Time-multiplexed laser self-mixing sensor for measurement of multiple material elastic moduli

The mechanical properties of materials hold significant importance in fundamental research, material, mechanical and civil engineering. These properties are often characterized by some elastic parameters, e.g., Young’s modulus, shear modulus and Poisson’s ratio. Self-mixing interferometry (SMI) is a unique non-destructive sensing technology that requires minimal components. In this work, we have developed a time-multiplexed fiber-coupled laser SMI sensor in conjunction with impulse excitation technique to simultaneously measure Young modulus, shear modulus and Poisson’s ratio of materials. Two specimens made of brass and aluminum 6061 were assessed to validate the feasibility of the designed sensor. The measured values of Young's modulus (101.2 GPa for brass and 69.5 GPa for aluminum 6061), shear modulus (36.3 GPa for brass and 29.5 GPa for aluminum 6061), and Poisson's ratio (0.39 for brass and 0.34 for aluminum 6061) aligned with values reported in existing literature and industry standards. The standard deviations for these three measured parameters were 0.4 GPa, 0.05 GPa, and 0.06 for brass and 0.12 GPa, 0.02 GPa, and 0.003 for aluminum 6061, respectively. The proposed sensor offers several advantages, including a simple structure, high measurement precision, and ease of operation, which contributes to a precise tool for assessing material mechanical properties, benefiting both fundamental research and practical engineering applications. It also provides a promising direction for the development of a serial multi-object measurement solution based on SMI using a single laser source.