Investigations on the thermo-mechanical behaviour of densified veneer wood for cryogenic applications

In this study, the thermo-mechanical behaviour of densified veneer wood (DVW) for cryogenic applications like load-bearing insulation elements for liquid energy sources is investigated. Mechanical tests with compression parallel and transverse to the veneer plane were performed after conditioning the material at five temperature levels: +60 degrees C, +20 degrees C, -40 degrees C, -78 degrees C (dry ice) and -196 degrees C (liquid nitrogen). The investigations showed increasing compression moduli but also increasing brittleness with decreasing temperature. The compressive strength increased with decreasing temperature until about -30 degrees C. Below this temperature, the strength slightly decreased again. The specific heat capacity was determined in the range of -150 degrees C to +60 degrees C and showed a linear dependency on temperature below +20 degrees C. Above +20 degrees C, a non-linear increase is observed due to evaporation of bound water. Finally, a technique is presented to mould DVW boards transverse to the lamination direction with a thermo-hygro-mechanical process in order to reduce waste material associated with commonly used chipping techniques.