A simplified inverse method for interlayer stiffness characterization in layered composites using bending tests

Interfacial properties critically govern the mechanical behavior of layered composite materials. Building upon an analytical model for the bending behavior of multilayer beams under static loads, this study develops a simplified inverse function to determine interlayer stiffness directly from force-deflection curves. After establishing and solving a general theoretical framework for predicting interlayer slip and bending deflection in multilayer beams, we propose a practical method to extract interlayer stiffness from simple bending tests. This function enables rapid experimental characterization of interfacial properties for both two-layer beams and multilayered beams with identical layers. The approach is validated using simply supported beams under common loading conditions, providing engineers with a direct tool for interfacial property measurement, which is crucial for design and quality control. The accuracy of the proposed fitting function is inherently linked to the structural configuration and material properties of the system. Detailed error analysis indicates that the method maintains high precision within a broad operational window, providing a quantitative guideline for assessing its suitability across various multi-layer composite systems and interfacial stiffness ranges.