Mechanical, morphological and water intake behavior of Mg-Si integrated carbon hybrid composite for marine deckhouse

: The automated boat’s deckhouse is made of deforested wood and glass fiber, harming producers, fishermen, and marine life. In context, researchers are attempting to make composites from waste and replace synthetic materials with natural composites. In the present work, a Carbon/Mg/Si/polyester hybrid composite is developed as a potential replacement for wood in marine deckhouse construction. Impact, tensile, flexural, Rockwell and Brinell hardness were tested using ASTM standards, as well as weight absorption in fresh and seawater. Scanning electron microscopy (SEM), microanalysis (EDAX), Fourier-transform infrared spectroscopy (FTIR) and Raman Spectroscopy techniques were used to identify microstructure, elements, and functional groups. Thermogravimetric analysis and differential scanning calorimetry (DSC) are used to determine the thermal stability and heat intake/rejection of the hybrid composite. Novel hybrid composites with Mg-Si fillers improve the mechanical strength, adhesion, corrosion resistance, and deckhouse life span in marine environments


INTRODUCTION
The mechanized boat's marine deckhouse is made of wood and glass fiber.The wood is obtained by felling trees, and glass fiber is extremely poisonous to marine canoe builders, fishermen and marine species.Metal-ceramics combine to form a particle-strengthened hybrid composite that can be used in a variety of applications.Power, stiffness, fatigue, resilience, crack resistance, thermal stability and other mechanical properties are being imparted.One of the key causes of internal structure formation with excellent stiffness and strength in hybrid composites is interfaces between reinforcing micro particles and metal binders resin (Astafurov et al., 2014).Ceramic composites are very hard, strong, rigid and Silicon Carbide (SiC) ceramics provide significant improvements in thermal and mechanical properties such as hardness, tensile strength and corrosion resistance, making them ideal for a variety of structural applications (Džunda et al., 2019).Carbon (C) is a nonmetal member in group 4A with an atomic number of 6 and an electron configuration of 1s 2 2s 2 2p 2 .For other metals that have weak Van der Waals bonds, the presence of atoms in the carbon layer has a strong bonding nature (Güler and Bağcı, 2020) .
The Indian coastline stretches about 8118 kilometers.In Tamilnadu and Kerala, about 16.5 million fishermen is working in fish industry, followed by 0.02 million canoes.Tamil Nadu and Kerala have 75-foot-long canoe boats with 13-21 layers of glass fiber and 5-9 layers of woven roving on bottom hull.The canoe's total weight is estimated to be between 40 and 60 tonnes (Chandrika et al., 2013;Singh et al., 2018;Report ICSF, 2023).For a long time, more than two lakhs canoe fishing boats have been used for fishing in the coastal areas of Tamilnadu and Kerala.Composites of Al/Mg 2 Si are very appealing materials for structural applications such as aerospace and automotive.The density and thermal expansion coefficient of Mg 2 Si are both very low at 1.99103 kg/m 3 and 7.5x10 -6 K -1 respectively.With melting temperatures of 1085 °C, hardness of 4.5 109 N-m 2 and elastic modulus of 120 GPa, it has a high melting temperature, hardness and elastic modulus.Segregation of primary Si from Mg 2 Si particles in the reinforcement layer confers superior wear resistance to the casting processes in hybrid composites (Roberton et al., 2009: Zhang et al., 2000;Kumar Gupta et al., 2018).
Monolithic materials cannot achieve the properties of modern applications derived from conventional materials functions in recent scenario.As a result, a modern production method for the fabrication of hybrid composites must be introduced.The key benefit of a hybrid composite is that it combines more than two materials without causing a chemical reaction, giving each material better characteristics than composites.Due to its broad range of excellent properties for a variety of applications, ceramics have been used as a matrix in the manufacturing of many composites (Moya et al., 2008;Rodriguez-Suarez et al., 2007;Smirnov A et al., 2019;Singh et al., 2019a).Ceramic-based composite materials are brittle and are not appropriate for extreme loading applications due to inadequate surface finish and induced cracking, which results in unpredictable part failure.By adding metal reinforcements, these failures can be resolved (Gutierrez-Gonzalez et al., 2008;Wing et al., 2016).The addition of a few ductile second phase materials in the composites will toughen the brittle natured ceramic matrix.These composites also known as cermets are used to enhance the mechanical, thermal, electrical and magnetic properties of ductile and high wear-resistant ceramics.This has the potential to avoid catastrophic failure by reducing the development of crack propagation (Smirnov and Bartolomé, 2012;Wing and Halloran, 2017).
The bonding nature of SiC and MgO between particle and metal matrix is found to be excellent, with higher tensile and yield strength and lower magnitude porosity (Smirnov et al., 2018).Using SEM micrographs, the impact of particles reinforced under the machined surface is observed with negligible craters, indicating that SiC particles with Mg matrix have better mechanical properties (Jayakumar and Annamalai, 2019;Vijayabhaskar and Rajmohan, 2019;Singh et al., 2019b).The aim of this work is to use novel metal integrated ceramic composites to fabricate the deckhouse of a boat.Wood and glass fiber make up a traditional boat deckhouse, whereas the glass fiber is extremely poisonous to producer, fishermen, marine species and wood is harvested by cutting trees, which results in deforestation.Hence, researchers looked for a better alternative to wood by using hybrid composites to replace deckhouses.However, because of seawater, the wood deckhouse decomposes after a few years.
In this study, carbon with Mg and Si as filler materials hybrid composites is used to replace wood in the construction of deckhouses.One of them is ceramic carbon powder (i.e coconut shell), which is discarded in large quantities every year.Using the hand layup process, ceramic carbon powder microparticles, as well as Mg and Si fillers, were mixed with polyester resin to form hybrid composites.The incorporation of metals Mg and Si into ceramic carbon hybrid composites improves mechanical strength, adhesion, corrosion resistance and life span of deckhouses that are exposed to the marine environment.

Materials
Carbon micro particles, Magnesium and Silicon microparticles were used in this research work (Fig. 1a and 1b).The carbon micro particle is made from the coconut shell's synthesis.The carbon, magnesium and silicon microparticles are 40 µm in size.Discarded coconut shells (i.e ceramic carbon powder), magnesium, silicon microparticles, polyester resin, cobalt and methyl ethyl ketone peroxide make up the hybrid composite.

Hybrid composite fabrication
One of the basic techniques used to produce composite and hybrid composite is the hand layup technique.By weight or volume fraction process, the resin and hardener are mixed in proper proportions.The hardener is a critical element in the setting and curing action of fabricated composite and it is carefully mixed.The powdered micro particles of carbon (i.e discarded coconut shell) and Mg-Si were combined with the unsaturated polyester resin in the proper proportions to form hybrid composites.The metal-incorporated ceramic micro particles were roughly mixed into the prepared resin.Then, by using the hand layup process the prepared reinforcement and matrix is distributed in the die layer by layer.Carbon serves as the reinforcing element within the composite material and are often organized in a particular configuration (random) to fabricate the hybrid composite material.The fabricated specimens of metal integrated ceramic hybrid composite are shown in Fig. 1c.Several hybrid composites containing a mixture of carbon micro particles and Mg/ Si (S1, S2, S3, S4 and S5) were made in proportions of 95 %/5 %, 90 %/10 %, 85 %/15 %, 80 %/20 %, 75 %/25 %, respectively.Table 1 shows the fabricated hybrid composite specimens along with the traditional material.

Mechanical property studies
The tensile and flexural tests were carried out on a Universal Testing Machine (UTM) in accordance with ASTM D638 and D790 respectively.The Charpy Impact Testing Machine is used to conduct the impact test in accordance with ASTM D256.Three samples of traditional composites (GF), S1, S2, S3, S4 and S5 hybrid composites were tested in this study.The Rockwell and Brinell Hardness Testing Machines were used to evaluate hardness in accordance with ASTM E18 and ASTM E10 using the Eq.
(1) where, N denotes the number of specific Rockwell hardness units, h denotes the permanent depth of an indentation in millimeters and s denotes the scale unit (0.001mm for 15N, 30N, 45N, 15T, 30T, 45T).Steel ball indenter scale of 130 units.
(2) where, F is the test force in N, D is the ball diameter in mm and d is the indentation's mean diameter in mm.

Weight absorption studies
Weight absorption method is used to determine the rate at which a material's weight is reduced as a result of absorption capacity.This experiment is carried out on fabricated specimens of traditional composites (GF), S1, S2, S3, S4 and S5 hybrid composites.The specimens were submerged in freshwater and seawater for 90 days and their weight is recorded at various intervals.The following Eq.( 3) is used to measure the water absorption potential. (3)

Composite characterization
Scanning electron microscopy (SEM), microanalysis (EDAX), Fourier-transform infrared spectroscopy (FTIR) and Raman Spectroscopy techniques were used to characterize the fabricated hybrid composites.The SEM, EDAX, FTIR and Raman Spectroscopy experiments were carried out according to ASTM standards ASTM E 1829-97, ASTM E1508-98, ASTM E168 and ASTM E1840 respectively.The mitigation or resolution of potential ageing effects in composite materials, such as Mg-Si integrated carbon hybrid composites, is a crucial factor to ensure their long-term performance and durability.The potential ageing effects encompass the selection of appropriate materials, the application of protective coatings and the execution of environmental testing.
The microstructure of the specimen is inspected using SEM analysis.The surface of the specimen to be examined is coated with gold until it is tested.The scanner's probe will travel over the specimen surface, capturing the image structure at various magnifications.The EDAX device is used in conjunction with the SEM to complete the mission.By moving the probe over the surface, the spectrum is reflected on the monitor.The existence of inorganic compounds, atomic weight and molecular weight are all explained by this spectrum.The FTIR is used to detect the presence of organic compounds in specimens by avoiding infrared rays that would otherwise fall on the surface.Via rotational and low-frequency modes, Raman spectroscopy analyses the presence of molecules in vibrational modes.The Raman scattering light experiment method can be used to measure it.The strength peak, stokes and anti-stokes peaks are used to analyze it.

Tensile Testing
From Fig. 2 it is observed that specimen S3 has a higher tensile strength than Specimens S1, S2, S4, S5 and conventional composites.The inclusion of 15% metal particles Mg and Si combined together with the 85% of carbon micro particles resulted in higher tensile strength in Specimen S3 hybrid composites owing to better withstanding capacity of load applied and enriches the tensile strength of composite.This S3 specimen with a high tensile strength can be recommended to build the deckhouse of a mechanized boat.

Flexural Testing
According to Fig. 3 Specimen S3 has a higher flexural strength than Specimens S1, S2, S4, S5 and conventional specimens.The addition of 15% metal particles Mg and Si together with the 85% of carbon micro particles resulted in higher flexural strength in Specimen S3 hybrid composites.The incorporation of Mg and Si in hybrid composite withstander the load applied and enriched the flexural strength of composite.

Impact Testing
The impact values of tested metal integrated ceramic hybrid composites is shown in Fig. 4. It is found that the specimen S3 has a higher impact intensity than other specimens S1, S2, S4, S5 and traditional composites.Similar to tensile and flexural samples, the addition of 15% metal particles Mg and Si as well as 85% of carbon micro particles resulted in higher impact strength in Specimen S3 hybrid composites due to improved load withstanding capacity of the composite.

Brinell Hardness of hybrid composites
The fabricated and sized specimen of the metal integrated ceramic hybrid composites subjected to the Brinell load of 2500 kgf is shown in Fig. 5. Specimen S3 has a higher Brinell hardness value than other combinations.The addition of 15% metal particles Mg and Si, as well as 85% of carbon micro particles resulted in a higher Brinell hardness value in Specimen S3 hybrid composites owing to the incorporation of filler particles as well as its withstanding capacity when subject to indentation loads.

Rockwell Hardness of hybrid composites
The fabricated and sized specimens of the metal integrated ceramic hybrid composites subjected to 200 kg Rockwell load are shown in Fig. 6.Specimen S3 has a higher Rockwell hardness value than other composite specimens.The addition of 15% metal particles Mg and Si, as well as 85% of carbon micro particles resulted in a higher Rockwell hardness value in Specimen S3 hybrid composites.The S3 Hybrid composites (85% Carbon + 15% Mg & Si) specimen has far more strength than the other hybrid composite specimens due to the addition of Mg and Si is used as a filler material.By adding small amount of filler materials and its incorporation in carbon-based hybrid composites with proper proportion enhances the mechanical behaviour, as obtained from the various experimental performance.Thus, we can recommend using this S2 Hybrid composites (85% Carbon + 15% Mg & Si) specimen to fabricate the marine deck house.The performance of Mg-Si integrated carbon hybrid composites in challenging environmental circumstances, such as storms, high humidity or prolonged sun exposure is contingent upon the precise composition of the composite, the manufacturing methodology employed and the intended purpose of material.The composite composition, ambient circumstances, maintenance practices and marine deck house type can affect the durability and longevity of such materials.From the experimental data, the mechanical properties enhanced due to the incorporation of Mg-Si in the carbon hybrid composites.

Sea Water medium
The effects of water absorption of fabricated hybrid composite specimens submerged in seawater are shown in Fig. 7a.Water intake behavior affects marine deckhouse composite structural integrity and durability in a complex way.Marine applications like deckhouses use composite materials for lightweight, corrosion-resistant and long-lasting solutions.The water-absorbing characteristics of composite materials, such as Mg-Si integrated carbon hybrid composites, under prolonged exposure to saltwater can be influenced by several factors, including the exact composition of composite and the manufacturing technique employed.In maritime applications, composites are typically engineered to exhibit a high level of resistance to water absorption, particularly in the presence of saltwater.As compared to other hybrid composites, the S3 Hybrid composites (85% Carbon + 15% Mg & Si) specimen consumed less seawater leading to the less intake of water into the specimen owing to the hydrophobic nature of composite.

Fresh Water medium
The effects of water absorption of fabricated hybrid composite specimens submerged in freshwater are as shown in Fig. 7b.As compared to other hybrid composites, the S3 Hybrid composites (85% Carbon + 15% Mg & Si) specimen consumed less freshwater due to the restriction of water flow into the composite as the rough surface of the composite is already filled with the matrix and reinforcement constituents promoting a better hydrophobic nature on the developed hybrid composite.
Scientific study comparing materials for use in marine environments typically takes into account characteristics including how much they weigh, how strong they are, how long they last and how much they cost.Because of their potential benefits in terms of weight reduction, high strengthto-weight ratio and corrosion resistance, advanced composite materials like magnesium-silicon (Mg-Si) and carbon fibers are commonly used from the investigation.

Microstructural analysis
Under different magnifications (50000x & 1, 3, 4 & 5 m), the surface microstructure of fabricated hybrid composites S3 (85% Carbon + 15% Mg & Si) is identified using a scanning electron microscope.Fig. 8 shows the morphological structure of S3 hybrid composites at different scales.Specific morphological adjustments will affect the performance of structure.Failure or reduced load-bearing capacity can result from structural integrity loss.Also, the biological growth can increase drag and reduce moving parts efficiency.Moreover, the surface characteristics can affect the material durability and longevity.
The morphological structure of the S3 (85% Carbon + 15% Mg & Si) hybrid composites in various sizes of 1 µm, 3 µm, 4 µm, and 5 µm.It demonstrates how the metal-infused ceramic composite attaches the reinforcement to the matrix.The inter-laminar bonding of the carbon micro particle and Mg-Si mi- cro particle with the polyester resin is excellent.The existence of pores/voids is discovered to be tiny and insignificant.The matrix adhesion of this metal-ceramic hybrid composite is excellent.The deckhouse of the boat is constructed using carbon and Mg-Si metal hybrid composites.

Energy Dispersive Atomic Spectroscopy analysis
The EDAX spectrum of the S3 Hybrid Composite (85% Carbon + 15% Mg & Si) is shown in Fig. 9.The inorganic elements are present in the S3 hybrid composites at peak stage, as shown by the graphical dispersive spectrum.Carbon, Potassium, Oxide, Magnesium, Sodium, Silicon, and Phosphorous are all visible as peaks in the spectrum.

Fourier Transforms Infra-Red Spectroscopy analysis
The FTIR spectrum for S3 hybrid composites (85% Carbon + 15% Mg & Si) is shown in Fig. 10.In the wavelength range of 400-4000 cm -1 , the FTIR peaks demonstrate the bonding and functional group of organic compounds present in the hybrid composites.The wavenumber corresponding to the bonding and functional group of S3 Hybrid Composite is represented in Table 3.
Six distinct peaks were observed in the S3 hybrid composite FTIR spectrum: 3436.81,2930.2,  1576.5, 1381.27,1123.8, and 568.68 cm -1 .Because of the range excess, the 3436.81cm -1 peak has no bonding or functional group.Axisymmetric CH 2 stretching bonding characterizes the 2930.2cm -1 peak, which belongs to the Fats, Wax, and Lipids functional group.The N-H plane amide II bonding peak at 1576.5 cm

Raman Spectroscopy analysis
Raman spectroscopy determines the vibrational modes of a molecule using rotational and low-frequency modes.The Raman spectroscopy technique is used to obtain the spectrum of S3 (85% Carbon + 15% Mg & Si) hybrid composite (Fig. 11).The spectrum of the S2 hybrid composite revealed two peaks.1220 cm -1 and 1610 cm -1 are the peak values.The stokes peak is 1220 cm -1 , while the intensity peak is 1610 cm -1 .There is no anti-Stokes peak.The applied nodular frequency is at a low level.With the presence of necessary molecules in the S3 hybrid composites, the presence of an intensity peak indicates better characterization behaviour of the sample.

Thermal behavior of hybrid composites
Thermogravimetry and a Differential Scanning Calorimeter were used to conduct the thermal analysis.The assay used is a 10 mg hybrid composite of S3 (85% Carbon + 15% Mg & Si The Differential Scanning Calorimeter curve for the S3 Hybrid Composite is shown in Fig. 12.It shows that an endothermic peak is found at 29.950C with a heat flow rate of -16.88 W/g and a heat flow rate of 793.7 W/g up to 7930C with a heat flow rate of 793.7 W/g.The DSC curve obtained above indicates that it can withstand a temperature of 793.70C.Despite the fact that the sea atmosphere does not hit that high a temperature, its highest temperature is equal to that of the atmosphere.
Thermo gravimetric curve for the S3 Hybrid Composite is shown in Fig. 13.The curve depicts the weight difference as a result of the applied temperature rise.It shows that at a temperature of 630 ºC, only a small amount of weight is lost, which is measured as 1.1%.Though the sea atmosphere does not reach that high a temperature, it does reach its highest temperature, which is the   temperature of the atmosphere.As a result, the deckhouse of the boat can be constructed using the S3 hybrid composite.

CONCLUSIONS
• The current project focuses on fabricating the boat's deckhouse using Mg-Si metal combined with carbon micro particles (i.e.discarded coconut shell) reinforced hybrid composites.Based on the investigations it was found that S3 hybrid composite (85% carbon and 15% Mg-Si metal) exposed better tensile, flexural, impact, Brinell and Rockwell hardness than traditional and other fabricated specimens.• Also, in both fresh and seawater, the water absorption potential of S3 hybrid composite is very low.SEM, EDAX, FTIR, and Raman spectroscopy techniques showed that S3 hybrid composite's microstructure connects metal-incorporated ceramic with unsaturated polyester resin, resulting in excellent adhesion.• EDAX and FTIR analysis revealed that the existence of inorganic and organic compounds is adequate.The presence of molecules in low-frequency modes was determined by the strength of Raman Spectroscopy peaks.• The thermal behaviour of the S3 hybrid composite, as measured by TGA and DSC demonstrates that it can withstand the requisite temperature for its weight and heat flow in terms of temperature.The findings revealed that fabricated novel S3 hybrid composites with Mg/Si as filler materials can be used to manufacture marine deckhouses.

FiguRe 7 .
FiguRe 7. Water Absorption of Fabricated Hybrid Composites a) Sea water & b) Fresh water

FiguRe 10 .
FiguRe 10.Fourier Transform Infra-Red Spectroscopy of the Hybrid Composite.