This communication provides initial information and understanding of the manner in which a newly developed theoretical mechanism (Soldatos in Int J Solids Struct 202:217–225, 2020) is applied in specific boundary value problems met in polar linear elasticity of fibrous composites and thus enables the determination of the spherical part of the couple-stress tensor. In this context, it tests the applicability of the implied mechanism/method in the case that a rectangular plate reinforced by a single family of unidirectional fibres is subjected to pure bending. The problem solution is obtained for either non-polar or polar material behaviour, where fibres are considered perfectly flexible or resistant in bending, respectively, and provides clear evidence of the correctness of the principal argument that underpins the proposed method. Namely, that the general rotation field of the plate deformation differs from the fibre rotation field. That newly discovered method enables an extra energy term that emerges in the strain energy function of the fibrous composite plate to relate with the spherical part of the couple-stress tensor outside conventional equilibrium conventions. It thus leads to the determination of the spherical part of the couple-stress and its distribution throughout the plate body in a complete and comprehensive manner.

本次交流提供了对新开发的理论机制（Soldatos in Int J Solids Struct 202:217–225, 2020）应用于纤维复合材料极性线性弹性中遇到的特定边界值问题的方式的初步信息和理解，从而使确定偶应力张量的球形部分。在这种情况下，它测试了隐含机制/方法在由单向纤维增强的矩形板经受纯弯曲的情况下的适用性。问题解决方案是针对非极性或极性材料行为获得的，其中纤维分别被认为是完全柔韧或抗弯曲的，并提供了支持所提出方法的主要论点的正确性的明确证据。即，板变形的一般旋转场不同于纤维旋转场。这种新发现的方法使纤维复合板的应变能函数中出现的额外能量项与常规平衡约定之外的耦合应力张量的球形部分相关。因此，它导致以完整和全面的方式确定耦合应力的球形部分及其在整个板体中的分布。