Abstract: For a special material needed is engineering, if it can be predicted on the basis of a certain theory and producing it to use the theory is successful, this is hoped to the of the engineering,For the aim,the author wants to investigate a proper theory and select a few materials to make a composite which is consistent with an object material given beforehand. In this paper, the theory is given in the preceding three parts,and the results are given in the fourth part. Theoretical calculations were made for the composites of the two object materials given in engineering. Composites are made according to the results of the calculations.The experiment is made yet to the composites. The results of them are satisfied.