Composite Failure Criteria Research Articles

Aeronautical composite/metal bolted joint and its mechanical properties: a review

PurposeBolted joint is the most important connection method in aircraft composite/metal stacked connections due to its large load transfer capacity and high manufacturing reliability. Aircraft components are subjected to complex hybrid variable loads during service, and the mechanical properties of composite/metal bolted joint directly affect the overall safety of aircraft structures. Research on composite/metal bolted joint and their mechanical properties has also become a topic of general interests. This article reviews the current research status of aeronautical composite/metal bolted joint and its mechanical properties and looks forward to future research directions.Design/methodology/approachThis article reviews the research progress on static strength failure and fatigue failure of composite/metal bolted joint, focusing on exploring failure analysis and prediction methods from the perspective of the theoretical models. At the same time, the influence and correlation mechanism of hole-making quality and assembly accuracy on the mechanical properties of their connections are summarized from the hole-making processes and damage of composite/metal stacked structures.FindingsThe progressive damage analysis method can accurately analyze and predict the static strength failure of composite/metal stacked bolted joint structures by establishing a stress analysis model combined with composite material performance degradation schemes and failure criteria. The use of mature metal material fatigue cumulative damage models and composite material fatigue progressive damage analysis methods can effectively predict the fatigue of composite/metal bolted joints. The geometric errors such as aperture accuracy and holes perpendicularity have the most significant impact on the connection performance, and their mechanical responses mainly include ultimate strength, bearing stiffness, secondary bending effect and fatigue life.Research limitations/implicationsCurrent research on the theoretical prediction of the mechanical properties of composite/metal bolted joints is mainly based on ideal fits with no gaps or uniform gaps in the thickness direction, without considering the hole shape characteristics generated by stacked drilling. At the same time, the service performance evaluation of composite/metal stacked bolted joints structures is currently limited to static strength and fatigue failure tests of the sample-level components and needs to be improved and verified in higher complexity structures. At the same time, it also needs to be extended to the mechanical performance research under more complex forms of the external loads in more environments.Originality/valueThe mechanical performance of the connection structure directly affects the overall structural safety of the aircraft. Many scholars actively explore the theoretical prediction methods for static strength and fatigue failure of composite/metal bolted joints as well as the impact of hole-making accuracy on their mechanical properties. This article provides an original overview of the current research status of aeronautical composite/metal bolted joint and its mechanical properties, with a focus on exploring the failure analysis and prediction methods from the perspective of theoretical models for static strength and fatigue failure of composite/metal bolt joints and looks forward to future research directions.

Flexural failure mechanism of bamboo composite plates with different construction technologies and tectonic patterns

To investigate the failure mechanism of bamboo fiber reinforced composite (BFRC) plates with different construction technologies and tectonic patterns, flexural experiments were performed. The flexural property of the parallel bamboo strand lumbers (PBSL) is better than that of the glued laminated bamboo (GLB), where the cracking load is increased by 141 % at most and the peak load is increased by 57 % at most. The orthogonal structure for the cross-laminated bamboo (CLB) improves the flexural property to a certain extent by inhibiting the initial cracking whether it is PBSL or GLB, and the peak load is increased by 9.83 % and 11.40 %, respectively. The residual bearing capacity of the PBSL is better than that of the CLB, the PBSL can basically maintain half of the ultimate bearing capacity while the damage factor of CLB is as high as 0.84 when the structure is damaged, revealing that the orthogonal layup structure results in weak interlayer interface after explosion. Orthotropic plate theory and composite failure criteria were proposed and consistently predicted the cracking load and the ultimate load. It is found that matrix fracture controls the cracking load, while fiber fracture determines the ultimate load.

Effect of strain rate on the in-plane orthotropic constitutive response and failure behaviour of a unidirectional non-crimp fabric composite

A comprehensive experimental campaign was performed to characterize the strain rate-dependent orthotropic constitutive response and failure behavior of a unidirectional non-crimp fabric (UD-NCF) carbon fiber/snap-cure epoxy composite. Shear and transverse compression strengths increased by 60% and 50%, respectively, over the range of strain rates considered, which is consistent with previously reported trends for unidirectional tape composites (UDTCs). The transverse tension strength increased by 18% with increasing strain rate, which is different from UDTCs. Owing to the distinct microstructure of UD-NCF composites, local damage mechanisms such as pullout of transverse supporting glass fibers and stitching were observed and are deemed to contribute to the rate dependency of transverse tension strength. The longitudinal compression strength increased by 35% with increasing strain rate. Observation of failed specimens revealed widespread inter-tow axial splitting and localized tow kinking, distinct from UDTCs. This important finding will aid in the development of failure criteria for UD-NCF composites.

Influence of unidirectional composite failure envelope shape on predicting compressive failure of a laminate with a filled-hole

In recent decades, several computational models have emerged at the mesoscale for predicting the failure development and strength of composite materials. Nevertheless, the intricate failure mechanisms of composites pose a formidable challenge in developing models capable of consistently reproducing diverse sets of experimental data. Furthermore, the absence of standardised multiaxial tests has hindered consensus on failure envelopes and criteria for composites. In this work, an in-house constitutive model implemented in a finite element code is employed to predict the failure strength of several filled-hole compressive carbon/epoxy experimental tests, varying in stacking sequences, sizes, bolt preloads, and other parameters. The influence the selected failure criterion has on the predictions is analysed. The findings indicate a large impact of the failure envelope on both the failure compressive strength and developed failure mechanisms. Therefore, the correct adjustment of the failure criteria can be as relevant as defining accurately the material input parameters. These results emphasise the importance of accurately establishing failure envelopes, rather than overemphasising the development of complex models.

Experimental and numerical investigation on Multiwalled carbon nanotubes (MWCNTs) dispersed CFRP laminate subjected to spherical and conical impacts

ABSTRACT As lightweight and load-bearing efficiency needs have grown, conventional metal has steadily given way to carbon fibre-reinforced polymer (CFRP) laminates. Also, CFRP laminates are more prone to localised damage due to impact loads like tool drop, runway debris and hail stone. This paper, investigated the penetration and perforation behaviour of CFRP laminate reinforced with 0.2 and 0.5 wt% MWCNTs. The projectile impact experiment was conducted using spherical and conical projectiles and the impact resistance was evaluated. The results revealed that 0.5 wt% MWCNTs embedded in CFRP laminate provided better impact resistance to both projectiles. The ballistic limit velocity was enhanced by 14.2% and 17.9% for spherical and conical projectiles, respectively, in the case of 0.5 wt% MWCNTs. Furthermore, numerical simulations were performed using an orthotropic model with Chang-Chang composite failure criteria. The results from numerical findings were consistent. It was concluded that MWCNTs reinforcement improves the projectile impact resistance and energy absorption.

Application research in multi-objective constrained optimization of composite wing structure

In order to explore the optimization of composite wing structure, this paper reviews the past research works of optimization of composite wing structures worldwide and in China. It concludes that most optimization methods and calculations are useful but only applied with specified theoretic model. Then relevant composite optimization theories and strength constraints with composite lamination failure criteria, stability, aeroelasticity are sorts out. Optimizing algorithm and applied solution rounding strategy are also listed. Concentrating on weight-reduction analysis on the thickness, sequence, and angle of the composite stacking under multiple constraints, a practical model of a composite wing structure example with a large aspect ratio is completed, and the calculation is based on the finite element analysis tool Nastran and the genetic algorithm Matlab program. Two optimal solutions are given with detailed differences and the comparison of the composite structure parameters before and after calculation is also recorded. The application example indicates the feasibility of the optimization method and quadratic rounding process, the detail structure performance improvements with skin lamination change under the calculation are illustrated at the same time.

Numerical generation of omnistrain failure envelopes

Traditional failure criteria for composites are usually formulated in material coordinates and depend on all three inplane stresses, hence failure evaluation depends on the ply angle. The omnistrain failure envelope describes the most critical failure envelope in strain space irrespective of ply orientation. This independence of ply orientation leads to an isotropic failure criterion that depends only on the principal strains. Omnistrain envelopes greatly simplify the task of design and optimisation of composite laminates. This paper proposes a numerical technique to generate omnistrain failure envelopes for different composite failure criteria. The failure index, describing how far a point in strain space is from the failure boundary, is used to describe the failure surface. Assuming convexity of the failure surface, a set of points is generated on the surface, and the convex hull algorithm is used to generate a polygonal approximation of the failure surface. Representing strains in terms of principal strains and the angle between the principal and material coordinates, allows us to eliminate the angle analytically by considering the worst case condition. The omnistrain envelope is thus directly generated from the approximate three-dimensional failure surface. The proposed algorithm does not require analytic expressions of the failure surface. An adaptive algorithm is proposed to generate the omnistrain envelope with relatively small number of points. As demonstration of the proposed algorithm, the omnistrain envelopes for various composite materials are generated for a number of composite failure criteria. The omnistrain envelopes generated for the Tsai-Wu criteria accurately match to existing analytic expressions.

Best Theory Diagrams for Laminated Composite Shells Based on Failure Indexes

This paper presents a novel approach to developing 2D structural theories for composite shells. The proposed approach uses the capabilities of the Carrera Unified Formulation (CUF) in conjunction with the Axiomatic/Asymptotic Method (AAM) to obtain the best theories for given structural layouts. Different structural cases are considered to analyze the influence of factors such as boundary conditions, lamination, and thickness on the accuracy of a model. The parameter chosen to evaluate a model’s performance is based on the Failure Indexes (FI) defined by the Hashin Failure criteria for unidirectional fiber composites. The outcome of this procedure is the Best Theory Diagram (BTD), containing the graphical representation of the highest accuracy as a function of the number of adopted unknowns. The results show the importance of higher-order terms to capture stress fields and the influence of thickness on the definition of the best theories.

Application research in multi-objective constrained optimization of composite wing structure

In order to explore the optimization of composite wing structure, this paper reviews the past research works of optimization of composite wing structures worldwide and in China. It concludes that most optimization methods and calculations are useful but only applied with specified theoretic model. Then relevant composite optimization theories and strength constraints with composite lamination failure criteria, stability, aeroelasticity are sorts out. Optimizing algorithm and applied solution rounding strategy are also listed. Concentrating on weight-reduction analysis on the thickness, sequence, and angle of the composite stacking under multiple constraints, a practical model of a composite wing structure example with a large aspect ratio is completed, and the calculation is based on the finite element analysis tool Nastran and the genetic algorithm Matlab program. Two optimal solutions are given with detailed differences and the comparison of the composite structure parameters before and after calculation is also recorded. The application example indicates the feasibility of the optimization method and quadratic rounding process, the detail structure performance improvements with skin lamination change under the calculation are illustrated at the same time.

Novel design of honeycomb hybrid sandwich structures under air-blast

In this study, dynamic explicit analysis was performed to examine the air-blast performance of various hybrid sandwich designs in terms of face plate deflections and energy dissipation capacity under the conventional weapons effects program (CONWEP) air-blast loads ranging from 3 kg to 8 kg trinitrotoluene for stand-off distance ranges from 150 mm to 200 mm. The blast resistance of honeycomb sandwich configurations was evaluated using steel honeycomb with different core topologies, crushable Al foam-filled steel honeycomb, and steel or steel with 3D Kevlar/polypropylene laminate employing fiber metal laminate (FML) front face. For an accurate prediction of the deformation mechanism of all steel parts, the Johnson-Cook (J-C) model was used. The composite failure criteria of Hashin, Puck, and Matzenmiller were implemented to accurately examine the fiber and matrix damage behavior. The novel hybrid design of the honeycomb sandwich structure’s blast resistance is improved by the employment of foam-filled honeycomb, an FML front face, and a circular honeycomb core. In comparison to other sandwich configurations, a novel designed hybrid sandwich construction composed of foam filled circular honeycomb with FML front facing and steel back facing (FCH-1KP0.5) achieved the highest blast resistance due to its lowest face deflection with the smallest plastic dissipation energy.

Consistent approach to onset theory

Onset Theory (previously known as Strain Invariant Failure Theory) is a physics-based composite failure criterion attempting to predict failure at the level of constituents rather than for a homogenized ply. Applying Onset Theory correctly requires a number of steps. As a starting point for other researchers, a consistent approach is developed by resolving contradictions found in literature. This includes the micromechanical FEA process used to determine the individual fiber and matrix strains, such as correct choice of representative volume elements (RVEs), the use of transformed RVEs, boundary conditions, and the location of data extraction points. Analytical expressions are provided to determine the full state of strain in a ply, including in-plane and out-of-plane Poisson’s strains and thermally induced mechanical strains. Literature definitions of the critical invariants are discussed, and a trend in critical distortional invariants is observed. Assumptions and limitations of the theory are identified. Finally, a failure envelope is compared to World Wide Failure Exercise test data.

Surrogate Modeling Accelerated Shape Optimization of Deployable Composite Tape-Spring Hinges

Composite tape-spring hinge (CTSH) is a simple yet elegant mechanical component for various deployable space structures. This paper formulates and addresses cut-out shape optimization of a CTSH, which is seldom touched upon in literature. Both the maximum strain energy stored during the folding process as well as the maximum bending moment during deployment were maximized in a concurrent way, and the multi-objective optimization problem was realized by merging data-driven surrogate modeling and shape optimization. Four different surrogate modeling techniques (radial basis function, kriging, Gaussian process regression, and artificial neural network) are evaluated and compared. The maximum stored strain energy at the fully folded state and the maximum bending moment during deployment for the optimal CTSH are increased by 50 and 35%, respectively, compared to the initial design under a previously developed composite failure criterion as constraint. To ensure reproducibility and foster future research, we publicly share our full implementation with the source codes and trained models with the community.

Discover failure criteria of composites from experimental data by sparse regression

Over the past few years, a few experimental failure data of composites have been collected. It would be of interest to leverage the existing data to improve the prediction of failure criteria. In this paper, we developed a framework that combines sparse regression with compressed sensing to discover failure criteria of composites from experimental data, which leveraging advances in sparsity techniques and machine learning. This framework does not need Bigdata to train the model and is remarkably robust to the noised data, which satisfies the constraints of the current failure data. To test the performance of the proposed method, we collected the experimental data from the first Worldwide Failure Exercise (WWFE I) and fed it to the proposed method. To satisfy the engineering design needs, we proposed an optimization approach to enforce a constraint to the discovered failure criterion to yield a conservative model. Three examples were presented to demonstrate the proposed framework. The result shows that the proposed framework can identify the most important features and the discovered failure criterion match the experiment result well. Besides, with the enforced constraint, the proposed method can yield a conservative failure criterion.

Tensile Mechanical Properties of Nanowoven Composites Based on Homogenization Theory

The nanocomposite is a multiphase material composed of two or more component materials with different properties and different forms through composite means. New material properties. The stress distribution of nano-braided composites in bending is much more complicated than in tension. Like the tensile condition, the braid angle is still the main factor affecting the bending failure mode. In order to study the tensile strength of nano-braided composites from a microscopic perspective, the nonlinear damage analysis under multiple tensile load steps is carried out in this paper. The damage analysis results show that the microscopic damage modes of different braided angle composites differ. Based on this, this paper determines the transformation of the failure mechanism to characterize the braided composites. An important parameter—critical braiding angle, established different tensile strength failure criteria for small braided angle composites and large braided angle composites and numerically predicted the tensile strength of nano braided composites based on these criteria. The value of each stress component increases with the increase of the braiding angle, and the ratio is about 1:1.25. The strength prediction results are in good agreement with the experimental results.

Experimental investigation on punching shear behaviour of RC-(R)UHPFRC composite flat slabs without transverse reinforcement

Strengthening existing reinforced concrete (RC) flat slabs by casting a thin layer of ultra-high performance fibre-reinforced cementitious composite (UHPFRC) over the top surface constitutes an efficient solution for significant durability and flexural capacity enhancements. Previous research has shown that also the punching shear capacity can be substantially increased. However, the existing experimental evidence is still limited and does not allow a systematic evaluation of the influence of the governing parameters.In the present work, eight slabs without transverse reinforcement were tested up to punching shear failure. The following parameters were studied: the contribution of the UHPFRC overlay with and without reinforcement bars, the shape of the column (square or rectangular), the effect of the reinforcement ratio in the existing slab, the eccentricity of the punching force and the material of the strengthening layer (UHPFRC or ordinary RC). The height of the RC substrate and UHPFRC layer thickness were kept constant at 180 mm and 40 mm, respectively.The results confirm the significant contribution of the UHPFRC layer to the punching shear strength. The experimental failure loads are compared to the predictions provided by a composite failure criterion based on the Critical Shear Crack Theory and taking into account the contribution of the UHPFRC layer. Good agreement was obtained with the model being capable of reproducing the effect of all the studied variables.

Modeling of Surface Fracture in Friction Interaction of Fiber Composites

The model of the frictional interaction of a fiber composite material with a rigid non- wearing body is proposed, which makes it possible to study the effect of the mechanical and strength characteristics of the fiber and matrix materials and the composite structure on its stress state, in particular, at the fiber-matrix interface. Analysis of the stress distribution in the subsurface layers of the composite was carried out for different values of the ratio of matrix to fiber materials hardness, the sliding friction coefficient and the distance between the fibers. For the known failure criteria of fiber composites, the conclusions about the effect of the structure and relative strength properties of a fiber (fiber bundle) and matrix on the pattern of subsurface fracture of the composite under sliding friction conditions are made

Partially-plastic theoretical model of thermoplastic composite pipes and comparison of composite failure criteria

Thermoplastic composite pipes (TCPs) are becoming potential alternatives to steel pipes for transporting hydrocarbon and other fluids in the oil and gas industry due to the superior properties including corrosion resistance, light weight, high pressure rating, etc. The cross section of TCPs generally consists of three layers: inner liner, composite laminate, and outer jacket; three layers are fusion-bonded together to form a solid-walled construction. The multi-layered structure and anisotropic material drive the analysis of TCPs much more complicated than those of steel pipes. In the present study, a partially-plastic theoretical model was developed for analysis of TCPs subjected to internal pressures. The theoretical model, benchmarked by FEA simulations, can accurately calculate the stresses which are not uniformly distributed along the radial direction of the TCP. Experiments were conducted on TCPs with the laminate layer of a different thickness. Comparisons of the experimental and theoretical results show that the partially-plastic theoretical model and the fiber failure criterion accurately predict the burst pressure of TCPs of winding angles of ±55°. The applicability of Tsai–Hill, Tsai–Wu, and fiber failure criteria were assessed using experimental data. The advantages of the partially-plastic theoretical model and influences of the thickness of the laminate layer were demonstrated using case examples. The present work provides some useful tools and guidance for the design and analysis of TCPs and other composite pressure vessels.

Micromechanical Modeling of Unidirectional CFRP Composites with Proportional Stressing

In this paper, we present a computational micromechanical analysis of unidirectional (UD) carbon fiber-reinforced plastics (CFRPs) using representative volume elements (RVEs). The RVEs consist of randomly distributed fibers, matrix, and interfaces between the fibers and matrix. Periodic boundary conditions (PBCs) and proportional stressing are implemented to facilitate micromechanical analysis of the composites under controlled stress states. In particular, the failure mechanisms of the RVEs under combined transverse and in-plane shear stressing are investigated. The ratio of in-plane shear stress over transverse stress is kept constant during each simulation. By varying this ratio, the mechanical responses of composites under different stress states are systematically studied and the failure envelopes for different fiber volume fractions are extracted. We find the failure envelope converges as the fiber volume fraction increases. The framework developed in this study can be extended to different stress states allowing us to conveniently examine the failure criteria for UD CFRP composites comprehensively.

Cross-section optimization of thin-walled open-section composite column for maximizing its ultimate strength

This paper focuses on the optimization of thin-walled open cross-section laminated composite column subjected to uniaxial compressive load. The cross-section of the column is parameterized in such a way that it can represent a variety of shapes including most of the regular cross-sections such as H, C, T, and I sections. The objective is to obtain the best possible shape of the cross-section, by keeping a constant total material volume, which can maximize the ultimate load carrying capacity of the column. The ultimate strength of the column is determined by considering both buckling instability and material failure. For material failure, Tsai-Wu composite failure criterion is considered. As analytical solutions for these parameterized column models are not tractable, the ultimate loads of the composite columns are computed through finite-element analysis in ANSYS. And, the optimization is carried out by coupling these finite-element results with a genetic algorithm based optimization scheme developed in MATLAB. The optimal result obtained through this study is compared with an equivalent base model of cruciform cross-section. Results are reported for various lengths and boundary conditions of the columns. The comparison shows that a substantial increase of the ultimate load, as high as 610%, can be achieved through this optimization study. Thus, the present paper highlights some important characteristics of open cross-sections that can be useful in the design of thin-walled laminated column structures.

Development of PMC Numerical Model for Soil and Stone Mixture

Soil and stone mixture is widely distributed in China, and its physical and mechanical properties are complex, which has a significant impact on geotechnical engineering. Usually soil and stone mixture shows anisotropic features along or perpendicular to the direction of settled layers, and the strength will be significantly affected by intermediate principal stress. True triaxial tests were carried on, Paul–Mohr–Coulomb (PMC) failure criterion was used for the strength analysis in soil-stone mixture, and related parameters of PMC model were obtained. A user-defined PMC numerical constitutive model was developed for FLAC3D. Composite failure criteria of shear failure and tension cut-off were applied for numerical analysis, and nonassociated flow rule was proposed based on the Mohr–Coulomb model. Verification modelling was applied as well, and deviation between analytical and numerical solutions in strains of X direction, Y direction, and Z direction was 1.0013, 1.0003, and 1.002, respectively.