在一個複合桿件上，基材和內含物之間有一個厚度為t的薄層界面，本論文的目的是推導這個複合桿件在受到扭轉的作用之下時，可以用一個界面來模擬這個薄層界面，而這個界面它會與基材、內含物和夾層的性質與厚度有關。本文藉由這個界面模型來探討非完美界面的情況，有別於位移和剪力皆連續的完美界面，非完美界面主要分成兩種型式：一種是剪力連續而翹曲位移不連續，另一種是翹取位移連續而剪力卻不連續。然後接下來將把所推導出的關係式將其精確度從交界面厚度 的一階擴展至多階，最後討論的焦點從等向性材料擴展到非等向性材料，並以正向性複合圓柱為例推導其界面關係式與討論其不完美的界面情況。

A thin curved interphase of thickness t between two media is considered on the torsion problem of composite shafts. The interphase is modeled by a surface between the two neighboring media, and appropriate interface conditions on it are derived for the warping function and shear traction fields. The derivation makes use Taylor expansions for the fields and is correct to O(tN), where t denotes the thickness of the interphase. The purpose of this thesis is discuss the imperfect interfaces. Two kinds of imperfect interfaces are considered: one which models a thin interphase of low shear modulus and the other models a thin interphase of high shear modulus. In the former case, the traction on the interface is continuous but the axial warping displacement undergoes a discontinuity. In the latter case, the warping displacement at the interface is continuous but the axial shear traction undergoes a discontinuity.

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