**2.1. Bamboo wear experiments**

fibers and the tensile strength across fibers. Bamboo has higher specific tensile strength than glass-reinforced plastic (GRP) and mild steel with chopped strand mat and woven roving, and comparable specific modulus with mild steel and GRP. Godbole and Lakkad [2] studied the influences of water absorption on mechanical performances of bamboo. The tensile strength, compressive strength, tensile modulus, and interlaminar shear of bamboo specimen reduced after soaking or boiling in distilled water. Li et al. [3] designed a double-fold spiral bionic composite model imitating the characteristic structure of bamboo. The tensile strength of carbon fiber reinforced tin composites processed by the bionic model was higher by 40% than

Yakou and Sakamoto [4] investigated abrasive performances of bamboo specimen with carborundum paper as the counterface. They indicated that the abrasive wear rate of the inner layer was higher than that of the outside surface layer for bamboo specimens of normal- and parallel-oriented cellulose fibers relative to the friction surface. Tong et al. [5] evaluated the abrasive wear properties of bamboo specimens by using quartz sand particles as abrasive material. The results showed that the abrasion resistance of bamboo specimen was decided by the relative orientation of the cellulose fibers with respect to the friction surface and by the size of abrasive particles. The abrasive wear rate increased with the increase of size of abrasive particles. Specimens with the normal orientation of cellulose fibers to the friction surface presented better abrasion resistance than those with the parallel orientation; the inner layer had lower abrasion resistance than the outside layer; and the cellulose fibers had better resistance than the matrix tissue. The dry sliding wear behavior of bamboo was studied in order

On the other hand, friction materials are the key parts of automobiles brake systems, and many studies have been investigated to improve brake properties in order to adapt the people's requirement for security and rapid development of automobile [6]. To acquire comfortable and dependable brake properties of the automobiles, braking friction materials usually contain more than 10 different components. The components are normally classified as reinforced fibers, binders, property modifiers, and fillers. Each component plays an important role for brake performance under different braking conditions. Many studies investigated the effect of different components on brake performance [7, 8]. A related review on frontiers of fundamental tribological research emphasized the concern over the environmental protec-

Asbestos fibers, which have been widely used in braking friction materials, are harmful to human health and environment; they have been forbidden to be used for manufacturing friction materi-

glass fibers, aramid fibers, copper fibers, and their hybrid fibers [10–12] have been studied and selected. Moreover, many study results showed that these fibers have excellent properties for friction materials; however, there are many shortcomings (such as weak combination strength, high cost, and high noise) to be resolved when these fibers are applied in friction materials.

Many researches have focused on the utilization of biological fibers with the function of protecting environment, such as betel nut fibers [13], cotton fibers [14, 15], jute fibers [16–18], kenaf and ramie fibers [19], sisal and flax fibers [20–22], and sugarcane fibers [23]. More and

O3

fibers, carbon fibers,

that of unidirectional carbon fiber reinforced ones.

88 Bamboo - Current and Future Prospects

to obtain some useful information for designs of friction materials.

tion, for instance, biodegradability in the development of tribo-materials [9].

als. Therefore, substitutes of the asbestos fibers, such as steel fibers, Al<sup>2</sup>

Bamboo specimens of dimensions 14 × 10 × 8 mm were cut from the air-dry bamboo (*P. pubescens*). Three types of specimens were prepared. The friction surface was normal to the cellulose fiber orientation for the N-type, and parallel to both the cellulose fiber orientation and the outside surface of bamboo stem for the PS -type and P<sup>I</sup> -type. The initial rubbing surface was 0.5 mm beneath the natural surface for the P<sup>S</sup> -type and 8.5 mm for P<sup>I</sup> -type. **Figure 1** shows the fiber orientation with the sliding direction.

Sliding wear properties of bamboo specimens were studied on a block-on-ring machine. The counterfaces were made of a gray iron (HT200) and had a diameter of 40 mm. The normal loads were from 30 to 120 N and the sliding velocity was set as 0.42 and 0.84 m s−1, respectively; the total sliding distance was about 504 m and the surrounding temperature was about 23°C during all these tests. Worn morphologies of bamboo specimens and gray iron rings and wear debris were examined by SEM and stereoscopy.
