Mechanical Properties of Side-Pressed Laminated Bamboo Lumber Based on Ultrasonic NDT Technology

The aim of this study was to investigate the relationship model between the ultrasonic propagation velocity and the mechanical property of side-pressed laminated bamboo lumber (SPLBL), as well as to provides a theoretical basis for non-destructive ultrasound testing on the mechanical properties of SPLBL. Taking SPLBL as the research object and using a microsecond ultrasound measuring instrument, the ultrasonic propagation velocity in SPLBL and small specimens was obtained through the ultrasonic propagation measurement test, and a contour distribution map of the ultrasonic propagation speed of SPLBL was drawn. After that, the flexural elastic modulus and flexural strength of the small specimens were obtained through the three-point bending test, and regression analysis was performed on the relationship between ultrasonic propagation velocity and flexural modulus and flexural strength. There were significant differences in the contour distribution of ultrasonic wave velocity obtained for each SPLBL sample, indicating that there may be differences in the gluing effect, resulting in certain differences in the mechanical properties. The higher the velocity of ultrasonic wave propagation, the better the gluing effect or mechanical properties of SPLBL. A good correlation was found between ultrasonic wave velocity and the flexural elastic modulus and flexural strength of small specimens (coefficient of determination R2 = 0.52 and 0.46, respectively). This shows that ultrasonic wave velocity can reasonably predict and evaluate the flexural elastic modulus and flexural strength of small specimens. A good correlation was also found between the dynamic elastic modulus and flexural elastic modulus of small specimens, with an R2 for both of 0.55. This shows that it is also possible to reasonably predict and evaluate the flexural elastic modulus by measuring the dynamic elastic modulus of small specimens. Non-destructive ultrasonic testing technology is a potentially effective means to reasonably predict and evaluate the mechanical properties of SPLBL.