Cell-Wall Crystallinity as a Function of Tensile Strain

Molecular orientation in wood as defined by X-ray diffraction techniques increases with a decreasing rate as applied load increases, is constant over a period of time with a sustained load, and does not return to original orientation after release of a load that approaches the ultimate. The response to increment loading was the same for yellow birch and sugar maple; however, the response to constant loading differed in that the sugar maple has a significantly lower residual deformation at the lower load levels. The immediate recovery of strain encountered when a load is removed is an elastic response. Residual deformation may be a result of the establishment of bonds formed through tensile loading thus restricting the return of the molecule to the non-stressed condition. It is a function of the applied load and probably differs with species. It remains constant with time provided the test environment is unchanged.

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