The Interfacial Testing System (ITS) system measures the interfacial shear strength (IFSS) of the bond between a reinforcing fiber and its surrounding matrix. It permits quantitative comparisons between fiber-matrix systems and different surface treatments.

The stage of an optical microscope is equipped with X-Y-Z axis stepper motors to permit precise movement and positioning, and an electronic balance. A diamond stylus presses on an single fiber, and the balance measures the load required to induce a debond of the fiber from the matrix. The IFSS is then calculated using an algorithm based on a FEM model.