Micromechanics Of A Class Of Damaged Composites

The objective of this work is to examine the influences of various micro-damages on the elastic and elastoplastic properties of the composite materials by means of Eshelby's principle and Mori-Tanaka's method. Four types of damaged composite systems are considered.Firstly, a class of porous materials with various distributions of spheroidal voids and cracks are studied. The elastic moduli and elasto-plastic stress-strain relations for each arrangement are derived explicitly. The second type of damage is interfacial debonding. The progressive debonding process and its influence on the overall properties are examined;the damaged criterion is established. For the mode of partial debonding, an fictitious, transversely isotropic inclusion is introduced to replace the damaged isotropic one so that the difficult problem can be solved easily. Lastly, the distributed damage of fiber-reinforced composites containing either aligned or randomly oriented spheroidal voids are studied. With aligned cracks, the present theory also corresponds to the condition of "random bridging".