High-Performance Liquid Crystal Adhesives

Cornerstone Research Group, Inc. and the University of Dayton propose to develop and evaluate a high-temperature, low-shrinkage Cornerstone Research Group, Inc. and the University of Dayton propose to develop and evaluate a high-temperature, low-shrinkage easy to process adhesive based on an advanced liquid crystal thermoset. This adhesive, coupled with an evanescent field absorption fiber-optic sensor, will be integrated with an aircraft patch to monitor chemical integrity of a repair. The technical objectives of this program are 1) to develop an easy-to-process, high-performance adhesive that has low moisture sensitivity and reduced cure shrinkage compared with conventional resins, and 2) develop specific fiber optic sensor approaches to detecting both hygrothennal and oxidative aging of adhesives. The materials system is based on a monomer type that is dual curing and can be polymerized at relatively low temperatures to form adhesives thermally stable to 300*c. The monomer has a smectic LC phase above room temperature. Because the LC phase allows tight packing of molecules it has a higher density than the isotropic phase. Cure in the smectic phase should result in lower overall cure shrinkage than typical isotropic monomers exhibit. Lower thermal expansion coefficients can also result from cure of a LC material. These parameters are important in the development of advanced adhesives for aerospace applications.