Development of a wood fiber composite using nonwoven textile technology

The feasibility of manufacturing engineered wood composites with nonwoven textile technology was investigated. Needlepunching is a nonwoven textile process which converts fiber mats into coherent fabric structures with a three dimensional character. This is done by means of barbed needles, which oscillate in a vertical or slanted direction with regards to the surface of the fiber mat. Hardwood fiber was blended with 10% urea formaldehyde and formed into mats (2.3, 4.6 and 6.9 mm thick) with target densities of 550 and 640 kg/m 3. The mats were then sandwiched with polypropylene/polyester bicomponent fiber webs and passed through a needleloom. The barbed needles mechanically bonded the bicomponent web to the wood fiber mat, and pulled some of the polymer fibers through the thickness direction of the mat. Bending and thickness swelling properties of the needlepunched wood composite were qualitatively assessed and compared to medium density fiberboard (MDF).;A macro-mechanical model predicting the elastic response of the wood-bicomponent fiber composite panel was developed. The strains at a given stress was determined by means of the model, and compared to strains determined experimentally. The model under predicted the strains along the fiber direction of the bicomponent fiber sheets by approximately 4.03 percent. A greater difference between predicted and measured values was observed in the lateral direction of 10 percent.;To further understand the behavior of the material, a hygro expansion model was developed for a wood-bicomponent fiber composite panel. The dimensional changes predicted by the model due to moisture fluctuation were compared to experimental data. No significant difference was found between the predicted and measured dimensions. However, significant differences were found between the state of strain predicted by the model and the measure state of strain in the x-direction in the panels.;The tensile behavior of the wood-bicomponent fiber composite under simulated long term load was studied. Short term creep tests were conducted at different temperatures and were shifted to a reference temperature to simulate long term creep tests. It was found that the shift factor used followed the WLF equation. Creep tests were conducted on bicomponent fiber sheets, MDF and the composite itself. It was observed that MDF creeped the least, with the greatest creep observed in the bicomponent fiber sheets. The wood-bicomponent fiber panel exhibited an intermediate creep.