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Quantification of slip planes in the stem wood of Eucalyptus grandis

Moulin, Jordão Cabral, Lima, José Tarcísio
Holzforschung 2019 v.73 no.3 pp. 269-275
Eucalyptus grandis, stems, stemwood, tensile strength, wood fibers
The objective of this work was to analyze the natural occurrence of slip planes (SPs) in Eucalyptus grandis wood fibers in terms of their characterization, distribution in the stem and associations with other wood characteristics. A 28-year-old E. grandis was studied, whose stems were sampled in the base-top direction. The longitudinal compressive stress regions (LCompSR, in the inner part of the stem) and longitudinal tensile stress region (LTensSR, in the outer parts of the stem) were separately considered. The following parameters were measured: microfibril angle (MFA), slip plane angle (SPA), number of SPs per millimeter (SP mm⁻¹), slip plane index (SPI) and the relative abundance of SP in the fiber. The SPAs differ only slightly between LCompSR (76°) and LTensSR (77°). The base of the stem, which supports a larger mass, contains the most SPs and the number of SPs decreases from the base to the top. In the LCompSR, the SPI reduction was from 21 to 8%, and in the LTensSR, from 18 to 7%.