Computational modeling of fiber reinforced composites as a complex material

J. OLIVER; A.E HUESPE; D. J. MORA

Coimbra

Congreso; International Conference on Recent Advances in Nonlinear Models – Structural Concrete Applications. CoRAN 2011; 2011

ECOMMAS

A formulation, initially based on the theory of complex bodies of Capriz1, hasbeen developed to model the mechanical behavior of the high performance fiber cementcomposites with arbitrarily oriented fibers. This formulation approaches a continuum withmicrostructure, in which the microstructure takes into account the fiber-matrix interfacebond/slip processes, which have been recognized for several authors2-3 as the principalmechanism increasing the ductility of the quasi-brittle cement response. In fact, the interfacesbetween the fiber and the matrix become a limiting factor in improving mechanical propertiessuch as the tensile strength. Particularly, in short fiber composites is desired to have a stronginterface to transfer effectively load from the matrix to the fiber. However, a strong interfacewill make difficult to relieve fiber stress concentration in front of the approaching crack.According to Naaman4, in order to develop a better mechanical bond between the fiber andthe matrix, the fiber should be modified along its length by roughening its surface or byinducing mechanical deformations. Thus, the premise of the model is to take into account thisprocess considering a micro field that represents the slipping fiber-cement displacement. Theconjugate generalized stress to the gradient of this micro-field verifies a balance equationhaving a physical meaning.The paper faces the computational modeling of those high fiber reinforced cementcomposites (HFRCC). To simulate the composite material, a finite element discretization isused to solve the set of equations given by the complex bodies theory for this particular case.Moreover, a two field discretization: the standard macroscopic and the microscopicdisplacements, is proposed through a mixed finite element methodology. Furthermore, asplitting procedure for uncoupling both fields is proposed, which provides a more convenientnumerical treatment of the discrete equation system.