Size dependency of tension strength in natural fiber composites

This paper reports on a combined experimental and theoretical study on the size dependency of tension strength of clear wood at loading parallel to fiber direction. The fracture behavior of the tested softwood specimens was found to be rather brittle with low precursory activity and a statistical variation of the strength. The distribution of the strength values can be well fitted with a Weibull distribution distinguished by a shape parameter ρ 8−10. A significant dependency of the mean strength of the material on the cross-sectional size of the specimens was obtained. The range of load redistribution in clear wood subjected to tension parallel to fiber was assessed by the theoretical concept of fiber bundle models for fiber composites. Hereby the macroscopic behavior was modelled in terms of the microscopic damage process.