In the design and construction of waterfront structures, there is a need for development of a corrosion resistant, lightweight, cost effective and environmentally friendly structural material. Hybrid wood-plastic composite (WPC) – fiber-reinforced polymer (FW) structural members would be corrosion resistant, and relatively lightweight (WPC-FW). An additional advantage is that the WPC portion can be produced from recycled plastics and wood residuals. T o use WPC in structural applications a better understanding of the material properties and behavior under sustained loads must be obtained. In this paper, a static and long term experimental program is presented with coupon and full size WPC samples. Coupon testing in tension, compression, and shear is conducted with the aid of a 3-D digital image correlation DIC ) system which allows a full field, non-contact measurement of strains o n the material’s surface. Full size, hybrid WPC – FRP members are also characterized experimentally in bending. This experimental response is used to generate and verify a non-linear model for long-term material behavior.
Marine construction materials have always suffered from a shorter life cycle than their terrestrial cousins. Historically, materials such as steel, concrete, and wood have been prevalent, and required routine replacements and/or maintenance to ensure safe marine structures. WPC is an exciting new material that has been successfully used in many marine construction applications. Typical WPC’s are composed of a thermoplastic resin and short (1- 5mm) wood fibers, which are mixed together at high temperatures. T h s molten mixture can then be forced through a die in a continuous process called extrusion, or injection molded to produce small parts. WPC has many advantages over traditional materials, which include relatively lightweight, corrosion and decay resistant, non-leaching, and recyclable. Tnis combination of desirable qualities has led to the use of WPC for many secondary components in marine construction, such as decking, railing, and fencing.
There is a need to develop this product to compete with traditional materials for primary structural components, such as joist, stringers, pilings and girders. However, material properties and behavior must be understood before WPC is to be used in demanding structural applications. The University of Maine, working in conjunction with the United States Coast Guard, and Washington State University is making an attempt to better understand this complex material and develop design guidelines for structural applications.
The work presented in this thesis is a step forward in the process of understanding how WPC materials behave so that they can be used more efficiently, and safely in the future.