Investigations into the photodegradation of wood using microtensile testing

Microtensile Testing of Wood – Overview of Practical Aspects of Methodology

“…They investigated the effect of temperature (Derbyshire et al, 1997) on photodegradation rates and applied the method to the assessment of photostabilisers of wood. They also evaluated artificial weathering devices and demonstrated that they offer a consistent, reliable and precise means of determining photodegradation rates for wood (Derbyshire et al, 1995(Derbyshire et al, , 1996. The strength changes were shown to be consistent with fractographic evidence of the structural changes in wood, namely with cell delamination, development of brittleness and loss in cell wall integrity (Turkulin and Sell, 2002).…”

“…Additional evidence to explain the weathering process was found in microscopic analysis, but the structural changes, especially in the early weathering phases, did not prove such a sensitive parameter as the tensile strength loss. Turkulin later showed (Derbyshire et al, 1996;Turkulin and Sell, 2002) that microscopic evidence can essentially corroborate the complete comprehension of the failure origin and mode.…”

“…Following this, it is easy to understand that any chemical changes of wood constituents will weaken either the lateral bonds and affect the stress transfer, or the cellulosic units themselves. The mechanical parameter that reflects most sensitively these changes is tensile strength parallel to the grain (Ifju, 1964;Evans and Banks, 1990; Derbyshire and Miller, 1981; Derbyshire et al, 1996). It was demonstrated by numerous experiments that the tensile strength may precisely reflect the chemical changes of wood constituents due to exposure to biodegradation, acid conditions or weathering (Razckowski, 1980 Lehringer et al, 2011).…”

“…Finally, the ensuing failures can be microscopically studied on a cellular level. The large number of replicates meets the requirements of the statistical processing of data Derbyshire et al, 1996).…”

“…The effect of temperature on weathering rates (Derbyshire et al, 1996) is estimated to be much smaller than the effect of light and moisture, and the relative effect of up to 5 % temperature oscillations was empirically shown to be practically negligible (Turkulin, 1996).…”