## 5 Numerical and Experimental Results  
The selected joint configurations were investigated and numerically simulated with the introduced material models based on the LS-DYNA procedure previously described, under a static pin-loaded tension test for experimental/numerical comparison and validation. The predicted peak loads of the composite specimens are listed in Tables 8 and 9 and corresponding force-displacement curve are shown in Figures 8 and 9. Moreover, the fracture morphology numerically reproduced for both the proposed composite samples is reported in Figures 10 and 11. The intralaminar composite material models available in current numerical solvers are typically defined with the application of two macro sections: the undamaged elastic region and the damaged region. The passage from one region to the adjacent one is typically controlled by strength-based failure criteria specifically associated with the selected material formulation. The damaged region related to MAT58 card is generally described with the introduction of two characteristic values: SLIM\({}_{XX}\) and ERODS. SLIM\({}_{XX}\) is related to the post-failure residual strength for each orthotropic material direction, while a single ERODS value is connected to the FE-element erosion during fracture initiation/propagation during numerical simulation. The MAT58 erosion parameter was calibrated at an absolute value of about 0.3, following the full tensorial formulation available in LS-DYNA (ERODS < 0 option). The same calibrated value was adopted for the advanced joint configuration and for the simple one. The calibrated value and its related numerical results were compared and discussed against the experimental evidence reported in [PERSON] et al. [2]. The characteristic force-displacement curve of the advanced composite joint is reported in Figure 8. There are two different curves: the blue curve represents the tensile load evolution in the function of the pin displacement; the red curve describes the contact load exchanged between the external rigid steel surface of the cylinder and the internal surface of the sandwich hole with respect to the global pin displacement. Both curves can be divided into three characteristic zones: (a) the first elastic part that describes the non-linear evolution of the loading inside the composite structural joint; (b) the second part of the curve that represents the initiation of the failure; (c) the third part that shows the fracture evolution process inside the entire specimen. For the advanced joint case, the curve is characterized by two distinct peaks in the failure zone. The first peak represents the initiation of failure inside the composite joint; instead, the second strength limit defines the failure of the entire sample and the beginning of the global fracture process. The load difference between the global failure point (blue curve) and the maximum internal contact force (red curve) is equally distributed around the hole by the presence of the steel circular plate, characteristic of the advanced composite joint. The fracture surfaces reported in Figure 10 show that the principal failure mode for the advanced composite joint is a pure complete tensile load. It shows a satisfactory correspondence with the experimental evidence, as indicated in Figure 5A, demonstrating the validity of the presented methodology in simulating such failure conditions. The characteristic force-displacement curve of the simple composite joint is reported in Figure 9. Both curves are comparable, and no remarkable differences are revealed. The  
Figure 11: The numerical fracture surface of simple composite joint model. (**A**) Fracture axonometry. (**B,C**) Fracture surface. Figure 10: The numerical fracture surface of advanced composite joint model. (**A**) Fracture axonometry. (**B,C**) Fracture surface.