Dynamic Elastic Modulus Variability in Anisotropic and Isotropic Materials: Comparison by Acoustic Emission

This study compared the variation of the dynamic elastic modulus (E) of three types of composite pipes made by the filament winding process and a steel alloy specimen, according to signal source changes. The specimens were produced with three different winding angles, i.e., ±50°, ±52.5°, and ±55°. The moduli were obtained through a known signal source and the angular variation, according to two sensors positioned over the specimen's surface. In a previous article, the variation in the velocity of acoustic emission (AE) signals, performed in the same type of pipes, was discussed based on the standards for glass fiber-reinforced epoxy (GFRE) filament wound specimens. This work took these preliminary findings to compare with the results found for steel alloy pipes (SAE 1020). This data was used with appropriate equations to determine the dynamic elastic moduli of each material. It was found that, even for small angular differences, the modulus changes position concerning the lamination angle. Thus, the lower the quality control, the lower the final product with composite materials. As expected, for isotropic materials such as steel alloys, the modulus remains constant along the angles, while for anisotropic ones, it is dependent on the principal directions of stress and strain, or on the other hand, dependent on the correlation between the angular wave velocity of the AE signals

Thermal Performance Investigation of Phase Change Materials in Concrete Blocks Masonry

Mortars containing phase change materials (PCMs) were tested to determine their applicability to the thermal control of buildings. One mini-wall prototype was coated with mortar without PCM, whereas the three other prototypes were coated with mortar added with 5%, 10%, and 15% PCM. All specimens were subjected to visual analysis, scanning electron microscopy coupled with energy dispersive X-ray analysis, and differential scanning calorimetry. Thermal analysis was conducted using K-type thermocouples under irradiation by 1000 W halogen lamps. Compared with the other samples, the sample containing 15% PCM required more water in the mixture to achieve a good consistency. Compared with the reference mortar containing 0% PCM, specimens containing 5%, 10%, and 15% PCM showed greater thermal delay. The results of this study reveal that the use of PCM in buildings might lead to significant energy savings