Relationship between non destructive and static modulus of elasticity of commercial wood plastic composites

The relationship between stress wave nondestructive (NDE) modulus of elasticity (MOE) and static MOE determined by four point bending test of commercial wood-plastic composites was evaluated in this study to assess the potential of using the NDE technique as a grading tool for wood plastics as it is currently done for solid lumber. The NDE MOE was evaluated on a Metriguard Model 340 E computer system, and the static MOE of the same boards measured on an Instron Universal Tester model 5587 according to the ASTM standard D 6109. Results showed that the NDE MOE values overestimated the static MOE from 3.5% to 17.6% depending on the boardwalk type. Regression analysis showed no significant correlation between the NDE MOE and the Static MOE. These results suggest that the stress wave NDE technique may not be appropriate to estimate the static MOE of wood plastic lumber. The trend however needs to be confirmed by further testing using a larger sample size and different combination of the raw materials.