Study on Mechanical Characteristics of Bonding Interface of Smooth Aluminum Composite Sheath in HV XLPE Cables

Abstract

In recent years, high voltage (HV) cross-linked polyethylene (XLPE) cable with corrugated aluminum sheath has suffered frequently from ablation failures of water-blocking buffer layer in China, which causes wide attention to both the failure mechanism study of the corrugated aluminum sheathed cables and the product development of smooth aluminum composite sheathed cables. One of the key technologies for smooth aluminum composite sheathed cables is to firmly bond the aluminum sheath and the outer serving by hot melt adhesive to ensure the bending resistance. Therefore, the study on the mechanical characteristics of bonding interface is of great significance. In this paper, a three-dimensional simulation model of four-point bending test of a cable with smooth aluminum composite sheath was established, where the cohesive zone model was adopted to simulate the mechanical behavior of the adhesive layer. Then, the stress state and cumulative damage of bonding interface under the specified bending radius were studied by changing the modulus of the adhesive. It is shown that when the sheath is bent, the maximum values of circumferential shear stress are always far higher than the normal stress and axial shear stress components in the adhesive layer. According to the damage analysis, the circumferential shear stress dominates the damage of bonding interface. Thus, when selecting the hot melt adhesive, in addition to the requirements of IEC and IEEE standards, more importantly, its shear strength also should be evaluated by tensile lap-shear strength test.