Plastic deformation of fiber coating in polymer matrix composites under hygrothermal loading

This paper is concerned with the study of elasto-plastic deformation of the coating, and consequently, the changes in the states of stress in the cons tituent phases of a unidirectional fiber reinforced polymer matrix composit e (PMC) under uniform thermal, hygral and hygrothermal loadings. A four-pha se composite cylinder assemblage (CCA) model has been used for the analysis . The coating interphase between the fiber and the matrix has been taken to be of lower modulus and lower yield stress value than that of the matrix. Only those combinations of temperature and moisture content are considered which give rise to plastic deformation in the coating, other phases still r emaining elastic. Plastic behaviour of the coating has been idealized by ta king a linear work-hardening constitutive relation.