Abstract: Aiming at the detection of debonding defects in the bonding structure between aluminum pipe and foam layer bonding material, the detection technology research and debonding defect type analysis were carried out. Based on the structural characteristics, artificial defect samples were made, and C-scan imaging detection was performed using air coupled ultrasonic penetration method. The abnormal areas detected by scanning were analyzed using microfocal CT, and the types and causes of debonding defects were summarized. The experimental results showed that the air-coupled ultrasonic penetration method can effectively detect debonding defects in materials. The causes of debonding defects included incomplete filling of the adhesive layer due to non fitting of the surface and formation of a gap layer inside the adhensive layer resulted by incomplete discharge of the air.