纤维取向随厚度变化的注塑FRP薄板的热屈曲
Thermal buckling of thin injection-molded FRP plates with fiber orientation varying over the thickness
摘要：
玻璃纤维和聚合物基体的不同热弹性性质会在注射成型的纤维增强塑料（FRP）物体中产生残余热应力。在从模具冷却到室温的过程中，这些应力可以通过由未翘曲构造的不稳定性引起的大变形而松弛（即，屈曲）。基于Foppl-vonKarman理论，通过解析公式研究了薄FRP圆盘的热屈曲。扩展我们以前的工作，圆柱正交各向异性与材料参数变化的磁盘厚度被假定为为了占厚度依赖性的玻璃纤维取向分布。引入了一个表征均匀正交各向异性圆盘热各向异性比的圆盘参数，并讨论了它与屈曲的发生和周期性的关系。这是针对蒙皮-芯层蒙皮模型完成的，芯层与总厚度的比率是针对该模型定义的。对于典型的注塑成型的磁盘的纤维取向分布，它被发现，存在一个值的厚度比，没有屈曲发生。它还表明，第一屈曲模式的周期性所描述的广义热各向异性比，从而扩展了均匀的纤维取向分布所获得的结果。在文献中的实验数据的预测精度的改进时，使用皮肤的核心皮肤模型。最后，我们研究了屈曲温度和圆盘厚度之间的关系，并提出了归一化屈曲温度对热各向异性比的依赖关系的表达式。有限元仿真结果验证了所提表达式的正确性和实用性。
英文摘要：
The different thermo-elastic properties of glass fibers and polymer matrices can generate residual thermal stresses in injection-molded fiber-reinforced plastic (FRP) objects. During cooling from mold to room temperature, these stresses can be relaxed by large deformations resulting from an instability of the unwarped configuration (i.e., buckling). This article investigates the thermal buckling of thin FRP disks via an analytical formulation based on the Foppl-von Karman theory. Expanding on our previous work, cylindrical orthotropy with material parameters varying over the disk thickness is assumed in order to account for thickness dependency of the glass fiber orientation distribution. A disk parameter generalizing the thermal anisotropy ratio for homogeneous orthotropic disks is introduced and its relation with the occurrence and periodicity of buckling is discussed. This is done for a skin-coreskin model, for which the core-to-total thickness ratio is defined. For fiber orientation distributions typical of injection-molded disks, it is found that there exists a value of the thickness ratio for which no buckling occurs. It is also demonstrated that the periodicity of the first buckling mode is described by the generalized thermal anisotropy ratio, thus extending the results obtained for a homogeneous fiber orientation distribution. Improvements in the accuracy of the predictions for experimental data available in the literature when using the skin-core-skin model are shown. Finally, we study the relation between buckling temperature and disk thickness and propose an expression for the dependence of the normalized buckling temperature on the thermal anisotropy ratio. Results of FEM simulations are used to validate the proposed expression, proving its applicability and accuracy.
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