Damage analysis of unidirectional Ti hybrid nanocomposites containing nanoparticles

In the present work, a nested micromechanical model is presented to analyze the biaxial initial damage envelopes of unidirectional silicon carbide (SiC) fiber-reinforced titanium (Ti) matrix hybrid nanocomposites containing SiC nanoparticles. Firstly, an effort is made to obtain the elastic modulus, yield strength and coefficient of thermal expansion (CTE) of the nanoparticle-reinforced metal matrix nanocomposites by developing an analytical micromechanical model. Size factor and agglomerated state for the nanoparticles into the metal matrix, generation of dislocations by nanoparticle/matrix thermal mismatch and Orowan strengthening mechanism are considered at the nanoscale. Then, a unit cell-based micromechanical model is proposed to extract the biaxial initial damage envelopes of the SiC nanoparticle/SiC fiber-reinforced metal matrix hybrid nanocomposites. The Fiber/matrix interfacial debonding and matrix yielding are included as the dominant damage modes. Also, thermal residual stress (RS) arisen from the fiber/matrix thermal mismatch during the MMC manufacturing process are considered in the analysis. A reasonable agreement is observed between the results of the present model and available experiments for both of the nanocomposite and hybrid nanocomposite thermomechanical properties. It is shown that the SiC nanoparticles are indeed a very effective strengthening agent for the MMCs which can postpone the deterioration initiation due to the interfacial debonding under transverse tension. The presented model is applied to examine the effects of several parameters, including the nanoparticles volume fraction, diameter, size factor and dispersion type and also the thermal mismatch and fiber/matrix interfacial conditions on the biaxial initial damage behavior of the metal matrix hybrid nanocomposites.