Abstract
This paper deals with the transition of Polymer Matrix Composites (PMC)- from Hard Composites to Soft Composites. The five kinds of typical stress-strain relations in PMC are shown at first. PMC is explained by dividing between the hard composites and the soft composites. The hard composite is difined as the composite with high strength and high rigidity. On the other hand, the soft composite is defined as the composite which have the high tensile strength and high tensile rigidity, but low flexible and compressive rigidities. The hard composites have about 60 years' history which consists of three generations, and the soft composites about 50 years' history. This paper storongly mentioned that the soft composites have the wide application field as same as the hard composites.
