Abstract:

Lamb waves， with the characteristics of long propagation distance， low cost， and good sensitivity to various damages， offer significant potential for studying the visually undetectable damage caused by low-velocity impact in carbon fiber reinforced polymer （CFRP） battery box. Although relative acoustic nonlinear parameters （RANP） have been shown to be effective in quantifying the degree of impact damage to composite materials， the mechanism by which damage affects them has not been explored. In this study， a combination of experimental and simulation method is used to study for the first time the effect of different impact damages on the propagation of Lamb waves in CFRP battery boxes. To this end， a geometric model of the battery box structure is first established. Then， impact tests are carried out on CFRP， and a simulation model for damage monitoring of CFRP battery boxes is built. Finally， the effect of delamination， matrix compression damage， and fiber tensile damage on the damage assessment parameters of CFRP battery boxes is studied. The results indicate that the established CFRP simulation model is reliable in calculation accuracy， with the RANP parameter being sensitive to the damage area of each mode， though not to the damage position in the thickness direction. Damage causes the Lamb wave to generate new frequency components during propagation. The calculation of the RANP parameter can thus analyze the degree of damage. When the degree of damage is low， the size of the RANP parameter depends more on the interlayer shedding damage， and once the damage exceeds a certain threshold， the size of the RANP parameter depends more on the intralayer damage such as the fiber damage of the CFRP. The research results have important guiding value for the structural-functional integrated design of automobile collision safety components.

Key words: battery box, lightweight, composites, impact damage, Lamb waves