| This study investigated the applicability of bio-based composites for housing construction. Since traditional wood-frame construction is vulnerable to hurricanes, especially the roof, the research focused on a proposed monolithic bio-based composite roof panel to replace the traditional built-up roof. The proposed monolithic roof panel is a web-core sandwich construction, with a top face, bottom face, and equally spaced webs that run perpendicular to the roof ridge. The roof panel is designed to serve as an integrated structural system, to carry all of the loads a traditional roof carries without the need for rafters or roof trusses. The roof also has a high inherent insulation value due to the integral foam cores.; The composite design for the roof consists of a soybean-based (Acrylated Epoxized Soy Oil) resin and recycled paper as reinforcement. Test beams and panels were fabricated using Vacuum Assisted Resin Transfer Molding (VARTM).; The design load for the roof panel on a hypothetical house was developed using the ASCE-7 Minimum Design Loads for Building and Other Structures. The controlling design load is -58 lb/ft2 and is due to the negative pressure (suction) due to wind.; Experimental studies were conducted that included: (1) flexural tests of seven different web-core sandwich "unit beams", which severed as a basis for choosing the final bio-composite materials and sandwich construction for the roof; (2) flexural tests of a true scale model web-core sandwich beam, which represents a unit width of the roof panel; the test results demonstrated that the proposed monolithic roof would have the necessary strength and stiffness to satisfy all of the design criteria; (3) Flexural and in-plane shear tests of two web-core sandwich "unit panels", which served to investigate the local flexural stiffness and in-plane shear stiffness and strength of the proposed sandwich panel, and the viability of using them as diaphragms in residential construction.; An analytical model for the composite web-core panel was developed by transforming it into a solid panel with equivalent orthotropic elastic constants. The constants were derived, including the material orthotropy and shear deformation, through a comparison between the panel governing equations and the stress resultants/deformation relationship of a web-core sandwich panel. With different boundary conditions, the Navier method and Ritz method were adopted to obtain the deflection solution. The solutions are in good agreement with the results of finite element analyses.; The roof panel design was optimized based on single and multiple constraints. The design constraints included deflection, face strength, web strength, face buckling, and web buckling. The failure mechanism map was constructed to understand the failure mode transition. An iterative optimization procedure was proposed for the web-core sandwich panel with multiple constraints. For the preliminary proposed roof panel design, the fully optimized design resulted in a nearly 60% saving in material. |
