Microstructural Differences between Woven Mat and Acrylic Binder TMC and their Relationship to Fatigue Damage Modes

Abstract

Extensive microstructural evaluations were performed on two titanium matrix composite (TMC) materials to examine any chemical and/or physical differences which explain fatigue crack growth patterns observed in these materials. These examinations included optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and Auger analysis. The results of these studies indicate that fatigue damage modes, in addition to being affected by obvious parameters like load and temperature are also affected by the process in which the TMC is consolidated. Fiber surface damage is visible on one of the two TMC systems which may have influenced the observed fatigue damage mode. The fiber surface damage can be traced back to the pressure applied to the laminate during consolidation. This paper provides a detailed explanation for the occurrence of the different fatigue damage modes and, therefore, provides an explanation for the significant difference in fatigue life of the two materials.

Keywords

titanium matrix composites fatigue life crack growth damage scanning electron microscopy

Get full access to this article

View all access options for this article.

References

1. Lisagor, B. W. 1991. Advanced Metallics for High Temperature Airframe Structures.

2. Colucci, F. 1991. "Hypersonic Materials," Aerospace Composites & Materials, 3(6):4-8.

3. Harmon, D. M. , C. R. Saff and C. T. Sun . 1987. "Durability of Continuous Fiber Reinforced Metal Matrix Composites—Final Report," AFWAL-TR-87-3060, October.

4. Harmon, D. M. and M. A. Finefield . 1994. "Thermomechanical Load History Effects in Metal Matrix Composites—Final Report," WL-FR-94-3015, Contract No. F33615-87-C-3219, McDonnell Aircraft Company.

5. Newaz, G. M. and B. S. Majumdar . 1992. "Crack Initiation around Holes in a Unidirectional MMC under Fatigue Loading," Engineering Fracture Mechanics, 42(4):699.

6. Harmon, D. M. and C. R. Saff . 1989. "Damage Initiation and Growth in Fiber Reinforced Metal Matrix Composites," Metal Matrix Composites: Testing, Analysis, and Failure Modes, W. S. Johnson , ed., ASTM STP 1032, American Society for Testing and Materials, Philadelphia, pp. 237-250.

7. Lerch, B. A. , T. P. Gabb and R. A. MacKay . 1990. "Heat Treatment Study of the SiC/Ti-15-3 Composite System," TP 2970, NASA Lewis Research Center.