Characterizing fracture process in lime wood

We committed ourselves to measure the fracture toughness of lime wood in a wide range of relative humidities (RH). Thanks to those experiments, we will better answer the question of what threatens wooden sculptures in historic interiors where climate fluctuations reach such extremes.

The samples were stabilized for weeks in sealed containers where the RH was maintained with saline solutions (if you want to know more about this topic read: Greenspan – Humidity Fixed Points of Binary Saturated Aqueous Solutions)

After performing tests according to the wedge-splitting method, we observed different behavior of the samples in low (ca. 38 and 60% RH) and high (ca. 80 and 92% RH) relative humidity conditions. At low RH, the samples were cracking catastrophically (and the crack crossed several annual rings on its way), while at high RH, the crack propagation was less dramatic.

Check out a short video documenting our experiment (RH=60%, the speed has been increased several times):

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