|Acquisition Program: ||Joint Strike Fighter|
| ||RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is “ITAR Restricted”. The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the “Permanent Resident Card”, or are designated as “Protected Individuals” as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected.|| Objective: ||Develop and demonstrate low cost, rapid methods for evaluating fiber coatings for ceramic matrix composites (CMCs).
|| Description: ||The Joint Strike Fighter and other military platforms are considering ceramic matrix composites (CMCs) for engine applications due to their potential for weight reduction, reduced cooling, and durability improvements. Most CMCs require one or more thin coatings (<1 micron thick) on the fibers in order to achieve the weak interface that is required for high toughness. These coatings turn out to be key to the composite properties and also cost and cycle time drivers. Routine evaluation of the coatings is required to ensure that they meet specifications. Key coating parameters that need to be evaluated include the thickness and chemistry with morphology and crystallinity also of interest. Traditionally, techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and auger analysis are used to characterize the coatings. These techniques are both expensive and time consuming. Lower cost, more rapid techniques are required to reduce coating cost and cycle time. The existing techniques are also limited to evaluation of extremely small areas; techniques that sample from larger surface areas are desirable.
Techniques exist and are used commercially to characterize thin coatings in various industries. However, the characteristics for fiber tow/fabric/preform coatings is more complex due to the substrates being non-planar, the coatings often having multiple layers with different chemistries, and the chemistries being more complex. Recent advances in advanced optical and other characterization techniques and instrumentation offer possibilities, but will need to be developed for this complex application. Nondestructive methods are highly desirable. Teaming which includes a military engine manufacturer and a composite fabricator will be key to ensuring that suitable and sufficient techniques are developed and demonstrated on composite systems of interest.
|| ||PHASE I: Adapt the characterization technique(s) proposed for the fiber coating application. Explore the capabilities and demonstrate the technique on samples with different coating thickness & chemistry. Estimate the cost and time required for coating characterization and identify improvements for Phase II.
|| ||PHASE II: Make the improvements identified at the end of Phase I and quantify the capability enhancement. Demonstrate the characterization technique in a commercial fiber coating setting. Characterize sufficient samples of coated fiber/fabric/preform to validate the capability, cost, and cycle time.
|| ||PHASE III: Optimize the coating characterization methodology for the chosen fiber coating process and chemistry. Modify the existing quality control (QC) specifications for the new methodology. Undertake the demonstration necessary to qualify the new QC methodology.
PRIVATE SECTOR COMMERCIAL POTENTIAL/|| ||DUAL-USE APPLICATIONS: The quality control methodology developed will benefit a broad range of CMCs with applications that include military and commercial aircraft as well as various industrial applications.
|| References: ||1. L. Sun, C. Berndt, A. Kucuk, R. Lima, K. Khor, "Surface Characterization of Plasma Sprayed Hydroxyapatite Coatings," Cer. Eng Sci. Proc., 21, , p251-258 (2000).
2. J. Eldridge, C. Spuckler, J. Nesbitt, and K. Street, " Health Monitoring of Thermal Barrier Coatings by Mid-Infrared Reflectance," Cer. Eng. Sci. Proc., 24, , p511-516 (2003).|
|Keywords: ||Ceramic Matrix Composite (CMC); Fiber Coatings; Coating Characterization; Nondestructive Evaluation (NDE); Quality Control, Cost Reduction|