CIEL*a*b* system Coniophora puteana Douglas-fir Eucalyptus Euler-Bernoulli European hardwoods FTIR High-Energy Multiple Impact (HEMI)–test Pinus massoniana Lamb Resistance to Impact Milling (RIM) acoustic resonance aluminium reinforcements artificial weathering bamboo bamboo grid packing bending stiffness blue staining fungi brittleness brown rot building culture background building material cell-wall mechanics chemical changes chemical composition coefficient of wood bendability color colour colour change colour changes compression