Shear mechanical properties of the core structure of biomimetic fully integrated honeycomb plates

Abstract

In the present study, the shear failure mode and mechanical properties of the core structure of biomimetic fully integrated honeycomb plates with sealing edges were investigated experimentally and through the finite element method. The findings are as follows: (1) the failure mode of the sealing edges and honeycomb walls perpendicular to the shear direction is mainly debonding between the fiber and matrix, whereas fiber breakage, debonding between the fiber and matrix and exfoliation of the resin matrix occur in the sealing edges parallel to the shear direction. Meanwhile, the reasonableness and feasibility of the double shear testing apparatus designed in this study were verified, thus confirming the results of research are reliable and valid. (2) Shear failure of the core structure of fully integrated honeycomb plates is mainly fiber debonding appearing in the middle surface of the core structure, which is a failure of the material interface. Stripping failure in the joint interface of the core layer and upper and lower plates does not occur, which indicates that the biological structure possesses excellent integral mechanical properties. (3) The sealing edges parallel to the shear direction and the honeycomb walls that are oriented 30 degrees to the shear direction are the first to fail, followed by the sealing edges and honeycomb walls perpendicular to the shear direction, which is consistent with the microscopic failure phenomenon observed in both directions. To prevent failure at the material interface, the fully integrated honeycomb plates manufactured in this experiment require further improvements. Thus, countermeasures are proposed, such as pre-treating the fiber surface. These findings will specify future research directions to perfect fully integrated honeycomb plates and improve the shear mechanical properties of core structures.

Effect of the length of basalt fibers on the shear mechanical properties of the core structure of biomimetic fully integrated honeycomb plates

“…Thus, the fractures of these structures are more severe than those of structures perpendicular to the shear direction, and there remain many fibers (rectangular box and circle in Figures 2(a) and 3(a), respectively) and pits where the fibers are stripped (Figures 2(b) and 3(b), thin red arrows) from the honeycomb walls or sealing edges perpendicular to the shear direction. That is, the failure mode of the sealing edges and honeycomb walls perpendicular to the shear direction is mainly debonding between the fiber and the matrix [25,28]. The above phenomena are the same as those reported in the previous papers [25,28].…”

“…Thus, the shear properties of SBFRPs with L f values of 3-9 mm were obtained. Additionally, a finite element analysis and an experimental study [25] on the shear mechanical properties of an FIHP core structure with an L f of 6 mm was conducted, and the results confirmed its excellent overall mechanical properties. For FIHPs, the three-dimensional structure of the FIHP core is more complicated than that of a solid single-layered plate, and the shear mechanical properties of the FIHP core structure will be influenced by two main factors: the core structure and L f .…”

“…Figures 2 and 3 show the shear fracture morphologies of FIHP core structures with L f values of 3 and 9 mm, respectively. By comparing this information with the fracture morphology of the sample with an L f of 6 mm [25], the characteristics of the structures can be described below.…”

“…This result occurred because the shear load is allocated on a structure based on the shear stiffness of the various parts of the structure. Specifically, because the shear stiffness of the core layer parallel to the shear direction is considerably larger than that of the core layer perpendicular to the shear direction, the shear stress of the core layer parallel to the shear direction would also be larger [25]. Thus, the fractures of these structures are more severe than those of structures perpendicular to the shear direction, and there remain many fibers (rectangular box and circle in Figures 2(a) and 3(a), respectively) and pits where the fibers are stripped (Figures 2(b) and 3(b), thin red arrows) from the honeycomb walls or sealing edges perpendicular to the shear direction.…”

“…That is, the failure mode of the sealing edges and honeycomb walls perpendicular to the shear direction is mainly debonding between the fiber and the matrix [25,28]. The above phenomena are the same as those reported in the previous papers [25,28]. However, the pulled-out condition of the fractured fibers occurring with different L f values and the distribution of the fibers and the resin indicate that the samples with L f values of 3 and 9 mm are significantly different from those with an L f of 6 mm.…”