Functional Composites and Structures

This paper presents a comprehensive review of the state-of-the-art in structural battery composites research. Structural battery composites are a class of structural power composites aimed to provide mass-less energy storage for electrically powered structural systems. Structural battery composites are made from carbon fibres in a structural electrolyte matrix material. Neat carbon fibres are used as a structural negative electrode, exploiting their high mechanical properties, excellent lithium insertion capacity and high electrical conductivity. Lithium iron phosphate coated carbon fibres are used as the structural positive electrode. Here, the lithium iron phosphate is the electrochemically active substance and the fibres carry mechanical loads and conduct electrons. The surrounding structural electrolyte is lithium ion conductive and transfers mechanical loads between fibres. With these constituents, structural battery half-cells and full-cells are realised with a variety in device architecture. The paper also presents an overview of material modelling and characterisation performed to date. Particular reference is given to work performed in national and European research projects under the leadership of the authors, who are able to provide a unique insight into this emerging and exciting field of research.

Many engineering structures, especially defense applications, need to be reinforced against blast loads due to a nearby explosion. Today, much more attention needs to be given to this issue because of increased exposure to explosions, and natural disasters. Different solutions have been used in the literature to mitigate blast-loading effects. One of these applications, sandwich panels, are a good candidate for blast-loading applications. In a sandwich panel structure, several parameters have considerable effects on deflections, deformations, and energy absorption capability. The most important of these parameters are: (i) the material and thickness of the front and back face sheets and core; (ii) core density and grading; (iii) core and face sheet types; (iv) filling and stiffening strategies of the core; (v) radius of curvature of the panel; (vi) mass of explosive charge; and (vii) standoff distance. The aim of this paper is to review these critical aspects of blast loading of sandwich panels to provide an overall insight into the state of the art of the application.

Additive manufacturing (AM) has drawn significant attention in the fabrication of soft actuators due to its unique capability of printing geometrically complex parts. This research presents the design and development of an AM process for bioinspired, deformable, and magnetic stimuli-responsive actuator arms. The actuator arms were fabricated via the material extrusion-based AM process with magnetic particle-polymer composite filaments. Inspired by the rhombus cellular structure found in nature, different design parameters, such as the line width of the interior rhombus sides, and 3D printing parameters were studied and optimized to fabricate actuator arms that exhibit enhanced flexibility while being magnetically actuated. The trigger distance and deformation experiments revealed that the width of the rhomboids' sides played a critical role in magnetic and bending properties. It was found that the sample with a line width of 550 µm and printing layer thickness of 0.05 mm had the maximum deflection with a measured bending angle of 34 degrees. The magnetic property measurement exhibited that the sample with a line width of 550 µm showed the maximum magnetic flux density of 3.2 mT. The trigger distance results also supported this result. A maximum trigger distance of 8.25 mm was measured for the arm with a line width of 550 µm. Additionally, tensile tests showed that the sample exhibited a 17.7 MPa tensile strength, 1.8 GPa elastic modulus, and 1.3% elongation. Based on these results, we successfully fabricated a 3D printed magnetic gripper with two rhombus cellular structured arms which showed grasping and extensive load lifting capability (up to ∼140 times its weight).

Electroactive polymers (EAPs) are materials that respond to electrical stimulation by exhibiting significantly large strains (to a maximum of a few hundred %) and vice versa. Thanks to their unique behaviors, EAPs have been widely and increasingly applied for sensing and actuating applications. EAPs are a promising material with many attractive properties such as fast electro-mechanical response, high mechanical and chemical stability, flexibility, low modulus, high strain capabilities, and shape adaptability. These features make them attractive for innovative applications such as wearable fabric sensors for IoT products and artificial muscles as bio-friendly actuators. In this article, we have presented a brief overview of electronic EAPs, especially PVDF-based materials, dielectric elastomers such as silicone and acrylic materials for sensors and actuators by focusing on their operation mechanisms and applications.

A dynamic mechanical thermal analyser operating in the single cantilever mode was used to examine the dynamic mechanical properties of unaged and hygrothermally aged discontinuous asymmetric helicoidal (Bouligand) carbon fibre reinforced plastic (CFRP) composites as a function of fibre architecture. The discontinuous Bouligand was manufactured using two major pitch angles as independent variables: 90° and 120° and from each major pitch angle, minor interply pitch angles were used as independent variables ranging 5°–25°. The composites were tested as either dry unaged specimens or following hygrothermal ageing in seawater at the constant temperatures of 40 °C and 60 °C for over 2000 h. We find that the viscoelastic properties E' and E'' are adversely affected by both hygrothermal aging and the minor pitch angle, but not the major pitch angle. Higher hygrothermal ageing temperatures and increasing minor pitch angles are found to decrease the energy absorption and dissipation capacities of discontinuous Bouligand structured CFRP composites. The tan-δ curves also indicate that hygrothermal ageing increases the heterogeneity of discontinuous Bouligand structured composites, with separate viscoelastic phases and glass transition temperatures.

Molecular dynamics (MD) simulation continues to be one of the most advanced tools in a wide range of fields and applications. The motion of atoms or molecules at various temperatures and pressures was analysed and visualised using the MD simulation through large-scale atomic/molecular massively parallel simulator (LAMMPS). This research focuses on a basic introduction to MD, as well as their determination and MD methods. LAMMPS works with a variety of external packages to determine the position of atoms and molecules over time. As the simulation has various procedures such as algorithm to step processing and results, the developers of MD are constantly pushing for the reduction of pre-steps. This classifies the performance competence that should be approached for increased portability of performance on a programmatic level, a key to implementing the solution for various problems that would come from inventors and possibly new research in programming languages.

The use of polymer composite has been implemented since 3400 B.C, the very first known composite's application is attributed to the Mesopotamians. These ancient people fabricated plywood with glued wood strips placed at various distinct angles and in the late 1930s glass fiber thin strands have been developed. Glass fibre polymer composites have a wide scope in various engineering structures submarines, spacecraft, airplanes, automobiles, sports, and many more, over traditional materials because of their superior properties including lightweight, high fracture toughness, corrosion, fatigue, wear & fire resistance, high strength to weight ratio, high modulus and low coefficient of expansion. Various technologies have been developed so far to create different types of polymer composites in accordance with their properties and applications. Glass fiber possesses better properties as great strength, better flexibility, stiffness, and chemical corrosion resistance. Glass fibers are generally in the form of cut-up strand, fabrics and mats. Every kind of glass fibers has different properties and has various applications as in polymer composites. The aim of this review paper is to provide updated technological insights regarding the evolution of composite, classification of gass fibre polymer composites, development methodology in contrast with various applications, advantages and limitations and their behavioral properties.

Auxetic structures with negative Poisson's ratio have received much attention due to their attractive behavioral properties in next-generation metamaterials and robotic applications. However, until now, there has been a lack of research into using soft materials to reliably develop a largely-deformable auxetic structures. Here, we develop soft polydimethylsiloxane (PDMS)-Ecoflex auxetic structures using a 3D printing technique, leading to high fabrication reliability and repeatability. Water-soluble filaments are employed to design sacrificial mold structures that quickly dissolve in warm water. By measuring the mechanical properties and light transmittance of soft composite membranes with various mixing ratios of PDMS and Ecoflex, the intrinsic characteristics of the composite membranes are determined. The newly fabricated soft auxetic structures composed of PDMS and Ecoflex composites always exhibit negative Poisson's ratio during stretching. The negative Poisson's ratio of the structure is maximized when PDMS and Ecoflex have a 2:1 mixing ratio and nominal strain is less than 5%. Advances in technology to reliably fabricate soft auxetic structures using 3D printers are believed to promote next-generation applications such as wearable sensors and energy-absorbing structures.

The objective of this paper is to study the performance of piezoelectric materials on a piezoelectric paint sensor. The paper begins by presenting a fabrication method for a paint sensor with piezoelectric properties using piezoelectric materials. The paint sensor is composed of piezoelectric powder and epoxy resin in a 1:1 weight ratio. Five different piezoelectric materials, including three soft-type and two hard-type materials, were used and their piezoelectric properties compared in paint sensors and ceramic sensors. The paint sensors were cured using a steel mold for producing a uniform specimen size of 20 × 10 × 0.2 mm³, and an electrode was made on the upper and lower sides using silver paste. Poling treatment was then successfully performed at room temperature (20 °C) under a 4 kV mm⁻¹ electric field for 30 min in order to activate the paint specimen as a sensor. Impact signals were monitored by measuring output voltage from the paint sensor in relation to impact force. The sensor's piezoelectric properties were then calculated using normalized piezoelectric properties. In addition, five different piezoelectric ceramic sensors were fabricated and their d₃₃ value measured to compare the sensitivity of paint sensors. As a result, Pb(Ni_1/3Nb_2/3)O₃-Pb(Zr, Ti)O₃ (PNN-PZT) powder showed higher sensitivity and higher piezoelectric properties than other piezoelectric materials in both paint and ceramic sensors.

With the growing importance of high-performance carbon fibers (CFs), researches have been conducted in many applications such as aerospace, automobile and battery. Since conventional CFs which were made from polyacrylonitrile, pitch and cellulose display either high tensile strength or high modulus properties due to structural limitations, it has been a challenge to develop CFs with both tensile strength and modulus with high conductivity. Therefore, various studies have been conducted to obtain high-performance multifunctional CFs. Among them, 1-dimensional carbon nanotubes (CNTs) have been used commonly to make CFs because of high mechanical and conducting properties. In this review, the recent development of CFs was introduced briefly, and CNT-based composite CFs were introduced. Many efforts are being made to create high-performance CFs by combining various carbon nanomaterials and polymers, which can have potential to be utilized in aerospace, defense and other industries. The those fibers may be nextgeneration high-performance fibers due to both high strength and high modulus as well as high conducting properties. The challenges and outlook for commercialization of CNT-based CFs are addressed in terms of aspect ratio of CNTs, solvent recycling, and mass-production.

Additive manufacturing (AM) has drawn significant attention in the fabrication of soft actuators due to its unique capability of printing geometrically complex parts. This research presents the design and development of an AM process for bioinspired, deformable, and magnetic stimuli-responsive actuator arms. The actuator arms were fabricated via the material extrusion-based AM process with magnetic particle-polymer composite filaments. Inspired by the rhombus cellular structure found in nature, different design parameters, such as the line width of the interior rhombus sides, and 3D printing parameters were studied and optimized to fabricate actuator arms that exhibit enhanced flexibility while being magnetically actuated. The trigger distance and deformation experiments revealed that the width of the rhomboids' sides played a critical role in magnetic and bending properties. It was found that the sample with a line width of 550 µm and printing layer thickness of 0.05 mm had the maximum deflection with a measured bending angle of 34 degrees. The magnetic property measurement exhibited that the sample with a line width of 550 µm showed the maximum magnetic flux density of 3.2 mT. The trigger distance results also supported this result. A maximum trigger distance of 8.25 mm was measured for the arm with a line width of 550 µm. Additionally, tensile tests showed that the sample exhibited a 17.7 MPa tensile strength, 1.8 GPa elastic modulus, and 1.3% elongation. Based on these results, we successfully fabricated a 3D printed magnetic gripper with two rhombus cellular structured arms which showed grasping and extensive load lifting capability (up to ∼140 times its weight).

Novel structural conceptualizations frequently incorporate inventive ideas, materials, or construction techniques. This study presents a unique design inspired by the traditional practice of sikku rangoli, a cultural tradition prevalent in the southern region of India, particularly in Tamil Nadu. Because it was novel, it was necessary to optimize the fundamental design for maximal outputs. In contrast to honeycomb structures, intercellular interactions are believed to contribute to the overall strengthening of the structure. By eliminating sharp corners from the structure, stress accumulation is prevented, resulting in improved stress distribution. Therefore, the design aspects that were deemed significant were taken into consideration and through the implementation of experimental design, an optimum design was determined. Utilizing the optimal base design as a foundation, the structure underwent several printing processes using diverse materials and incorporated multiple fillers. Furthermore, the structure was subjected to modifications employing the functional grading design concept. The study employed the functional grading design concept to examine the variations in load bearing capability, load distribution, and failure mode. The findings indicate that the compression strength of the composite structure was mostly influenced by the wall thickness. The combination of a carbon fiber reinforced base material with silicone rubber as filler, together with a functional graded cell structure featuring top and bottom densification, exhibited the highest compression strength compared to all other combinations. In order to investigate the accurate impact of the FG structures, every cell design was printed using PLA-CF, subjected to testing devoid of any additives, and the output parameters were computed. The results indicated that the center densified cell design exhibited significant values for specific energy absorption, relative density, and compressive strength (52.63 MPa, 0.652, and 2.95 kJ kg⁻¹, respectively). The design of the base cell exhibited the greatest crushing force efficacy of 0.982.

Enhancing attributes such as abrasion resistance, wet grip, and rolling resistance significantly impacts the overall performance optimization in tire tread applications. These attributes are predominantly influenced by the dispersity of silica filler within tire tread compounds. Therefore, it becomes imperative to enhance silica dispersion by thoroughly investigating the impact of each constituent in the tire tread compound. This study aims to elucidate the effects of silica particle size and silane coupling agents on tire tread compound properties. The results demonstrate that larger specific surface area silica particles alongside 3-mercaptopropyltrimethoxysilane coupling agents effectively reduce filler–filler interactions and enhance silica dispersion within the tire tread compound. Consequently, these improvements contribute to the overall enhancement of tire tread compound performance. These findings offer valuable insights into advancing the reinforced performance of tire tread compounds through the synergistic utilization of each constituent.

This study aims to investigate the viability of untreated sisal fibers (N.F.), NaOH-treated sisal fibers (NaOH.F.) and cellulose extracted from sisal (CELL.F.) as an alternative to synthetic materials to produce biocomposites. The main objective was to conduct an in-depth study of the properties of these fibers whose aim is to limit matrix/fiber slippage and improve adhesion by modifying reinforcement surfaces, and to improve the efficiency of sisal fibers as reinforcements for composite materials using various analytical techniques including Fourier transform infrared spectroscopy, scanning electron microscopy, x-ray diffraction, and thermogravimetric analysis. In addition, the study aimed to produce a composite material by reinforcing plaster with the aforementioned fibers and then compare the mechanical and physical properties of the resulting material. The results showed that cellulose fibers exhibited higher mechanical strength and better compatibility with the plaster-matrix compared to sisal fibers by an increse of 324% in their tensil strength compared to natural sial fibers. In particular, the flexural strength showed a significant increase of 35% in the cellulose fiber reinforced composite. The reinforced composite material exhibited improved properties such as better flexural strength, increased absorption by 12.8% and descres the density by 21.3%, highlighting the promising prospects of cellulose fibers in advancing biocomposite technology.

Multilayer thin-wall structures have demonstrated significant application potential in wearable devices, pressure vessels, and aerospace industries, with additive manufacturing (AM) poised to further unlock their capabilities. Although path planning, a crucial aspect of AM, has been extensively studied for homogeneous structures, research on path planning for heterogeneous structures remains limited. This study introduces a novel path planning algorithm, termed CPCNHTS, for generating continuous paths in complex non-rotating bodies with hierarchical thin-walled structures. CPCNHTS encompasses adaptive slicing, path offset, and robotic postprocessing techniques. The adaptive slicing method is employed to enhance the slicing model's accuracy through volume error control. Moreover, the path offset method is designed to derive the printing path using a parallel curve of the inner contour. Identification of the inner contour is based on the curvatures and areas of single and double contours, respectively. The robotic postprocessing method is employed to convert the printing path into executable codes for multimaterial additive equipment. As a compelling application of the CPCNHTS algorithm, a limb prosthetic socket was successfully fabricated, highlighting the remarkable potential of this approach within the wearable devices domain.

Auxetic materials, possessing a negative Poisson's ratio, can be arranged in various geometric configurations, such as tubular structures. Unlike conventional materials, which contract in lateral dimensions when stretched longitudinally, auxetic tubular expands in response to applied forces. This comprehensive review article amalgamates the latest experimental data and insights from preceding scholarly works, offering a detailed analysis of the structural design, fabrication processes, and mechanical characteristics of auxetic tubular structures. The review encompasses an analysis of their tensile properties, comparative evaluations with different materials, impact resistance, enhanced bending, and flexibility. Furthermore, the article explores the wide-ranging applications of auxetic tubular in diverse sectors such as automobile manufacturing, aerospace, medicine, and textiles. Furthermore, investigated not only new suggestions and future considerations for the advancement of these materials and structures but also a rigorous examination of the forthcoming and new challenges. This multifaceted approach distinguishes it from prior studies within the same scientific domain.

Thin-walled energy absorbing structures based on hybrid structural concepts have a lightweight benefit along with great potential of enhancing the crashworthiness characteristics. Inspired by the huge number of research investigations performed on novel additively manufactured hybrid metal-composite configurations and their latest developments, the current review article extensively reports the latest advances along with promising outcomes of the impact response of various additively manufactured hybrid metal-composite structures for crashworthiness applications. Specific consideration is given to the crushing performance of the hybrid structures fabricated from fused deposition modelling technique. The significant additive manufacturing techniques, their material selections and exceptional customized structural designs explored in recent times are discussed elaborately. Crushing patterns obtained by hybrid energy absorbing structures under various loading conditions are recognized. Furthermore, comparison of various hybrid structures and their latest advances revealed the efficiency of the thin-walled hybrid configuration based on 3D printing techniques in terms of weight reduction, crashworthiness and energy absorption behaviour. This review article will serve as a catalyst to boost the scientific improvement of hybrid energy absorbing structures utilized as passive safety protective devices in modern vehicles.

Many engineering structures, especially defense applications, need to be reinforced against blast loads due to a nearby explosion. Today, much more attention needs to be given to this issue because of increased exposure to explosions, and natural disasters. Different solutions have been used in the literature to mitigate blast-loading effects. One of these applications, sandwich panels, are a good candidate for blast-loading applications. In a sandwich panel structure, several parameters have considerable effects on deflections, deformations, and energy absorption capability. The most important of these parameters are: (i) the material and thickness of the front and back face sheets and core; (ii) core density and grading; (iii) core and face sheet types; (iv) filling and stiffening strategies of the core; (v) radius of curvature of the panel; (vi) mass of explosive charge; and (vii) standoff distance. The aim of this paper is to review these critical aspects of blast loading of sandwich panels to provide an overall insight into the state of the art of the application.

Molecular dynamics (MD) simulation continues to be one of the most advanced tools in a wide range of fields and applications. The motion of atoms or molecules at various temperatures and pressures was analysed and visualised using the MD simulation through large-scale atomic/molecular massively parallel simulator (LAMMPS). This research focuses on a basic introduction to MD, as well as their determination and MD methods. LAMMPS works with a variety of external packages to determine the position of atoms and molecules over time. As the simulation has various procedures such as algorithm to step processing and results, the developers of MD are constantly pushing for the reduction of pre-steps. This classifies the performance competence that should be approached for increased portability of performance on a programmatic level, a key to implementing the solution for various problems that would come from inventors and possibly new research in programming languages.

Biomimetics enables the use of nature as a source of inspiration for the elaboration of high-performance materials. In this scenario, the development of bioinspired composites emerges as a promising proposal, capable of generating technological innovation in numerous areas of engineering, considering the exceptional mechanical performance of materials of this kind. That said, this review article characterizes the design principles and fundamental parameters for bioinspired composites design. In addition, the main challenges to be overcome in the development of bioinspired materials are discussed, with the presentation of some experimental studies that lead to the practical application of such principles. Future applications for this class of materials are also highlighted.

Additive manufacturing (AM) has drawn significant attention in the fabrication of soft actuators due to its unique capability of printing geometrically complex parts. This research presents the design and development of an AM process for bioinspired, deformable, and magnetic stimuli-responsive actuator arms. The actuator arms were fabricated via the material extrusion-based AM process with magnetic particle-polymer composite filaments. Inspired by the rhombus cellular structure found in nature, different design parameters, such as the line width of the interior rhombus sides, and 3D printing parameters were studied and optimized to fabricate actuator arms that exhibit enhanced flexibility while being magnetically actuated. The trigger distance and deformation experiments revealed that the width of the rhomboids' sides played a critical role in magnetic and bending properties. It was found that the sample with a line width of 550 µm and printing layer thickness of 0.05 mm had the maximum deflection with a measured bending angle of 34 degrees. The magnetic property measurement exhibited that the sample with a line width of 550 µm showed the maximum magnetic flux density of 3.2 mT. The trigger distance results also supported this result. A maximum trigger distance of 8.25 mm was measured for the arm with a line width of 550 µm. Additionally, tensile tests showed that the sample exhibited a 17.7 MPa tensile strength, 1.8 GPa elastic modulus, and 1.3% elongation. Based on these results, we successfully fabricated a 3D printed magnetic gripper with two rhombus cellular structured arms which showed grasping and extensive load lifting capability (up to ∼140 times its weight).

Many engineering structures, especially defense applications, need to be reinforced against blast loads due to a nearby explosion. Today, much more attention needs to be given to this issue because of increased exposure to explosions, and natural disasters. Different solutions have been used in the literature to mitigate blast-loading effects. One of these applications, sandwich panels, are a good candidate for blast-loading applications. In a sandwich panel structure, several parameters have considerable effects on deflections, deformations, and energy absorption capability. The most important of these parameters are: (i) the material and thickness of the front and back face sheets and core; (ii) core density and grading; (iii) core and face sheet types; (iv) filling and stiffening strategies of the core; (v) radius of curvature of the panel; (vi) mass of explosive charge; and (vii) standoff distance. The aim of this paper is to review these critical aspects of blast loading of sandwich panels to provide an overall insight into the state of the art of the application.

A dynamic mechanical thermal analyser operating in the single cantilever mode was used to examine the dynamic mechanical properties of unaged and hygrothermally aged discontinuous asymmetric helicoidal (Bouligand) carbon fibre reinforced plastic (CFRP) composites as a function of fibre architecture. The discontinuous Bouligand was manufactured using two major pitch angles as independent variables: 90° and 120° and from each major pitch angle, minor interply pitch angles were used as independent variables ranging 5°–25°. The composites were tested as either dry unaged specimens or following hygrothermal ageing in seawater at the constant temperatures of 40 °C and 60 °C for over 2000 h. We find that the viscoelastic properties E' and E'' are adversely affected by both hygrothermal aging and the minor pitch angle, but not the major pitch angle. Higher hygrothermal ageing temperatures and increasing minor pitch angles are found to decrease the energy absorption and dissipation capacities of discontinuous Bouligand structured CFRP composites. The tan-δ curves also indicate that hygrothermal ageing increases the heterogeneity of discontinuous Bouligand structured composites, with separate viscoelastic phases and glass transition temperatures.

The purpose of this project was to introduce a way to improve the mechanical properties of dissimilar welded material, which provides benefits such as affordability, high speed, and a suitable bond property. This experimental project applies the friction welding method, including combining parameters, such as a numerical control machine, two different speeds, and three different cross sections, including flat, cone, and step surfaces. When the welding process was done, samples were implemented and prepared via a bending test of materials. The results have shown that, besides increasing the machining velocity, the surface friction increased, and so did the temperature. Considering the stated experimental facts, the melting temperature of composite materials increased. This provides the possibility of having a better blend of nanomaterial compared to the base melted plastics. Thus, the result showed that, besides increasing the weight percentage of nanomaterial contents and machining velocity, the mechanical properties increased on the welded area for all three types of samples. This enhancement is due to the better melting process on the welded area with the attendance of various nanoparticle contents. Also, the results showed that the shape of the welding area could play a significant role, and the results also change drastically where the shape changes. Optimum shape in the welding process has been dedicated to the step surface. The temperature causes the melting process, which is a significant factor in the friction welding process.

Coarse-grained molecular dynamics simulations are a widely accepted methodology in the field of studying the viscoelasticity of elastomers. In this paper, a thermophysically balanced multiscale coarse-grained potential for glass-forming polymers is presented with the energy renormalization (ER) method by redefining temperature transferable correlation effects between rescaling factors for energy parameter and length-scale parameter. The correlation effects have not been investigated in the literature, to the best knowledge of authors. The coarse-grained potential was demonstrated for the polyisoprene model generated from the anionic polymerization. The ER enables temperature transferability by adopting renormalization parameters as function of the temperature. Considering the correlation effects, a multi objective-optimization algorithm was adopted to find proper solution sets of $\alpha$ and $\beta$ matching mean square displacement (MSD) and density to the all-atom model simultaneously. Meanwhile, shear stress was matched to find $\alpha$ first, then, density was fitted in the low-temperature regime. To verify the coarse-grained potential in the middle-temperature regime, MSD was compared to those from the all-atom model, and it was successfully matched.

Carbon nanomaterials including, but not limited to, carbon nanotubes (CNTs) and graphene have attracted considerable attention due to their nanoscale electrical conductivity. Flexible sensors have experienced a growing demand due to several potential applications, such as personalized health monitoring and robots. In this study, CNT/cellulose composite sheets were manufactured using spray methods for flexible sensors. MWCNTs were ultrasonically dispersed in an acetone solvent and flexible plain paper was used as a substrate on which the CNT suspension was sprayed. At the end of the coating process, to remove the acetone solvent, the specimens were dried in an oven. Electrical resistance (ER) three-dimensional-mapping and optical observation were used to confirm and evaluate the dispersion of CNTs on the paper. To access the wettability of CNT/cellulose sheets, the changes of static contact angle of distilled water droplets on the sheets were measured. The critical point of the CNT coating numbers was determined using the ER method as well as the change of wettability using the static contact angle measurements.