Mode I fracture properties of thermally-modified spruce wood (<i>Picea abies</i>) at different moisture contents

The influence of moisture content and density on fracture properties unmodified thermally modified spruce wood (Picea abies) has been investigated. Thermal modification was done at 180 °C, 200 230 samples were conditioned 20%, 44%, 76%,% 88% relative humidity. Double cantilever beam specimens with TL RL orientation used for testing. crack length determined via digital image correlation, the compliance specimen multiple loading-unloading cycles specimen. strain energy release rate calculated, which decreased an increasing degree increased content. analysis showed that more samples, while dependence less obvious samples. values are higher in than orientation, no significant influence. highest 0.256 N/mm exposed to humidity, lowest 0.071 °C then From all measurements, functions fitted calculate as a function modification, content, wood, can be any combination factors studied.