Advanced Composite Structural Members for Tall, Narrow Structures

Composite Support & Solutions Inc (CSSI), proposes a Phase-II Project that involves the design, testing, and construction of a 135 foot tall prototype tower. The innovative nature of this tower is not only that it is made of composite materials, but also that it is completely fastenerless. Therefore tower design has the potential to operate for its design lifetime of 50 years in hot and humid environments with virtually no maintenance. As such the project adequately solves a significant problem posed by the Air Force engineers and managers, and their customers. In Phase-I a three legged tower was selected and designed for adequate stiffness and strength. Finite element modeling revealed that for the combined 50 mph wind load plus equipment load, plus its own weight it deflected no more than 21” at the top. Therefore the three legged composite tower matches the stiffness of its steel counterpart at roughly half of the weight. Additionally, the composite structure can survive gale winds of 150 mph and there is substantial evidence that it won’t collapse catastrophically, like a metal tower, in case one of its cross members or fastenerless joints fail. In Phase-I we also detailed the fiber architecture of the truss member tubing, and developed these elements as pultrusions. The the manufacturing thus occurs with an automated process which points to the feasibility of an as installed cost which is competitive to that of a steel tower structure. The selected resin is a vinylester with an added UV stabilizing agent. Demo truss members were made in Phase-I. The Phase-II project consists of 25 tasks, each of which has a number of subtasks. The project will start off with a search for the most optimum tower configuration by using modern “genetic” optimization algorithms. A substantial part of the project is dedicated to the development of a design database on the basis of coupons, truss members, and fastenerless connections. Effects of environmental exposure such as UV and temperature and also joint fatigue loading effects will be investigated. Pultrusion process design will lead to the pultrusion of the truss elements using CSSI’s Glastruder pultrusion machine. These are assembled into a test section which is then instrumented and tested at CSSI. Subsequently a full scale 135 foot tower is delivered to Vandenberg AFB, where it is erected, instrumented, and monitored. The qualifications of the CSSI personnel are well documented and respected in the composites industry. The final tasks are the dissemination of information and the commercialization of this technology. In order to facilitate this CSSI has developed a strategic alliance with Composite Technology Corporation in Irvine, CA.