2. Materials and Methods
2.1. Elaboration of the Composite Material
2.1.1. Process for Obtaining Short and Long Fibers from Papaya
The fibers of the papaya tree trunks are obtained in a long process as shown in Figure 1.
We used the male papaya trees after the second flowering. The papaya tree trunks were cut into 40 cm long pieces, then cut longitudinally. The elements thus acquired were soaked in water without additive for a period of one month as shown in Figure 2. The extraction of our papaya trunk fibers is done by retting as shown in Figures 2(c) and Figure 3 .
The folds thus obtained were immersed in hot water (70˚C) mixed with a molar concentration sodium hydroxide for two days then we extract the fibers. Figure 3 shows the process for obtaining papaya fibers.
Figure 1. Process for obtaining fibers from papaya tree trunks [Author].
(a) (b) (c)
Figure 2. (a) Trunk of papaya tree cut; (b) Trunk of papaya cut longitude; (c) Soaked papaya trunk [author].
(a) (b) (c) (d)
Figure 3. (a) Honeycomb structure of the papaya tree; (b) Papaya fibers after extraction; (c) Long papaya fibers; (d) Short papaya fibers [author].
2.1.2. Process for Obtaining Particles from the Seeds of the Garlic
The cores obtained are illustrated by Figure 4.
The kernels of the pili fruit are crushed in order to extract the fines. The empty cores are grounded and sieved with 800 μm and 1.60 mm sieves (Figure 5) to obtain the corresponding particles (Figure 6)  .
The particle sizes obtained are as follows ≤ 800 µm (fine particles) and ≤1.60 mm (large particles) as shown in Figure 6.
2.1.3. Implementation of Samples
The samples with reinforced rate of 30% are used because it the composite exhibits poor characteristics . Table 1 gives the dimensions and the proportions of the elements used the polyester resin is mixed with 1% hardener .
2.1.4. Preparation of Test Pieces/Samples
The test pieces shaped according to standard BSI 2782 are parallelepipedic block of 150 × 10 × 10 (mm). The main steps in shaping our test pieces are given in Figure 7.
The samples obtained and classified by type of reinforcement are shown in Figure 8.
3. Results and Discussion
3.1. Physical Characterization
3.1.1. The Density
To determine the density of our composite material, we calculate the apparent density for each of the samples using Equation (1).
with: : apparent density; : mass of reinforcement; : the reinforcement volume.
For each formulation, the experimental density of the composite is obtained by averaging Equation (2) for each test piece .
Figure 4. Process for obtaining particles from the kernels of garlic [Authors].
(a) (b) (c)
Figure 5. (a) Standardized sieve; (b) vibrating machine; (c) Screening [Authors].
Figure 6. (a) Fine particles (≤800 µm); (b) Large particles (≤1.60 mm) [Authors].
Figure 7. Sample molding steps [Authors].
(a) (b) (c) (d) (e)
Figure 8. (a) Pure polyester; (b) Long fibers; (c) Short fibers; (d) Large particles; (e) Fine particles [Authors].
Table 1. Dimensions and proportions of the elements.
with: : experimental density; : mass of test piece; : paraffin mass; : paraffin density; variation of water volume.
Finally, the analytical density of the composite material (in Kg/m3) of each sample for each formulation was determined using Equation (3)
The densities of the reinforcements are Kg/m3, the density of the matrix is Kg/m3; : volume fraction of reinforcements; : volume fraction of matrix; : analytical density (Table 2, Figures 9-11).
Table 2. Densities.
Figure 9. Apparent density as a function of reinforcement type.
Figure 10. Experimental density as a function of reinforcement type.
Figure 11. Analytic density as a function of reinforcement type.
From these histograms, it appears that the density of the papaya fiber-reinforced composites is comprised/varies between [1047.5; 1062 Kg/m3] the addition of papaya trunk fiber to the polyester reduces the density of the latter and for composites with particle reinforcement of the kernels of fruit of the wing is between [1240.5; 1346 Kg/m3] the addition of black fruit kernel particles in the polyester increases the density value of the latter. In addition, the length of the fibers (long or short) and the particle size of the kernels of fruit of the pili have a negligible influence of the order of on the density (of the order of 0.02% to 0.05% for the composites with reinforcement of fibers of trunk of papaya and of the order of 0.08% to 0.09%).
3.1.2. The Rate of Water Absorption
The amounts of water absorbed by our composite materials reinforced with papaya trunk fibers and particles of the seeds of the garlic shown by Figure 12 are determined by Equation (4).
The water absorption curves of the various composites reinforced with papaya trunk fibers (long and short) and particles of the seeds of the winged fruit (large and fine) are similar to room temperature, the one given by Fick’s law of diffusion in a binary medium . The following observations are made:
• For composites with particle reinforcement of the kernels of garlic, the particle size does not influence the rate of water infiltration.
• In the case of composites with a reinforcement of trunk fibers from papaya trees, the longer the fibers, the less water the material takes up.
• Composites with short fiber reinforcement take more water than composites with particles of garlic kernels which absorb more than those with long fiber reinforcement.
Figure 12. Water absorption rate according to the type of reinforcement.
3.2. Mechanical Characterization
The mechanical properties are obtained from the three-point compression and bending tests of different composite samples.
3.2.1. Compression Test
The samples for each formulation are submitted to compression test carried out with a PERRIER 14570 200 KN. Equation (5) is used to determine the Young Modulus/the elasticity modulus    .
The comparative study of the average values of the Young’s moduli obtained during the compression test helped us to plot the histogram of Figure 13.
From Figure 13 we see that:
• The Young’s modulus of long fiber reinforced composites is greater than that of short fibers.
• The length of the fibers influences the mechanical behavior of the composites, composites with long fiber reinforcements have better behavior in the elastic range compared to those with short fiber reinforcement.
• The Young’s modulus of fine particle reinforcement composites is greater than that of medium black fruit core particles. The mechanical characteristics of composites with reinforcement of black fruit kernel particles fluctuate with the particle size distribution (of the interstices in the material).
• Reducing the particle size of the particles improves their behavior in the elastic range.
3.2.2. Bending Test
The three points bending test is carried out using a CBR press (CONTROLS T1004) and Equation (6) and Equation (7) enable us to determine the modulus
Figure 13. Young’s modulus according to the type of reinforcement.
of elasticity in bending (MEF) and modulus of resistance to bending (MRF) respectively    .
with: L: distance between supports; b: width of the test piece; e: thickness of the test piece; α: slope of the straight line determined by the plot of the force-deformation curve in the elastic domain; : force measured at break.
The results are presented in Table 3.
The comparative study of flexural elasticity modules (FEM) and flexural resistance modules (FRM) of fiber and particle reinforced composites is given in Figure 14 and Figure 15 respectively   .
These histograms reveal that:
· The elastic modulus of flexion does not vary with the size or the type of reinforcement because the difference between the different values of modules is minimal;
· The multidirectional nature of composites with short fiber reinforcement gives it a modulus of flexural strength significantly higher than the composites one with long fiber reinforcement (report 1.27);
· The resistance modulus of composites with fine particle reinforcement (≤800 µm) is 2.27 times higher than the composites with medium particle reinforcement (≥1.6 mm). This difference may be caused by the particle size and the presence of a gap in large-particle composites which is not completely homogenized with the resin.
The aim of this paper was to determine some physical and mechanical properties of composites reinforced with papaya fiber. These fibers are made of short, long and shell of kernels of winged fruits.
The tests carried out show that:
• The long fibers improve the characteristics in traction/compression of the composites while short fibers improve the flexural strength of composites.
Figure 14. Flexural modulus according to the type of reinforcement.
Figure 15. Flexural strength module depending on the type of reinforcement.
Table 3. Values of MEF and MRF according to the type of reinforcement.
• The addition of fibers decreases the density of the final composite material and the rate of water absorption increases with the length of the fibers.
• The particle size (fine particles ≤ 800 µm and large particles ≥ 1.6 mm) of composite materials reinforced with the cores of winged fruits has no influence on the Young’s Modulus and therefore no effect on the mechanical behaviour (regarding tension and compression)
• The size (fineness) of the particles of the kernels of the fruit of the wing improves the bending resistance of the composite materials and increases have a density of 19% relative to the density of the polyester.
• The rate of water absorption is not influenced by the size of the particles.
• The laboratory of Civil Engineering of the NASEY.
• The Local Materials Promotion Authority (MIPROMALO).
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