This study investigates residual strains and stress behavior in intrinsic hybrid materials using non-destructive methods such as Fiber Bragg Grating (FBG) sensors and X-Ray Diffraction. The specimens, which included a hybrid structure consisting of external metal sheets and an internal unidirectional Fiber-Reinforced Polymer (FRP), were subjected to mechanical and thermal tests. Computational models, in line with Classical Laminate Theory and existing literature, guided the hybrid specimen's development. A custom device was also designed to consistently apply preload forces to the integrated optical sensor, enabling the measurement of compressive stresses within the FRP. Interlaminar Shear Strength (ILSS) tests were conducted and revealed good adhesion between the steel and FRP interface, evidenced by an average shear strength of approximately 17 MPa. These results were further validated by XRD measurements, which confirmed stress-free conditions and maximal residual stresses in the materials. Despite these advancements, there were discrepancies between the manually set preload forces and the actual forces measured by the FBG sensors, highlighting the need for further optimization. Future research is directed towards comprehensive computational simulations to accurately predict mechanical properties and behavioral changes under varying conditions. These simulations will serve as a foundation for optimizing manufacturing processes and predicting material lifetime.