Comparative study on bending performances of 3D-printed monolithic and adhesively bonded sandwich structures with various auxetic cores: An innovative production approach

The cores of sandwich structures are typically produced monolithically using lightweight materials and specific geometries. In recent years, the advancements in additive manufacturing have enabled the design and production of novel sandwich core configurations with auxetic behavior and high energy absorption capability. In this study, an innovative production approach, namely adhesively bonded sandwich structures with auxetic cores, was proposed to ensure significant manufacturing advantages for industrial applications. Each part of the sandwich core structures with auxetic core configurations was printed separately and then bonded using an epoxy-based adhesive. To evaluate the mechanical performance of the proposed bonded sandwich structures, three-point and four-point bending tests with DIC (Digital Image Correlation) analyses were conducted. The bending test results of adhesively bonded sandwich structures were compared with those of monolithic sandwich structures and the effectiveness of the proposed innovative production method was evaluated. Re-entrant, star-shaped, and V-shaped auxetic core configurations were compared in terms of the bending performances of the adhesively bonded and monolithic sandwich structures. Monolithic and adhesively bonded sandwich structures showed similar bending behavior as far as load-carrying capacity, deformation stages, and crashworthiness performance are concerned based on three and four-point bending tests. Hence, the proposed innovative production approach can be applied to sandwich structures to enhance their repairability and support sustainable manufacturing.