Energy-Based Stiffness Degradation for Alleviation of Mesh Sensitivity for Progressive Failure Analysis of Center-Notched Composite Panels

2012 ◽  
Author(s):  
Pierre Minguet ◽  
Kazbek Karayev ◽  
Vladimir Balabanov ◽  
Sangwook Lee ◽  
Nav Muraliraj ◽  
...  
Keyword(s):  
Failure Analysis ◽  
Progressive Failure ◽  
Stiffness Degradation ◽  
Composite Panels ◽  
Progressive Failure Analysis ◽  
Mesh Sensitivity

Progressive failure analysis of marine sandwich joints with a modified material degradation model

2018 ◽  
Vol 38 (9) ◽  
pp. 426-438
Author(s):  
Mengzhen Li ◽  
Renjun Yan ◽  
Wei Shen ◽  
Kang Liu
Keyword(s):  
Failure Analysis ◽  
Progressive Failure ◽  
Woven Fabric ◽  
Stiffness Degradation ◽  
Displacement Curve ◽  
Material Degradation ◽  
Degradation Model ◽  
Failure Patterns ◽  
Progressive Failure Analysis ◽  
Load Displacement

The progressive failure analysis based on a modified stiffness degradation model was proposed to predict mechanical response of sandwich L-joints for ships. A representative volume element was established for the derivation of the modified material degradation model for two-dimensional orthogonal woven fabric structures based on micromechanical theory. The modified Shokrieh failure criterion and six field variables were applied in ABAQUS user subroutines. Three different coordinate systems were used to assign reasonable material orientation. The predictions of ultimate load, stress distribution, load-displacement curve and failure patterns were compared with experimental results. The good consistence indicates the effectiveness of the proposed stiffness degradation model. The FE results show the edge of the arc bracket is the stress concentration area due to the shear lag effect, and the declined slope of load–displacement curve is caused by delamination failure due to the stiffness difference of laminates and foam core.

Damage-tolerant composite design principles for aircraft components under fatigue service loading using multi-scale progressive failure analysis

2017 ◽  
Vol 51 (15) ◽  
pp. 2181-2202 ◽  
Author(s):  
Saber DorMohammdi ◽  
Cody Godines ◽  
Frank Abdi ◽  
Dade Huang ◽  
Massimiliano Repupilli ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Failure Analysis ◽  
Air Force ◽  
Progressive Failure ◽  
Stiffness Degradation ◽  
Multi Scale ◽  
Progressive Failure Analysis ◽  
Damage And Fracture ◽  
Open Hole ◽  
Air Force Research Laboratory

Virtual testing has lately gained widespread acceptance among scientists as a simple, accurate, and reproducible method to determine the mechanical properties of heterogeneous microstructures, early in the production process. As a result of the rapid expansion of the use of composites in aerospace design, virtual testing techniques are, in fact, deemed extremely useful to eliminate unnecessary tests and to reduce cost and time associated with generating allowables for lengthy lifing analyses of structures. Leveraging on a limited set of experimental data, a Progressive Failure Analysis can accurately predict the life and safety of a component/assembly, simply tapping on the physics of its micro-/macro- mechanics material properties, manufacturing processes, and service environments. The robust methodology is showcased using blind predictions of fatigue stiffness degradation and residual strength in tension and compression after fatigue compared with test data from Lockheed Martin Aeronautics and Air Force Research Laboratory). The multi-scale progressive failure analysis methodology in the GENOA software considers uncertainties and defects and evaluated the damage and fracture evolution of three IM7-977-3 laminated composite layups at room temperature. The onset and growth of composite damage was predicted and compared with X-ray CT. After blind predictions, recalibrations were performed with knowledge of the test data using the same set of inputs for all layups and simulations. Damage and fracture mechanism evolution/tracking throughout the cyclic loading is achieved by an integrated multi-scale progressive failure analysis extended FEM solution: (a) damage tracking predicts percentage contributing translaminar and interlaminar failure type, initiation, propagation, crack growth path, and observed shift in failure modes, and (b) fracture mechanics (VCCT, DCZM) predicts crack growth (Crack Tip Energy Release Rate vs. Crack Length), and delamination. The predictive methodology is verified using a building block validation strategy that uses: (a) composite material characterization and qualification (MCQ) software, and (b) the GENOA multi-scale progressive failure analysis fatigue life, stiffness degradation, and post-fatigue strength predictions for open-hole specimens under tension/compression at RTD. The unidirectional tension, compression, and in-plane shear lamina properties supplied by Lockheed Martin Aeronautics and the Air Force Research Laboratory (based on the D3039, D638, D3518 tests) were used by MCQ to reverse engineer effective fiber and matrix static and fatigue properties for the IM7-977-3 material system. The use of constituent properties identified the root cause problem for composite failure and enabled the detection of damage at the micro-scale of the material where damage is incepted. For all three case studies (namely, layups [0/45/90/−45]2s, [+60, 0, −60]3s, and [+30, +60, 90, −60, −30]2s), the blind predictions on the fatigue stiffness degradation and residual strength of the open-hole coupon in tension/compression under cyclic loading (with R = 0.1) at RTD were evaluated using a FE mesh (made of 2k shell elements), in which only one shell element, containing all plies, was employed through the thickness. The results of all analyses correlated very well with the tests, including the damage micro-graphs generated during the cyclic loading.

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