*3.2.2. Static bending (modulus of rupture and modulus of elasticity)*

Modulus of rupture is the maximum flexural stress sustained by the specimen during bending test or in other words can be defined as the maximum stress in bending that can be withstood by the outer fibers of a specimen before rupturing. Tamizi [31] reported the comparative results of modulus of rupture with reference to different position of different species of bamboo. Both dry and green sample exhibited different values of modulus of rupture. The order was (*G. scortechinii > G. wrayi > G. levis > G. brang*). It was reported that air dry samples showed better modulus of rupture (30–40%) compared to green samples. This can be ascribed to the fact that bamboo behaves similar to wood whereby the mechanical properties increases with decrease in moisture content. The data presented that results at inner surface (130.71 MPa) direction were higher compared to the outer surface direction (111.07 MPa). The difference in MOR showed that the outer layer has less than 5% stronger from the middle layer, and the middle layer has less than 5% stronger than inner layer. Difference in MOR, the outer layer strength was less than 10% higher than the inner layer. The value for MOR (green) at the node is relatively higher than the internode. This is reflected due to the density of the node are higher compared to the internode as node contain lesser presence of parenchyma. This is similar to the earliest report mentioning that the strength properties in bending of bamboo are greatly correlated with specific gravity [53].

Biswas et al. [54] reported utilized wastes from two species of bamboo viz. *B. balcooa* and *B. vulgaris*. The waste was a type of shavings acquired during planning operation of bamboo splits for production of rectangular strips of constant thickness. This raw material was utilized for the formation of particle board. The modulus of rupture (MOR) values of boards made from planer waste was 15.7 N/mm2 and 17.7 N/mm2 for *B. balcooa and B. vulgaris,* respectively. Varied results were obtained and particle geometry had significant influence on modulus of rupture in both species. The bamboo planer waste had no definite pattern of particle geometry with light and curly shape with good tendency to fold. Authors revealed that based on modulus of elasticity a significant effect was observed on the particle board geometry.

Based on modulus of elasticity Li et al. [55] published an interested report that bamboo has high modulus of elasticity as compared to human bones. The average modulus of elasticity across the thickness of bamboo culm can be 18 GPa, equivalent to that of human cortical bone. Ghavami et al. [56] studied the modulus of elasticity of bamboo with some degree of precision. Authors stated that fiber distribution in bamboo follows an organized pattern with an increased amount of fibers on the outer surface of the culm. While proving how this variation occurs, the basic equations from the bamboo approach can be changed in order to model the mechanical behavior of bamboo. Yu et al. [22] revealed that modulus of elasticity of bamboo varied greatly from the inner layer outwards. Modulus of elasticity at 1.3 m was less than those at 4.0 m from the base. This report suggests that layer had important effect on the modulus of elasticity. It was observed that modulus of elasticity decreased as the layer decreased from the outer (layer 6) to the inner (layer 1) layers, but the difference between layers 3 and 4, and between layers 1 and 2 were not considerably less.
