The standard theory of classical continuum mechanics has certain limitations when addressing crack initiation and growth in materials because partial differential equations of motion include spatial derivatives of displacement components which are not valid in the presence of displacement discontinuities such as cracks.Īn alternative theory, known as the peridynamic theory, is a nonlocal theory that does not require spatial derivatives and removes the obstacles concerning the prediction of crack initiation and growth in materials based on classical continuum mechanics. Existing numerical methods for calculating fracture parameters encounter challenges due to this topological evolution.Īlthough mature, powerful, and versatile, finite element analysis (FEA) simply fails to predict failure initiation and complex crack growth because the FEA formulation is not mathematically suitable for the simulation of failure. The presence of manufacturing or service related residual stresses and the sequence of load interactions introduces additional challenges, requiring more complicated numerical techniques. Often these are multiple cracks exhibiting complex pattern forming within non-planar 3-D surfaces. They are generally computationally expensive and require a fine scale description of structural and mechanical properties.Īlthough the existing failure criteria for isotropic materials are applied to many problems with acceptable success, there still exist challenges when predicting the evolution of an arbitrary crack shape that may be non-planar. Current numerical methods are damage based or rely on discrete cracks. Several mathematical models and numerical methods have been developed over the years to assess various limit states such as failures due to permanent deformation, cracks, or de-cohesion/delamination in composite materials. Simulating damage initiation and subsequent global structural failure is one of the most active topics in computational mechanics. Lack of predictive capability for crack propagation paths in fiber-reinforced composite structures under cyclic loading continues to prevail despite the extensive amount of research. Reliable methods to predict 3-D crack propagation will reduce maintenance inspections and life of in-service components can be extended providing huge monetary savings. This effort will provide a pro-active approach in the design of next generation air vehicles as they will be constructed from lighter, stronger materials such as fiber-reinforced composites. The ability to predict crack path progression in fiber-reinforced composite structures is essential in the design of new aircraft and the sustainment of legacy fleet. This leads to stress redistribution in the layers and constituents. The presence of such failure modes result in stiffness reduction.
Long path tool crack series#
Failure of fiber-reinforced composites involves a progressive series of events with discrete failure modes such as matrix cracking, fiber-matrix shear, fiber breakage and delamination. Damage initiation and subsequent propagation in fiber-reinforced composites are not understood as clearly as metals because of the presence of stiff fibers within soft matrix material causing inhomogeneity. The financial costs involved when an in-service component is found to contain a defect is a major factor in the search for numerical methods to predict 3-D crack propagation.
OBJECTIVE: Develop an innovative technique utilizing peridynamic theory to determine crack path in fiber-reinforced composite structures.ĭESCRIPTION: Accurate prediction of crack growth behavior is essential in determining inspection intervals and maintenance schedules of aerospace structures where failure could lead to catastrophic consequences and loss of life. TECHNOLOGY AREA(S): Air Platform, Space PlatformsĪCQUISITION PROGRAM: PMA 275, V-22 Osprey