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Massive insulation of intumescent coatings may reduce the temperatures that structural materials are exposed to and allow less exotic composites in solid rocket motor designs and high-temperature applications.
The processes for using ceramic matrix composites (CMCs) in air-breathing propulsion systems to form a matrix in solid rocket motors are lengthy and iterative. There is a need to reduce the time and cost of manufacturing CMCs and expand the supply chain beyond a smaller number of domestic CMC manufacturers. Research must be performed to develop composite laminate architectures that can withstand extreme temperatures. Intumescent coatings have the potential to reduce the manufacturing cost and schedule of high temperature composites by using additively manufactured materials, thermosetting bismaleimides (BMIs), and cyanate ester laminates. However, the mechanical bonding properties between intumescent coatings and composite layers, as well as the temperature performance in these applications, are unknown.
The objective of this project is to identify and test intumescent coatings that will allow the use of bismaleimide (BMI) and cyanate esters in composite casings used in solid-propellant rocket motors.
This project explores the use of an intumescent coating system to create a thermal protection system between solid rocket fuel and the casing structure. The reason for the use of an intumescent coating is that it swells when exposed to heat, which impedes heat transfer, and will not fully expand when sandwiched between casing and propellant. Intumescent coatings that are not subjected to supply chain issues will be identified and screened. Screening will consist of lap shear testing per ASTM D3163 and climbing drum peel testing per ASTM D1781. Measures will be taken to keep the intumescent layer in place when measuring the physical properties through shear and peel strength testing. Intumescent coatings that demonstrate sufficient bonding performance will be further tested to determine the steady state thermal conductivity reduction and deformation of intumescent expansion in the annular space between coaxial cylinders. Results and recommendations will be summarized in the final report.