Bio-based composite roof structure: Manufacturing and processing issues

Bio-based composite materials were tested for suitability in roof structure. Structural beams were designed, manufactured and tested, yielding good results. Based on the beam results, large-scale composite structural panels were made. Soy oil-based resin and cellulose fibers, in the form of paper sheets made from recycled cardboard boxes, were successfully used to manufacture the composite structures. This recycled paper was previously tested in composite sheets and structural unit beams and gave the required stiffness and strength required for roof construction. The roof was designed and a 1/3 scale structure was manufactured. Following this 1/3 scale design, two composite panels of 2.59 m × 1.52 m × 0.089 m were manufactured to serve as the two sides of a pitched roof connected at the ridge. The depth of the panels and thickness of the composite skin were dictated by the design as a function if the two other dimensions to give the optimum strength and cost result. To test the manufacturing process for a full-depth roof structure, a 1.27 m × 0.53 m × 0.279 m panel was successfully manufactured. In the latter structure, a modified VARTM process was used to replace the solid mold surface with a bagging film. This enabled a visual inspection of the resin flow and provided a window for using additional vacuum and injection lines on the normally hidden bottom side. This bagging method was very successful without the need for mold modification or electronic sensors. Issues related to natural fibers composite processing such as moisture inhibition and drying are also discussed in this work.