Chief, Sikorsky Aircraft Division of United Aircraft Corp., Stratford, Conn.
Pages: 27 Published: Jan 1972
Composite materials appear to offer substantial improvements over metals for application to structures subject to fatigue loadings. Their characteristic response to fatigue, however, is substantially different from that of metals. Whereas metals exhibit one failure mode, cracking, composites can exhibit one or a combination of failure modes, including fiber breakage, delamination, matrix cracking, interface debonding, and void growth. Much of the fatigue data for composites in the published literature relate to cycles to fracture, whereas composites generally exhibit changes in elastic and strength properties, which could result in structural failure at a fraction of the fracture life. In addition, the relatively flat S-N behavior exhibited by composites indicates that consideration of high amplitude, low cycle fatigue loading will be more critical than for metal structures. This paper reviews the available literature on the fatigue behavior of composites. It is suggested that fatigue test data be reported in terms of cycles to a given change in stiffness rather than cycles to fracture. It is further suggested that multiple damage detection schemes be used for both material and structural testing.
composite materials, composite structures, whisker composites, polymers, fiber laminates, fiberglass reinforced plastics, failure, fatigue (materials), fatigue life, damage, design, tolerance, cracking (fracturing), crack initiation, crack propagation, fatigue strength, delaminating, dissimilar materials bonding, elastic properties, anisotropy, stiffness, metals
Paper ID: STP27745S