MODULUS OF ELASTICITY

Modulus Of Elasticity



1. Introduction

Extensive experimental and analytical studies have been undertaken during the last couple of decades to establish the fundamental mechanical properties of thin cement composite [1] and [2]. The application of finite element method for analyzing thin cement composite has been investigated by Prakhya and Adidam [3] and Hossain and Hasegawa [4]. They have reported the modeling technique and load-deflection behavior of thin cement composites containing square and chicken meshes. Rao investigated the load deformation data in the form of stress-strain relationships of thin cement composites reinforced with chicken meshes under uniaxial compression [5]. He concluded that the stress-strain relationships under compression possess non-linearity at the initial and final loadings with the linearity at mid-section. The properties of impact damage of thin cement composites were obtained by the lateral single impact tests undertaken by Kobayashi et al. [6]. Later, bending behavior of thin cement composites has been studied by Ghavami et al. [7] and Naaman [8].

2. Research significance

A new design equation for flexural modulus of elasticity of thin cement composites reinforced with different types of meshes is proposed in this paper. A flexural section of thin cement composite is theoretically analyzed, and an experimental investigation is carried out for validation of the proposed equation. The paper also depicts the required mesh factor (MF) for the sake of ease in the design process when a flexural composite is reinforced with different meshes. It is anticipated that this study dealing with the development of flexural modulus of elasticity of thin cement composites will be useful for the construction of composite structures.

3. Typical equations for composite modulus of elasticity

The modulus of elasticity (Ecom.) of a composite member consisting of different materials under uniaxial loading is usually expressed as follows(1)Ecom.=Em+Rr(Er-Em)where Rr is the effective reinforcement, Em is the modulus of elasticity of mortar and Er is the modulus of elasticity of reinforcement.

The effective reinforcement (Rr) given in Eq. (1) is defined as the ratio of the area of mesh wires in the longitudinal direction to the total area of specimen in the same direction. Here, the effective reinforcement (Rr) for cement composite element containing square mesh (Fig. 1) in the longitudinal direction is derived as:(2)where d is the diameter of wire, NL is the number of layers, t is the thickness of cement composite and D is the center-to-center distance of mesh wires. The numerical value 25 is a conversion factor for expressing the Rr in percentage.

Fig. 1.

Various types of mesh (all dimensions in mm).

For cement composite reinforced with chicken mesh, the effective reinforcement (Rr) can be expressed as:(3)where ? is the angle of the mesh wires to the panel axis and has a value of 59.53° for the mesh used in the present research work.

4. Derivation of composite modulus of elasticity in flexure

For a flexural section of cement composite containing four mortar layers and two mesh layers as shown in Fig. 3, the equation of equilibrium in the elastic range can be written as follows:(4)where t is the thickness ...