Structural integrity of aerospace textile composites under fatigue loading

High specific modulus and high specific strength are the most required characteristics of the materials in the aerospace structural applications. Unidirectional and multidirectional composites exhibit good properties in in-plane directions. Fibers in textile form exhibit good out-of-plane properties and good fatigue and impact resistance. Additionally, they have better dimensional stability and conformability. The variety of fabric architectures include weaves, knits, braids, stitched, and Z-pinned fabric. Vacuum assisted resin transfer molding (VARTM) is a low-cost closed molding process with the capability of producing complex parts. It is well known fact that majority of structural failures are due to fatigue. VARTM manufactured textile composites can be confidently used in the primary structures only if their fatigue performance is well understood. The biaxial braided carbon/epoxy composites with different braid angles (25°, 30°, and 45°) were investigated for primary structures of small business jet applications under tension-tension fatigue loading. Carbon/epoxy unstitched, stitched, and Z-pinned plain-woven composites were investigated for aerospace applications under tension-compression fatigue loading.