Continuum damage micromechanics description of the compressive failure mechanisms in sustainable biocomposites and experimental validation
Vedad Tojaga, Alexandros Prapavesis, Jonas Faleskog, Thomas C. Gasser, Aart Willem Van Vuure, Sören Östlund
Abstract
We investigate the compressive failure mechanisms in flax fiber composites , a promising eco-friendly alternative to synthetic composite materials, both numerically and experimentally, and explain their low compressive-compared-to-tensile strength, the compressive-to-tensile strength ratio being 0.28 − 0.6 . We present a novel thermodynamically consistent continuum damage micromechanics model capturing events on the fiber-matrix scale. It describes the microstructure of a unidirectional composite and includes the instantaneous constitutive behavior of matrix and fibers. We show that flax fibers behave as elastic-plastic-damaged solids in compression. Furthermore, we show that fiber damage plays an utmost role in the compressive failure of flax fiber composites – it is a major determinant of the material's compressive stress-strain response. Using X-ray Computed Tomography (XCT) and Scanning Electron Microscopy (SEM), we identify the fiber damage as intra-technical fiber splitting and elementary fiber crushing. Due to microstructural similarities among natural fibers , the same micro-mechanisms are likely to appear in other bio-based fibers and their composites.