Date of Award

1996

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Renewable Natural Resources

First Advisor

Elvin T. Choong

Abstract

The effects of silvicultural treatments on mechanical and physical properties of loblolly pine (Pinus taeda L.) wood composites, veneer tensile and bending properties, and basic chemical properties were investigated. Stands managed in a plantation setting showed higher extractive contents. Holocellulose and alpha-cellulose were minimally affected by the silvicultural strategies. Klason lignin showed an inverse relationship with holocellulose. The effect of wood type was significant for the extractives because the innerwood region yielded much greater values than the outerwood. Holocellulose and alpha-cellulose increased in concentration from innerwood to outerwood. Veneer tensile strength was significantly affected by silvicultural practice, but other mechanical properties were unaffected. The differences between the stands were minimal for the mechanical properties investigated. Specimens tested in the ovendry condition yielded higher mean mechanical property values than specimens tested airdry. The stands had laminated veneer lumber panels produced using either all A-grade or all C-grade veneer. Also, five different veneer grade based layups were investigated for one stand only. Stand one (sudden sawlog) produced the highest flexural strength and stiffness mean values for the all A-grade panels in both testing orientations. The optimal location of A-grade veneer placement in a panel influenced modulus of elasticity but not ultimate bending strength. Plywood panels were produced according to four different veneer grade arrangements for each stand. Bending and shear properties were significantly affected by silvicultural practice. Plywood fabricated with all A-grade veneer gave the most favorable mechanical properties. The effect of panel layup was significant for most mechanical properties. Particleboard and Fiberboard panels were produced according to stand and wood type. On average, stand 2 (conventional), stand 3 (natural regeneration) and stand 4 (single tree selection) yielded the most favorable mechanical properties. However, differences within the stands were typically minimal and nonsignificant for most properties. Innerwood composites did show a higher compaction ratio than outerwood composites, but the differences in panel density, thickness swell, water adsorption, modulus of rupture, modulus of elasticity, and internal bond were minimal between the wood types for all stands.

ISBN

9780591288889

Pages

91

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