Date of Award

2000

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Forest Resources

Advisor

Sephen M. Shaler

Second Committee Member

Roberto Anido-Lopez

Third Committee Member

Habib J. Dagher

Abstract

Hybrid composites of wood and fiber reinforced polymers (FRP) exhibit a flexibility of design properties through choices in fiber type, amount, orientation and resin type. With this flexibility comes the need to measure the durability of the composite material system, especially the bond between these two materials due to their markedly different responses to moisture. This study is two-fold; the first section examines methods for the mechanical testing and durability of wood/FRP laminations. Six mechanical tests were evaluated and a modified block shear method was identified as the most suitable due to its ability to provide representative results independent of material integrity. The second section evaluated the wood/FRP bond durability for PRF and epoxy adhesives through chemical kinetics. The control maple laminates were projected to retain 30% of their post vacuum pressure soaked strength for 12 years. When PRF and epoxy/HMR adhesive systems were used to bond the FRP reinforcement to maple the time projections to 30% bond strength were 57 and 34 years, respectively. The epoxy resin was found to reinforce the wood/FRP at the bonded interface and this system, after exposure to a vacuum pressure soak cycle had a mean shear strength of 2,058 psi which was 23% greater than the PRF system. The ability of the epoxy to make the porous FRP impermeable to water was also recognized. The rate process assessment from chemical kinetics was combined with moisture cyclings, maple/PRF/FRP laminate shear blocks were evaluated. It appears that an interaction exists between the level of accelerated aging and the stress induced by moisture cycling. There is considerable experience with the successful use of wood/PRF systems in outdoor use and their durability has been proven. This study indicated the PRF and epoxy bonds between maple and FRP reinforcement are more durable than those between maple and PRF.

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