Ply Failure Research Articles

A unit circle failure criterion for carbon fiber reinforced polymer composites

A novel invariant-based approach to describe elastic properties and failure of composite plies and laminates has been recently proposed in the literature. An omni strain failure envelope has been defined as the minimum inner failure envelope in strain space, which describes the failure of a given composite material for all ply orientations. In this work, a unit circle is proposed as a strain normalized failure envelope for any carbon fiber reinforced polymer laminate. Based on this unit circle, a failure envelope can be generated from the longitudinal tensile and compressive strains-to-failure of a unidirectional ply. The calculated failure envelope was found in good agreement with experimental data published in the well-known World Wide Failure Exercise.

Numerical analysis of bearing failure in countersunk composite joints using 3D explicit simulation method

In this paper, tensile experiments were conducted into single-lap bolted joint between composite laminate and steel with countersunk fastener, and two three-dimensional explicit finite element models were developed using Abaqus/Explicit. Continuum shell elements (SC8R) were used to model in-plane ply failure with built-in damage model while cohesive elements were selected to predict interlaminar damage in model I. 8-node reduced integration solid elements (C3D8R) were chosen to model all the parts with 3D Hashin-type initiation criteria and Camanho degradation law implemented in a VUSDFLD subroutine in model II. The results simulated by both models accurately predicted the elastic loading response and captured overall damage profile compared with the experimental results. The numerical analysis using explicit solver provided acceptable accuracy which highlighted the robust nature and high computational efficiency without convergence issues compared with implicit solver. In addition, the effect of cohesive elements on computational efficiency was investigated to simplify the countersunk joints analysis.

Effects of winding angle on the behaviour of glass/epoxy pipes under multiaxial cyclic loading

The effects of winding angle on the behaviour of glass/epoxy composite tubes under multiaxial cyclic loading were investigated. The performance of such composite tubes was studied using an indigenous automated test procedure that is compatible with the internal qualification requirements of the composite pipe manufacturers. Glass fibre reinforced epoxy (GRE) composite pipes with three winding angles, namely, [±45°]4, [±55°]4, and [±63°]4, were tested. A novel automated test rig was fabricated to accommodate five stress ratios, ranging from pure axial to pure hoop loadings. The cyclic pressure test was conducted until droplets of water were seen on the outer surface of the pipe. Failure envelopes were then constructed based on the first ply failure (FPF) points determined from the axial stress to hoop strain response at five stress ratios. Three functional failure modes, namely, tensile axial, weepage, and local leakage failures, were observed during the tests. The results indicate that each winding angle dominates a different optimum pressure loading condition, namely, [±55°]4 for pure hydrostatic loading, [±45°]4 for hoop to axial loading, and [±63°]4 for quad hoop to axial loading. The envelopes show a strong dependence on the stress ratio and winding angle.

Mechanisms of penetration in polyethylene reinforced cross-ply laminates

The mechanisms of progressive penetration for two ultrahigh molecular weight polyethylene (UHMWPE) reinforced laminates have been investigated. One used an UHMWPE fiber reinforcement while the other utilized molecularly aligned tape. Both materials had similar out of plane compressive strengths, but the fiber system had a 40% higher in plane tensile strength than the tape. Laminated, 6 mm thick plates with a [0°/90°] ply architecture were impacted by a 12.7 mm diameter sphere under conditions that either allowed out of plane plate deflection or eliminated this deflection by rear support of the target. The depth of penetration and the ballistic limit in the rear-supported tests were identical for the two materials, and proceeded by progressive ply failure. However, tests in the edge clamped condition resulted in a substantially higher penetration resistance, especially for the higher tensile strength fiber-reinforced material. Edge clamped testing of a bilayer target, where the front third was composed of the tape material and the remainder comprised fiber reinforced laminate, had the same ballistic limit as a target composed of only the higher ply tensile strength fiber reinforced material. Penetration in both test support conditions was discovered to occur by tensile ply rupture under the projectile, consistent with a recently proposed mechanism for converting out of plane compression to in plane ply tension. Lateral displacement of plies was also observed near the sides of impact craters in both materials, indicating the existence of a second mechanism impeding penetration of the spherical shaped projectile.

Stress Analysis and Progressive Failure Analysis of Multilayered Basalt/Epoxy Composites

Constructions of pressure vessels like rocket launch vehicles, missiles, rocket propellant tanks, and filament wound pipes for civil and military applications are made out of high strength, high stiffness and light weight composites filaments. Filament winding techniques are used for fabrication of such cylinders and pipes. Many materials like glass fibers, carbon fibers and Kevlar fibers are used due to their good strength when it is subjected to internal pressure as well as external pressure. Basalt fibers are new materials that are fabricated from hard dense basalt rocks. Basalt fibers can be used in the place glass fibers due to their good mechanical behavior when subjected to internal pressure. Plates and beams generally resists bending loads and pipes and tube structures resists internal forces developed through internal and external pressure. This work concentrates the fabrication of filament wound pipes using filament wound techniques and the burst pressure test is carried out. In fuel tanks of rockets, If any one of the layer fails due to internal pressure, there will be mild leakage. For this reason it is mandatory to find out the ply by ply failure. The first ply failure of basalt filament wound pipes subjected to internal pressure is calculated using Finite element analysis. Then the stress and progressive failure analysis was carried out. Maximum stress failure criterion is used for the finite element analysis.

An experimental and finite element study of the transverse bending behaviour of CFRP composite T-joints in vehicle structures

The behaviour of a woven fabric carbon/epoxy composite T-joint (representing a simplified version the T-joint located at the connection between the B-pillar and the longitudinal rocker in a car body structure) is investigated using experimental and numerical methods. Details of the manufacturing process and experimental design factors are considered to understand their influence on the performance of the T-joint structure. The experimental results reveal the influence of manufacturing process and experimental setup on the load-carrying capacity and failure mode of the T-joint. Numerical simulation accurately predicts the stress distribution and load-carrying capacity of the T-joint obtained from experimental tests. The FEM model, which includes the adhesive interface layers at the edges, convincingly represents the experimentally found stiffness: the error is less than 3%. According to Hashin matrix tension criteria, the first ply failure occurs at 3.746 kN when the Hashin failure index (R) becomes equal to 1. Whereas, in the case of experimental tests, the first ply failure occurs around 3.4 kN, at which force the first load drop is observed.

First Ply Failure Loads of Composite Conoidal Shell Roofs with Varying Lamination

A number of industrial structures need large column free open spaces. Though the conoidal shells are doubly curved they are singly ruled too and are easy to fabricate and thus preferred in the industry. The laminated composites are well established today and there is a relevant question regarding the performance of different stacking options when the laminates are used to fabricate structural units. First ply failure analysis of conoidal shells are missing in the literature. This article uses the finite element method to evaluate relative performances of conoidal shells with varying laminations in terms of their first ply failure loads.

Fracture of Carbon Fiber-Reinforced Plastic Composite for Light Weight Electric Vehicle under the Tensile Loading

Damage behavior of carbon fiber-reinforced plastic composite (CFRP) under the tensile loading was investigated. Four lay-up sequences were considered: [0o]4, [90o]4, [0o/90o]2, and [0o/45o/90o/-45o]. Experimental results showed that the specimen [0o]4 showed highest stiffness and strength followed by [0o/90o]2 , [0o/45o/90o/-45o], and [90o]4. The behavior was analyzed by finite element method. Progressive damage model Hashin’s damage initiation criteria and energy based damage evolution law were applied. It was shown that FEA results quite well agree with experimental results. The fracture strength was strongly dependent on the failure of the 0o directional ply.

Progressive Failure Analysis of Laminated Composite Cylindrical Shell Roofs

A progressive failure analysis of laminated composite cylindrical roofs under transverse uniformly distributed static loadings has been carried out in the present paper using the finite element method. In the finite element analysis, an eight-noded isoparametric shell elements are taken up. The first-ply failure load and the ultimate ply failure load are evaluated and compared using different stress-based failure criteria. The effect of orientation of fibers in a lamina, stacking sequence, and varying boundary conditions, on the strength of the laminate is carried out. Factors of safety and load factors are suggested based on the values of first and ultimate ply failure loads. The damage progression using the failure criterion corresponding to the first-ply failure load has been shown. The areas of damage are correlated with deflection values through explicit equations so as to get an idea about the damage extents without going into elaborate testing. The results are interpreted from practical engineering standpoint to extract meaningful conclusions.

Progressive damage modeling of open-hole composite laminates under compression

Despite the recent success of modeling progressive damage of open-hole fiber reinforced composites subjected to tension (OHT), it is still a challenging task to predict the strengths and the damage progression of open-hole composite laminates under compressive loading (OHC). Herein, we propose a progressive damage model for OHC based on our early model for OHT and apply it to study the size effects of OHC. In the proposed model, continuum shell elements are used to account for both in-plane and out-of-plane deformation and delamination is modeled using cohesive elements. A smeared crack model is used to model the progressive failure of composite plies. It is found that the proposed model can predict accurately the experimental strengths and damage patterns with the assumption that the translaminar fracture toughness for blocked plies increases. The different failure mechanisms of the sublaminate scaled laminates of the stacking sequence 45/90/-45/0ms and the ply-level scaled laminates of stacking sequence 45n/90n/-45n/0ns are found to be closely related to the in-plane shear stress of the central 0° ply block and the initiation of interface delamination.

Prediction of post-buckling and ultimate compressive strength of composite plates by semi-analytical methods

An efficient, semi-analytical method is developed for estimating the ultimate strength of simply supported, rectangular plates of laminated composite material subjected to uniaxial in-plane compression. The method is based on large deflection theory combined with first order shear deformation theory. Two degradation models have been developed, where instantaneous material degradation has been applied either to the entire failed ply or to the affected regions of a failed ply. Further, two different types of in-plane displacement fields have been examined, and their influence on the strength predictions is found to be significant for some of the cases.

Influence of fibre misalignment and voids on composite laminate strength

This article studies the effects of manufacturing defects of laminate composite materials on the first ply failure load and ultimate strength of the laminate, which are calculated using finite element modelling with Zinoviev’s damage model. The following types of defects are considered for cross-ply and quasi-isotropic layups: in-plane misalignement and out-of-plane waviness of fibres, misorientation of the layers and void content. The list of laminates studied in this article includes cross-ply and quasi-isotropic layups, loaded in tension and compression in 0°, 90°, 45° and 5° directions. The limits of the first ply failure load and strength degradation for a realistic range of the defect intensities are estimated.

Failure analysis of composite plates under static and dynamic loading

The present paper deals with the first ply failure analysis of the laminated composite plates under various static and dynamic loading conditions. Static analysis has been carried out under patch load and triangular load. The dynamic failure analysis has been carried out under triangular pulse load. The formulation has been carried out using the finite element method and a computer code has been developed. The first order shear deformation theory has been applied in the present formulation. The displacement time history analysis of laminated composite plate has been carried out and the results are compared with those published in literature to validate the formulation. The first ply failure load for laminated composite plates with various lamination schemes under static and dynamic loading conditions has been calculated using various failure criteria. The failure index-time history analysis has also been carried out and presented in this paper.

Failure Analysis of Composite Laminates under Biaxial Tension: A Review and Framework

The designing of composite structures for modern and precision application is complicated due to its anisotropic and inhomogeneous material behaviour. Therefore, reliable methodology for fully predicting the performance of composite structures must be developed. Hence, analytical and numerical solution will be implemented in order to perform failure analysis of composite laminates under biaxial loading. There are many approaches developed in order to study the failure behaviour of composites materials. This paper reviews and proposes a research framework that employs analytical method, numerical method using MATLAB programming and finite element method using ANSYS 14.0 to investigate the failure behaviour of composite structures. The First Ply Failure (FPF) and Last Ply Failure (LPF) analysis will be performed to determine the failure curves. Finally, the failure curves obtained from both analytical and finite element simulation will be compared with results published from previous experiments.

Simplified ultimate strength analysis of compressed composite plates with linear material degradation

Simply supported, rectangular, composite plates subjected to in-plane compressive load have been investigated for ultimate strength. An efficient, semi-analytical method has been established based on large deflection theory and first order shear deformation theory. After damage initiation, linear degradation of the material properties has been applied to the affected region of a failed ply. Two different displacement fields have been examined for their influence on the strength predictions. The approach is validated against earlier advanced finite element calculations, and can be readily applied in specific design situations or to generate parametric design curves.

Prediction of Progressive Failure Behaviour of Composite Skewed Hypar Shells Using Finite Element Method

Progressive failure behaviour of laminated composite skewed hypar shells is investigated in this paper through finite element approach. For composite materials which are weak in transverse shear, failure may initiate at any inner lamina or interface and may remain undetected and unattended to. Such latent damages may progress gradually and lead to a sudden total ply failure. An iterative method is adopted using the various failure theories to predict the first ply failure load. After the first ply failure, the stiffness of the failed element is totally discarded from the laminate and the remaining laminate is considered for further analysis. The developed finite element code is validated through solution of a benchmark problem. Numerical experiments are carried out to obtain the first ply and progressive failure of simply supported hypar shells under transverse distributed load. While obtaining the failure loads, the shell is considered to be under plane stress condition and in linear elastic range. Results are studied meticulously to extract a set of conclusions of practical significance regarding the failure characteristics of composite hypar shells.

Finite element analysis of stress concentrations and failure criteria in composite plates with circular holes

In this study, the stress concentration factors (SCF) in cross-and-angle-ply laminated composite plates as well as in isotropic plates with single circular holes subjected to uniaxial loading is studied. A quadrilateral finite element of four-node with 32 degrees of freedom at each node, previously developed for the bending and mechanical buckling of laminated composite plates, is used to evaluate the stress distribution in laminated composite plates with central circular holes. Based up on the classical plate theory, the present finite element is a combination of a linear isoparametric membrane element and a high precision rectangular Hermitian element. The numerical results obtained by the present element compare favorably with those obtained by the analytic approaches published in literature. It is observed that the obtained results are very close to the reference results, which demonstrates the accuracy of the present element. Additionally, to determine the first ply failure (FPF) of laminated plate, several failure criterions are employed. Finally, to show the effect of E 1/E 2 ratio on the failure of plates, a number of figures are given for different fiber orientation angles.

Progressive Failure Analysis of Laminated Composite Plate by Using Higher Order Shear Deformation Theory

A finite element analysis procedure is developed for progressive failure analysis of laminated composite plates under in plane tensile loading. A finite element model is based on higher order shear deformation theory (HSDT) with seven degrees of freedom. The degradation technique used for degradation of material properties of a failed ply is a ply discounting approach. The mode dependant Hashin and Lee failure criterion is used for the progressive failure analysis. The results of first ply failure load and last ply failure load are obtained for different stacking sequence of composite plate. The results shows that a considerable amount of strength remains un utilized in composite laminates after first ply failure of laminates.

An invariant-based theory of composites

A novel invariant-based approach to describe elastic properties and failure of composite plies and laminates is proposed. The approach is based on the trace of the plane stress stiffness matrix as a material property, which can be used to reduce the number of tests and simplify the design of laminates. Omni strain failure envelopes are proposed as the minimum inner failure envelope in strain space, which defines the failure of a given composite material for all ply orientations. The proposed approach is demonstrated using various carbon/epoxy composites and offers radically new scaling to improve design and manufacturing.

Determination of the first ply failure load for a cross ply laminate subjected to uniaxial tension through computational micromechanics

A method for determining the in situ strength of fiber-reinforced laminas for three types of transverse loading including compression, tension and shear is presented. In the framework of this method, an analysis of local stresses that are responsible for the coalescence of matrix cracks is carried out by using a multi-fiber unit cell model and finite element method. The random distribution of fibers, fiber–matrix decohesion and matrix plastic deformations are taken into account in the micromechanical simulations. The present study also shows that the nonlinear hardening behavior of matrix reflects more realistically the influence of plastic deformations on the in situ transverse strength of lamina than the perfectly plastic behavior of matrix. The prediction of the in situ transverse strength is verified against the experimental data for a cross ply laminate subjected to uniaxial tension.