Driven by efficiency, structural designs often incorporate composite materials displaying higher stiffness and strength to weight ratios, compared to metallic materials. With applications on the automotive, aviation and space industries, composite materials have contributed to increase performance, reduce emissions and lower environmental impact. For commercial aviation, composites not only reduce fuel burn rates and operational costs associated but also enable the integration of embedded sensors and actuators, leading the way for smart structural designs. Piezoelectric ceramics, such as led zirconate titanate (PZT), are commonly employed as sensors and actuators due to their high piezoelectric coupling. However, their high stiffness and brittleness are unsought characteristics for flexible structures lightweight components. For that reason, polymer-based piezoelectric materials display great significance. This study showcases a numerical and experimental application of thermoformed electret as a piezoelectric sensor, embedded on a laminated thermoplastic carbon fibre composite laminated beam. Additionally, a Macro Fibre Composite (MFC) sensor and accelerometers were used to generate frequency response functions for the specimen under different configurations. The specimen was subjected to both free and forced vibration experimental analysis, performed by an impact hammer and a modal exciter, respectively. A concentrated mass was added to the composite beam to induce changes in its dynamic behaviour, simulating damage conditions. For each scenario, the resonant frequency shift and amplitudes were compared between the transducers to assess the effectiveness of the thermoformed electret as a piezoelectric sensor for damage detection in composite structures. Finally, a numerical model was implemented, using Abaqus/Implicit finite element code. Modal and harmonic analysis have been carried out, in the presence of piezoelectric sensors. Predicted FRFs were compared to experimental data, assisting on the understanding of the experimental curves. Damage indices for the different conditions were generated, for experimental and numerical result databases, showing an increase in damage indices over increasing additional mass. Therefore, this study highlights the potential of electret-based sensors for smart structural applications that require tough, lightweight and flexible components, offering an innovative approach to SHM in composite materials.