最大弯曲正应力是衡量夹层梁弯曲性能的重要参数之一，本文推导出了将软夹芯夹层梁等效成等 截面均质单层梁计算最大弯曲正应力的方法，并在此基础上进行三点弯曲试验的算例研究。结果表明：修正单层梁理论与层合梁理论计算的结果是一致的。当破坏载荷与夹层梁横截面的尺寸一定时，随着芯层与总厚度比的增加，修正单层梁理论计算的最大正应力值逐渐增加，而单层梁理论计算的结果为一恒定值。最大弯曲正应力修正公式的建立为夹层梁的工程应用提供理论基础。

Maximum bending normal stress is one of the important parameters to measure flexural property of sandwich beam. Therefore，new methodology to calculate the stress is proposed based on the equivalent single beam theory，after that the numerical examples are demonstrated according to three point flexure test. The results showed that revised single beam theory (RSBT) are equivalent to multi-layer theory (MLT). When cross section of beam and maximum loading are fixed，the maximum bending normal stress calculated by RSBT is increased accordingly with increasing ratio of core thickness to the whole，but the result is constant for single beam theory (SBT). RSBT is set up to provide a new method for sandwich construction application in engineering industry.