Mechanical properties of wood fiber composites under the influence of temperature and humidity

Abstract

Woodfiber-thermoplastic composites (WPC) have received considerable attentions from the forest product industry for civil engineering applications due to its superior properties over wood and plastics alone. Particularly WPCs can be easily fabricated using traditional plastic processing techniques. The major limitation in the applications of WPCs is the poor understanding of their mechanical properties and especially the environmental impacts on these properties. The aim of this research is to systematically study the mechanical properties of aspen-fiber polypropylene composites (APCs), evaluate the typical temperature and humidity influences on the mechanical properties of APCs, and such find an optimal composition of APCs for high mechanical reliability and long life span in service conditions. This was accomplished by examining APCs of 30 and 50 weight percent wood fiber contents with/without 2 wt. % maleic anhydride grafted polypropylene MAPP additives. Specimens of these specially selected APCs were exposed for 7,000 hours to four temperature and moisture conditions, typically experienced by structures in domestic housing industry: 1. hot/dry (Arizona), 2. hot/wet (Florida), 3. cold/dry (Montana), and 4. cold/wet (Wisconsin). Tensile and flexural tests according to ASTM specifications were used to evaluate the mechanical properties of these APCs after conditioning. Especially flexural strengths after conditioning were reported here at room, near zero (4°C), and elevated (40°C) temperatures. Large reductions in both tensile and flexure strengths of APCs were observed after 7,000 hours ageing at all four ageing conditions.

Citation

Xue, Yibin; Veazie, David; Glinsey, Cindy; Wright, Meagan; Rowell, Roger M. 2003. Mechanical properties of wood fiber composites under the influence of temperature and humidity. Seventh International Conference on Woodfiber-Plastic Composites (and other natural fibers), May 19-20, 2003 ... Madison, Wisconsin, USA. Madison, WI : Forest Products Society, 2003: Pages 339-343