Computational simulation of internal damage accumulation in filamentary composite material systems

Abstract

Advanced filamentary composite materials suffer loss of strength and stiffness when subjected to service loads. This loss can be attributed to the effect of several mechanisms which include matrix microcrack growth, fiber/matrix debonding, and fiber breakage. Stiffness loss and eventual failure is caused by complex interactions among these damage modes. Some are time-dependent and most are irreversible. Subsequently, any time that a composite material system is subjected to a relatively high load its structural integrity is significantly diminished. Advanced composites can also fail when they are subjected to constant-magnitude loads that are substantially lower than the ultimate strength of the composite if the loads are sustained for long periods of time. This phenomenon, which is commonly referred to as creep-rupture, is accelerated if the structure was initially subjected to a proof-test load. The effect of this test on the reliability of the vessel is a major concern. A better understanding of proof-test damage and creep-rupture requires a great deal of study and modeling of the interacting damaging processes.