Based on the continuummechanics theory, amixedmodewas setup to investigate the valid
elastic modulus of composites. An improved mixed-mode method was proposed, and the revised
formula of calculating the valid elastic modulus of compositeswas given. The calculational results of
the valid elasticmoduli of two composites show that the biggest error is 9% for the improved method
and over23% for theVoightmode,l theReussmodel and theHalpain-Tsaimodified formula, and the
difference between the calculational and experimental curves of the valid elastic moduli of the two
composites is small for the improvedmethod and great for the threemodels.