Out of Autoclave Processable Prepregs and Resin Films — An Overview of Recent Developments and Shared Databases

Since the early 1990's composite prepreg materials capable of being processed under oven vacuum bag as opposed to autoclave conditions have been used to produce low cost prototype and limited production structures. The low temperature cure capability of some of these systems has also permitted the use of inexpensive tooling materials with significant impact on delivered part costs. ACG's LTM45EL prepregs, which were used to build Scaled Composites Spaceship One and other space and military aircraft, is an example of such a material. While these first generation out of autoclave processable prepregs lacked the performance required for production structures, a new generation of resins has been developed which address all of the shortcomings of the original systems. The characteristics of some of the new generation materials such as ACG's MTM45-1 and MTM46 resin systems are examined and discussed. The work done to provide the required B and A basis property databases necessary to use the new materials on certified aircraft structure is also described. The practice of the material supplier providing these databases for use by multiple end users is seen as a major step forward in composite material qualification practices and is an additional factor which will lead to more affordable structures.