Abstract
This study combines experimental testing and computation analysis to reveal the role of defects and sub-micrometric microstructure in tensile behavior of hemp bast fibers. In particular, these structural defects represent the footprint of the processes to which the fibers elements are subject along the whole transformation chain from the plant to the end use product. Tensile experiments performed on elementary fibers and bundles in a wide diameter range (40–200 μm) are simultaneously conducted with X-ray micro-tomography observation. 3D images of ultra-fine resolution (voxel size of 280 nm) are achieved at different deformation magnitudes up to the complete failure thanks to the use of synchrotron radiation (ESRF, Grenoble, France). A Finite element (FE) model is implemented based on the conversion of the tomograms into 3D meshes. High performance computing is used to simulate the tensile response of the hemp bast fibers. In particular, the effects of notching and sub-micrometric structure of the fibers are explored. Results show the presence of different types of diffuse damage kinetics, which are related to the variability in the fiber size, surface defects and the presence of the lumen space. The damage behavior is found to be sensitive to the type of stress criterion implemented in the FE computation. The predictive analysis demonstrates the relevance of using embedded microstructure simulations to reveal the extent of stress localization and predict the failure properties in bast fibers for innovative composite manufacturing for instance.
Highlights
Fiber demand continues to increase despite the recent Financial Crisis of 2008, when the world economy faced perhaps its most dangerous crisis since the great depression of 1928, according to economists
Following the source data from Tecnon OrbiChem company, the future of cellulosic fibers is promising more because of positive projections driven by Damage Kinetics Bast Fibers Finite element (FE)/X-μCT
The potential of natural reinforced plastics as light-weight structures sharing most of the technological processing routes with fossil-based composites is proved (Müssig, 2010; Summerscales et al, 2010; Shah, 2014)
Summary
Fiber demand continues to increase despite the recent Financial Crisis of 2008, when the world economy faced perhaps its most dangerous crisis since the great depression of 1928, according to economists. The mechanical performance dependence on fiber dimensions (Thomason and Carruthers, 2012; Placet et al, 2014) and accuracy of the measurement (Legland and Beaugrand, 2013; Hamdi et al, 2015; Garat et al, 2018) are serious concerns for attempting a proper evaluation of the technical part performance against failure Defects such as external fibrillation can weaken the hemp fiber structure (Pickering et al, 2007), which makes the fracture of the material highly defect sensitive. Starting from bundles or individualized fibers, laser ablation process is performed on hemp specimens to create notches of different sizes and geometries (U- and V-notched) These notches act as effective defect sites to concentrate stress during loading and trigger rupture of the natural fiber. The model uses the experimental loading conditions and the fiber material properties with the main hypothesis of homogeneous properties for the solid phase combined to an explicit implementation of the void structure
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