The Cure Behavior of Out-of-Life Prepregs and An Investigation of The Mechanical Properties of Composite Parts Manufactured from Plasma-Treated Prepregs
Monjur Morshed Rabby, Partha Pratim Das, Minhazur Rahman, Vamsee Vadlamudi, Rassel Raihan
Conference: SAMPE 2022, Charlotte, NC
Abstract:
Many industries, including aircraft, automobiles, and marine, are using prepreg (pre-impregnated fibers and a partially cured polymer matrix) to manufacture composite parts to achieve optimum fiber and resin volume ratio and part repeatability. Since prepregs have a short out oflife (i.e., the maximum storing time allowed at room temperature), they must be stored in refrigerators at low temperatures, which, if not maintained, have an unfavorable influence on the intended quality of the final product. For the present study, glass/epoxy prepregs (expired out-life) were plasmatreated before being used to make the composite part to compensate for the room temperature aging effect. Plasma treatments contribute to the conversion of low-energy surfaces to higher energy surfaces by attaching oxygen-containing species. After plasma treatment, the surface energy change has been measured by measuring the contact angles formed by a polar liquid (water) and a non-polar liquid ( diiodomethane) using the Double Sessile Drop technique. The effect of plasma treatment on curing behavior was monitored in real-time using temperature-controlled Broadband dielectric spectroscopy and then compared to untreated prepreg curing. Using differential scanning calorimetry, the cure kinetics (change in activation energy) of plasma-treated prepreg has been studied. Furthermore, the shear and tensile strength of the final product have been investigated to observe how plasma treatment helps to improve the mechanical performance of the composite part made with plasma-treated prepreg. Overall, this study will provide a thorough understanding of how surface modifications using plasma treatment affects curing behavior and improve mechanical performance.
Follow here for more info:https://rc.library.uta.edu/uta-ir/handle/10106/30340
2021
Bryan Durham, Gayathri Kola, MohammadKian Mahroumi, Vamsee Vadlamudi, Rassel Raihan, Kenneth Reifsnider, Minhazur Rahman, Monjur Morshed Rabby, Partha Pratim Das, Muthu Ram Prabhu Elenchezhian
Conference: CAMX- The Composites and Advanced Materials Expo- Conference Proceedings 2021, Dallas, TX, USA
Abstract:
A composite is generally defined as a material composed of two or more separate sub-materials that complement each other's characteristics when combined. Composites are widely used in several major industries due to their low density, high strength, and relatively predictable chemical and electrical properties. One of the significant challenges of integrating composites into more diverse fields is the ability to accurately and consistently test for damages. Due to the myriad number of microscopic structures available in composite materials, a single-use testing system is a large contributor to current research. One approach to the non-destructive testing of composites lies in exploiting the dielectric properties of the material. Using a strong electric field, the molecules in the constituent materials of both damaged and non-damaged samples can be polarized and examined for differences. Broadband Dielectric Spectroscopy (BbDS) is one method to measure the dielectric properties such as conductivity, resistivity, impedance, and permittivity. This paper observes how permittivity changes in quasi-isotropic Glass Fiber Reinforced Polymer (GFRP) specimens over a broad frequency spectrum. In addition to BbDS, Thermally Stimulated Depolarized current (TSDC) is used to vary the electric field to understand the relaxation of the polarized material over a temperature gradient. The overall objective is to obtain a relationship between various damage levels and dielectric properties using BbDS and TSDC that can help to identify damage sites in composites and assess the level of accrued damages in the material as a whole.
Follow here for more info: https://rc.library.uta.edu/uta-ir/handle/10106/30056
7. A Comparative Study of Thermal Aging Effect on the Properties of Silicone-Based and Silicone-Free Thermal Gap Filler Materials
A S M Raufur Chowdhury, Monjur Morshed Rabby, Mehzabeen Kabir, Partha Pratim Das, Rabin Bhandari, Rassel Raihan and Dereje Agonafer
Journal: MDPI Materials (Impact Factor 3.057)
Abstract:
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.
Follow here for more info: https://doi.org/10.3390/ma14133565
6. Stiffness degradation in fatigue life of composites using dielectric state variables
Muthu Ram Prabhu Elenchezhian, Partha Pratim Das, Minhazur Rahman, Vamsee Vadlamudi, Md Rassel Raihan, Kenneth Reifsnider
Journal: Elsevier Composite Structures (Cite Score 9.6, Impact Factor 5.138)
Abstract:
Composite materials are widely used in aerospace and automotive structures for decades and over the years the community has gained a better understanding of the damage and failure modes of composites under fatigue. In this article, a dielectric characterization methodology for in-situ monitoring of composites under fatigue environments is proposed. A novel method of measuring the dielectric state variables in Broadband Dielectric Spectroscopy (BbDS) using Extremely Conductive Silver Epoxy Adhesive (ECSEA) paste is presented. These dielectric state variables serve to identify the precursor of the beginning of the end of life of the composite material under fatigue loading. The reliability of using this method for in-situ monitoring to provide fatigue life estimates and to indicate the immediate need for maintenance, repair and/or replacement of the structural component is discussed.
Follow here for more info: https://doi.org/10.1016/j.compstruct.2021.114272
5. The Effect of Room-Temperature Aging on Enthalpy and Dielectric Property of Carbon-Fiber/Epoxy Composite Prepreg and the Mechanical Property of Manufactured Composite
Monjur Morshed Rabby, Minhazur Rahman, Partha Pratim Das, Muthu Ram Prabhu Elenchezhian, Relebohile George Qhobosheane, Vamsee Vadlamudi, Kenneth Reifsnider, Rassel Raihan
Conference: SAMPE Conference 2021
Abstract:
Fiber-based reinforced plastics are widely used materials in different industries - e.g., Automotive, Aerospace, Defense- because of their various advantages. The most reliable raw materials for manufacturing fiber-based composites are pre-impregnated reinforcing fiber (prepreg). However, the limitation of using prepreg lies in its instability at room temperature. Prepregs have a specific out-life which sometimes makes the manufacturing process difficult. The objective of this study is to find out a way to investigate the room temperature aging effect on prepreg by analyzing the enthalpy and dielectric properties. In this study, differential scanning calorimetry (DSC) was used to measure the reaction enthalpy in the aged prepreg. The dielectric property of aged prepreg has also been analyzed using broadband dielectric spectroscopy (BbDS). We observed a significant effect on the enthalpy and dielectric properties of the aged prepreg. Furthermore, this study concentrates on how the aging of prepreg can affect the mechanical properties of the final composite parts. This study shows that the manufactured composite from aged prepreg shows inconsistency and a slight reduction in its tensile strength. Finally, a manufacturing strategy is suggested that will minimize the inconsistency of the strength of the final composite part manufactured from aged prepreg. [Copyright 2021. Used by the Society of the Advancement of Material and Process Engineering with permission. Proceedings of SAMPE neXus 2021, Virtual Event, June 29 – July 1, 2021, Society for the Advancement of Material and Process Engineering – North America.
Follow here for more info: https://rc.library.uta.edu/uta-ir/handle/10106/29934
2020
4. RealPi2dDIC: A Low-cost and open-source approach to in situ 2D Digital Image Correlation (DIC) applications
Partha Pratim Das , Muthu Ram Prabhu Elenchezhian, Vamsee Vadlamudi, Kenneth Reifsnider, Rassel Raihan
Journal: Elsevier SoftwareX (Cite Score 2.6)
Abstract:
In this current work an open-source 2D Digital Image Correlation (DIC) tool, RealPi2dDIC, is presented to monitor in situ full field deformation and strain responses of structures during loading. This software is coded in Python3 and uses Raspberry Pi as the computation and Pi camera as the imaging device. This low-cost approach to in situ DIC analysis enables its application in a broad field of research and industry problems where 2D strain field tensor is one of the principal interests of study. This code is provided with an interactive user interface (UI) making it user friendly and easy-to-use. Furthermore, RealPi2dDIC offers a simple software architecture which can be adopted, modified and extended to suit users’ purpose.
Follow here for more info: https://doi.org/10.1016/j.softx.2020.100645
Github Link: https://github.com/utaresearch/RealPi2dDIC
3. Smart Self-Sensing Composite: Piezoelectric and Magnetostrictive FEA Modeling and Experimental Characterization Using Wireless Detection Systems
Relebohile George Qhobosheane, Muthu Ram Prabhu Elenchezhian, Partha Pratim Das, Minhazur Rahman, Monjur Morshed Rabby, Vamsee Vadlamudi, Kenneth Reifsnider, Rassel Raihan
Journal: MDPI Sensors (Cite Score 5.0)
Abstract:
This research work focuses on the development of a piezoelectric magnetostrictive smart composite with advanced sensing capability. The composite piezoelectric property is achieved from the dispersion of single-walled carbon nanotubes (SWCNTs) and the magnetostrictive property from Terfenol-D nanoparticles. Finite element analysis (FEA) is used to examine the feasibility of modelling the piezoelectric (change in electric field) and magnetostrictive (change in magnetic field) self-sensing responses in the presence of applied stress. The numerical work was coupled with a series of mechanical tests to characterize the piezoelectric response, magnetostriction response and mechanical strength. Tensile tests of the composite samples manufactured as is (virgin), samples with SWCNTs, samples with Terfenol-D nanoparticles and samples with both SWCNTs and Terfenol-D nanoparticles were conducted. It was observed that an increase in volume fraction of Terfenol-d nanoparticles increases the change in magnetization, therefore increasing voltage response up to the point of saturation. The optimum change in amplitude was observed with 0.35% volume fraction of Terfenol-D nanoparticles. A constant ratio of SWCNTs was maintained, and maximum change in electrical resistance was at 7.4%. Fracture toughness for the samples with all nanoparticles was explored, and the results showed improved resistance to crack propagation.
Follow here for more info: https://www.mdpi.com/1424-8220/20/23/6906
2. Assessment of Material State for Predicting the Durability of Composites
VAMSEE VADLAMUDI, MUTHU RAM PRABHU ELENCHEZHIAN, PARTHA PRATIM DAS, RASSEL RAIHAN, KENNETH REIFSNIDER
Conference: Proceedings of the American Society for Composites—Thirty-fifth Technical Conference
ABSTRACT
The long term behavior of composites have been extensively studied for the last four decades. Given the heterogeneity of these materials, the damage accumulation mechanisms lead to superior fatigue performance of composites compared to metals. However, due to the ‘sudden death’ behavior controlled by defect coupling, the precursor to fracture plane development of these materials, the challenge remains on how to assess the real-time material state and predict when it becomes critical? In the recent past, broadband dielectric spectroscopy (BbDS) has been used successfully to assess the material state and predict the material state change (triggered by defect coupling) for quasi-static loading. In this work, we perform insitu monitoring of material state change for tension-tension fatigue loading (low cycle fatigue) and attempt to capture the material state change for quasi-isotropic laminates. The insitu response can be used to predict the formation of a ‘critical’ material state- the final frontier to predict the durability of composites and discuss the repeatability of the methodology.
Follow:
https://rc.library.uta.edu/uta-ir/handle/10106/29549
http://www.dpi-proceedings.com/index.php/asc35/article/view/34886
2019
1. Experimental Study on the Fabrication and Mechanical Properties of Medium-Density Particleboards from Coconut Coir
Partha Pratim Das, Fariha Musharrat Haque, Md Ashiqur Rahman
Conference: 13th International Conference on Mechanical Engineering (ICME), Dhaka
Abstract
The abundance of coconut coir in the South Asian subcontinent opens an alternative to the commercially available wood-chip particleboards that are gradually increasing pressure on the natural carbon sinks or forest. The present study aims to analyze the fabrication process of medium density particle boards using widely available indigenous agricultural raw material coconut coir and analyze the mechanical properties of the fabricated boards to determine its potential. Coconut coir and binder (urea formaldehyde) resin have been used as the raw materials while examining the effects of parametric variations such as the resin percentage, and coarse layer to fine layer ratio. The crucial mechanical properties of particleboards such as tensile and compressive strength, screw withdrawal strength, thickness swelling, water absorption show satisfactory values. These properties are found to vary slightly depending on the amount of resin percentage or coarse to fine layer mass ratio. Experimental analysis shows an optimum property for a combination of 10% resin (wt) and 80%-20% coarse to fine layer mass ratio. The findings of the present study suggest that the medium density particleboard prepared from coconut coir has the potential to become suitable substitutes for commercially available boards.
