Dow,B.W. Rosen and others evaluated X_c based on the principle of energy,having adopted in the model of composition a fibre of rectangular cross-section,the derived two formulae of Xc in pair hold simplified forms.

• 道、罗森等人根据能量原理对 X_c 进行了估算。 在他们采用的复合模型中,纤维具有矩形横载面,导出的关于 X_c 的一组两个公式,形式较为简单。