Dear Monishita Deb, not only fiber content but there are other additional deciding parameters, such as the fibers' dimensions and orientation, tight interface and so on. When the elastic modulus increases, it means that the matrix is becoming progressively resisting deformation, and this in turn means that the major stress input is well supported and transmitted by the reinforcing fibers. Please have a look at the following documents. My Regards

https://doi.org/10.1016/j.compositesa.2005.10.006

https://doi.org/10.1016/j.compositesb.2013.09.020

Article Effect of fiber volume fraction on the mechanical properties...

Article A review on the tensile properties of natural fiber reinforc...

After achivement of some critical value of fiber content the decrement of modulus is really possible due to reducing of adhesion between filler and matrix.

The modulus of elasticity (also known as Young's modulus) is a measure of the stiffness of a material and is defined as the ratio of the applied stress to the resulting strain within the elastic limit of the material. In general, the modulus of elasticity of a natural fiber reinforced hybrid polymer composite will increase with increasing volume percentage of fibers.

This is because the fibers act as reinforcement within the composite material, providing additional stiffness and strength. As the volume percentage of fibers increases, the composite material becomes more stiff and less deformable, leading to an increase in the modulus of elasticity.

However, it is important to note that the effect of fiber volume fraction on the modulus of elasticity may not be linear and may depend on the specific properties of the fibers and matrix material, as well as the processing conditions used to manufacture the composite. Additionally, the modulus of elasticity may be influenced by other factors, such as the orientation of the fibers within the composite and the degree of bonding between the fibers and matrix.