Failure Analysis Of Composite Structures Research Articles

Damage and Fracture Analysis of Bolted Joints of Composite Materials Based on Peridynamic Theory

Abstract It is clear that the advantages of fibre glass-reinforced plastics surpass those of steel, but the failure analysis of composite structures is much more complex than that of isotropic materials as composite materials may fail in a variety of ways. In order to simulate the damage and fracture of bolted joints of fibre reinforced composite, the bond-based peridynamic method suitable for elastic, brittle and anisotropic characteristics of composite material is used. The peridynamic model for composite laminate is validated by the finite element method. Then a peridynamic program of composite damage is applied to calculating the damage of bolted joint structure and the damage propagation process and failure mode of the structure is obtained.

A novel material degradation model for unidirectional CFRP composites

Abstract A novel material degradation model (MDM), which is an essential component of progressive damage models for failure analysis of composite structures, is proposed based on the representative volume element (RVE) method. In this model, a material degradation rule accounting for seven failure modes in a modified Hashin-type failure criterion is proposed. This rule determines the mechanical parameters that are degraded when a failure occurs. The degradation factors of these parameters are calculated from the RVE models for perfect and damaged materials corresponding to the seven failure modes, which are based on the fundamental properties of transverse isotropic fibers and isotropic matrix. To verify the proposed method, the calculated MDMs are used in the progressive failure analyses of open-hole laminates made of three types of CFRP composites under tensile and compressive loadings. Furthermore, the failure analyses of four kinds of double-lap single-bolted joint structures with various layups and geometry dimensions are also conducted under tensile loading. The numerical predictions of failure loads, failure patterns and load-displacement curves are compared to the experimental results. Good agreement between the model predictions and the experimental results demonstrates the effectiveness of the proposed MDM for the progressive damage analyses of open-hole laminates and composite bolted joints.

$$\varvec{N}$$-Layer concentric cylinder model (NCYL): an extended micromechanics-based multiscale model for nonlinear composites

A validated multi-scale computational mechanics framework for progressive failure modeling of composite structures is developed. Zhang and Waas (Acta Mech 225(4–5):1391–1417, 2014) proposed a micromechanics-based two-scale multiscale model which is able to predict the nonlinear response of a composite. Their proposed micromechanics analysis uses the analytical solutions derived from the concentric cylinder model along with the generalized self-consistent model to find the effective properties of the unidirectional fiber reinforced composites, which are dependent on constituent level fiber–matrix mechanical properties and fiber volume fraction. In this model, the composite material is represented by an inner fiber core and an outer matrix annulus. It should be noted that the 2-CYL fiber–matrix concentric cylinder micromechanics model can be extended to a concentric fiber and any number of \((N-1)\) matrix layers in general, keeping the volume fraction constant, hence called the N-cylinder model (NCYL), which can analytically calculate the strain and stress field within the fiber and matrix cylinders for a given applied remote composite strain field, acting on the outer boundary of the matrix cylinder. The spatial variation of strain and stress fields within the cylinder are the key determinants for progressive damage and failure analysis of composite structures and hence, they need to be predicted accurately. The advantage of the NCYL concentric cylinder model is that the matrix strain and stress fields can be found in a discrete manner for each layer and the evolution of damage can be localized at a particular layer of matrix. These results can be used at the sub-scale in a multi-scale analysis to calculate the effective nonlinear composite response at a global scale. This work is based on a full analytical solution, and hence, it delivers a distinct computational advantage in composite failure analysis. That is, high fidelity and computational efficiency are gained at the same time.

Progressive failure analysis of composite structure based on micro- and macro-mechanics models

Based on parameter design language, a program of progressive failure analysis in composite structures is proposed. In this program, the relationship between macro- and micro-mechanics is established and the macro stress distribution of the composite structure is calculated by commercial finite element software. According to the macro-stress, the damaged point is found and the micro-stress distribution of representative volume element is calculated by finite-volume direct averaging micromechanics (FVDAM). Compared with the results calculated by failure criterion based on macro-stress field (the maximum stress criteria and Hashin criteria) and micro-stress field (Huang model), it is proven that the failure analysis based on macro- and micro-mechanics model is feasible and efficient.

A progressive failure analysis model for composite structures in hygrothermal environments

A progressive failure analysis model involving hygrothermal effects is presented for predicting failure of composite structures in hygrothermal environments. The model introduces a constitution equation accounting for the hygrothermal strains. Synchronously, the temperature-induced modification of stiffness and strength parameters are involved in the stress analysis model, failure criterion and material degradation rules. A user defined subroutine was developed and embedded into a FEA package to perform the failure analysis of composite structures in hygrothermal environments. To verify the proposed model, specimens made of carbon/bismaleimide composites with two typical lay-ups were tested under tension and compression loadings, respectively, in which both dry and moisture specimens were tested at 25°C, and only moisture specimens were tested at 75°C and 105°C. The good consistency between the numerical and experimental results, either the failure load or failure pattern, validates the proposed model. It follows that hygrothermal environments can hardly affect the tensile mechanical properties while significantly reduce the compressive behaviors of laminated composite structures. In addition, the failure mechanisms of typical tension and compression specimens are disclosed.

Micromechanical-based hybrid mesoscopic 3D approach for non-linear progressive failure analysis of composite structures

A new micromechanical-based hybrid mesoscopic 3D approach has presented for the prediction of failure under triaxial loadings. The failure criterion is based on physical principles and introduces micromechanical aspects (such as the effect of the local debonding) at the mesoscopic scale. It is capable of distinguishing between various modes of failure (e.g. fibre tension, fibre compression, in-plane and through-thickness interfibre (matrix or fibre/matrix failure modes). The model was successfully implemented to provide predictions of failure envelopes and non-linear stress–strain curves of isotropic, unidirectional and mutli-directional laminates made of glass/epoxy and carbon/epoxy materials and subjected to 3D loadings, including through-thickness stresses.

Delamination modelling of GLARE using the extended finite element method

In this paper, an application of the Extended Finite Element Method (XFEM) for simulation of delamination in fibre metal laminates is presented. The study consider a double cantilever beam made of fibre metal laminate in which crack opening in mode I and crack propagation were studied. Comparison with the solution by standard Finite Element Method (FEM) as well as with experimental tests is provided. To the authors’ knowledge, this is the first time that XFEM is used in the fracture analysis of fibre metal laminates such as GLARE. The results indicated that XFEM could be a promising technique for the failure analysis of composite structures.

Capability Assessment of Finite Element Software in Predicting the Last Ply Failure of Composite Laminates

Finite element programming using language such as FORTRAN, C++ and MATLAB has been the common and traditional tool to perform the progressive failure analysis of composite structures. This procedure requires high programming skills and strong mathematical understanding. This paper for the first time assesses the capability of a commercially available finite element analysis (FEA) software, ANSYS, to perform the Last Ply Failure (LPF) analysis of a laminated composite plate. The analysis is carried out by employing Maximum Stress and Tsai-Wu failure criteria. It is modelled and performed using ANSYS software which has a feature that supports the failure criteria and analysis procedure. The feature allows determination of maximum strength on individual layers in a composite laminate, thus provide an easier way to predict the failure progression. Based on analysis, the ultimate failure load and failure curves (LPF) are determined. The failure curves are compared and discussed with respect to previous experimental and FEA (both LPF and FPF) works. The results show that the LPF curves are very close to experiment that exhibits average errors as low as 16%. Finally, it can be concluded that the ANSYS software is applicable in predicting an accurate composite laminate LPF.

Progressive Failure Analysis of Composite Structures Using a Constitutive Material Model (USERMAT) Developed and Implemented in ANSYS ©

Composites are materials characterized by complex failure phenomena that onset and interact. Several approaches are available in literature to predict the behaviour of composite structures taking into account failure modes. However, most of them require the knowledge of experimental parameters, which generally are not provided by composite suppliers. Progressive failure techniques represent a valuable alternative to these methodologies because they rely on failure criteria and ply-discount techniques often based on the choice of a single degradation factor whose value is chosen by the analyst as small enough to prevent convergence problems in finite element analyses. The aim of this work is to analyze the behaviour of a composite structure taking into account the damage onset and evolution. The analysis is performed by using a constitutive material model (USERMAT) developed and implemented in the Finite element software ANSYS©. The accuracy of the procedure proposed is assessed by comparing numerical results and experimental data taken from literature.

Review of Degradation Models for Progressive Failure Analysis of Fiber Reinforced Polymer Composites

The success of any progressive failure analysis of composite structures is influenced by the failure criteria and the associated material property degradation models. The failure criteria are the conditions for the prediction of the occurrence of material damage. The degradation models are mathematical representations of the residual properties for each material damage state predicted by the failure criteria. A brief summary of the major classes of failure criteria pertaining to the degradation models is followed by a review of degradation models that have been developed for unidirectional polymer matrix composite laminates. The review is organized around the relationships of the various models to associated failure criteria as well as the various constitutive frameworks for finite element implementation. Models that invoke residual properties as a one-time sudden degradation of the original properties are described followed by models where the mathematical representation of at least one property invokes gradual property degradation as a function of some other evolving field variable.

Stress and failure analysis of composite structures

This paper describes the capabilities of the finite element program COMPASS (COMPosite Analysis of Structural Systems). COMPASS was developed under a grant from the NASA Goddard Space Flight Center, for the analysis of composite structures. COMPASS has the capability to perform non-linear static stress analysis, delamination growth analysis and progressive failure analysis of composite structures. The constitutive relations, failure criteria and boundary conditions employed in COMPASS are presented. Three analyses are performed which exemplify the capabilities of the code.

Progressive failure analysis of composite structures made of thermo-elastic solids

The constitutive relations and failure criteria of linear anisotropic thermo-visco-elastic solids are presented. The post-failure material behavior is proposed and the dynamic finite element equations for composite structures made of thermo-mechanical solids are formulated. A general-purpose finite element program COMPASS (COMPosite Analysis of Structure Systems) was developed. COMPASS is capable of performing stress and failure analyses of composite structures. In this work, to exemplify the capabilities of the code, progressive failure analysis of a composite laminate with a centred hole was performed.