**3.1. Physical properties**

#### *3.1.1. Moisture content*

In Malaysia, government has classified bamboo as a non-timber forest and is next in importance to rattan. It has been used as food as well as traditional and commercial products since ages. There are more than 50 species of bamboo reported in Malaysia, an integral part of forestry, but it is also commonly spread outside forests including farmlands, riverbanks, roadsides and urban areas. Based on Fourth National Forest Inventory, bamboo occupies about 7% of the total forest area in Peninsular Malaysia (the total area of Peninsular

is given **Table 2**. The genera found in the country are *Bambusa*, *Dendrocalamus*, *Dinochloa*, *Gigantochloa*, *Racemobambos*, *Schizostachyum*, *Thyrsostachys*, *Chusqua*, *Phyllostachys* and *Yushania* [18]. Among all the species available, 14 Malaysian bamboo have been identified as commercial species [19] To maximize the exploration of bamboo industry in Malaysia, bamboo resources are needed to be maintained for industries particularly for joss sticks, chopsticks, basket-making, toothpicks and joss-papers. A systematic policies for the production bamboo is the need of present economic scenario of Malaysia, otherwise there will be depletion in demand of bamboo. The sustainable future of bamboo in Malaysia needs sustainable plantation of bamboo resources. In context to this, Malaysian government has disseminated trial of Malaysian commercial bamboos at few sites but not on the whole

The advancement of science and technology has led to new methods to make bamboo more durable and usable in terms of building materials. Bamboo has helped to uplift the rural economy through the establishment of industries and opportunities of employment. Bamboo based industries could be a sustainable option to ease the domestic demand and bring foreign currency by exporting newly designed products to international markets. The use of bamboo can be exploited to greater extent as it is cheap and found in abundance. The properties like rapid growth rate, short rotation age, excellent flexibility and high tensile strength has transformed bamboo into a wide variety of products ranging from domestic household products to industrial applications [21]. The uses in platforms (floors for transport vehicles such as trucks, busses and rail coaches), concrete molding boards (in building industries), flooring, furniture, pulp and handicraft works has provided new dimensions to bamboo utilization [22–24]. To elevate the utilization of bamboo, its fundamental physical and mechanical properties must be fully understood [25]. Researchers have proved that physical and mechanical properties of bamboo vary with respect to position in the bamboo. Lee et al. [26] found that the physical and mechanical properties of bamboo are affected by height location. Xian and Ye [27] studied the variation in mechanical properties of bamboo and established an equation for predicting the tensile modulus of elasticity from the radial position. Li [28] investigated the variation of the specific gravity and bending properties of bamboo and found that the specific gravity and bending

**3. Physico-mechanical properties of bamboo for commercial** 

properties decrease from the outer to inner layers of the bamboo culms.

). The list of bamboo species available in Malaysia with proper uses

Malaysia is 131,600 km2

150 Bamboo - Current and Future Prospects

Peninsular Malaysia.

**utilization**

Utilization of bamboo has now advanced from traditional to structural applications such as composites and advanced materials [29, 30]. The advancement in usage of bamboo needs further understanding of the material characteristics such as the physical properties. Terminology of a bamboo culm is illustrated in **Figure 1**. Physical properties of the node and internode positions of bamboo have been investigated by Tamizi [31] with small size specimens (strips of bamboo). The statistical data obtained showed a great variation according to the sources and position of the samples obtained from the bamboo. It was observed that moisture content was higher at the inner layer and reduced in the outer layer of the bamboo culm. Liese [32] claimed that different bamboo species showed different moisture values which can be attributed to difference in some inherent factors such as age, anatomical features and chemical composition. But in this case, the age factor is not involved since all samples were taken from 3 years bamboo culms. In this chapter, discussion is focusing on moisture content, specific gravity, shrinkage and fracture roughness.

The higher moisture content could be influenced by the anatomical structure of bamboo. The inner layer contains lower vascular bundles concentration which leads to higher moisture content as compared to outer layer as shown by Li [28]. This phenomenon is similar to nonwood plant, i.e., oil palm trunk which shown higher content of parenchyma in core part. Engler et al. [34] has reported the relation between moisture content and thermal use of one of the bamboo species. Authors stated that moisture content is one of the most relevant characteristics, which significantly influences the thermal use and efficiency. A comparison study with other species of wood has been done and authors revealed that the moisture content of bamboo was higher at an average of 136.9% and spreading widely. Related to the ages, the

**Figure 1.** Terminology of a bamboo culm [33].

young culms in general show significant higher moisture contents, compared to the older culms. It was also found that moisture content at the bottom of bamboo culm was higher as compared to the top.

dangerous and external force is exerted. Authors also explained that fracture toughness distribution with radius was in accordance to the values obtained for volume fraction of fibers, which means the proportionality depends directly to each other. The value of fracture toughness is increased at outer surface while moving towards outer surface. Moreover, it was found that fracture toughness of bamboo was higher than aluminum alloy and way better than other

Recent Advancement in Physico-Mechanical and Thermal Studies of Bamboo and Its Fibers

http://dx.doi.org/10.5772/intechopen.76475

153

Bamboo is known for its orthotropic character meaning, it has specific mechanical properties in x, y, z directions i.e., longitudinal, radial, and tangential. A pool of knowledge of the mechanical properties of bamboo helps in safe design as bamboo responses in the same manner as other building materials do. However, being a natural composite or biological material like wood, it is exposed to greater variability and complexity, due to various growing conditions as availability of moisture and soil conditions. Preparation of bamboo samples prior to

**Figure 2.** Preparation of bamboo samples for mechanical testing including tensile test, compression test and flexural

wood species.

test [9, 42].

**3.2. Mechanical properties**

mechanical testing is presented in **Figure 2**.

Studies by Kamthai [35] on different physical and mechanical properties of sweet bamboo found that the moisture content was 60.2%. On the other hand, Chen et al. [36] investigated the moisture content of modified bamboo strips. Alkaline treatment enhanced the moisture absorption, while esterification treatment, oxidation and silane treatments has reduced the moisture content. The results revealed that moisture content directly affects the other properties like interfacial shear strength.

#### *3.1.2. Specific gravity*

Different observation by various researchers has been put forward in order to get in-depth knowledge about the specific gravity of bamboo, for example a study on nodes and internodes of *Gigantochloa* has been carried out by Tamizi [31]. The specific gravity of samples from outer layer was higher compared to middle and inner layer for both internodes and nodes of all the *Gigantochloa* species. *G. levis* node recorded the highest specific gravity value among all of the species while *G. wrayi* node gave the least values. The bamboo density has a close relation with vascular and ground tissues percentages as proposed by Janssen [37] and Espiloy [38]. It was revealed that specific gravity of internode and node part of each bamboo species was marginally different. In contrast to report by Hamdan et al. [39], it was found that the nodes present along the culms height generally have higher density than the internodes due to lesser presence of parenchyma as well as lower moisture content and volumetric shrinkage.

#### *3.1.3. Shrinkage and fracture toughness*

Shrinkage is a characteristic property of bamboo which describes tendency of bamboo towards shrinkage under different conditions. Unlike wood, bamboo has a tendency to shrink from the very beginning of drying. The elimination of moisture in the cell wall that is hygroscopic or bound water leads to shrinkage as a result of the contraction of microfibrillar net in proportion to the amount of liquid evaporated [40]. Yu et al. [22] reported a study on shrinkage at different locations of Moso bamboo (*Phyllostachys pubescens*). The results revealed that both height and layer had a substantial effects on tangential and longitudinal shrinkages, but the interaction between height and layer had no significant effect on shrinkage. It was observed that tangential and longitudinal shrinkages appeared to be divided into two 3-layer zones (i.e., outer 3-layers consisting of layers 4, 5 and 6 and inner 3-layers consisting of layers 1, 2 and 3). It was found that tangential shrinkage was slightly greater at 4.0 m and longitudinal shrinkage was slightly greater at 1.3 m.

Amda and Untao [41] studies about the physical properties such as fracture toughness and tensile tests of bamboo culm and nodes. Authors reported that fracture toughness of bamboo culms depends on the volume fraction of fibers. It was observed that bamboo culm has a high value of fracture toughness for outer surface layer and decreases towards the inner surface, meaning that bamboo offers a greater fracture toughness on the outer surface where the most dangerous and external force is exerted. Authors also explained that fracture toughness distribution with radius was in accordance to the values obtained for volume fraction of fibers, which means the proportionality depends directly to each other. The value of fracture toughness is increased at outer surface while moving towards outer surface. Moreover, it was found that fracture toughness of bamboo was higher than aluminum alloy and way better than other wood species.
