Micromechanical Modeling of Effective Orthotropic Elastic and Viscoelastic Properties of Parallel Strand Lumber Using the Morphological Approach

Strand-based wood and bamboo composites are a class of structural materials which are increasingly being used in the construction industry. These bio-based composites consist of orthotropic wood or bamboo strands bonded together with small amount of resin (glue). In order to estimate the effective properties of such composites, a specific micromechanical approach from the literature, called the "morphological approach" (MA), is employed. The accuracy of the MA in estimating the effective elastic and viscoelastic properties of an idealized unit cell of a special strand-based wood composite product, a parallel strand lumber (PSL) beam, is investigated using numerical reference solutions obtained by full-field finite-element (FE) simulations. The MA is also compared to analytical micromechanics equations previously proposed by the authors for predicting the effective properties of strand-based composites. MA results are shown to be closer to the numerical reference solutions than previous analytical estimates. Thus, the MA can be used as a valuable alternative for computing the effective properties of strand-based composites with rectangular shaped orthotropic strands. More generally, it could be used in efficient multiscale analysis of large structural composites made from various wood and bamboo strands using less restrictive unit cells. From a fundamental viewpoint, this paper shows a novel application of the MA to orthotropic reinforcements in a Prony series-based viscoelastic matrix.