Modulus Of Composites Research Articles

Thermo-mechanical and morphological studies of Hal-reinforced PEEK

This study is focused on exploring the thermo-mechanical properties and behaviour of PEEK-Hal nanocomposites as a case study for understanding the interactions between nanoparticles and polymers, as well as to explore potential applications of nanocomposites in the field of engineering. The selection of Poly (ether ether ketone) (PEEK) polymer is based on its notable chemical resistance, exceptional mechanical properties and high thermo-oxidative stability. Halloysite nanotubes (Hal) are chosen for their environmentally friendly nature, non-toxic properties, cost-effectiveness, tuneable release and rapid adsorption rates. This research paper focuses on the fabrication of PEEK-Hal polymer composites with varying concentrations using a co-rotating twin screw extruder. The prepared composites are thoroughly characterized using various analytical techniques such as Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The mechanical properties are assessed using a universal testing machine (UTM), impact tester, and hardness tester, respectively. The surface morphology is examined using field emission scanning electron microscopy (FE-SEM) technique. The results highlight the substantial benefits of incorporating Hal, improving interfacial adhesion, and establishing favourable interactions between the PEEK and Hal. The incorporation of Hal notably enhances the stiffness and storage modulus of the PEEK-Hal composites. Additionally, the presence of Hal restrains the mobility of the macromolecular chains within the composite. This study demonstrates that the PEEK-Hal composite with a 3% concentration of Hal (PH3) exhibits remarkable thermo-mechanical properties.

Analysis of epoxy composites reinforced with jute, banana, and coconut fibers and enhanced with Rubik's layer: Tensile, bending, and impact performance evaluation

This research paper presents a comprehensive analysis of epoxy composites fortified with natural fibers such as jute, banana, and coconut, further augmented by the incorporation of Rubik's layer, aimed at evaluating their mechanical performance in terms of tensile, bending, and impact properties. As sustainable alternatives to traditional reinforcement materials, these natural fibers offer the advantage of low environmental impact, renewability, and biodegradability. The Rubik's layer, known for its three-dimensional interlocking structure, holds promise in enhancing composite properties due to its unique geometry and material characteristics. The study involves the fabrication of composite specimens through a systematic layering process, varying the composition of natural fibers and Rubik's layer. A comprehensive experimental campaign is conducted to assess the tensile strength, bending modulus, and impact resistance of the resultant composites. The results are systematically compared against those of pristine epoxy composites to ascertain the influence of the added reinforcements and enhancement layer. The findings reveal distinctive trends in mechanical behavior based on the type and proportion of natural fibers employed. Notably, the jute-reinforced composites exhibit commendable tensile and bending properties, while banana and coconut reinforcements contribute to improved impact resistance. The introduction of the Rubik's layer further refines these properties, with discernible variations based on its placement within the composite structure. This paper offers valuable insights into the multifaceted impact of natural fiber reinforcements and Rubik's layer incorporation on epoxy composites. The systematic evaluation of mechanical attributes provides a comprehensive understanding of the synergistic effects among these constituents. As the demand for sustainable and high-performance materials escalates, this research contributes to the growing body of knowledge on composite design, catering to diverse engineering applications that prioritize mechanical excellence and ecological responsibility.

An analytical closed-form solution for the in-plane elastic modulus of plain-woven textile composites

Engineering application of textile composites needs simple relations for the estimation of their mechanical properties. Many homogenization and simplified models have been already proposed for the analytical characterization of the elastic moduli of this class of materials. Along this route, the current study introduces an analytical solution for the longitudinal elastic modulus of plain-woven textile composites. A hybrid beam-spring model of the representative unit cell (RUC) is postulated consisting of a horizontal beam connected to an inclined beam, two supporting springs beneath the free end of the horizontal beam and the common end of the horizontal and inclined beams, and a torsion spring at the free end of the inclined beam. The mechanical and geometrical properties of the beams and springs are calculated from the weave structure and the symmetry conditions. A reduction technique from the matrix analysis of structures is borrowed to consider the effect of internal degrees of freedom on the in-plane stiffness coefficient and a closed-form formula is extracted for the elastic modulus. The proposed analytical formula is finally verified against available experimental data and a wide range of FE predictions for the GFRP and CFRP plain-woven composites.

The Mechanical Properties and Degradation Behavior of 3D-Printed Cellulose Nanofiber/Polylactic Acid Composites.

Polylactic acid (PLA) has been widely used in many fields because of its good biodegradability, biocompatibility, and renewability. This work studied the degradation behavior and mechanical properties of cellulose nanofiber (CNF)/PLA composites. In vitro degradation experiments of 3D-printed samples were conducted at elevated temperatures, and the degradation characteristics were evaluated by mechanical tests, gel permeation chromatography (GPC), differential scanning calorimetric (DSC), and scanning electron microscope (SEM). The results indicated that the addition of CNF (0.5 wt%) accelerated the degradation rate of PLA. The decreases in number average molecular weight (Mn) and weight average molecular weight (Mw) of composites were 7.96% and 4.91% higher than that of neat PLA, respectively. Furthermore, the tensile modulus of composites was 18.4% higher than that of neat PLA, while the strength was 7.4% lower due to poor interfacial bonding between CNF and PLA. A mapping relationship between accelerated and normal degradation showed that the degradation experienced during 60 days at 37 °C was equivalent to that undergone during 14 days at 50 °C; this was achieved by examining the alteration in Mn. Moreover, the degradation process caused a notable deformation in the samples due to residual stress generated during the 3D printing process. This study provided valuable insights for investigating the in vitro degradation behavior of 3D-printed products.

Surface engineering and functionalization of MoS2-based nanoarchitecture for constructing epoxy composites with excellent fire resistance and mechanical properties

To overcome the shortcomings of epoxy resins (EP) such as high flammability and emission of toxic gases, a MoS2-based nanoarchitecture (CeZrOx-MoS2@PDA) was designed and prepared through surface engineering and functionalization method. At 2 wt% incorporation, the nanoarchitectures were homogeneously dispersed in EP matrix, showing good conditions for the formation of strong labyrinth barrier effect. Concurrently, EP/CeZrOx-MoS2@PDA offered enhanced thermal stability with higher char residues and lower maximum weight loss rate (MLR) value. Furthermore, the peak heat release rate (PHRR), total heat release (THR) and smoke factor (SF) of EP/CeZrOx-MoS2@PDA were reduced by 35.5%, 29.1% and 54.5%, respectively, while the CO release rate and CO2 release rate were dropped significantly, which was associated with the strong labyrinth effect, good char-forming effect and beneficial free radical quenching effect of CeZrOx-MoS2@PDA nanoarchitecture. Moreover, the ternary nanoarchitecture also resulted in a 56.8% increase in the storage modulus of EP composites. Therefore, the CeZrOx-MoS2@PDA developed in this work contributed to the generation of high performance EP with excellent fire resistance and mechanical properties, providing a promising strategy for the design of superior EP composites.

Water aging effects on the flexural properties of fully biobased coir fiber composites

AbstractThis work describes the flexural behavior of biocomposites composed of a polyurethane matrix derived from castor oil plants and coir fibers. A statistical design is performed to identify the effects of fiber alkaline treatment and aging on the flexural modulus and strength of the composites. Physical tests and failure analyses are carried out to better assess their mechanical performance. A second experiment at 100% relative humidity is performed on treated fiber composites to compare with those obtained by immersion in water. The flexural modulus of the composites is not significantly affected by the fiber alkali treatment, while the strength is reduced by 35.17% when treated fibers are considered. Increasing the exposure time of composites under both aging conditions progressively reduces their flexural properties. The aging process of biocomposites in an environment with 100% relative humidity takes twice as long to reduce to the same flexural properties as those aged in water.Highlights Composites made with treated fibers showed higher apparent density and lower porosity. Water aging reduces flexural modulus and strength of biobased coir composites. The bending properties are strongly dominated by the properties of biobased polymer. 100% relative humidity takes twice as long to reduce to the flexural properties as those aged in water. Untreated coir fibers achieve superior bending properties under moisture aging.

Particle size effect of PTFE on friction and wear properties of glass fiber reinforced epoxy resin composites

Self-lubricating spherical plain joint bearings play a crucial role in aerospace equipment, with their performance primarily depending on the self-lubricating materials positioned between the inner and outer rings. As a typical polymer-based self-lubricating material, glass fiber reinforced epoxy resin composites receive high expectations. Polytetrafluoroethylene (PTFE) as an additive can significantly improve the friction and wear performance of glass fiber reinforced epoxy resin composites. The primary objective of the present study is to reveal the effect law of PTFE particle size on friction and wear properties of glass fiber reinforced epoxy resin composites under dry sliding conditions. Hence, the four particle sizes (P1, average < 1 μm; P2, average 12 μm; P3, average 25 μm; P4, 75–180 μm) of PTFE-filled epoxy composites were prepared. The hardness, compressive strength, and compressive modulus of the epoxy resin composites filled with four particle sizes of PTFE were measured. The coefficient of friction (COF) was evaluated using a reciprocating ball-on-disk tribometer, with a GCr15 ball as the stationary part and the composite disc as the reciprocating component. The wear rate was determined using a Mahr profilometer. The results show that the friction coefficients of four PTFE-filled epoxy resin composites have little difference. However, the wear rate of epoxy composite filled with PTFE particles of the large size (RE/P4) is an order of magnitude lower than that of epoxy composites filled with PTFE particles of the other size. The wear morphology of the composites was analyzed by scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The higher wear resistance of RE/P4 can be attributed to it exhibiting a stronger role in anchoring glass fibers (GF), compared to other particle-sized PTFE-filled epoxy resin composite materials.

Effect of Photoinitiators Doped in PDMS for Femtosecond-Laser Writing: Characterization and Outcomes.

Herein, we have characterized in depth the effect of femtosecond (fs)-laser writing on various polydimethylsiloxane (PDMS)-based composites. The study combines systematic and nanoscale characterizations for the PDMS blends that include various photoinitiators (organic and inorganic agents) before and after fs-laser writing. The results exhibit that the photoinitiators can dictate the mechanical properties of the PDMS, in which Young's modulus of PDMS composites has higher elasticity. The study illustrates a major improvement in refractive index change by 15 times higher in the case of PDMS/BP-Ge [benzophenone (BP) allytriethylgermane] and Irgacure 184. Additional enhancement was achieved in the optical performance levels of the PDMS composites (the PDMS composites of Irgacure 184/500, BP-Ge, and Ge-ATEG have a relative difference of less than 5% in comparison with pristine PDMS), which are on par with glasses. This insightful study can guide future investigators in choosing photoinitiators for particular applications in photonics and polymer chemistry.

Sustainable composites from Carbon Dioxide-Derived Poly (propylene carbonate) and biosourced poly(3-hydroxybutyrate-co-3-hydroxyvalerate) fiber with enhancing mechanical properties and heat resistance

Biodegradable and biosourced poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) fibers were used as reinforcing materials, and sustainable Carbon Dioxide-Derived Poly (propylene carbonate) composites with balanced strength and ductility were prepared by melt compounding. The PHBV fiber was proved to be an effective reinforcing agent. With the addition of PHBV fibers, the PPC composites showed a significant increase in Young's modulus and tensile strength. When the PHBV fiber content was 40 wt%, the Young's modulus and tensile strength were 317% and 145% higher than that of neat PPC. Especially, the composites still exhibited a certain level of ductility. With increasing the PHBV fiber content, the dynamic storage modulus and glass transition temperature of PPC composite were also increased. The Vicat softening temperature (VST) of PPC/PHBV fiber composites was increased significantly, suggesting the heat resistance of PPC was improved after composites preparation. Such sustainable composites from PHBV fiber reinforced PPC could be used in packaging field, which will promote the practical application of PPC.

Evaluation of three-component boron-free glass fiber/TiO2/polyimide nanocomposite properties prepared by 3D turbula dispersion and spark plasma sintering method

Interest has grown in recent time on the development of three-component polymer nanocomposite with enhanced properties. However, the study focuses on the effect of TiO2 nanofiller on the mechanical, tribological, dielectric, and corrosion resistance properties of boron-free glass fiber (BGF) reinforced polyimide (PI) composite produced with spark plasma sintering route. Microstructure of the samples was examined using scanning electron microscopy. Mechanical, tribological, dielectric, thermal, and corrosion behaviour of the samples were characterized by nanoindenter, ball-on-disc, LCR meter, TGA, and potentiodynamic polarization test, respectively. The SEM results show that the introduction of the nanoparticles into the BGF/PI composite aids in more uniform distribution of the BGF particles within the PI matrix, and thus good interfacial interaction of the glass fiber and the PI matrix structure. Comparing the BGF/PI composite sample with BGF/TiO2/PI nanocomposite, it was observed that the nanocomposite depicted better hardness, elastic modulus, low friction coefficient and wear rate, dielectric, and enhanced corrosion properties. With TiO2 additions, hardness and modulus of the PI composite was improved by 56.6% and 10.1%, respectively. In addition, PI composites filled with TiO2 depicted a 0.07 coefficient of friction and wear rate of about 67.7% in reduction than that of neat PI and 9.0% in reduction than that of the pristine BGF/PI composites. Improved interactions between the reinforcements and the host matrix are suggested as the possible mechanism resulting to the desirable properties of the three-component PI nanocomposite recorded. Finally, the developed nanocomposite is suggested to be favourable for automobile, aerospace, and microelectronic device applications.

Solid-state reaction mediated microstructural evolution in a spark plasma sintered in situ Ti–B4C composite

A novel porosity-free in situ Ti–B4C composite was fabricated via spark plasma sintering (SPS). Detailed analysis of the phase evolution, coupling results from XRM, XRD and SEM-EBSD-EDS, indicate that primarily TiB2 precipitates formed due to the in-situ reactions between the boron-carbide and titanium powders. The precipitation of TiB2 resulted in the formation of a graphitic C-rich thin layer circumscribing the partially reacted B4C particles. Further progression of the in-situ reaction leads to the out-diffusion of the excess carbon from the B4C particles, across the graphite and TiB2 phases, forming TiC upon reacting with the titanium matrix. Therefore, the final microstructure primarily consisted of TiB2, TiC, and partially reacted B4C phases, with small amounts of TiB, α-Ti, and graphite. Furthermore, the microstructure in these SPS processed in situ composites appeared to be the product of a solid-state Ti–B4C diffusion couple, substantially different from their fusion-based additively manufactured counterparts. Nano-indentation tests revealed a remarkably high average hardness of ∼25 GPa for this SPS-processed Ti–B4C composite and comparable (with literature) phase-specific hardness and modulus values for the constituent TiB2, TiC, and B4C phases.

Investigating the Mechanical Properties of Annealed 3D-Printed PLA-Date Pits Composite.

Biomedical applications are crucial in rehabilitation medicine, assisting individuals with disabilities. Nevertheless, materials failure can sometimes result in inconvenience for users. Polylactic Acid (PLA) is a popular 3D-printed material that offers design flexibility. However, it is limited in use because its mechanical properties are inadequate. Thus, this study introduces an artificial intelligence model that utilizes ANFIS to estimate the mechanical properties of PLA composites. The model was developed based on an actual data set collected from experiments. The experimental results were obtained by preparing samples of PLA green composites with different weight fractions of date pits, which were then annealed for varying durations to remove residual stresses resulting from 3D printing. The mechanical characteristics of the produced PLA composite specimens were measured experimentally, while the ANSYS model was established to identify the composites' load-carrying capacity. The results showed that ANFIS models are exceptionally robust and compatible and possess good predictive capabilities for estimating the hardness, strength, and Young's modulus of the 3D-printed PLA composites. The model results and experimental outcomes were nearly identical.

High damping and modulus of aluminum matrix composites reinforced with carbon nanotube skeleton inspired by diamond lattice

Damping and modulus are mutually exclusive properties, and optimizing the overall performance of damping and modulus of materials is of high interest nowadays. In this study, a novel aluminum matrix composite reinforced by a diamond lattice-inspired carbon nanotube skeleton is presented. By means of molecular dynamics simulation, it is demonstrated that the structure can not only increase the internal friction by introducing interface defects, but also ensure the sufficient modulus of the material through the cooperative deformation of sliding and extrusion between the carbon nanotube skeleton and the aluminum matrix. Furthermore, the effect of frequency on energy dissipation is calculated. In contrast to conventional materials possessing a single internal friction peak, this composite structure material has two internal dissipation peaks as a function of frequency. This is due to the fact that viscous and phonon dissipation dominate the energy dissipation in this structural material. The viscous dissipation is caused by the relaxation of disordered atoms in the interface after deviating from the equilibrium state, and the phonon dissipation is created by the coupling of mechanical waves and normal modes of crystalline atoms. The designed composite achieves an unprecedented loss modulus through a trade-off between modulus and damping.

Deep-learning-assisted printed liquid metal sensory system for wearable applications and boxing training

Liquid metal (LM) exhibits a distinct combination of high electrical conductivity comparable to that of metals and exceptional deformability derived from its liquid state, thus it is considered a promising material for high-performance soft electronics. However, rapid patterning LM to achieve a sensory system with high sensitivity remains a challenge, mainly attributed to the poor rheological property and wettability. Here, we report a rheological modification strategy of LM and strain redistribution mechanics to simultaneously simplify the scalable manufacturing process and significantly enhance the sensitivity of LM sensors. By incorporating SiO2 particles into LM, the modulus, yield stress, and viscosity of the LM-SiO2 composite are drastically enhanced, enabling 3D printability on soft materials for stretchable electronics. The sensors based on printed LM-SiO2 composite show excellent mechanical flexibility, robustness, strain, and pressure sensing performances. Such sensors are integrated onto different locations of the human body for wearable applications. Furthermore, by integrating onto a tactile glove, the synergistic effect of strain and pressure sensing can decode the clenching posture and hitting strength in boxing training. When assisted by a deep-learning algorithm, this tactile glove can achieve recognition of the technical execution of boxing punches, such as jab, swing, uppercut, and combination punches, with 90.5% accuracy. This integrated multifunctional sensory system can find wide applications in smart sport-training, intelligent soft robotics, and human-machine interfaces.

On the chemo-mechanical evolution process of high-volume slag cement paste

This study investigated the evolution process of high-volume slag cement (HVSC) paste from a chemo-mechanical standpoint. HVSC specimens with a 70 w.t. % slag replacement rate were studied at various ages. Evolution of phase assemblage, microstructure development, and micromechanical properties were analyzed using TGA/XRD/MIP/SEM-EDS and nano-/micro-indentation techniques. A two-scale micromechanical model was built to predict the effective elastic modulus based on the nanoindentation results. Key findings include: 1) Between 7 and 28 days, the formation of calcium silicate hydrate (C-S-H) gel phase improves the effective elastic modulus by filling capillary pores; 2) From 28 to 90 days, the phase assemblage and microstructure remain stable, with a transition from low-density to high-density C-S-H; 3) Between 90 days and 2 years, slag rims produced by slag grains result in increased elastic modulus; 4) The two-scale micromechanical model, combined with nanoindentation data, accurately predicts the effective modulus of HVSC composites, although the unhydrated slag grains-hydrated cement matrix interface may cause an overestimation at an early age. With longer curing time, this interface disappears owing to the continuous hydration of large slag particles and therefore a good match is found between the modelling and experimental results.

Thermal properties and mechanical behavior of hot pressed PEEK/graphite thin film laminate composites

This work studies high-performance laminate composite materials made of graphite and poly(ether-ether-ketone) (PEEK). The main objective was to enhance graphite's inherent properties by the addition of PEEK to produce materials with improved thermal and mechanical stability for high-performance applications. The composites were fabricated using a hot press method at a temperature below 310 °C. The newly formed materials were then subjected to various tests, including Scanning Electron Microscopy, Thermogravimetric Analysis, mechanical properties tests, nanoindentation tests, and X-Ray Diffraction to assess their structural, thermal, and mechanical properties. Our findings showed a substantial interfacial interaction between PEEK and graphite, indicating successful composite formation. Both three-layered PEEK/graphite/PEEK (PGP) and five-layered PEEK/graphite/PEEK/graphite/PEEK (PG)2P composites exhibited superior thermal stability at high temperatures compared to neat PEEK. Moreover, our mechanical tests demonstrated a 172% increase in ultimate tensile strength of PGP compared to neat graphite. Additionally, nanoindentation tests confirmed an increase in both Young's modulus and hardness of composites. Furthermore, XRD analysis revealed a 35.5% increase in crystallinity in the fabricated composites compared to pristine PEEK. These findings significantly contribute to the field of high-performance composite materials, confirming that the hot pressing of PEEK and graphite sheets results in enhanced thermal and mechanical properties.

A comparative study of polylactic acid (PLA)-Based unidirectional green hybrid composites reinforced with natural fibers such as kenaf, bamboo and coir

Plant-based composites are considered as new generation materials that offer sustainability, eco-friendly and green chemistry, utilized by numerous sectors. Composites of green hybrid made from polylactic acid (PLA) and three different plant fibers were prepared using two symmetrical fibers stacking sequences; namely high modulus and brittle (HMB) fibers (kenaf-bamboo-coir/PLA) and low modulus and ductile (LMD) fibers (coir-bamboo-kenaf/PLA) in the outmost layers. The stacking sequence was prepared using a simple slot tool to properly align the fibers and it was dried at 50 °C before being compressed using hot press. It was found that the tensile strength and tensile modulus of both hybrid composites increased linearly up to 158 MPa and 7 GPa respectively. It shows that the stacking sequences had no significant effect on tensile strength, but fracture strain increased by 58% produced by LMD fibres. However, the use of HMB fibres in the outmost layers significantly improved flexural strength up to 49% higher than that of LMD fibres. In contrast, the impact strength of the green hybrid composites using LMD fibres in the outmost layers was 21% higher than that of its counterpart. Like other plant fiber composites, both composites had an increased water absorption capacity of up to 39% due to increased fibre content. These stacking sequence properties are essential to fabricate a specific application to ensure properties suitable for the job's features. High modulus and brittle composites require a high load to deform permanently, as well as low modulus and ductile composites. Both exhibit versatile mechanical characteristic, providing a balance of sealant toughness and the ability to retain overall shape, such as in sound absorption and vibration in transportation.

Effects of Carbon Nanotubes on Thermal Behavior of Epoxy Resin Composites

Human society’s need to build low-weight, high-strength and durable structures has increased the demand for composite materials. In this case, composites are used where high mechanical strength, low weight, sound and thermal insulation properties are required. One of the most important issues now is designing materials and coatings aimed at reducing heat loss and resisting high temperatures. One way to address this problem is to develop a technique for preparing and applying composite materials that slow down their heating applied to a surface. In this study, carbon nanotubes (CNTs) reinforced composites were fabricated using silicone molding to be applied to honeycomb sandwich structures. To determine the effect of CNTs on the thermal behavior of the sandwich panels, different weight percentages of this material (0.025, 0.05. 0.075 wt.%) were added to the epoxy resin. The results showed that the thermal stability of the epoxy composites was directly related to the increase in the percentage of CNTs as the CNT content increased to 0.075 wt.%, and the thermal degradation temperature of the epoxy composites increased by 14 °C. In addition, the energy absorption increased by 4.6% with an increase in CNTs up to 0.075 wt.%. Density measurements showed that the density of the nanocomposite samples increased by adding CNTs to pure epoxy resin. The actual densities of the samples reinforced with 0.025, 0.05, and 0.075 wt.% CNTs are 0.925, 0.926, and 0.927 of the theoretical density, respectively. Since the CNT dispersion uniformity in the epoxy matrix can significantly affect the properties of the composites, in this study, a new method of dispersing CNTs in the epoxy resin matrix resulted in higher thermal conductivity while using lower amounts of CNTs compared to other studies. The storage modulus of the epoxy matrix composites reinforced with 0.05 wt.% in this study was 25.9% and 6.9% higher than that from the previous study reinforced with 0.1 wt.% and 0.25 wt.% CNTs, respectively. Furthermore, the tanδ and loss modulus of the composite reinforced with 0.05 wt.% CNTs in this study were 52% and 54.5% higher than that from the previous study with 0.1 wt.% CNTs, respectively. This study provided an optimal approach for designers and engineers who want to effectively design their composite honeycomb sandwich structure with better thermal properties.

An eigenstrain-based micromechanical model for homogenization of elastic multiphase/multilayer composites

This paper presents a novel micromechanical procedure for the linear elastic homogenization of composites with periodic microstructures. The procedure is developed for composites with arbitrary number of phases and geometric shapes of the inhomogeneities, in contrast with most existing homogenization approaches. Also, no restriction is made in relation to the mismatch between the properties of the phases and volume fractions of the inhomogeneities. The proposed procedure is based on the Eshelby equivalent inclusion approach and extends a model originally derived for evaluating the effective elastic moduli of periodic two-phase composites. The procedure represents the fluctuating elastic fields within each multiphase repeating unit cell (RUC) using Fourier series, resulting in Lippmann-Schwinger integral equations governing the unknown eigenstrain fields of the inclusions. Unlike traditional iterative algorithms used in Fast Fourier Transform (FFT)-based approaches, the procedure solves the integral equations straightforwardly from a scheme of partition of the domain of each inclusion. The efficiency of the proposal procedure is demonstrated through applications to composites with different arrays of coated fibers and constituent materials.

Mechanical-Thermal Stability of Micro Composite Based Porous Carbon from Coconut Shell (&lt;i&gt;Cocoa nucifera&lt;/i&gt;) Charcoal

Research on the mechanical thermal stability of micro-porous carbon-based micro composites with marine paint matrices has been carried out. Microporous carbon has the property of absorbing radar waves so it is very interesting to research and develop into a microwave shielding material synthesized from coconut shell (cocoa nucifera) by carbonization process at 600°C for 45 minutes. The molecular structure and phases of micro porous carbon were characterized using Fourier Transform Infrared (FTIR) and X-Ray Diffraction (XRD) with the results confirmed of micro carbon with reduced graphene oxide (rGO) phase. Furthermore, micro-composites made from porous micro carbon with marine paint as a binder were made using the wet mixing-casting method. Mechanical thermal testing was carried out by means of a shear test at a temperature range of 30 – 70°C using a Dynamics Mechanical Analysis (DMA) tool. The test results showed that the value of the storage modulus of porous micro carbon composites was 1.653 MPa, 10.196 MPa, 13.068 MPa, 118.567 MPa, respectively. The value of the composite storage modulus increases with increasing concentration of porous micro carbon with an optimum value of mechanical thermal stability at a composition of 70:30 %wt. The results of mechanical thermal testing showed that porous micro carbon with rGO phase from coconut shells has the potential to be used as an anti-radar shielding material. 068 MPa, 118.567 MPa. The value of the composite storage modulus increases with increasing concentration of porous micro carbon with an optimum value of mechanical thermal stability at a composition of 70:30 %wt. The results of mechanical thermal testing showed that porous micro carbon with rGO phase from coconut shells has the potential to be used as an anti-radar shielding material. 068 MPa, 118.567 MPa. The value of the composite storage modulus increases with increasing concentration of porous micro carbon with an optimum value of mechanical thermal stability at a composition of 70:30 %wt. The results of mechanical thermal testing showed that porous micro carbon with rGO phase from coconut shells has the potential to be used as an anti-radar shielding material.