**2.2. Preparation of bamboo fiber specimens**

Bamboos possess the excellent wear properties, and in present paper, bamboo fibers are selected as the reinforced fibers. The fresh bamboo (*Phyllostachys heterocycla*) was first cut into pieces after removing the outer and inner surface materials. The bamboo pieces were

**Figure 1.** (a) A photograph showing section structure of bamboo stem shell; (b) schematic diagram showing fiber orientation with respect to the rubbing surface for the N and P (P<sup>S</sup> and PI ) specimens; and (c) the contract model of block-on-ring wear.

immersed into the softener solution (2%vol NH<sup>3</sup> ∙H2 O, 4%vol CON<sup>2</sup> H4 ) and boiled for 1 h at 100°C. Then these pieces were kept in NaOH (4%vol) solution for 30 min at 70°C. The pieces with softened fibers were broken mechanically and carded into fiber bundle. Finally, the fibers were dried in an oven at 60°C for 30 min. Every specimens of the bamboo fiber were 40 mm (for tensile test) or 3–5 mm in length and 1–3 mm in diameter. The diameters of bamboo fibers were measured and marked using a stereo microscope, which has a precision of 0.01 μm.

#### **2.3. Mechanical testing of the bamboo fiber**

The mechanical properties of the bamboo fibers were evaluated by tensile testing machine. The specimens of the bamboo fibers for tensile tests were 40 mm in length and 0.5 ± 0.05 mm in diameter. The tensile speed was 100 mm min−1 referring to the pulling speed of the tensile test machine during test. Ten tests were run for each bamboo fiber. The elongation at fracture, tensile strength, and elastic modulus of the fiber were recorded.

The raw components used for preparing the friction materials are listed in **Table 1**. Phenolic resin was used as adhesive; powders (such as Al<sup>2</sup> O3 , Sb2 S, graphite) were used as fillers. The mass fraction of the bamboo fibers added in the friction materials was 0, 3, 6, 9, and 12wt.%, respectively. All raw components were mixed using a blender for 10 min. The mixed materials were blocked with the dimension of 25 × 25 × 6 mm by compression molder equipment for 30 min at 165°C under pressure of 25 MPa, followed by heat treatment. The posttreating was segmented at 140°C for 1 h, 150°C for 3 h, and 180°C for 6 h continually as shown in **Figure 2**.

**2.4. Friction and wear tests**

**Figure 2.** Heating process for preparation of friction materials.

**Raw ingredients Bamboo fiber content (wt. %)**

Vermiculite powder

Foam iron powder

Al2

Sb2

The tribological property of friction materials was investigated using a constant speed friction tester with speed of 7.54 m s−1 under pressure of 0.98 MPa. The rotating disc (HT250 cast iron) was used as the counterpart. Friction and wear tests were implemented at the test temperature

**0 3 6 9 12**

Bamboo Wear and Its Application in Friction Material http://dx.doi.org/10.5772/intechopen.69893 91

5 4.85 4.72 4.59 4.46

11 10.68 10.38 10.09 9.82

Mineral fiber 17 16.5 16.04 15.6 15.18 Glass fiber 10 9.71 9.43 9.17 8.93 Phenolic resin 13 12.62 12.26 11.93 11.61

BaSO4 20 17.47 16.98 16.51 15.57 Petroleum coke 6 5.81 5.66 5.5 5.36 Graphite 8 7.76 7.55 7.34 7.14

O3 4 3.88 3.77 3.69 3.57

S3 3 2.91 2.83 2.75 2.68 Friction powder 1 0.97 0.94 0.92 0.89 Zinc stearate 2 1.94 1.89 1.83 1.79 Carbon black 3 1.9 1.1 1.08 1

**Table 1.** Relative contents of raw ingredients in the designed specimens of friction materials.

(*i*)) (under the

of 100, 150, 200, 250, 300, and 350°C, respectively [28]. The friction coefficients (*μI*


**Table 1.** Relative contents of raw ingredients in the designed specimens of friction materials.

**Figure 2.** Heating process for preparation of friction materials.

#### **2.4. Friction and wear tests**

immersed into the softener solution (2%vol NH<sup>3</sup>

orientation with respect to the rubbing surface for the N and P (P<sup>S</sup>

**2.3. Mechanical testing of the bamboo fiber**

resin was used as adhesive; powders (such as Al<sup>2</sup>

tensile strength, and elastic modulus of the fiber were recorded.

of 0.01 μm.

block-on-ring wear.

90 Bamboo - Current and Future Prospects

**Figure 2**.

∙H2

at 100°C. Then these pieces were kept in NaOH (4%vol) solution for 30 min at 70°C. The pieces with softened fibers were broken mechanically and carded into fiber bundle. Finally, the fibers were dried in an oven at 60°C for 30 min. Every specimens of the bamboo fiber were 40 mm (for tensile test) or 3–5 mm in length and 1–3 mm in diameter. The diameters of bamboo fibers were measured and marked using a stereo microscope, which has a precision

**Figure 1.** (a) A photograph showing section structure of bamboo stem shell; (b) schematic diagram showing fiber

The mechanical properties of the bamboo fibers were evaluated by tensile testing machine. The specimens of the bamboo fibers for tensile tests were 40 mm in length and 0.5 ± 0.05 mm in diameter. The tensile speed was 100 mm min−1 referring to the pulling speed of the tensile test machine during test. Ten tests were run for each bamboo fiber. The elongation at fracture,

The raw components used for preparing the friction materials are listed in **Table 1**. Phenolic

mass fraction of the bamboo fibers added in the friction materials was 0, 3, 6, 9, and 12wt.%, respectively. All raw components were mixed using a blender for 10 min. The mixed materials were blocked with the dimension of 25 × 25 × 6 mm by compression molder equipment for 30 min at 165°C under pressure of 25 MPa, followed by heat treatment. The posttreating was segmented at 140°C for 1 h, 150°C for 3 h, and 180°C for 6 h continually as shown in

O3 , Sb2

O, 4%vol CON<sup>2</sup>

and PI

H4

) specimens; and (c) the contract model of

S, graphite) were used as fillers. The

) and boiled for 1 h

The tribological property of friction materials was investigated using a constant speed friction tester with speed of 7.54 m s−1 under pressure of 0.98 MPa. The rotating disc (HT250 cast iron) was used as the counterpart. Friction and wear tests were implemented at the test temperature of 100, 150, 200, 250, 300, and 350°C, respectively [28]. The friction coefficients (*μI* (*i*)) (under the temperature-increasing condition) were automatically recoded. The friction coefficients (*μI* (*i*), *μD*(*i*)), and specific wear rate (*V*(*i*)) were obtained after 5000 rotations of the disc, where *i* = 1, 2, …, 6, corresponding to the temperature of 100, 150, 200, 250, 300, and 350°C, respectively. The volume wear rate of the friction materials was evaluated and calculated as follows:

$$V(t) = \frac{1}{2\pi R} \frac{A}{l^l} \frac{d\_1 - d\_2}{f\_w} \tag{1}$$

**3.3. Wear of PS-type bamboo specimens**

and (b) 0.84 m s−1.

**Figure 4.** Stereographs of wear track of the gray iron ring.

**Figure 5** illustrates typical morphologies of worn surfaces of P<sup>S</sup>

mainly three wear features: pits, microcracks, and grooves. Pits were produced because of adhesion between bamboo specimens and iron. Some materials from these pits were transferred onto the gray iron ring surface and the remainder became wear debris. Because of asperities of the gray iron ring surface, a tensile stress existed in the bamboo surface layer at the rear of the contacting asperity and a compressive stress at front. This stress distribution could easily lead to microcracking of the bamboo surface layer across the friction direction. Moreover, the adhesion force existing at the contacting interface strengthened this microcracking process. However, microcracks along the friction direction may be directly nucleated and propagated due to the tensile stress. As the normal load was raised, the influence of microploughing-microcutting on the wear of the bamboo specimens surface layer became stronger, and the microploughing-microcutting grooves on worn surfaces generated under 60–90 N load at 0.42 m s−1 velocity were shallow (**Figure 5a**–**d**). For this case, damage of cellulose fibers was not severe. However, when the normal load reached 120 N, particularly at 0.84 m s−1 velocity, the cellulose fiber walls had been cut, but leptodermous

**Figure 3.** The wear volume of the three types of bamboo specimens versus the normal load at sliding velocity of (a) 0.42 m s−1


Bamboo Wear and Its Application in Friction Material http://dx.doi.org/10.5772/intechopen.69893 93

where *n* is the number of revolutions of the disk (*n* = 5000), *R* is the distance between the center of the rotating disk and friction material specimen (*R* = 0.15 m), *A* is the contact surface between the specimen and the disk (*A* = 625 m2 ), *d*<sup>1</sup> is the average thickness of specimen before test (mm), *d*2 is the average thickness of specimen after test (mm), and *f <sup>m</sup>* is mean value of the force.

Worn morphologies of the specimens after tests were observed using the SEM (JEOL JSM-5600) at a voltage of 25 kV.
