The ability of composite structures to handle harsh environmental conditions such as UV damage from sunlight and other weather-aging phenomenon is critical to Air Force structures such as composite Rigid Wall Relocatable Structures (RWRS) and ISO containers. Inherent weaknesses in composite matrixes make them vulnerable to degradation from UV radiation and eventual failure of the matrix resulting in delaminating. The normally selected solution has been to paint or coat the composite structure with an UV resistant coating. However, this solution mandates costly and environmentally unfriendly lifecycle maintenance such as stripping, repairing and repainting operations. It is the intent of this investigation to develop structural composite materials that will maintain mechanical properties when exposed to direct solar, UV radiation and have an expected life cycle of 30+ years. Thermoplastic Composite Design (TCD) will conduct research to determine the best combinations of commercially available materials, additives and manufacturing processes to develop a low cost UV resistant shelter. It is the intent of this investigation to develop structural composite material combinations that will maintain mechanical properties when exposed to direct solar, UV radiation and have an expected life cycle of 30+ years. Fundamental to the success of this effort is the elimination of the environmental burdens associated with the overcoat/paint process, a reduction in lifecycle maintenance costs and compliance with ASTM E1925. Thermoplastic Composite Design (TCD) will conduct research and use its extensive polymer formulation experience to determine the best combinations of materials, additives and manufacturing processes to develop a low cost UV resistant shelter for both thermoplastic and thermoset composites. Since development of a new UV inhibitor typically would require 3-5 years of design, testing, and permitting prior to commercial availability, the development of a new UV inhibitor is obviously not supportive of the Topics objectives. Therefore TCD's research efforts will be confined to the numerous UV inhibitors and other chemical adducts that are commercially available. In addition TCD will investigate the innovative concept of using pigmentation along with other UV inhibitors to achieve the desired lifespan and reduction in environmental costs. A test protocol will be developed to compare formulated coupons with combinations of Thermoset and Thermoplastic resins, chopped and/or woven fiberglass, pigmentation and UV stabilizers, as well as other commercially available anti-weathering agents. Test coupons produced from these formulations will be tested for mechanical values such as Flexural Modulus, Tensile Strength, etc. to determine any detrimental effect of the additives on controlled mechanical properties. In addition, fire resistance, accelerated sunlight, and weather-aging test will be done on the coupons to determine the efficacy of these additives for UV protection in mechanical values and surface cosmetics. It is anticipated that an environmentally friendly manufacturing methodology which allows for use of the selected materials and additives with the lowest production cost will then be utilized to produce the lowest cost structures for use in RWRS. This effort will directly facilitate the design, fabrication, and testing of prototype composite sandwich panels for UV deterioration, mechanical strength, fire resistance and impact properties in accordance with ASTM E1925 and the design and building of shelter components to allow prototype manufacturing of composite shelters.
Keywords: Composite, Shelters, RWRS, ASTM E1925, Ultra-violet, UV, thermoplastics, Solar
