Modelling the correlation between damage state and electrical resistance in multidirectional laminates with cracks and delamination

Structural Health Monitoring (SHM) strategies based on Electrical Health Monitoring (EHM) have gained increasing attention as a cost-effective and lightweight solution for detecting damage in fibre-reinforced polymer composites. However, existing analytical models correlating the electrical resistance change to the damage scenario are generally limited to simple lay-ups or to single damage mechanisms, and a comprehensive formulation capable of handling multiple cracks and delamination in generic multidirectional laminates is still lacking. In this work, an extended analytical model is developed to predict the electrical resistance increase induced by off-axis cracks and delamination in any laminate configuration. The formulation combines realistic assumptions in the representation of damage, enabling the simultaneous treatment of multiple damaged plies within a unified and computationally efficient framework. The accuracy of the model is thoroughly assessed through extensive comparisons with high-fidelity Finite Element simulations, showing prediction errors below 2.2% across a wide range of stacking sequences and damage scenarios. Thanks to its generality and negligible computational cost, the proposed model provides an effective and practical tool for SHM applications, enabling reliable damage detection in composite structures through simple electrical measurements.