composite modulus increases when the reinforced particle modulus is below 150 GPa in a parabolic trend whereas it reduces when the difference between the matrix and reinforcement is high..
Interesting query! A possible reason maybe the stiffness gradient that rises abruptly inside the inclusions. This leads to an excessive stress concentration in the interfacial region which may be the weakest local zones leading to a decrease in overall stiffness.
Dear Sumeru Nayak Thank you so much for the answer. I would like to know if there is any method to map the stress concentration or quantitatively find out the excessive stress concentration in order to justify this answer.
Definitely K. Deenadayalan ! Continuum methods use kinetic relations for damage propagation. However, a meshfree peridynamic approach is more robust since it permits autonomous damage initiation and propagation. Peridynamics captures the stress concentration around areas with stiffness gradients. This is possible owing to the state based approach followed in peridynamics where the force and deformation states mapping an undeformed configuration to a deformed configuration are related by a constitutive relation. The constitutive relation for a particle becomes zero as the failure criterion is met thereby shutting off interactions with surrounding particles. Such stress concentrations can be simulated when the interacting forces are determined only by material properties and not by externally enforced kinetic relations (as is followed in CZM etc). And Peridynamics allows it right on!