Micromechanical Viscoelastic Characterization of Fibrous Composites

Abstract

An efficient computational algorithm is proposed to evaluate the viscoelastic properties of fibrous composites. A repeating unit cell (RUC) based on a pre-determined fiber packing is assumed to represent the microstructure of the composite. Finite element analysis of this unit cell under six specified loading conditions is carried out to study and quantify the time-dependent composite viscoelastic property of the unit cell. Volume averaging scheme is implemented to determine the averaged response as function of time in terms of stresses and strains. This time history analysis constitutes the data for characterization of the composite and determination of the viscoelastic parameters and coefficients. The individual viscoelastic properties of the constituents' materials as well as the composite are assumed to follow the Prony series definitions. To verify the algorithm certain examples are included. In these examples, the constituting fiber materials are assumed to be elastic and the matrix is assumed viscoelastic. Three different types of fiber packings; hexagonal (HEX), square (SQR) and bidirectional crossed fibers (BCF), will be used and each packing will be examined for different fiber volume (V f/V) fractions. The accuracy and verification of the results have been examined with known circumstances. The methodology is to be accurate and efficient so far the periodicity of the composite material rules. This micromechanics tool could make a powerful viable algorithm for determination of many linear as well as nonlinear properties in continuum mechanics material characterization and analysis.

A micromechanical procedure for modelling the anisotropic mechanical properties of brain white matter

“…Through periodicity assumptions, several investigators have used finite elements analysis, in elastic and thermoelastic of the so-called periodic unit cells, to determine the mechanical properties and damage mechanisms of composites; see Sun and Vaidya (1996), Adams and Crane (1985), Pindera and Aboudi (1998), Garnich and Karami (2005), Karami and Garnich (2005b). Micromechanical analysis has also been extended to viscoelastic behaviours; see Chen et al (2001), Brinson and Lin (2003), Fisher and Brinson (2003), Naik et al (2008).…”

Rheological characterization of continuous fiber—reinforced viscous fluid

“…The averaged power per RVE volume is calculated during squeeze flow and it was used to determine the material parameters using Eq. (18). Fig.…”

“…Based on three orthogonal symmetry planes of RVE and periodicity constraints, it was shown [17,18] that boundary surfaces of RVE remain flats and effective response of microstructure under uniaxial compression can be determined considering only one-eighth of RVE geometry. Fig.…”

“…The response of the unit cell under specified loading conditions is analyzed to study and quantify the properties of RVE. The micromechanical results have been used to determine material parameters describing the constitutive law of heterogeneous materials subjected to small deformations [18,19]. The micromechanical approach has also been used to evaluate finite deformation of heterogeneous materials like polyphase materials [20] and elastomers [21,22].…”

Thermoelastic Characterization and Evaluation of Residual Stresses in Bi-Directional Fibrous Composites

“…2, the finite element discretization of three RUCs, at fiber cross angles of 0 o , 45 o and 90 o is shown. The periodicity and constraint constraints as well as the loading conditions are described in [9][10][11][12].…”