Integrated Measurement Technique To Measure Curing Process-dependent Mechanical And Thermal Properties Of Polymeric Materials Using Fiber Bragg Grating Sensors

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An innovative technique based on a fiber Bragg grating (FBG) sensor is proposed to measure the critical mechanical and thermal properties of polymeric materials. The properties include (1) chemical shrinkage evolution during curing, (2) modulus evolution during curing, (3) glass transition temperature (4) coefficient of thermal expansion (CTE), and (5) visco-elastic properties. Optimum specimen configurations are proposed from the theoretical analysis. Then an efficient numerical procedure is established to determine the material properties from the measured Bragg wavelength (BW) shift. The technique is implemented with various polymeric materials. The measured quantities are verified through a self-consistency test as well as the existing testing methods such as a warpage measurement of a bi-material strip, and a TMA measurement. The evolution properties obtained at a curing temperature are extended further by combining them with the conventional isothermal DSC experiments. Based on the existing theories, the evolution properties can be predicted at any temperatures.

The proposed technique greatly enhances the capability to characterize the mechanical properties and behavior of polymeric materials. Since the specimen preparation is very straightforward, the proposed method can be routinely practiced and the measurement can be completely automated. It will provide a much-needed tool for rapid but accurate assessment of polymer properties, which, in turn, will enhance the accuracy of predictive modeling for design optimization of a microelectronics product at the conceptual stage of product development.