Robert H. Falk

Mechanical Performance of Hemp Fiber Polypropylene Composites at Different Operating Temperatures

In order to quantify the effect of temperature on the mechanical properties of hemp fiber polypropylene composites, formulations containing 25% and 40% (by weight) hemp fiber were produced and tested at three representative temperatures of 256, 296, and 336 K. Flexural, tensile, and impact tests, as well as dynamic mechanical analysis, were performed and the reduction in mechanical properties were evaluated. Impact resistance was independent of temperature, whereas flexural and tensile properties were strongly affected. The highest reductions were observed in stiffness (modulus) values and flexural properties were reduced to a higher degree. The reductions in mechanical properties were well explained by a simple quadratic curve-fitting procedure applied to experimental data. Dynamic mechanical analysis revealed no change in glass transition temperature when the fiber content was increased but the composite material had better temperature resistance at higher fiber content. The results of the present study will be helpful in determining the end-use application of these composite materials.

Effect of Cellulose Fiber Reinforcement on the Temperature Dependent Mechanical Performance of Nylon 6

In order to quantify the effect of temperature on the mechanical properties of pure nylon 6 and its composite with cellulose fibers (containing 25 wt% cellulose fibers), the materials were sampled and tested at three representative temperatures of 256, 296, and 336 K. Flexural and tensile tests were performed and the reductions in mechanical properties were evaluated. The highest reductions were observed in stiffness (modulus) values and the cellulose fibers remarkably enhanced the high temperature resistance of nylon. The reductions in mechanical properties were well explained by a simple quadratic curve fitting procedure applied to experimental data. Dynamic mechanical analysis (DMA) was also performed to study the effect of temperature on mechanical performance. No shifting in glass transition temperature was observed, but the composite material showed less viscous behavior as seen by its lower mechanical loss factor (tan δ) values in the rubbery state. The results of the present study will be helpful in determining the end-use application of these composite materials.

Stress-relaxation behavior of lignocellulosic high-density polyethylene composites:

In this study, stress-relaxation performance of HDPE-based injection-molded composites containing four types of natural fibers (i.e., wood flour, rice hulls, newsprint, and kenaf fiber) at 25 and 50 wt% contents, and the effect of prescribed strain levels were investigated. The results indicated that incorporating more filler causes lower relaxation values and rates, and stress retention and prescribed strain level were reversely correlated. Among the studied filler types, wood flour and kenaf fiber presented more similar behaviors, whereas newsprint resembled rice hulls performance. Strain—time superposition was applied to the experimental data. Due to complex rheological behavior of the studied composites, single horizontal shifting method, with respect to strain levels, was found to be inadequate to satisfactorily superpose data.

Mechanical Performance of Nail-Laminated Posts Manufactured from Reclaimed Chromated Copper Arsenate–Treated Decking Lumber

Abstract This study determined the mechanical properties of nail-laminated (nail-lam) posts manufactured from reclaimed chromated copper arsenate (CCA)–treated decking lumber. Though CCA-treated lumber is no longer accepted for use in residential applications, it is permitted in agricultural and industrial applications where health and environmental impacts are deemed to be minimal. This project focused on the reuse potential of this lumber for fabricating structural nail-lam members commonly used in agricultural post frame utility buildings. Significant amounts of waste CCA-treated lumber are generated by people replacing decks. Currently, this lumber is mostly landfilled as disposal waste. Finding other uses for this discarded material could reduce the waste burden of decking removed from service each year. For this study, 15-year-old decking material slated for removal and composed of nominal 2 by 6 CCA-treated Southern yellow pine (SYP; Pinus spp.) lumber was carefully reclaimed for structural post me...

Framing Lumber from Building Removal: How Do We best Utilize this Untapped Structural Resource?

ABSTRACT Compared with other construction materials, wood products are environmentally attractive because they sequester carbon, are renewable, and are low in embodied energy. Lumber salvaged from ...