The objective of this proposal is to develop and demonstrate the feasibility of high modulus carbon fiber reinforced, VARTM processable vinyl ester laminates with an improved fiber / matrix interface that will provide increased modulus and other mechanical properties. The appropriate choice of resin will also provide composite structures with reduced flammability, smoke and toxicity. The goal is to produce a fiber sizing that will be applied in a conventional carbon fiber manufacturing process and improve adhesion between the high modulus reinforcing fiber and the vinyl ester resin when cured in a VARTM process. We propose to achieve this improvement in interfacial bonding by sizing the fiber with a combination of a polymeric film former and a coupling agent. The degree of adhesion between the fibers and the matrix as well as the nature of the fiber / matrix interphase have a major influence on the mechanical properties and the durability of a composite. Significant interfacial adhesion is required to obtain effective stress transfer from the matrix to the load bearing reinforcing fibers. If the interfacial adhesion between carbon fiber and vinyl ester resin could be improved then the full potential of these advanced composites could be realized. Benefit Glass fiber matrix composites can achieve strengths greater than steel at only 1/3 of the density. This can provide significant weight savings in many structural applications. Unfortunately, the stiffness of these composites is only about 1/10th that of steel due to the relatively low modulus of glass fiber. If higher modulus fibers, such as carbon fiber, could be used then even lower densities and higher modulus composites could be achieved. If the interfacial adhesion between carbon fiber and vinyl ester resin could be improved then the full potential of these advanced composites could be realized. This would allow the Navy to incorporate higher modulus, low density composites into many structural applications. In addition to the many uses projected by the Navy, this product will have many civilian applications to replace similar vinyl ester and unsaturated polyester composites as well as epoxy composites and metal. For example, the off-shore oil industry is concerned with lightweight flame retardant housing and deck structures, which could be produced with carbon fiber and brominated vinyl ester. Seismic building upgrades are becoming more critical due to California legislative requirements and could also be achieved by carbon fiber reinforced vinyl ester if the interfacial properties were improved. The automotive industry is also evaluating numerous applications using carbon fiber to take advantage of the inherent higher modulus and lower density obtainable with carbon fiber if the interface were improved. Another area that is seeing significant growth is the wind energy market. Carbon fiber is used to provide windmill blades with higher modulus that could be obtained with glass fiber; however, they have been forced to use epoxy resins in most cases. If the interfacial adhesion problems of carbon fiber and vinyl ester were solved then this cost sensitive industry could utilize the less expensive and more easily processable vinyl ester resins. Keywords carbon fiber, vinyl ester, interfacial adhesion, sizing, VARTM
