Impact Performance Analysis of Encapsulated Structures Considering Nonlinearity of Material and Adhesive Interfaces

Encapsulation is an effective solution for protecting electronic devices in impact environments. However, current research overlooked the impact of adhesive interfaces on stress wave attenuation. Additionally, most studies on the buffering properties of encapsulating materials have focused on epoxy resin, while silicone rubber is also used in impact environments. Moreover, research on the buffering performance of silicone rubber encapsulating systems and comparative analyses of these two materials remain lacking. To address this limitation, this study presented a modeling approach based on the nonlinear viscoelastic behavior of encapsulated materials and the nonlinear characteristics of adhesive interfaces, and compared the buffering properties of epoxy resin and silicone rubber. Impact tests on epoxy resin and silicone rubber encapsulated structure specimens were conducted using a 100 mm diameter Split Hopkinson Pressure Bar (SHPB) apparatus under varying impact loads. Subsequently, static and dynamic compression tests on both materials were performed to obtain the nonlinear viscoelastic constitutive parameters of the Zhu-Wang-Tang (ZWT) model. Furthermore, Double Cantilever Beam (DCB) tests were carried out to acquire cohesive zone model parameters for the adhesive interfaces between the materials and outer shell. On this basis, the finite element models incorporating the nonlinear characteristics of the materials and interfaces were developed. The results showed that high-speed impacts induced interface failure during the testing process. The finite element model, which considered the nonlinear characteristics of the interfaces, showed good agreements with the experimental results, with acceleration errors not exceeding 10%. Compared to models neglecting the interface effects, the model with interfaces demonstrates reduced internal stress, confirming the impact of the adhesive interfaces on stress wave attenuation. Additionally, the study revealed that under low-speed impact loading, silicone rubber exhibited better buffering performance. However, under higher impact loads, adhesive interface failure occurred in the silicone rubber specimens, resulting in severe relative displacement and threat for inner down-lead. This study considered the nonlinear effects of materials and adhesive interfaces on the stress wave propagation in encapsulated structures, and compared the response of silicone rubber encapsulants under impact loading with that of epoxy resin. These findings offer a reference for future calculations and design of encapsulated structures.