The rule of mixture cannot be used accurately to estimate the properties of metal matrix composites. It can only compute the properties approximately. The following factors also should be accommodated in the rule of mixture to estimate the properties accurately. The distribution factor, interfacial bonding strength, inter-particle distance, micro pores, particle size and shape factor. Unfortunately, it is nearly impossible to incorporate all these factors into a single relationship to predict or calculate the properties precisely. Because, the above mentioned factors do not influence the properties of metal matrix composites in linear manner.

Thanks Issac for your answer.

This is for metal composite and there are different factors for fibre- reinforced composites.