Failure Modes In Composite Laminates Research Articles

Dynamic responses and interactive failure mechanisms of carbon fiber composite face sheets/double-layer corrugated core sandwich structures under low-velocity impacts loading

A single-layer and double-layer corrugated core sandwich structure consisting of carbon fibre–reinforced polymer (CFRP) panels and aluminium alloy core layers was designed. Numerical simulations were carried out in HyperMesh/LsDyna, and the simulation results of single-layer and double-layer corrugated sandwich structure were compared with the experimental results to verify the reliability of the proposed numerical model. Compared with the results of single-layer and double-layer corrugated sandwich structure, the superiority of a double-layer corrugated sandwich structure in anti-collision performance is verified. Considering the effects of impact energy and impact position on impact force, energy absorption capacity, and failure mode, a series of low-velocity impact finite element simulations was carried out. It was found that the main failure mode of composite laminates included fibre damage, matrix damage and delamination, and core buckling. At the same impact position, the higher the impact energy, the greater the initial slopes of the contact force-time and absorbed energy-time curves, the higher the peak force, and the larger the energy absorption capacity. Under the same impact energy, when the impactor hit the wave crest of the sandwich structure, the damage to the structure was small; however, the maximum impact force on the structure was large (∼8 kN).

Delamination mechanism in CF/EPOXY with open hole under mode II loading at different distances

This research addresses limitations in current aviation composite assembly techniques, often constrained by certification challenges. To enhance bonded composite components, open holes are frequently introduced, leading to increased vulnerability to delamination, a prominent failure mode in composite laminates. This study focuses on observing the impact of open holes on the mode II behavior of composites under various distances and hole diameter conditions. Results illustrate distinct load–displacement curves influenced by hole size, with shorter distances accelerating crack propagation, evidenced by reduced elastic regions and lower load values. Analyzing specimen appearances and crack patterns highlights stress concentration at the hole, influencing initiation and propagation. In the absence of a hole, cracks exhibit a zig-zag pattern near the loading point, while with a hole, they concentrate around it. Elastic region length varies with the pre-crack-to-hole distance, indicating accelerated crack propagation in shorter distances. This study underscores the direct influence of hole size on load values, emphasizing its pivotal role in determining composite mechanical properties. This research provides valuable insights into hole characteristics’ interplay with delamination behavior in carbon fiber-reinforced composites, essential for optimizing aerospace component design and structural integrity.

An improved peridynamic model for failure analysis of composite laminates

The study presents an improved peridynamic (PD) model for predicting the failure mode of composite laminates without any limitation to fiber orientation. In order to describe the directional dependency of composite laminae, the structural rotation angle is introduced into the PD framework to overcome the flaw that the fiber orientation is a specific value in conventional PD models. In improved PD model (IPM), two types of material points are used to model laminated structures, and a new force function mapping relationship is derived to achieve stable load transfer between in-plane and interlayer material points. As a result, the discrete grid of in-plane material points do not have to coincide with interlayer material points, and the technical difficulties in modeling multilayer laminates with general layups can be addressed. Since the IPM matches the microscopic configuration of practical composite structures, these damage characteristics, such as the damage path, crack initiation point, etc., correlate well with the experimental results. The numerical accuracy of the developed PD model are verified by simulating a series of examples of composite laminae with different fiber orientations, and the damage example further demonstrates the strong capability of the IPM in capturing failure modes of laminates with general layup.

Residual tension behavior and damage evolution mechanisms of fiber metal laminates with various low-velocity impacted damage

This paper mainly investigates the initial low-velocity impact behavior and the residual tension performance of FMLs with different composite layer directions through experimental and numerical methods. First, the detailed studies for the impact response and failure behavior of FMLs under different impact loadings are carried out experimentally, including various impact energies and impact numbers. Then, the post-impact tension behavior of FMLs with various impacted damage are further characterized through tension tests. Meanwhile, an integrated numerical model in virtue of VUMAT subroutine in ABAQUS is developed to simulate the impact and post-impact tension behavior of FMLs. The Hashin and Yeh failure criteria are employed to predict the complex failure modes of composite laminates, and the cohesive model is utilized to simulate the delamination damage between metal alloy and composite laminates. The reliability and accuracy of the integrated model can be demonstrated through comparison with the experimental results. Subsequently, the progressive damage evolution process of FMLs during the loading can be characterized in detail from the numerical predictions. It can be demonstrated that the aluminum alloy plays a decision role in the protection of structure perforation, while the composite laminates mainly dissipate the impact energy through the complex failure modes.

Behaviors of Composite Laminates Under Low-Energy Impact Using a Novel Analytical Framework

Carbon fiber-reinforced polymer (CFRP) composite laminates have the characteristics of orthogonal anisotropy and heterogeneity, so the failure mechanism under low-energy impact is very complex. As a supplement to the experiment, it is necessary to develop numerical tools to predict the mechanical behavior of composite laminates under low-energy impact. In this paper, the mechanical behavior analysis framework of composite laminates under low-energy impact load is established by using the micromechanics of failure (MMF) theory and the mixed mode exponential cohesive zone model (CZM). The failure modes of intralaminar components in composite laminates are determined by MMF theory. The damage onset and evolution process of interlaminar delamination is described by the mixed mode exponential CZM. The finite element model of composite laminates under low-energy impact is developed using the Python scripts on ABAQUS/Explicit platform. The user-defined material subroutine VUMAT is written in Fortran language. The impact responses of composite laminates with several impact energies are predicted. The intralaminar failure modes and interlaminar delamination behavior are discussed in detail. The results show that the tensile failure of matrix and interlaminar shear delamination failure are the main failure modes of composite laminates under low-energy impact load. The experimental results present better consistency with the numerical analysis, indicating that the constructed multiscale analysis method is efficient and accurate. This study expands the analysis method of mechanical behavior of composite laminates under low-energy impact. The constructed mixed mode exponential CZM also has guiding significance for the failure analysis of other bonding materials.

Modeling the delamination failure under compressive loads in CFRP laminates based on digital image correlation analysis

Laminate composite materials such as CFRPs are highly susceptible to delamination, being one of the common failure modes in composite laminates. The combination of severe delamination with uniaxial compressive loads leads to the loss of stability and structure failure. In this study, the authors present an experimental and numerical analysis of this effect in laminates. A series of tests were carried out with four different specimens including delamination-free plates and plates with incipient delamination with different damage size and location. 3D Digital Imagen Correlation technique was applied to predict the buckling initiation and propagation and to validate the numerical models implemented, showing good agreement between the numerical and experimental results. Model material failure includes Hashin criterion and cohesive zone model (CZM) to predict delamination. Finally, numerical models have been used to predict the crack initiation and progression in the rest of samples.

Analysis of Delaminated Hybrid Carbon Fiber Composites in MODE-I

Failure analysis of laminated composite structures has attracted a great deal of interest in recent years due to the increased application of composite materials in a wide range of high-performance structures. Intensive experimental and theoretical studies of failure analysis and prediction are being reviewed. Delamination, the separation of two adjacent plies in composite laminates, represents one of the most critical failure modes in composite laminates. In fact, it is an essential issue in the evaluation of composite laminates for durability and damage tolerance. Thus, broken fibers, delaminated regions, cracks in the matrix material, as well as holes, foreign inclusions and small voids constitute material and structural imperfections that can exist in composite structures. Imperfections have always existed and their effect on the structural response of a system has been very significant in many cases. These imperfections can be classified into two broad categories: initial geometrical imperfections and material or constructional imperfections

Parameter studies and evaluation principles of delamination damage in laminated composites

Delamination represents one of the most severe failure modes in composite laminates, especially when they are subjected to uniaxial compression loads. The evaluation of the delamination damage has always been an essential issue of composite laminates for durability and damage tolerance in engineering practice. Focusing on the most typical and representative elliptical delamination issue, an analytical model simultaneously considering the conservative buckling process and non-conservative delamination propagation process is implemented. Various computational cases considering different delamination depths, directions, aspect ratios, and areas are established, and the predicted results based on the analytical model are carefully compared. Effects of these geometrical delamination parameters on the buckling, delamination propagation, and failure behaviors of composite laminates are thoroughly analyzed, and innovative evaluation principles of the delamination damage have been concluded. It is found that the delamination area is the key factor that truly affecting the failure behaviors of delaminated composites, and the local / global buckling and failure loads show clear linearity with the delamination area, whilst the delamination depth and direction only have slight effects.

Delamination Phenomenon in Composite Laminated Plates and Beams

Failure analysis of laminated composite decks structures has attracted a great deal of interest in recent years due to the increased application of composite materials in a wide range of high-performance structures. Intensive experimental and theoretical studies of failure analysis and prediction are being reviewed. Delamination, the separation of two adjacent plies in composite laminates, represents one of the most critical failure modes in composite laminates. In fact, it is an essential issue in the evaluation of composite laminates for durability and damage tolerance. Thus, broken fibers, delaminated regions, cracks in the matrix material, as well as holes, foreign inclusions and small voids constitute material and structural imperfections that can exist in composite structures. Imperfections have always existed and their effect on the structural response of a system has been very significant in many cases. These imperfections can be classified into two broad categories: initial geometrical imperfections and material or constructional imperfections. Delamination is a critical failure mode in fiber-reinforced composite decks plates and beams. It may lead directly to through-thickness failure owing to interlaminar stresses caused by out of plane loading, curved or tapered geometry, or discontinuities owing to cracks, ply drops or free edges. Impact loading causes multiple delaminations, which can propagate in conjunction with sub laminate buckling, greatly reducing the residual compressive strength.

An analytical model for evaluating the buckling, delamination propagation, and failure behaviors of delaminated composites under uniaxial compression

Laminated carbon fibre reinforced composite materials are very susceptible to delamination, which is one of the most serious failure modes in composite laminates. According to the requests of damage tolerance evaluation, to completely evaluate the buckling responses and failure behaviors of delaminated composites under uniaxial compression, an analytical model was established. Based on the principle of minimum potential energy and brittle damage mechanics, the analytical model incorporated both the delamination propagation and failure evaluation into the buckling analysis. Uniaxial compression tests of three specimens containing embedded delaminations were conducted. The predicted results are highly consistent with the experimental outcomes, thus validating the applicability and accuracy of the proposed analytical model. It is found that the out-of-plane deflections and energy release rate of the delaminated laminate are closely related to the buckling states; the choice of GC in a range from GIC to GIIC has little effect on the predicted results with the proposed model.

Experimental and numerical investigation of open hole carbon fiber composite laminates under compression with three different stacking sequences

The open hole composite laminates with different stacking sequence were tested and the failure modes and strength were recorded. A progressive damage model of the open-hole composite laminate under compression was developed and in-plane damage is modeled by using the three-dimensional continuum shell elements and cohesive element was adopted for delamination failure simulation. Based on the ABAQUS user subroutine UMAT, this model simulates damage initiation, propagation and final failure. With different failure criteria, the strength and failure modes of open-hole laminates under compression were predicted in this model. Compared with the experiment results, the effects of different stacking sequences on the strength and final failure modes of composite laminates are analyzed.

Bearing failure of single-/double-shear composite bolted joints: An explicit finite element modeling

A three-dimensional explicit finite element method was presented to investigate the bearing failure of single- and double-shear composite bolted joints. To predict the various failure modes of composite laminates, three-dimensional solid elements accompanied by mixed-mode failure criteria considering nonlinear shear behavior were employed in the model. A linear damage propagation law based on the fracture energy and the characteristic length was adopted to alleviate the mesh dependency. In addition, reduced integration elements were used in the models of single- and double-shear joints to avoid the overstiffness. The simulated models were implemented in the Abaqus/Explicit solver with a user-defined material subroutine. The numerical analysis run successfully without any convergence issues. The predictions of mechanical behavior agreed well with the experimental results, with typical damages in the laminates including matrix crack and fiber failure. The effect of secondary bending in the single-shear bolted joint was also analyzed in the explicit modeling.

On the role of kinking in the bearing failure of composite laminates

Fibre kinking is one of the main failure modes of composite laminates under compression loading. In this paper, the role of kinking in the failure of quasi-isotropic composites subjected to a bearing load is investigated. High-resolution CT scans show that kinking is largely involved in the events leading to laminate collapse, notably by triggering other damage modes such as delamination. Kink bands develop extremely progressively, leading to the formation of a wide localization zone (or FPZ, failure process zone). Such behaviour calls for a non-local modelling approach. Local damage models would lead to overly conservative sizing. A simple model, based on Hashin failure criteria and non-local effective stresses is confronted to experiments, and its limits are highlighted. It will be shown that proper modelling of the bearing failure requires the characteristic behaviour of kink bands to be taken into account.

Progressive damage analysis of open-hole composite laminates under compression load

Firstly,compressional experiments were conducted on open-hole composite laminates. The progressive damage during the loading process and the final damage mode of the specimen were detected with a digital microscope,scanning electron miroscope and an X-scan equipment. Damage initiation and delamination between layups of 45° and 90° were observed during the experiments. Secondly,the failure modes of composite laminates are divided into intra-laminar failure and inter-laminar failure. A multiscale model based on the micro-mechanics of failure MMF3 theory and the interface cohesive element method for the damage analysis of open-hole compression laminates was developed. At last,the initiation and propagation of the damage and the failure modes of the laminates were predicted with the model. Numerical results such as the damage initiation position of fiber and matrix,the delamination propagation process and the final failure modes are in good agreement with experimental results,which indicates that the model is applicable to analysis of progressive damage of open-hole composite laminates under compression load.

Progressive Failure Analysis of Laminated Composite Plates With Two Serial Pinned Joints

This study presents experimental and numerical failure analyses for two serial pin loaded holes in unidirectional carbon fiber/epoxy resin composite laminates. The failure loads and failure modes of composite laminates are determined for different geometrical parameters and different stacking sequences. Three-dimensional ANSYS Parametric Design Language codes are developed in the ANSYS® finite element software. Hashin Failure Criteria and material degradation rules are used to determine failure loads and failure modes in the numerical analysis. Experimental and numerical results show that failure loads and failure modes were affected with geometrical parameters.

Compressive failure analysis of quasi-isotropic composite laminates fabricated with quasi-unidirectional woven fabric

The effect of configuration of quasi-unidirectional woven fabric on the compressive failure modes of quasi-isotropic composite laminates was investigated in this study. Two kinds of out-of-plane fiber waviness were formed in the composite laminates due to different quasi-unidirectional woven fabrics and measured using a fast Fourier transform method. The compressive failure modes of the composite laminates were identified using experimental and numerical methods. It was found that the compressive strength of a composite laminate fabricated using long-pitch weft fabrics was greater than that fabricated using standard-pitch weft fabrics. The relationship between the compressive strength and the configuration of quasi-unidirectional woven fabrics was investigated in a parametrical study, and four compressive failure modes were found: the axial compressive, normal, bending, and shear failure modes.

Available Theories for an Analysis of Stresses and Assessment of Strength of Laminate Structures

Theories for analyzing the stresses and strain in laminated structures and for assessment of their strength are briefly reviewed. In actual practice, a realistic assessment of strength, in many cases, still is a challenge, because in general, there are different failure modes in composite laminates that compete with each other. In addition, in laminate structures, situations with highly localized stresses frequently occur that cannot be assessed by employing a pure stress-based strength-of-materials approach. Sometimes, the stress localizations go along with a high, but finite, stress concentration, and sometimes it goes along with stress singularities, which, within the scope of elasticity theory, means infinitely high stresses. A promising way to predict the effective strength in such cases is the use of hybrid failure criteria within the framework of finite fracture mechanics. This approach is also considered in the present article.

The Mechanical Behavior of a Pin-Loaded Hole in a Thermoplastic Composite Laminate

The paper deals with the structural response of mechanically fastened fiber-reinforced laminated thermoplastic composite joints. An experimental investigation was carried out to analyze the behavior of single-pinned joints made with woven glass-reinforced polypropylene composite laminates. A detailed experimental analysis was performed in order to predict the bearing response, failure strength, and failure mode of composite laminates containing a pin-loaded hole. The results obtained allow one to evaluate the influence of geometric parameters and the stacking sequence of laminates on the behavior of such joints.

New Two-Dimensional Polynomial Failure Criteria for Composite Materials

The in-plane damage behavior and material properties of the composite material are very complex. At present, a large number of two-dimensional failure criteria, such as Chang-Chang criteria, have been proposed to predict the damage process of composite structures under loading. However, there is still no good criterion to realize it with both enough accuracy and computational performance. All these criteria cannot be adjusted by experimental data. Therefore, any special properties of composite material cannot be considered by these criteria. Here, in order to solve the problem that the criteria cannot be adjusted by experiment, new two-dimensional polynomial failure criteria with four internal parameters for composite laminates are proposed in the paper, which include four distinct failure modes: fiber tensile failure, fiber compressive failure, matrix tensile failure, and matrix compressive failure. In general, the four internal parameters should be determined by experiments. One example that identifies parameters of the new failure criteria is given. Using the new criteria can reduce the artificialness of choosing the criteria for the damage simulation of the failure modes in composite laminates.

Multiscale shear-strain gradient for detecting delamination in composite laminates

Delamination is a typical failure mode in composite laminates. For detecting delamination, a new physical concept of a multiscale shear-strain gradient (MSG) is formulated from a vibrational mode shape of a Kirchhoff plate. In a laminate containing a small delamination, the MSG characterizes shear-strain singularities with an explicit physical implication and no need for material properties, in turn manifesting the distribution of the delamination; moreover, multiscale property enables the MSG to identify delaminations at a high noise level. Numerical and experimental results show that the MSG defies the traditional understanding that vibrational features are inappropriate to localize a slight delamination.