Sandwich structures are widely used in aeronautics both for primary and secondary structures such as landing gear doors, flaps or floors. Multi-cores materials sandwich structures presents many advantages. By adding layers with another materials that the core one, extra properties can be obtained as heat or impact protection. Manufacturing quality must be controlled and therefore bonding needs to be inspected. In this paper bonding defects between multi-layers of sandwich specimen are inspected through Non Destructive Tests. Due to its large use in industry, ultrasonic phase array is used to detect manufacturing bonding defects. Three different type of multi-cores materials specimen are investigated. Results show that due to the high PVC foam porosity, defects cannot be detected both between composite skins and foam and between foam and core material.