The process for obtaining fibers from oil palm petioles (the Elaeis guineensis) is illustrated in the flowchart of Figure 1.

The petioles were collected in the: Nanga Eboko, a locality in the centre region of Cameroon from a young/five-year-old palm oil trees (the Elaeis guineensis) that produced for the first time. The risk of alteration of the physical and mechanical characteristics by the chemicals, the difficulty of obtaining enzymes and

the monitoring of the reactions led us to choose the traditional extraction method (Retting with water) which presents as a main disadvantage the decomposition time of the cellulose. Figure 2 and Figure 3 briefly show the process to obtain fibers.

Our samples are made by varying the rate of reinforcement. Table 1 gives the proportions in the formulations adopted.

The proportions of reinforcement, polyester in composite are determined by Equation (1), Equation (2) and Equation (3) respectively:

P r = ρ r * v r   or   v r = v c * t (1)

⇒ P r = ρ r * v c * t (2)

Similarly

P m = ρ m * v c * ( 1 − t ) (3)

With: ρ r , ρ m the respective densities of the reinforcements (1125 Kg/m³) and of the matrix 1140 Kg/m³) [8] [9]; v r , v c (m³): respectively the reinforcement volume and composite volume; P r (Kg): mass of reinforcement, P m (Kg): mass of the matrix and t: reinforcement rate.

Table 2 presents the different formulations of the constituents of our material.

Our composite was made with a hardener rate of 1% of the mass of the matrix

[10] [11] [12] for each reinforcement rate.

The test pieces produced according to the recommendations of standard BSI 2782 150 × 10 × 10 mm parallelepipedic block, of regular section [9]. The procedure is in the flowchart given in Figure 4. The samples obtained after demolding are presented in Figure 5.

The density of our composite material is given by Equation (4);

ρ a = P r v r (4)

With: ρ a (Kg/m³): apparent density; P r (Kg): mass of reinforcement; v r (m³): the reinforcement volume.

For each formulation, the experimental density of the composite is obtained by averaging Equation (5) for each test piece [13] [14] [15].

ρ exp = P e Δ v − m p ρ p (5)

With: ρ exp (Kg/m³): experimental density; P e (Kg): mass of test piece; m p (Kg): paraffin mass; ρ p (Kg/m³): paraffin density; Δ v (m³): variation of water volume.

The density of the composite material can also be obtained analytically by using Equation (6).

ρ a n = ρ r V r + ρ m V m (6)

The densities of the reinforcements are ρ r = 1125 Kg/m³, the density of the matrix is ρ m = 1140 Kg/m³; V (m³): volume fraction of reinforcements; V m (m³): volume fraction of matrix; ρ a n (Kg/m³): analytical density.

Table 3 presents the average values of the densities obtained after the experiments on the test pieces of each of the formulations.

Following Table 3, the average values of each of the densities obtained for each formulation. This comparative study allowed us to plot the histograms of Figures 6-8.

The density of the polyester/fiber composite material of oil palm petioles ranges from 928.66 Kg/m³ to 935 Kg/m³. Furthermore, increasing the volumic fraction of the reinforcement (fibers of oil palm petioles) has no influence on the density. The analytical density independently of the rate of reinforcement in oil palm petiole fibers is greater than the other densities. This may be linked to the fact that the analytical calculation does not take into account the shape of the

test pieces or the distribution of the fibers.

The water absorption rate of this material is given by Equation (7) [16].

% H = M i − M f M i × 100 (7)

With: % H absorption rate; M i (Kg): initial mass; M f (Kg): final mass.

The water absorption rate of each formulations values obtained with equation (7) are plotted in Figure 9.

We see that formulation A has the highest water absorption rate (6%) it is observed in Formulation B and Formulation C that increasing the fibers proportion reduces the water absorption rate.

In addition, the coordinates of the inflection points for each of the formulations are:

· Formulation A: A (45; 6%);

· Formulation B: B (90; 5%);

· Formulation C: C (120; 5%);

· Formulation O: O (120; 4%).

This test was carried out with a PERRIER 14570 200 KN press

E = F L 0 S 0 Δ L (8)

where E (GPa): is the Young’s modulus ( E O : Young modulus of formulation O; E_A: Young modulus of formulation A E_B: Young modulus of formulation B E_C: Young modulus of formulation C; F: load; L₀: initial length; S₀: initial section of sample; ΔL: length variation.

The comparative study of the average values of the Young’s moduli obtained during the compression test allowed us to plot the histogram of Figure 10.

We notice that:

· E O < E A < E B < E C ; where E O , E A , E B   and   E C stand for the Young’s modulus for the formulations 0, A, B and C respectively.

· The ratio between E A and E O is of the order of 1.025 at a reinforcement rate of 10%, the Young’s modulus is closed to the one without reinforcement.

· Between E B and E O we have 1.25 and the ratio between E C and E O is 2.475.

Consequently, the addition of oil palm petiole fibers almost doubles the tensile/compression characteristics of polyester.

Figure 11 presents a comparative study of the Young’s modules of composite

materials with vegetable fiber reinforcement and polyester matrix with our composite material (oil palm petiole/polyester).

It appears that:

The composite material (Oil palm petiole/Polyester) has a Young’s modulus higher than that of the Sisal/Polyester, Kénaf/Polyester [13], Bamboo/Polyester [15] composite materials; while those of the Linen/Polyester and Jute/Polyester [14] composite materials belong to the interval [3.33; 8.035] (GPa).

The 150 × 10 × 8 mm test pieces were subjected to bending three with a CBR press (CONTROL T1004). The stresses, strains, breaking stresses were deduced from Equation (9), Equation (10) and Equation (11) respectively [17] [18] [19].

σ = 3 F b 2 l e 2 (9)

ε = 6 f e b 2 (10)

σ r = 3 b F R u p 2 l e 2 (11)

With: σ (N/m²⁾: stress; F: load (N); l: distance between supports (mm); b: width of test piece (mm); e: thickness of test piece (mm); f : deformed (mm); F R u p (N): force measured at break; ε: distortion; σ r : breaking stress (N/m²).

The mean values of the transverse modules obtained during the three bending test for each formulation allowed us to make a comparative study on it. Which is presented in the histogram of Figure 12.

From the analysis of the histogram in Figure 12, the following observations emerge:

· E C < E O < E B < E A ;

· The ratio between E C and E O is around 0.801; the Young’s transverse modulus of the formulation C is lower than the one of the formulation O;

· Between E B and E O we have a ratio of 0.991; from this report, we note that for the formulation B, the material has a greater flexural strength than formulation O.

· In addition between E A and E O 1.034; it appears that the formulation A has a better resistance to bending than formulation O. At more than 10% reinforcement rate, a reduction of the transverse module in bending is observed.

The average values of the three-point bending rupture stresses of the test pieces of each of the formulations allowed us to plot the histogram of Figure 13.

It emerges that, the breaking stress increases proportionally with the rate of fibers reinforcement.