Ply Failure Research Articles

Isogeometric analysis based on non-uniform rational B-splines technology of stress and failure strength in inter-ply hybrid laminated composite

In the present study, the stress distribution and first ply failure strength of hybrid laminated composites subjected to uniaxial tensile and compression loads are predicted using Isogeometric analysis (IGA) based on non-uniform rational B-splines technology, commonly referred to as non-uniform rational B-splines (NURBS) technology. The obtained results were compared to finite element method results (ANSYS) published in the literature and analytical results using Autodesk Helius Composite software. Graphite-glass/epoxy hybrid composite plates are analyzed for different lamination orientations and used to calculate first ply failure strength. Non-interactive theories such as maximum stress, maximum strain, and fully interactive criteria such as Tsai-Wu, Tsai-Hill and Hoffman are used to predict the failure strength of different laminates. The failure envelopes of the hybrid composites are developed using the same failure criteria used for the graphite-glass/epoxy hybrid composite. The effects of IGA refinement and plate’s dimension on the present analysis were also established. The IGA results showed good accuracy, robustness and good convergence speed with the analytical software results and the finite element method (FEM) reference value.

Numerical and experimental investigation of first ply failure response of multi-walled carbon nanotubes/epoxy/glass fiber hybrid laminated tapered curved composite panels

In this study, first ply failure (FPF) analysis of multi-walled carbon nanotubes (MWCNTs)/epoxy/glass fiber laminated curved composite panels with various taper configuration under transverse uniform pressure load distributed over the panel surface has been performed. In this regard, various failure criterion were considered, including Hoffman, Tsai–Wu, Tsai–Hill, and maximum stress, to investigate the numerical FPF load using finite element (FE) formulation with displacement fields derived from high order shear deformation theory (HSDT) with displacement field having seven degrees of freedom. The effectiveness of the proposed formulation was validated by comparing the numerically predicted FPF load with experimentally obtained FPF load using a universal testing machine from displacement/strain measurement. Finally, the effects of aspect ratio, different weight fraction of MWCNTs, taper configuration, curved geometry, and aspect ratio on the FPF load of the laminated tapered composite panels are studied. The numerical and experimental studies of the first ply failure behavior have demonstrated that the use of MWCNTs ensures a significant improvement in the FPF load of the analyzed laminated tapered curved composite panels. The taper configuration 3 (TC-3) with hyperbolic curved geometry exhibited the highest resistance to failure than taper configuration 1 (TC-1) and taper configuration 2 (TC-2). Moreover, the aforementioned parameters significantly influence the FPF load of laminated curved panels with various taper configurations. Furthermore, this study can be effectively used as a benchmark problem for researchers and as a tool to design practical laminated tapered curved composite panels with sufficient accuracy.

Post-failure behavior of 2-ply laminated glass plates with different interlayers

Modern design codes, such as the new Eurocode on the design of structural glass components, consider the prediction of the post-failure behavior of these elements of paramount importance for a proper and safe design. In this view, an experimental investigation is presented in the paper, on the mechanical response of undamaged and damaged 2-ply Laminated Glass (LG) under quasi-static loads, with different interlayers, namely polyvinyl butyral (PVB), SentryGlas (SG) and a plasticized version of PVB, Saflex DG41 (DG41). Firstly, undamaged specimens (UDLG) were tested in simply supported configuration (configuration 0) with a vertical load in the middle increased up to the failure of the bottom glass ply. damaged LG specimens (PDLG) were then tested into two different configurations: configuration I, with broken ply below (bottom ply) and configuration II, with broken ply above (top ply). All the presented tests were performed under displacement control. For both configurations, the interlayers influence on the post-breakage behavior was discussed. It is underlined that the global response of the two configurations was completely different: configuration II, which was characterized by a deformed shape opposite to the load direction, showed a good residual stiffness and reached high failure loads. On the contrary, in configuration I, the response was characterized by a low stiffness and load carrying capacity. In addition, also the influence of different glass types was discussed, focusing attention on tempered and toughened glass. The results showed that the contribution of the fractured layer cannot be disregarded in the evaluation of the global stiffness of a PDLG and its contribution is strictly related to the interlayer and glass typologies.

Computational modeling of impact failure of polymer coatings

Automotive coatings are typically a multi-layered polymer composite structure, whose impact resistance are closely related to the appearance, body corrosion and safety of a vehicle. Currently, it still remains a challenging task to accurately simulate the impact failure behavior of polymer coatings. In light of this, we propose a novel computational framework to address this issue. The main appeal of our presented method is that it can account for both of the two main failure patterns, i.e., polymer-ply and interlaminar failure, of polymer coatings. Towards this end, a multi-mechanism damage model is employed to describe the brittle and ductile damage of polymer ply, and a large deformation cohesive zone model is developed to simulate interlaminar delamination. With the help of the proposed method, we simulate the impact failure behavior of a single-layered polymer coating. The effectiveness of the novel method is validated by comparing numerical results with experimental observations in terms of failure patterns. Numerical results show that polymer ply failure includes both brittle and ductile damage, and the failure mechanisms of polymer ply have been numerically revealed. Finally, the effects of interfacial properties and coating damage parameters on impact failure of the polymer coating are numerically investigated.

The relation between in-plane fiber waviness severity and first ply failure in thermoplastic composite laminates

The influence of in-plane fiber waviness on the first ply failure of quasi-isotropic thermoplastic composite laminates was investigated. The failure mode and stress at first failure were studied by using a four-point bending test and an end-loaded bending (ELB) test. The experimental results confirm that no undesirable stress concentration due to load introduction occurred in the ELB test, thereby supporting the use of this test as an alternative method to measure stress at failure. The experiments demonstrated that waviness severity affects stress at first failure and compressive damage development. The stress at first failure initially decreases with increasing maximum waviness angle and levels off as the angle starts exceeding 20°. These results reinforce the hypothesis from previous research which suggests that wavy ply compressive strength is less sensitive to changes in severity at larger angles. Furthermore, it was found that kinking failure was the dominant failure mode for maximum waviness angle up to about 45°. No kink band was observed in wavy regions with maximum angles above 45° when there was another wavy region with a lower maximum angle in the same specimen. This means that failure is not necessarily initiated at the location where waviness is most severe.

Effect of Cutout on the Stability and Failure of Laminated Composite Cylindrical Panels Subjected to In-Plane Pulse Loads

In this investigation, the nonlinear dynamic buckling analysis and the failure analysis of laminated composite cylindrical (LCC) panel with different shapes of cutouts under the action of rectangular in-plane pulse loads are performed in the finite element framework. Cross-ply laminates which are balanced symmetric are considered in the investigation. The first ply failure load (FPFL) of the panel is evaluated and checked whether it occurs before the nonlinear dynamic buckling phenomenon considering Tsai–Wu failure criterion. Convergence and validation studies are undertaken, and the results are compared with those from the existing literature. The effects of loading duration, cutout area and cutout geometry on the panel are investigated in detail and results are reported. The results indicate that for the panel with cutout, its dynamic buckling load (DBL), in certain cases, compared to the static buckling load (SBL), can be lower even if the loading duration is half of its first natural period. Additionally, the vibration and the static buckling analyses of the panels are carried out as and when required.

Effect of statistical scatter in the elastic properties on the predictability of first ply failure of a polymer composite pressure vessel

Statistical variations in the elastic properties of composites are unavoidable. This work is concerned with the assessment of the probabilistic first ply failure of pressure vessel in response to the variations of elastic properties of T700 carbon/epoxy composite among the published literature. Initially, deterministic failure pressure is estimated using Finite Element Analysis software ANSYS. The uncertainties with respect to elastic properties are quantified by using Statistical software MINITAB. Then, the probability design system platform in ANSYS software has been utilized to perform probabilistic failure analysis by Monte Carlo simulations. The statistical results in terms of the mean and standard deviation of first ply failure pressure are computed. The probabilistic first ply failure pressure range determined is within 3 limits with 99.997% confidence level. It is helpful to the designers to assess the factor of safety in the case of anticipated variations in properties.

Effect of cutout geometry on the failure strength of symmetric laminates under uniform heat flux

The present work aims to investigate the thermal stress distribution in an infinite symmetrical laminated composite plate with a polygonal cutout to determine the laminate failure strength based on the first ply failure according to Hashin–Rotem and Tsai–Wu criteria. Lekhnitskii’s solution technique has been used to obtain the required potential functions. The extension of the technique used for the circular and elliptical cutouts into polygonal cutouts was performed using conformal mapping function in accordance with the procedure of complex variables. The main parameters such as cutout orientation, bluntness factor, the aspect ratio of the cutout, as well as stacking sequences in composite plates with symmetrical laminates made of glass/epoxy material containing triangular, square, pentagonal, and hexagonal cutouts have been examined. According to the research findings, it is possible to improve the failure strength of perforated plates by appropriate selection of cutout shapes along with the optimum values of the effective parameters. The unexpected result was that circular geometry was not always the best choice for the cutout because the selection of appropriate values for the parameters under consideration for a laminate with non-circular cutout leads to higher failure strength compared to the same plate with circular cutout.

Influence of microstructure on the failure of ultra-high molecular weight polyethylene composite beams impacted by blunt projectiles

Increasing the fibre tensile strength is well-known to improve the ballistic performance of ultra-high molecular weight polyethylene (UHMWPE) fibre composite beams. Here we investigate modifying ply microstructure as an alternate way to enhance ballistic performance. Specifically, we numerically investigate the mechanisms via which failure is initiated in [0o/90o]nlaminates comprising UHMWPE tape plies and compare with the commonly used UHMWPE fibre composites. Each ply of the beam is discretely modelled using a pressure-dependent crystal plasticity framework with the deformation mechanisms of the tape and fibre-based microstructures modelled by recognising differences in the available slip system in these two material systems. The numerical calculations are used to construct failure mechanism maps for a range of impact velocities, ply shear strengths and ply tensile strengths. Three dominant failure mechanisms emerged from the study: (i) failure of plies immediately under the projectile via an indirect tension mechanism in which compressive stress imposed normal to the plies by the projectile induces tensile in-plane ply stress due to the anisotropic expansion of the alternating 0o/90o plies; (ii) failure due to tensile straining at the rear of the impacted beam resulting from a combination of beam bending and stretching and (iii) a shear plugging like failure mode due to tensile straining at the edge of the impact site. Tensile stress generation by indirect tension is significantly reduced in the tape-based microstructures due to the unavailability of the slip systems that result in lateral plastic expansion. In fact, our calculations suggest that over the entire range of parameters modelled here the tape-based microstructures outperform the fibre-based microstructures. This suggests an alternate route to enhancing the ballistic performance compared to the traditional methods that rely mainly on increasing fibre strength.

Finite element prediction of first-ply failure loads of composite thin skewed hypar shells using nonlinear strains

The application of skewed hypar shell as civil engineering roofing unit is an established fact. Such use has gained a greater momentum when this shell is fabricated with advanced materials like the laminated composites. Research attempts in studying the first ply failure behaviour of laminated composite structural units are common now among engineers and the novelty of this paper lies in continuation of such efforts being applied to composite skew hypar shell. For accurate modelling of the failure behaviour of this thin shell, nonlinear strains are considered together with eight noded isoparametric serendipity finite element. Different well-established failure criteria including the failure criterion of Puck are used to extract the first ply failure pressure values, failure locations and failure modes as well. The finite element code developed is used for numerical experimentation with parametric variations and the results are post processed and interpreted to extract meaningful engineering conclusions.

Simultaneous analysis and optimum design of synthetic and vegetable fiber-reinforced composites for buckling - failure phenomena

Simultaneous analysis of buckling resistance and first ply failure behavior for synthetic and vegetable fiber-reinforced composites have been evaluated. The Modified Nelder-Mead Algorithm has been used to find the optimum buckling loads, and the failure criteria are selected to find the failure loads. The highlighted point in the present study is the probability of the first ply failure before the buckling. This may occur especially on vegetable fiber-reinforced composites. The study results show that first ply failure occurred before buckling for various loading cases of the structure.

Failure analysis of delaminated carbon/epoxy composite under pure bending: validation with numerical analysis

PurposeDelamination is a common and crucial damage mode which occurs during manufacturing of layered composites or their service life. Its existence leads to degradation in mechanical properties or even structural failure of composites. Hence, the purpose of this article is to study the effect of induced delamination on flexural performance of CFRP composites.Design/methodology/approachIn this article, the flexural behaviors of intact and delaminated carbon/epoxy laminates were investigated under pure bending. A circular PTFE film was introduced during fabrication to create artificial delamination. Moreover, finite element models were developed for intact and delaminated composites using ANSYS. The created models were discretized using 3D structural eight node solid elements.FindingsThe delamination influenced considerably flexural properties of composite. The composite exhibited a linear elastic nature prior to the damage of top ply on the compression side. The flexural strength and stiffness of the composite reduced to 44.5% and 18.2% respectively due to the existence of artificial delamination. The results of four point bending experiments and finite element analysis agreed for both intact and delaminated composites within acceptable error. Finally for same composites, first ply failure analysis was carried out using Tsai-Hill, Tsai-Wu and Hashin failure criteria.Originality/valueIn pure bending, beam section of the middle portion is free from shear. It is not so in case of three-point bending. Hence, the effect of embedded artificial defect on bending performance of CFRP composite due to pure bending has been investigated.

Predicting the Nonlinear Damage Response of Imperfect Laminates Using Linear Material Degradation Model and a Semi-Analytical Technique

This paper investigates nonlinear damage response and ultimate collapse of laminates under in-plane and lateral pressure loadings. The in-plane loading was in the form of end-shortening strain, while the lateral pressure was sinusoidal. The plates had initial geometric imperfection to which simply-supported boundary conditions were applied. Ritz techniques with nonlinear strain terms in kinematic relations as well as the first-order shear deformation theory were applied. Hashin and Rotem failure criteria were used for failure analysis. Two models were also employed for degradation of material properties in the plates. The complete ply degradation model was implemented along with the ply region degradation model, in which stiffness reduction was applied only to one region of the ply in which failure had occurred. Note that the stiffness degradation after the failure was investigated as both instantaneous and linear models. In both complete ply and region ply degradation models with instantaneous degradation of material properties, at any location in a ply or region, which has exceeded the given stress criterion, the corresponding stiffness properties are instantaneously degraded throughout that ply or region but with linear material degradation model, the stiffness diminishes gradually and linearly. Finally, the results were then validated against the findings of different references as well as finite element analysis. According to the results, it was seen that in the ply region degradation model, last ply failure loads are generally larger than those of the complete ply degradation model.

Progressive failure analysis of laminated plate containing elliptical cutout

PurposeThe prediction of accurate failure strength and a composite laminate failure load is of paramount importance for reliable design. The progressive failure analysis helps to predict the ultimate failure strength of the laminate, which is more than the first ply failure (FPF) strength. The presence of a hole in the laminate plate results in stress concentration, which affects the failure strength. The purpose of the current work is to analyze the stress variation and progressive failure of a symmetric laminated plate containing elliptical cutouts under in-plane tensile loading. The effect of various parameters on FPF and last ply failure (LPF) strength is studied.Design/methodology/approachThe ply-by-ply stresses around elliptical cutouts are obtained analytically using Muskhelishvili's complex variable formulation. To predict the progressive failure, Tsai–Hill (T-H) and Tsai–Wu (T-W) failure criteria are used, and depending on the mode of failure, lamina modulus is degraded.FindingsThe study has revealed that fiber orientation and stacking sequence for given loading have the most significant effect on the laminate's failure strength.Originality/valueComplex variable method and conformal mapping are simple and proficient for studying failure analysis of a laminated plate with elliptical cutout.

Investigation of ultrasonic welding of carbon fiber reinforced thermoplastic to an aluminum alloy using a interfacial coating

ABSTRACT An investigation on joining of carbon fiber-reinforced thermoplastics to an aluminum alloy 6061 has been demonstrated using ultrasonic plastic welding process. A separate energy director, as required for focusing heat generation at interface during ultrasonic plastic welding, is replaced by high-performance thermoplastic coating on aluminum via a fluidized bed to make the process convenient for industrialization. Besides this, the functional coating acts as an insulator that resists galvanic corrosion and avoids fretting damage on metallic substrates. Critical welding parameters were experimentally realized (weld time: 900 ms, hold time: 1200 ms, and horn pressure: 0.5 MPa) for a maximum shear failure load in a lap-type joint configuration that showed uniform melting with higher fusion between thermoplastics. The fracture surface and cross-section morphology were examined for different joint nomenclatures. Delamination and first-layer ply failures associated with interlaminar shear of composites were predominant with an effective interfacial adhesion (mechanical anchoring) on aluminum asperities yielding a structurally rigid joints. A significant strength improvement of 40% was attained in mechanically treated aluminum substrates. An appreciable joint strength in comparison with adhesive bonding was obtained within a cycle time of 2.1 s. The real-time transient temperature analysis during welding provided a strong correlation with the weld formation.

An analytical model for the progressive failure prediction of reinforced thermoplastic pipes under axial compression

AbstractAn analytical model is presented to predict the progressive failure of reinforced thermoplastic pipes (RTPs) under axial compression, in which the existing homogenization method and a nonlinear stiffness degradation model are combined to predict the continuum damage mechanical response in an iterative and cyclic way. As the homogenization method ignores the effect of the cross‐sectional curvature on the damage sequence, a stress correction factor is defined to consider this effect. Once corrected stresses satisfy Hashin‐Yeh failure criteria, the nonlinear stiffness degradation model is adopted to update the constitutive relationship established by the homogenization method. The proposed model is capable of identifying the damage location and failure mode, analyzing damage accumulation and predicting the ultimate compression. Meanwhile, ABAQUS Explicit quasi‐static analyses calling a user‐defined subroutine were conducted to capture the progressive failure mechanisms in 3D composites and verify the proposed model. The proposed model was found to give accurate prediction on the elastic stiffness, first ply failure, the damaged stiffness, the ultimate compression, and stress distributions. Furthermore, the effects of fiber's winding angles and the thickness‐radius ratios have been discussed, which illustrate that tensile failure mode would appear even when RTPs are under axial compression.

A Numerical Approach to Estimate First Ply Failure of Fibre Metal Laminate

Fibre Metal Laminates (FMLs) are laminates consisting of metal layers and fibre reinforced composite layers. These laminates are designed to improve some specific properties of constituent metals and composites layers. Estimation of First Ply Failure (FPF) Loads of these FMLs is a part in the broad characterization of these materials. A numerical method is developed for the estimation of FPF when these laminates are used as simply supported plates subjected to uniformly distributed load. Various failure criterions are used to identify these loads. The proposed method has been validated with the results of exact (Navier) solution available in the literature. FPFs are estimated for different groups of FMLs based on Aluminum, Titanium and Magnesium layers. The results are presented in the form of non-dimensional FPF and deformation values for various aspect ratios.

Progressive failure analysis of laminated composite plates

Failure of laminated composite plates has been a crucial issue that numerous researches have been conducted on the matter. Several modes of failure of laminated composites include fibre failure in tension, matrix failure in tension, fibre failure in compression, matrix failure in compression and delamination. This paper analyses failures of the composites to determine the first ply failure load (FPL) and last ply failure load (LPL) using the progressive failure approach that combines the effect of several modes of failure. Finite element method (FEM) was used via the commercial software of ANSYS APDL where the laminated composite plates were first modelled. Validation of the analysis was firstly conducted through a simple stress and deflection analysis. Progressive analysis was then conducted as the composite is loaded with an incremental combined tensile and transverse loading. The Tsai-Wu failure and the maximum stress criteria have been used to detect the FPL. With the failure occurred in an element, the degradation of that element mechanical properties was applied. As the load was further increased, more elements will fail and be degraded until the LPL was reached. A parametric study was conducted on the effect of varying angles of orientation of the composite. The results showed that the FPL and the LPL of the composites due to the Tsai-Wu criterion and the maximum stress criterion were in good agreement. The progressive failure behaviour of laminated composite plates subjected to uniaxial load and combined uniaxial load and transverse load was successfully established.

Examination of selected failure criteria with asymmetric shear stresses in the collapse analysis of laminated shells

The paper is concerned with failure analysis of composite shells performed with the usage of the nonlinear 6-parameter shell theory with drilling rotation degree of freedom. This special theory embodies naturally unlimited translations and rotations and is suitable for analysis of irregular shells for instance with various, particularly orthogonal, intersections. The presence of the drilling rotation is inherently accompanied with asymmetry of in-plane shear stresses and strains which must be taken into account in the composite failure criteria. In the paper in general two failure measures are applied: Hashin criterion and Tsai-Wu criterion which are appropriately modified to accommodate the stress asymmetry. It is shown, that depending on the used failure criterion, it is possible to obtain slightly different damage zones and values of the first ply failure and ultimate load. These values are compared with those obtained experimentally.

Nonlinear first ply failure study of laminated composite skew plates

The present work reports the first ply failure investigation of laminated composite clamped skew plates subjected to uniformly distributed transverse static load considering geometric linear and nonlinear strains. An eight-noded isoparametric curved quadratic plate element based on Sanders’ and Von Karman's nonlinearity is employed to develop the finite element code used in the present research. The first ply failure loads are evaluated based on various well-acknowledged failure theories like maximum stress, maximum strain, Hoffman, Tsai – Hill, Tsai – Wu, Hashin and Puck failure criteria. Effect of variation of skew angles on first ply failure loads of laminated composite skew plates for various stacking pattern is reported and studied in depth. The failure criterion corresponding to which the failure load value is minimum, for each skew angle, is only reported in this paper. The effects of skew angle on the first ply failure load are summarised in the form of charts and working equations. The engineers and researchers may use the charts and equations directly to predict the first ply failure load provided the geometry of the plate is known. Besides first ply failure loads the failed plies as well as the failure modes are also reported in the present paper.