Layer- and position-specific characterization of the fracture behavior of the small intestine.

In this study, we investigate the mechanical elastic and failure behavior of porcine small intestinal walls (SIWs). In order to comprehensively examine the small intestine (SI) mechanically, all three sections of the SI, the duodenum, jejunum, and ileum, are examined. Single-edge notched tensile (SENT) experiments are performed on the entire wall structure as well as on the individual layers (serosal, muscular, and mucosal layer). In addition, the experiments are carried out in different loading directions (0°, 45°, and 90°) with respect to the tissue orientation. Overall, the elastic mechanical behavior for all regions and all layers is characterized by a typical, exponential, nonlinear behavior in combination with a partially distinct anisotropic behavior, featuring an broad elastic region λmax of 1.1 to 1.7, with corresponding stresses Pe of approximately 2 to 330 kPa. Failure behavior, as characterized by the critical energy release rate GC, exhibits obvious layer dependence. The average GC value of the mucosal layer is approximately four times higher than that of the muscular layer (1-2 N/mm), while the serosal layer has the highest values, reaching 6-10 N/mm. Additionally, the fracture behavior of the combined muscular and serosal layers of the duodenum, jejunum and ileum can be explained by classical laminate theory. However, the results of the entire wall indicate complicated interlayer behavior between the mucosal and muscular layers. Furthermore, the crack-tip tracking method and local deformation obtained from optical measurements help achieve a clearer understanding of crack initiation and propagation. These results provide a comprehensive dataset about the failure characteristics of the SI that can be used as input or for validating failure models in the future. Statement of Significance: This study is the first to report on experiments involving the failure of the porcine small intestine. The study investigates the region-, orientation-, and layer-specific mechanical properties of the small intestine in order to gain insight into its behavior under intact and failed conditions. Although layer-specific experimental studies are essential for a comprehensive understanding of small intestine function, they have received little attention to date. Additionally, this study examines crack propagation direction during uniaxial tensile tests. The study provides a unique database that improves our understanding of small intestine failure behavior and serves as a basis for corresponding models.