The dissemination of additive manufacturing methods has facilitated the design and production of complex structures which have a high strength-to-weight ratio. Cellular materials such as honeycombs have low-weight and high capacity to absorb energy which makes them desirable for the aerospace and automotive industries. The present work covers the study and comparison of metal-based regular honeycombs and functionally graded honeycombs. The latter encompass radial and linear/longitudinal gradients. Three repeating unit cells were studied: regular hexagons, Plateau and lotus. The structures were produced in aluminium using the laser powder bed fusion technique. Selected samples were submitted to a stress-relieving heat treatment. Numerical and experimental methods were used to assess the in-plane compressive properties. Finite element analysis was used to obtain the simulated force–displacement curves of each structure, allowing for the calculation of specific stiffness, absorbed energy and yield strength. The experimental method consisted of the compression of three specimens of three types of regular structures with and without stress-relieving heat treatment. The heat treatment reduced the yield strength and stiffness whilst increasing the ductility of the samples. The mechanical behaviour of the structures was found to depend upon a combined effect of the type of gradient, relative density, and unit cell structure. The results showed that an increase in the relative density would enhance the specific mechanical properties. The lotus configuration displayed the highest specific mechanical properties, as its geometry reduces the stress concentrations. The numerical results showed a reasonable match with the experimental results.

中文翻译：

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通过增材制造生产的具有质量梯度的新型蜂窝结构的建模和表征

增材制造方法的传播促进了具有高强度重量比的复杂结构的设计和生产。蜂窝等多孔材料重量轻，吸收能量的能力高，这使其成为航空航天和汽车工业的理想选择。目前的工作涵盖金属基规则蜂窝和功能梯度蜂窝的研究和比较。后者包括径向和线性/纵向梯度。研究了三种重复晶胞：正六边形、高原和莲花。该结构采用激光粉末床熔合技术由铝制成。选定的样品经过去应力热处理。使用数值和实验方法来评估面内压缩特性。有限元分析用于获得每个结构的模拟力-位移曲线，从而可以计算比刚度、吸收能量和屈服强度。实验方法包括对经过和不经过消除应力热处理的三种规则结构的三个样本进行压缩。热处理降低了屈服强度和刚度，同时增加了样品的延展性。研究发现，结构的机械行为取决于梯度类型、相对密度和晶胞结构的综合效应。结果表明，相对密度的增加会提高特定的机械性能。莲花配置显示出最高的特定机械性能，因为其几何形状减少了应力集中。数值结果与实验结果吻合良好。