The Effect of Reinforce Powder Size on The Properties of Pineapple Leaf Fiber – Bagasse Sandwich Composites

The growth of ship production in Indonesia encourages the shipping industry to utilize the composite material in order to be more efficient. Natural fibre-reinforced composite (NFRC) is one option that should be considered for use safer than fiberglass. The usage of fiberglass could trigger several health problems. Sugarcane and pineapples are one of the most common agricultural commodities, yet their waste has not been treated optimally. This research is going to analyse the effect of reinforcement powder size on its bending strength in pineapple leaf fibre – bagasse reinforced sandwich composites. Pineapple leaf fibre use as skin reinforcement whereas bagasse use as core reinforcement. Sandwich composites were reviewed for their bending strength on specimens on reinforcement powder size 40, 60, and 100 mesh. The composite was made using the hand lay-up method with skin composition is 20:80% and core composition is 25:75%, each layer of skin and core have 2 mm thickness. The highest bending strength for sandwich composite is 52,72±0,85 MPa as a result of the experiment using 100 mesh of reinforcement powder. The bending strength of sandwich composite increase as finer particle powder use for the reinforcement. The highest bending strength in this study can be used as bulkhead material for the interior of the ship’s accommodation space based on SNI 01-4449-2006.


Introduction
The growth of ship production in Indonesia has increased continuously to realize Indonesia as the world's maritime nexus.This growth encourages every shipbuilding industry to consider the efficiency of the materials used.The application of material efficiency could provide benefits for the industry.Besides being able to reduce production costs, they can still have good-quality materials.
The use of composites as a substitute for metal or wood is one form of material efficiency that can be applied.One type of composite material commonly used in the interior is a sandwich composite.The sandwich composite component is composed of three or more materials consisting of a flat composite as a skin and a core in the middle [1].sandwich composite in the interior of the ship that can be applied as a ceiling, or as partition wall material in the accommodation room.As a material in 2 galuhanitasari@student.ppns.ac.id 1265 (2023) 012019 IOP Publishing doi:10.1088/1755-1315/1265/1/012019 2 the interior of the ship, sandwich composites must be able to be good insulators.Thus, the selection of plates as part of the composite skin should be avoided.
Nowadays, fiberglass is still used as a sandwich composite material by the shipbuilding industry.Fiberglass is a reinforcing fiber that is generally used for Fiber Reinforced Plastic (FRP).There are still many uses of fiberglass in the shipping industry because its use is considered more effective, and the price is more affordable.Whereas Fiberglass has a weakness that can endanger human health, which can cause irritation to the skin and can trigger asbestosis.Asbestosis is a chronic lung disease caused by inhalation of asbestos fibers [2].Asbestosis can occur because the characteristics of fiberglass are thin and light, so this material allows it to be inhaled by humans.
Natural fiber composites (NFC) may offer a solution to the aforementioned issues.NFC reinforcement fiber is more environmentally friendly because the fiber is taken from agricultural waste.That way NFC can reduce health risks that can arise due to the use of fiberglass.Natural fibers play an important role in developing biodegradable composites to solve current ecological and environmental problems [3].Pineapple and sugarcane are abundant agricultural commodities in Indonesia.However, agricultural waste from the two so far has not been handled optimally.This can harm the environment.Even though pineapple and sugarcane fibers have high cellulose, both are considered good enough to be used as reinforcement in composites.
The principal subject in this research is the skin and core which are composed of fiber and matrix.Pineapple leaf fiber and a polyester matrix are used in the skin part, and bagasse and an epoxy matrix are used in the core.The size of the reinforcement powder used is one of the numerous procedures utilized to manufacture sandwich composites with the best possible bending strength.The mechanical characteristics of the composite are influenced by the fiber particle size [4].Therefore, the author was interested in researching how powder size affected bending strength.The results of this study are expected to increase knowledge about composite engineering technology.

Methodology 2.1 Specimen Mold Making
The specimen mold is made with acrylic material.Autodesk Inventor is used to designing patterns on specimen mold.The dimensions of the mold refer to ASTM C393-00as shown in Figure 1 below

Figure 1. Specimen Mold
Acrylic material with a thickness of 6 mm is used for cutting following the mold pattern.In addition, acrylic material with a thickness of 5 mm was prepared to be cut without a pattern as the mold's base and cover.A laser cutting machine is used to cut acrylic material.After the cutting is finished, the mold is assembled and attached to the mold hole, and the mold is ready to use.

Fiber Preparation
To obtain the required size of reinforcement powder, pineapple leaf fiber and bagasse fiber that will be used as reinforcement in sandwich composites are processed.

A. Pineapple leaf fiber preparation
To eliminate clinging contaminants, pineapple leaves collected from agricultural waste are washed with clean water.Next, the pineapple leaves are extracted using a decorticator machine.Iron brush is carried out on the extracted pineapple leaf fiber to remove the leaf flesh that is still attached, then the pineapple leaf fiber is washedagain with clean water.Pineapple leaf fiber is sun-dried for 7 days.The pineapple leaf fiber is then cut into small piecesto ease grinding.A blender is used to grind the pineapple leaf fiber.The fiber powder is next sieved using a wire mesh according to the size of the powder, namely 40 mesh, 60 mesh, and 100 mesh.

B. Bagasse fiber preparation
Bagasse is soaked in clean water for 24 hours to eliminate contaminants and lower sugar content.The bagasse is sun-dried for a week.An iron brush is used to remove the dregs clingingto the sugarcane fiber.The bagasse fiber is cut into small pieces to ease the grinding process.The bagasse fiber is then processed in a blender to the required powder size.The mesh size determines the grinding time; the greater the mesh size, thelonger the grinding time.Sifting is performed on ground fibers using a wire mesh sieve based on the size of the powder as the variables in this study, namely 40 mesh, 60 mesh, and 100 mesh.

Density Testing
To determine the density of reinforcing powder, density testing is performed.The density will then be used to calculate the amount of reinforcing powder and resin required to manufacture sandwich composites.The density ofpineapple leaf fiber powder and bagasse was determined using the pycnometer technique in this study.The mass ofthe empty pycnometer; the pycnometer mass and powder; and the pycnometer mass, powder, and oil were all weighed using a digital balance.The density is then calculated using the following equation based on the data obtained: Where : m = mass (g) v = volume (cm 3 )  = density (g/cm 3 )

Sandwich Composite Manufacturing
In this research, sandwich composites were made using the hand lay-up method, which is a manual composite production procedure.The steps of the sandwich composite manufacturing process are as follows: Determine the fiber and matrix compositions to be used.The percentage ratio of reinforcement powder and resinin the skin composite sandwich is 20:80%, whereas it is 25:75% in the core.Put the powdered pineapple leaf fiber on the mold next tocreate the initial section of the skin (layer 1).The mold being utilized has a 6 mm thickness.1% polyester resin and catalyst are combined to create the matrix in layer 1.After pouring the polyester matrix into the mold, it is flattened with a spatula.After layer 1 has dried halfway, bagasse powder is added on top of it.In addition, the core's (layer 2) matrix is created by combining epoxy resin and hardener in a 2:1 ratio.Next, the layer 2 epoxy matrix is poured into the mold (above layer 1), and the matrix is flattened using a spatula.After layer 2 has dried halfway, layer 2 is topped with thepowdered pineapple leaf fiber.1% polyester resin and catalyst are combined to create the matrix on layer 3 (the second skin).After being poured into the mold (above layer 2) and flattened with a spatula, the polyester matrix is then sealed and secured.After being dried, the specimen is taken out of the mold and finished with sandpaper.The specimen is also put through a bending test.

Bending Test
The ASTM C393-00 testing standard is utilized for bending testing on the Universal Testing Machine HT-2402.Three times each version was used.The bending test was conducted in the FMIPA Laboratory at Jember StateUniversity's Faculty of Mathematics and Natural Sciences.Based on SNI 01-4449-2006, the study's best sandwich composite bending test results indicated the composite's suitability as a replacement material for the bulkhead wall of the ship's internal living quarters.The following equation canbe used to determine the specimen's bending strength. (2)

Statistical Test
Statistical tests were then run on the bending strengthdata.Because just one independent variable has an impact onthe response variable, this approach is used.The residuals forthis method must be homogeneous and normaly distributed.As a result, tests for homogeneity and normalcy were run on the residuals.The One-Way ANOVA approach was used to conduct the statistical analysis using the Minitab19 program.The used significance level is 0.05.The One-Way ANOVA method's wording of the hypothesis is as follows: H 0 = variations in the size of the reinforcing powder didn't affect the results of the bending test.H 1 = variations in the size of the reinforcing powder didn't affect the results of the bending test.

The Result of Reinforcing Powder's Density
The density of bagasse powder and powder made from pineapple leaves was tested three times each.
Following the results received from the density test using the pycnometer method, the density is calculated using Equation 1.The density of the reinforcement powder tested was then calculated using the average density value obtained from the three repetitions.The findings of determining the density value of pineapple leaf fiber powder as reinforcement on the skin composite sandwich are shown in The results of the calculation of the density value of bagasse powder as reinforcement in the sandwich composite core can be seen in Table 2 as follows: According to Tables 1 and 2 above, the density of pineapple leaf fibre powder is 1.36 g/mL and that of bagasse powder is 1.01 g/mL.The presence of void caught in the oil during the test led to the varying density readings for each repetition.These voids can be reduced by agitation vertically and a good stirring method, namely the stirring method number 8.

The Needs for Resin and Reinforcement Powder
Volume fraction calculations are used to determine whether powder and resin reinforcement is required when creating composite materials.For each component of the sandwich composite's skin and core, the amount of reinforcing powder and resin required was estimated in this study.Equations 2 and 3 are used to compute the demand for reinforcing powder and resin in the skin portion, whereas Equations are used to determine the need for reinforcing powder and resin in the core.Table 3 provides the findings on the requirement for reinforcing powder and resin in sandwich composites.

Bending Tests Results
This study used a three-point bending test as its bending test.Reinforcing powder with a size of 40 mesh, 60 mesh, and 100 mesh are a few examples of the different sizes available.In order to determine how the material will bend under various circumstances, a partition wall for an accommodation room is tested.When a material is subjected to certain situations, like colliding with other objects or being used by people as a backrest, the external load that results from those circumstances may cause the material to deflect.
The units used to express bending strength are N/mm 2 or MPa.The bending test was carried out for 3 repetitions.The maximum load data that the sandwich composite can tolerate is determined by the results of the bending test.The value of each specimen's bending strength is then determined from the data using Equation Bending strength levels and standard deviation values tend to vary for each repeat based on the outcomes of the tests that have been performed.This is because the production process for sandwich composites uses a hand lay-up technique.The use of a manual lay-up technique can result in composite manufacturing procedures that are not flawless, such as uneven resin pouring and reinforcing powder application or varying resin levelling times that could result in air bubbles (voids).Additionally, the sandwich composite becomes increasingly void-filled as a result of the composite manufacturing process taking place in a hot, humid environment, which lowers its mechanical strength.Air bubbles entrapped in the matrix, known as voids, prevent it from filling the mold's empty space, resulting in a gap in the composite [5].The graph in Figure 2 shows the average value of the bending strength of sandwich composites on the size of the powder, where the sizes of the reinforcement powders varied were 40 mesh, 60 mesh, and 100 mesh.Sandwich composites with a size of 40 mesh reinforcing powder obtained an average bending strength of 44.66±2.45MPa.Furthermore, the average value of the bending strength of sandwich composites with variations in the size of the 60-mesh reinforcement powder increased by 12.96% to 50.45±0.39MPa.Then, the average value of the bending strength of the sandwich composite with the size of the 100-mesh reinforcing powder increased from the previous variation of 6.88% to 52.72±0.85MPa.Based on the Paired-T Test that has been carried out, the increase in bending strength in each variation is stated to be significant with a P-Value of less than 0.05.

Relationship Between Reinforcement Powder Size and Bending Strength
Through the graph, it can be seen that the bending strength of the sandwich composite increases with the size of the mesh used.In this case, the larger the mesh size used, the smaller the hole in the sieve will be.The finer the size of the reinforcing powder, the greater the contact area between the reinforcing powder.Thus, the reinforcing powder and matrix have a better bond.A good bond between the reinforcing powder and the matrix can minimize the occurrence of voids in the composite, where these voids can reduce the strength of the sandwich composite because the load received by the composite is also transmitted to the voids.
The finer the size of the reinforcing powder also makes it easier for the powder to be evenly distributed in the Mold.If the reinforcement powder is well distributed, it can minimize the occurrence of agglomeration, namely agglomeration of the reinforcing powder in certain parts, where this agglomeration can reduce the ability of the composite to distribute the received load.The highest bending strength value was achieved by sandwich composites with a size of 100 mesh reinforcement powder, which was 52.72±0.85MPa.This value meets the material requirements as high-density fibreboard with treatment based on SNI 01-4449-2006 which is 45 MPa.
Thus, the composite can be used as an alternative material for the walls of the ship's interior accommodation room, which is not included in the main structure of the ship.Based on the three macro-o b s e r v a t i o n s above, it can be seen that the fracture mode that occurs in all specimens is a brittle fracture.This indicates that the entire specimen still has a large number of voids so that the load received by the composite is also distributed through the existing voids and makes it easier to fracture.In addition, there was no bond failure in all of these specimens, which means that the skin and core in all specimens had a good bond.

Macro Observations
Agglomeration occurs in specimens with a powder size of 40-mesh as shown in Figure 2. Agglomeration can occur due to the large size of the 40-mesh powder, so the reinforcement powder is difficult to distribute evenly.In addition, the 40-mesh specimen has voids that are scattered on the fracture cross-section so that it can be seen on macro-observations.The presence of voids indicates the incomplete bond between the reinforcing powder and the matrix.Then at the fracture cross-section of the 60-mesh specimen, as shown in Figure 3, there is no visible agglomeration.The voids that occur in the 60-mesh specimen are also not as large as in the 40-mesh specimen.This is due to the smaller 60 mesh powder size so that it can be more easily distributed evenly.
That way, the resin can bind the reinforcing powder better.Furthermore, in the cross-section of the 100-mesh specimen fracture, as shown in Figure 4, voids are still found.The voids contained in the 100-mesh specimen are minimal compared to other specimens.This happens because the size of 100 mesh powder has the smallest size so the reinforcing powder and resin in this specimen have the best bond compared to other specimens.Thus, the 100-mesh specimen has the best morphology compared to other specimens, but the manufacturing process for sandwich composites needs to be improved.

Statistical Test
The statistical test in this study was carried out using the One-Way ANOVA method.Before the analysis using the One-Way ANOVA method, the residuals must be normally distributed and homogeneous.Therefore, the normality test and homogeneity test were carried out before being analysed through One-Way ANOVA.The significance value used in this series of statistical tests is 0.05.
The results of the normality test using the Kolmogorov-Smirnov method and the homogeneity test showed a P-Value> 0.05 so the residuals were declared to be normally distributed and homogeneous.Then, through the One-Way ANOVA method, the P-Value value is 0.002, where this value is less than 0.05.Thus, it can be stated that the variation in the size of the reinforcing powder affects the bending strength of the material.

Conclusion
The conclusion obtained in this study is that the finer particle size of the reinforcement powder results in an increase in bending strength.The highest bending strength of 52.72±0.85MPa was achieved by sandwich composite with 100 mesh reinforcing powder.The highest bending strength in this study can be used as bulkhead material for the interior of the ship's accommodation space based on SNI 01 -4449 -2006. .

Figure 2 .
Figure 2. Relationship Between Reinforcement Powder Size and Bending Strength

Table 1 .
Pineapple Leaf Powder Density Result

Table 3 .
The Needs for Resin and Reinforcement Powder