Abstract In this research, the hybrid structure consisting of porous honeycomb structure with positive Poisson's ratio and the re-entrant structure with negative Poisson's ratio is studied under off-axis compression. The lateral expansion and sliding are calculated for different ratios of the base stractures. The geometric models of the structures are created in Inventor software and analyzed in Abaqus software with finite element method. The effect of the design parameters of each base structure of the hybrid structure on their elastic modulus and Poisson's ratio are investigated. The simulation results are compared with analytical formulations. According to the results, the maximum of the lateral expansion for hybrid structure is more than the entirely auxetic or the entirely honeycomb structures, and it does not necessarily occur in an equal ratio of the two base structures. The lateral expansion increases until the ratio of about 0.4 and then decreases. Furthermore, the maximum stress in the hybrid structure is lower than the entirely auxetic or the entirely honeycomb structures. The location of the neutral axis is also calculated in different ratios of the base structures. According to the results, the location of the neutral axis is not necessarily in the middle of the structure's width, even for entirely honeycomb or entirely re-entrant structures. This is due to the presence of compressive loading beside bending loading. A number of factors, for example, the different elastic modulus of base structures, the variable moment of inertia of the cross-section, and as a result, the change in the ratio of the strain caused by the compression loading to the strain caused by the bending loading, are involved in determining the location of the neutral axis. Finally, the effect of the mechanical properties of the base structures on the lateral expansion of the hybrid structure is eva‎luated, and according to the results, the lateral expansion of the hybrid structure increases with decreasing the elastic modulus and increasing the amount of Poisson's ratio of the base structures. Using these hybrid structures in the Hip implant stem, the structure expands from both sides under off-axis loading, and as a result, the implant is prevented from loosening at its connection with the bone. Also, by changing the ratio of the auxetic and honeycomb structures and their geometrical parameters, it is possible to adjust the amount of the lateral expansion and sliding in different parts of the hybrid structure in order to improve the implant fixation and the bone growth.

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