MODELING THE MINIMUM CREEP RATE OF DISCONTINUOUS LAMELLAR-REINFORCED COMPOSITES

An analytical model has been developed to predict the creep rate of di scontinuous lamellar-reinforced composites in which both phases plasti cally deform. The model incorporates effects associated with lamellar orientation relative to the uniaxial stress axis. For modest to large differences between matrix and reinforcement creep rates, lamellar asp ect ratio has a significant impact on composite creep rate. For a pres cribed reinforcing phase volume fraction, microstructural inhomogeneit y can have a pronounced effect on composite creep properties. In the c ase of uniaxially aligned rigid lamellar-reinforced composites, an inh omogeneous distribution of reinforcing lamellae in the microstructure substantially increases the composite creep rate. Model results demons trate that there is no significant improvement in creep resistance for aligned fiber-reinforced composites compared to aligned lamellar-rein forced composites, unless the reinforcing phase is essentially nondefo rming relative to the matrix phase.