RED MAPLE AND YELLOW-POPLAR LVL FROM ULTRASONICALLY RATED VENEER

This paper presents the results of an exploratory study that investiga ted the performance enhancement of experimental hardwood laminated ven eer lumber (LVL) materials through the application of ultrasonic sorti ng of veneer quality. LVL was manufactured from red maple and yellow-p oplar. Peeler blocks for LVL fabrication were rotary peeled to a nomin al thickness of 1/6 inch and were then clipped and dried into processe d 52- by 102-inch veneer plies. Ply quality was subsequently evaluated using an automated veneer test machine to measure ultrasonic propagat ion time (UPT). The UPT measurements were plotted to establish frequen cy distributions. The UPT frequency distributions for both species ser ved as a basis for veneer segregation into plies of ''high'' and ''low '' quality for layup fabrication of two different LVL materials. The f irst LVL was limited to a mixed veneer quality layup with a 24-ply cou nt to fabricate 3.5-inch-thick material. The other LVL material was fa bricated using an optimized 24-ply count layup. Optimized layup consis ted of 12 low quality core plies with 6 high quality (lower observed U PT) plies toward each face. Test results are reported on the observed edgewise modulus of elasticity (MOE(e)) and flatwise MOE and modulus o f rupture (MOE(f) and MOR(f)) flexure properties, and shear strengths parallel and perpendicular to glueline orientation. Test results were also collected to examine the significance of the optimized layup to e nhance nail (withdrawal and lateral resistance) and bolt fastener prop erty values. Flatwise flexure properties for both species were observe d to be of greater magnitude with the optimized layup. Statistical ana lyses (t-tests) indicate observed differences were most commonly signi ficant for MOE(f). Enhancements in fastener performance were also obse rved for the optimized layup LVL materials. Observed differences in fa stener performance were only statistically significant with higher nai l withdrawral and bolted joint performance in the optimized yellow-pop lar LVL.