Progressive Failure Analysis Approach Research Articles

Experimental and numerical investigations of wrinkle effect on failure behavior of curved composite laminates

Compared with flat laminates, curved composite laminates are more susceptible to wrinkle defects which must be considered in the design and structural integrity assessment. Combined experimental testing and numerical simulations were carried out in this paper to investigate the influence of wrinkles on the failure behavior of L shaped laminates. Special lay-up and forming processes were used to generate the pre-defined wrinkle profiles, and mechanical test together with the DIC measurement were carried out to illustrate the impact of wrinkles. Numerical modelling with progressive failure analysis approach was developed to simulate the failure process and the influence of the wrinkles. It is revealed that wrinkles triggered premature delamination and alter the propagation process by inducing damages near wrinkle plies. A significant strength reduction of about 30–40% was observed for the specimen containing wrinkles by both the numerical simulation and experimental results. Failure mechanism analysis revealed that the influence of wrinkles on the failure behavior was attributed to local stress concentrations around the wrinkles. The geometrical features such as amplitude and locations of the wrinkles are important factors to be evaluated for engineering application of curved composite structures.

Progressive Failure Analysis of Fiber Reinforced Polymer Matrix Composites

Abstract The mechanical properties of composite materials undergo degradation with an increased number of loading cycles. The objective of this paper is to propose a progressive failure analysis approach using Hashin’s criteria. The initiation and propagation of intralaminar failure mechanisms: matrix tension, matrix compression, fiber tension and fiber compression are identified. The stiffness degradation at a specific integration point in the material is observed. Complimentary FE simulations are performed to investigate the progressive failure analysis of composite materials employing Hashin’s criteria. The efficient use of Hashin’s criteria identifies the different failure modes. An attempt is made to demonstrate the interaction mechanism between the intralaminar damage and interlaminar delamination occurring in composite laminates. The effectual use of Hashin’s criteria helps to obtain different damage indices and damage variables using allowable material properties. The proposed new insights of progressive failure analysis approach ensure the high fidelity of these materials in generic aerospace and underwater structures. However, the efficacy of progressive failure analysis for the strain localization problems in composites is still regarded as open for the future advancement of this work

Modeling multiple failures of composite box beams used in wind turbine blades

Large composite structures, such as composite wind turbine blades, may exhibit multiple failure modes that challenge the modeling strategies and methodologies designers adopt in finite element (FE) analysis. This study develops a comprehensive and general FE modeling method to simulate interactive failure process of composite box beams used in wind turbine blades. The composite box beams are the primary loading-carrying members and could show different failure modes due to competing failure mechanisms. A continuum-damage mechanics based progressive failure analysis approach is developed in three-dimensional stress/strain domain to simulate failure behavior of the box beams. Structural nonlinearities associated with geometry, materials and contact are included. The material failures considered in this study are composite failure with three material failure modes, foam core crushing and adhesive failure. The in-plane shear stress versus strain relation of unidirectional composites is included in the material damage model. Comprehensive comparisons are made between numerical simulations and experimental observations with respect to strain response, ultimate loads, failure modes and failure progress. The modeling approach is found to be capable of predicting both strength and failure of box beams with reasonable accuracy and it exhibits great potential to predict failure response of composite wind turbine blades.

Numerical and Experimental Study of the Effect of Orientation and Stacking Sequence on Petalling of Composite Cylindrical Tubes under Axial Compression

Composite tubes are gradually being used in modern automobile structures, for enhancing structural efficiency and their performance. The energy absorbing ability of composite cylindrical tubes depends on the way in which the tube material is crushed. i.e., trend of petalling. This paper experimentally investigates the influence of fiber orientation and stacking sequence on the petal formation and specific energy absorption (SEA) of composite cylindrical tubes made of three layers under axial compression. The composite tubes consist of glass and carbon fiber unidirectional and woven cylindrical tubes with external triggers. A series of test components were made and several experiments were performed. To understand better about the crush process, numerical (FEM) studies on the crushing of tubes were carried using ABAQUS/Explicit ®. A progressive failure analysis approach is developed for fiber reinforced composite tubes using Hashin's criteria and the initiations of intra-laminar failures are identified. The crash performance of the optimum composite tube is compared to an optimal aluminium tube.

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

The overall objective of this effort was to provide theoretical prediction for damage development for a set of laminated composites using Alpha STAR Corporations’ commercial code GENOA (GENeral Optimization Analyzer) for the Air Force Research Laboratory program entitled “Damage Tolerance Design Principles (DTDP)”. Damage progression and prediction for advance composite benchmarks were done under static and fatigue service loading using test data from Lockheed Martin Aeronautics and Air Force Research Laboratory. In the current paper, the results for the static analysis are presented. Emerging and innovative multi-scale (MS) modeling using computational structural mechanics and progressive failure analysis were proven to address the Air Force’s vision to perform predictive evaluation of composite materials using a building block validation strategy and certification process. Three layups were tested in tension and compression for unnotched and openhole configurations. Calibration of the fiber and matrix properties was performed using in plane, 3pt bend and DCB test data. After this, mesh convergence, solver selection based on CPU time, and mesh sensitivities was performed. The static blind simulations of strength showed an average error of 12.9% between simulation and the test data. For stiffness, the percent difference was found to be 23.5% on average. Although the focus was on the ability to blindly predict test data, recalibration efforts show an average of 9.2% difference between simulation and test for strengths and 12.4% for stiffness computations. Damage at ∼60–75% and ∼90% of max loading was comparable with X-ray observations of specimens set aside solely for that purpose. All simulations used the same set of inputs (constituents, voids, fiber waviness, etc.) except for the noted analysis setting differences between blind and recalibration simulations. The method is consistent and follows a building block simulation approach that has an advanced yet simplistic theoretical multi-scale progressive failure analysis approach all contained in the commercial GENOA software. The method was demonstrated to work having GENOA directly run sequential NASTRAN simulations and, post project completion, with the ABAQUS solver using GENOA as a material subroutine.

Appropriate Wood Constitutive Law for Simulation of Nonlinear Behavior of Timber Joints

AbstractIn structural analysis, because of its anisotropic behavior, wood requires an appropriate constitutive law covering different behavior modes, such as ductile compressive behavior and brittle character in shear and tension. In this study, nonlinear material models were proposed to describe the behavior of timber in a finite-element method (FEM) model. An anisotropic elastoplastic constitutive law with hardening according to Hill yield criterion was used to describe the compressive behavior. Brittle behavior in tension and shear were modeled by using the progressive failure analysis approach, which is based on a failure criterion representing the evolution of damage in timber by a reduction of the elastic modulus. The wood material model was implemented in a three-dimensional FEM model to simulate the nonlinear behavior of timber joints with various types of loadings. The numerical model reliably predicted the stiffness and failure load of the joints. Furthermore, the failure index provided by the n...

Progressive Failure Behaviors of 2D Woven Composites

This paper focuses on understanding the progressive failure behavior of woven composites. Five weaves, i.e. plain, 4-, 5-, 8-harness satin and twill, are considered. Rather than developing a new progressive failure analysis approach, the focus is placed on comparing the damage behaviors of the various weaves predicted by the selected failure criterion and property degradation model. The loading conditions include uniaxial tension and compression. The discussions focus on (1) the effect of the woven architecture on the predicted progressive failure behaviors (2) the similarities and difference in the damage initiation and evolution mechanisms between the plain and satin weaves and (3) the sensitivity of the predicted progressive failure behavior to assumptions about geometric nonlinearity and the property degradation model. The results have shown that the weave architecture (i.e. weave pattern) has significant effects on the predicted progressive failure behaviors even if the composites have the same overall fiber volume fraction, tow waviness and tow cross-section. Comparisons of the damage initiation and evolution mechanisms in the plain and 4-harness satin weaves indicate significant similarities in the damage behaviors in the comparable regions for the two weaves. The results also show that the predicted response of low waviness composite, which is more commonly seen in most structural applications, is quite insensitive to the assumed property degradation model. This imposes difficulties in validating a model by comparison with test results for low waviness composites.

Progressive Failure Analysis of Adhesive Bonded Joints with Laminated Composite Adherends

The paper presents novel 3-D variational approach aimed at analyzing crack propagation in adhesively bonded composite joints. The analysis is based on the 3-D mosaic model of a composite body allowing for step-wise material property variations in all three coordinate directions, and variational principle of minimum total potential energy. The displacement field in a composite structure is approximated for all coordinate directions in terms of triple series with Bernstein basis functions. The progressive failure analysis approach utilizes critical strain energy release rate criterion to predict various scenarios of the adhesive, cohesive or interlaminar crack propagation. Several cracks of the same type or different types can be analyzed simultaneously. Two numerical examples consider double-lap adhesive bonded joint of unidirectional and cross-ply laminated composites. The results for the "sliding" and "opening" displacements show that for the bonded joint and loading conditions under consideration, both Mode I and Mode II significantly contribute to the progressive failure process.

Progressive failure analysis of composite cylindrical shells considering large rotations

A progressive failure analysis approach is presented for cylindrical shells. A geometrically non-linear finite element formulation (with large rotation capability based on the total Lagrangian approach is used to predict the onset of various failure modes in laminated composite plates and shells. Some of the failure modes considered include matrix cracking, fiber breakage and delamination. Failure relations in terms of 2nd Piola Kirchhoff stresses and changes in the constitutive relations due to large strain are taken into consideration. Load-carrying capabilities of the composite cylindrical shell structures, after the first ply failure, are discussed.