Creep deflection of Wood Polymer Composite profiles at demanding conditions

Durability and low maintenance make Wood Polymer Composite (WPC) profiles popular in decking applications. EN 15534-4 specifies minimum performance levels to guarantee WPC quality. However, despite such quality specifications, occasionally high temperature creep issues are reported. This paper evaluates the creep performance of three commercial WPC decking profile grades. All three WPC grades meet the requirements specified in EN 15534-4. Nevertheless, at slightly more demanding load conditions, some WPC samples fail around the creep deflection limits specified in the standard, and which are supposed safe. Reference outdoor testing in the moderate climate of the Netherlands shows creep deflection rates which are expected to lead to fatal failure of these WPC samples in a couple of years. It is concluded that predictive testing requires insight in progressive creep strain development relative to fatal failure strain level.