考虑刚度特性的零热膨胀复合材料高许用温变设计

Design of higher allowable temperature range for zero thermal expansion composites considering stiffness characteristic

  • 摘要: 材料的宏观零热膨胀可以通过两种不同的正热膨胀材料在单胞尺度上的复合实现。该类材料虽然能在较大温度波动环境下保持较高的几何稳定性,但两种材料之间过大的热应力很容易导致材料失效,从而限制其许用温度变化范围(简称许用温变)。为此,提出以单位温升的最大热应力作为零热膨胀材料许用温变的衡量指标,通过解析和有限元数值仿真两种方法,对三种典型弯曲变形机制的零热膨胀材料进行许用温变和刚度特性分析,揭示了单胞可设计参数对其性能的影响规律。结果表明:在满足零热膨胀条件下,通过合理的单胞结构设计和选材设计,可以实现刚度与许用温变双目标共赢。

     

    Abstract: The macroscopic zero thermal expansion of material could be obtained through combining two kinds of materials with different positive thermal expansion coefficients within a unit cell. These composites usually possess higher thermally geometric stability in the large temperature fluctuation. However, it readily produces excessive thermal stress on the interface between the two constituent materials and therefore limits the allowable temperature range of the material. A new evaluation index of the maximum thermal stress of unit temperature rise was resorted to perform allowable temperature and stiffness analyses for the three types of typical bending-dominated zero expansion materials. Both the analytic and numerical simulation methods were adopted and the influences of cell design parameters on these aspects were also discussed. The results show that when the designed zero expansion attribute is achieved, the high stiffness and high allowable temperature range can be obtained at the same time if the reasonable constituent materials and structural parameters are selected.

     

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