Properties of sheet formed wood fiber and polymer fiber composite materials

Abstract

This project was carried out at Chalmers University of Technology in Gothenburg in collaboration with one of the largest companies in the forest industry. The company that is currently interested in possibilities to produce sheet formed composite materials with high wood fiber content, which could be formed into 3D objects by conventional thermoforming. The goal of this project was to develop a moulding process and evaluation methods to produce and analyze a novel composite material. A search for standardized characterization methods from the leading organizations was performed and standards for different classifications of materials were compared. Considering that the end products are structural applications, a final testing protocol was designed based on the standard ASTM 1037:12 for wood based fiberboard. A compression moulding process with four stages was developed using tensile testing to ensure the favourable parameters which enhanced strength and stiffness of the material. This process was then used to characterize 12 samples with different composition and pre-processing. Characterization was done to assess tensile, bending, internal bond strength and water absorption properties. The optimal parameters for the process developed in this project differ between the four stages. A higher processing temperature was favourable to increase the tested mechanical properties. It was shown that the polymer content did not affect mechanical properties significantly. However, higher amounts decreases water absorption drastically. If water absorption is set aside, a polymer content of 10 % is enough to ensure easier handling of the raw material. Altogether, it can be concluded that the material is not sensitive for small changes in process parameters or composition.