Environmentally Friendly Removal of Fluid Contamination from Composite Aircraft Structure

Aerospace composite structures (e.g., carbon/epoxy) have enjoyed increasing use in aircraft manufacture over the last few decades. With strength-to-weight ratios superior to metal, their use has facilitated large decreases in aircraft weight. Composite structures often become contaminated by various aircraft fluids during maintenance or repair. Hydraulic fluid is the most wide spread contaminate encountered. Contaminated structures must be cleaned efficiently to maintain the strength of these high performance materials. Hydraulic fluid contamination, left unattended or poorly cleaned, can cause composite weakness due to plasticization, delamination, and disbanding. The solvent of choice for cleaning composite structures has historically been hexane, which efficiently removes hydraulic fluid contamination without adversely affecting the composites. However, environmental regulations have forced the Navy to use methylisobutylketone (MIBK) for cleaning instead. Unfortunately, MIBK is inefficient for this purpose, and contaminated parts often must be sent to a controlled facility for cleaning with hexane after several failed attempts using MIBK. This results in extra costs in terms of both time and money. In response to this problem, TRI/Austin is proposing to develop a new solvent based on non-toxic, zero-VOC, and non-HAP materials that can be used without regulation to efficiently decontaminate composite structures. The solvents utilized will be both environmentally and personnel friendly, and will have no regulations for shipping and handling, making them easily accessible to the Navy. TRI/Austin will examine both single solvents and multi-solvent formulations for this purpose. Both organic and aqueous systems will be tested. Composite samples will be subjected to contamination, cleaned, and the efficacy of the solvent will be determined by the retention of composite physical properties. The resulting solvent formulation will save the Navy time and money, and will also be a step towards a healthier environment.