Mixed Failure Criterion Research Articles

Thermo-mechanical coupling failure modeling of 3D four-directional braided composite I-beam under four-point flexure at room temperature, −50°C and 85°C

This paper aims to experimentally and numerically probe thermo-mechanical coupling behaviors of 3D4D (three-dimensional four-directional) braided composite I-beam under four-point flexure. An improved algorithm based on thermo-mechanical coupling constitution model, and mixed failure criterion are devised for modeling thermo-mechanical coupling failure process of 3D4D braided composite I-beam under four-point flexure. Quasi-static four-point flexure tests are, respectively, performed on 3D4D braided composite I-beam at RT (room temperature), −50 ° C and 85 ° C , and mechanical behaviors and failure mechanisms are analyzed and discussed from experiment results. To validate the aforementioned model and algorithm, novel global-local FE (finite element) model is generated and integrated with new algorithm for modeling failure process of 3D4D braided composite I-beam under four-point flexure at three temperatures, and numerical predictions agree well with experimental findings, demonstrating the effective and rational use of the proposed model in the paper.

Progressive damage characteristics of screwed single-lap CFRPI-metal joint subjected to tensile loading at RT and 350°C

This paper outlines progressive damage characteristics of screwed single-lap CFRPI-metal joints subjected to tensile loading at RT (room temperature) and 350°C. Quasi-static tensile tests were performed on screwed single-lap CCF300/AC721-30CrMnSiA joint at RT and 350°C, and the load versus displacement curve, strength and stiffness of joint were gauged and discussed. With due consideration of thermal-mechanical interaction and complex failure mechanism, a modified progressive damage model (PDM) based on the mixed failure criterion was devised to simulate progressive damage characteristics of screwed single-lap CCF300/AC721-30CrMnSiA joint, and simulations correlate well with experiments. By using the PDM, the effects of geometry dimensions on mechanical characteristics of screwed single-lap CCF300/AC721-30CrMnSiA joint were analyzed and discussed.

Damage evolution analysis of open-hole tensile laminated composites using a progress damage model verified by AE and DIC

A three-dimensional finite element model of composite laminates for progressive damage analysis has been established based on continuum damage mechanics. The model contains four kinds of damage modes of composite laminates under three-dimensional stress states, which include matrix damage, fiber breakage, delamination and fiber pull-out. Damage initiations adopt the mixed failure criterion composed by Linde criterion and Hashin criterion, which choose strain as parametric description. An improved exponential non-linear evolution model is adopted for damage variables, which take into account the effect of material dissipated energy on the damage variables. The damage variables calculated by material dissipated energy are different from that calculated by fracture dissipation energy employed by Linde, the material dissipated energy is the result of various damage accumulation of composite material, which can reflect the gradual damage evolution process of material. The progressive damage simulations have been performed to investigate damage evolution of unidirectional laminate and bidirectional laminate with a hole under tension, the damage evolutions simulated by FEA have a good agreement with that obtained from real-time acoustic emission (AE), digital image correlation (DIC) monitoring and load–displacement relationship, which validate efficiency of the proposed 3D FEM model.

Constitutive modelling of composite laminates under uniaxial compression

A nonlinear constitutive model for a single lamina is proposed for the failure analysis of composite laminates. In the material model, both fiber and matrix are assumed to behave elastic-plastically and the in-plane shear is assumed to behave nonlinearly with a variable shear parameter. The damage onset for individual lamina is detected by a mixed failure criterion, composed of the Tsai-Wu criterion and the maximum stress criterion. After damage takes place within the lamina, the fiber and in-plane shear are assumed to exhibit brittle behavior, and the matrix is assumed to exhibit degrading behavior. The proposed nonlinear material model is tested against experimental data of composite laminates subjected to uniaxial compressive loads, and good agreement is obtained.

Shimming effect on the mechanical behaviors of composite assembly structures of aircraft

The mechanical behaviors of composite assembly structures of aircraft might change due to filling the fit-up gap between two components with liquid shim or laminated shim. In order to investigate the change qualitatively and quantitatively, a kind of implicit nonlinear finite element models are developed, and mixed failure criteria considering the nonlinear shear relationship between composite matrix and fiber, out-of-plane stresses, and buckling of fiber are incorporated into finite element models. And tensile experimental research is also performed to validate the finite element models. Good agreement between the numerical and experimental results builds confidence that the finite element models are effective in predicting the shimming effect. And it is also observed that the mechanical behaviors of composite assembly structures with different filling present obvious differences.

Influence of interference-fit percentage on stress and damage mechanism in hi-lock pin installation process of CFRP

The interference-fit technology is an effective way to enhance fatigue life of mechanical structures. However, for composites, oversized interference-fit percentage causes damages and then decreases the joint performance directly. Influence of percentages on stress and damage around Carbon Fiber Reinforced Plastics interference-fit hole is analyzed in this paper. The progressive damage theory is introduced into a three-dimensional finite-element model, which consists of the mixed failure criteria combining Hashin criteria and maximum stress criteria and the corresponding property degradation rules. A nonlinear shear stress–strain relationship is also built to solve the nonlinear material behavior. Three groups of 0.4%, 0.8%, and 1.2% interference-fit percentages are analyzed. Corresponding pin installation experiments are conducted to validate the accuracy of the model. The inserting force, stress distribution, and damage initialization around the hole are investigated and discussed in this model.

Stress analysis and damage evolution in individual plies of notched composite laminates subjected to in-plane loads

This work aims to investigate local stress distribution, damage evolution and failure of notched composite laminates under in-plane loads. An analytic method containing uniformed boundary equations using a complex variable approach is developed to present layer-by-layer stresses around the notch. The uniformed boundary equations established in series together with conformal mapping functions are capable of dealing with irregular boundary issues around the notch and at infinity. Stress results are employed to evaluate the damage initiation and propagation of notched composites by progressive damage analysis (PDA). A user-defined subroutine is developed in the finite element (FE) model based on coupling theories for mixed failure criteria and damage mechanics to efficiently investigate damage evolution as well as failure modes. Carbon/epoxy laminates with a stacking sequence of [45°/0°/−60°/90°]s are used to investigate surface strains, in-plane load capacity and microstructure of failure zones to provide analytic and FE methods with strong validation. Good agreement is observed between the analytic method, the FE model and experiments in terms of the stress (strain) distributions, damage evaluation and ultimate strength, and the layer-by-layer stress components vary according to a combination effect of fiber orientation and loading type, causing diverse failure modes in individuals.

Bearing strength and failure analysis on the interference-fit double shear-lap pin-loaded composite

Interference-fit technology has a wide effect on the strength and fatigue life of composite structures. The damage around the hole may accelerate the structure failure. In this paper, a progressive damage model is developed to predict the response of interference-fit pin-loaded composite laminates during the installation and loading process with the ABAQUS subroutine user-define-field (USDFLD). The model takes contact at the pin–hole interface, the nonlinear shear stress–strain relationship and the property progressive damage into consideration. The loading procedure is separated into two parts: (a) installing the Hi-Lok pin. (b) Applying the tensile load. To predict progressive failure, the mixed failure criteria combining Hashin criteria and the maximum stress failure criteria, and the Camanho and Matthews degradation rules are conducted. The insertion load, stress and damage around the hole, load–displacement curve, and the bearing strength are predicted. A series of experiments have also been performed and the rationality of the model is testified. The parametric study is also made to analyze the effect of fit conditions on insertion load, damage, and load–displacement curve.

Progressive damage modelling of hybrid RTM-made composite Π-joint under four-point flexure using mixed failure criteria

This paper deals with four-point flexure tests on hybrid Π-joints, made out of multi-layer carbon fiber/epoxy resin reinforced composites, processed using the RTM (resin transfer moulding) technique. Static bending properties and failure mechanism were determined by experimental observations. Failure of the Π-joints in four-point flexure tests was through interlaminar debonding in triangular zone followed by debonding propagation along the interface between the triangular zone and the adjacent boundary angle until complete breakage of the top skin. A progressive damage model (PDM) based on mixed failure criteria was developed to predict failure loads. Good correlation was achieved between experimental and numerical results.

Failure analysis of fiber-reinforced composite laminates subjected to biaxial loads

A nonlinear constitutive model for a single lamina is proposed for the failure analysis of composite laminates. In the material model, both fiber and matrix are assumed to behave as elastic-plastic and the in-plane shear is assumed to behave nonlinearly with a variable shear parameter. The damage onset for individual lamina is detected by a mixed failure criterion, composed of the Tsai-Wu criterion and the maximum stress criterion. After damage takes place within the lamina, the fiber and in-plane shear are assumed to exhibit brittle behavior, and the matrix is assumed to exhibit degrading behavior. The proposed nonlinear constitutive model is tested against experimental data and good agreement is obtained. Then, numerical analyses are carried out to study the failure behavior of symmetric angle-ply composite laminates and symmetric cross-ply composite laminates subjected to biaxial loads. Finally, the conclusions obtained from the numerical analysis are given.

Numerical simulation for delamination during drilling of CFRP/AL stacks

This paper is devoted to predicting the critical thrust force at delamination onset by finite element method in order to contribute the delamination-free drilling process of carbon-fiber-reinforced polymer/aluminum (CFRP/AL) stacks. First, taking the tapered drill point into account, a qualitative finite element analysis of push-out delamination is carried out to ascertain the location where the delamination first occurs. Mixed failure criteria and Camanho–Matthews stiffness’ degradation criterion are applied to represent the damage initiation and evolution of CFRP. Second, three-dimensional finite element models are developed for predicting the critical thrust force of drilling CFRP/AL stacks at different stages by using traction-separation law to represent the interlaminar property. Finally, to validate the rationality of the finite element (FE) models, the results are compared with the previous theoretical and experimental results, and acceptable agreements have been obtained.

Numerical Study on Crack Propagation by Using Softening Model under Blasting

A mixed failure criterion, which combined the modified maximum principal stress criterion with the damage model of tensile crack softening, was developed to simulate crack propagation of rock under blasting loads. In order to validate the proposed model, a set of blasting models with a crack and a borehole with different incident angles with the crack were established. By using this model, the property of crack propagation was investigated. The linear equation of state (EOS) was used for rock, and the JWL EOS was applied to the explosive. In order to validate the numerical simulation results, experiments by using PMMA (polymethyl methacrylate) with a crack and a borehole were carried out. The charge structure and incident angle of the blasting experimental model were the same as those in the numerical models. The experiment results agree with the numerical simulation results.

Time to Creep Failure of Thin-Walled Cylindrical Pipes under Torsion

The time to creep failure is calculated for rectilinear thin-wall pipes subjected to pure torsion, torsion with uniaxial tension, and torsion with internal pressure. The problem is solved using the concept of equivalent stress. The equivalent stresses are found from the generalized mixed failure criterion whose form depends on the signs of the principal stresses. The criterion relates the maximum normal stress and the intensity of shear stress if the signs coincide, and the maximal shear stress and the octahedral shear stress if the signs are opposite. A technique for determining the material constants is developed. The calculated and experimental data are compared and found to be in satisfactory agreement

Parametric Study on the Failure of Fiber-Reinforced Composite Laminates under Biaxial Tensile Load

A numerical constitutive model for a single layer of fiber-reinforced composite laminates, including nonlinear stress–strain relations, mixed failure criterion and post failure response, is used to predict the ultimate strengths of the composite laminates under biaxial tensile loads. The nonlinear constitutive law uses a variable shear parameter to model the nonlinear behavior of the in-plane shear. The onset of failure for individual lamina is determined by a mixed failure criterion composed of the Tsai-Wu and the maximum stress criteria. After the initial damage occurs, the response of the lamina is described by brittle or degrading modes up to the collapse of the entire laminate. The constitutive model is tested against experimental data and satisfactory results are obtained. In addition, parametric studies for composite laminates with different laminate layups and under various biaxial tensile load ratios are presented.

Nonlinear Analysis of Fiber-Reinforced Composite Laminates Subjected to Uniaxial Tensile Load

A nonlinear constitutive model together with a mixed failure criterion for a single lamina is developed to simulate the behavior of composite laminates under uniaxial tension. In the model, fiber and matrix are assumed to behave elastic–plastic and the in-plane shear to behave nonlinear with a variable shear parameter. The damage onset for individual lamina is detected bya mixed failure criterion, which is composed of Tsai–Wu criterion and maximum stress criterion. After damage is taken place within the lamina, fiber and in-plane shear are assumed to exhibit brittle behavior and matrix to exhibit degrading behavior. This material model has been tested against experimental data and good agreement has been obtained.