Meso-level heterogeneous distribution of interface mechanical parameters has been investigated. Numerical models for twin fibers pull-out test have been created by using finite element method. Influence of interface strength on damage pattern and mechanical properties have been studied on twin fibers pull-out test specimens. By applying load with displacement control

load-displacement curves

AE accumulative curves and interface shear stress distribution curves of twin fibers and concrete matrix test specimen have been plotted. The damage pattern and AE pattern of pull-out test specimen changed along with the interface strength. As interface strength is low

both peak load and toughness increase with interface strength

and both peak load and toughness dont change obviously with high interface strength.