Progressive Failure Analysis Research Articles

Progressive failure analysis of laminates with an open hole subjected to compressive loading (OHC) using the enhanced semi-discrete modeling framework

The Open-hole compressive (OHC) strength of a fiber reinforced laminate is one of the most critical allowables for design of aerostructures. In this paper, results for predicting the OHC strength using the semi-discrete damage modeling framework are presented. The predictions are seen to capture experimentally observed failure mechanisms and measured failure loads. The constitutive model includes local axial compressive failure (and subsequent load bearing at a reduced plateau stress) while maintaining numerical robustness. Standard stacking sequences (quasi-isotropic, “hard” and “soft”) have been analyzed and compared to publicly available databases. Additionally, the model is challenged to predict delamination-dominated failure due to ply-scaling. Overall, the model is able to capture relevant failure mechanisms, while the ultimate loads are predicted with good accuracy. Therefore, this framework can be used with confidence in predicting OHC strengths of laminates.

Investigation of the notch sensitivity of tailorable long fiber discontinuous prepreg composite laminates

Tailorable discontinuous fiber composite laminates provide relative formability beyond that of continuous fiber laminates, while achieving improved mechanical performance over comparable stochastic systems. In this work, the notch sensitivity of engineered prepreg platelet molded composite (PPMC) laminates is investigated using the open-hole tension (OHT) test and compared to available data for stochastic PPMCs and continuous fiber laminates made with the same material. The press-formed thermoplastic composites (AS4/PEKK) were molded with a quasi-isotropic stacking sequence. The discontinuous PPMC laminate was found to be notch insensitive with OHT strengths ranging from 145.4 MPa (CV = 7%) for d/w=0.5 to 229.3 MPa (CV = 9%) for d/w=0.25. The highly ordered meso-structure of the engineered PPMC laminate yields comparatively excellent mechanical properties for relatively thin laminates in contrast to stochastic systems. Both net- and gross-section failures were observed for d/w=0.25, which suggests that the engineered PPMC laminates studied here maintain a degree of inherent, internal stress concentrations that compete with those caused by geometric features such as a circular hole. Computational simulations of the OHT tests with explicitly represented platelets were found to be in good agreement with experimental measurements. The progressive failure analysis was used to conduct a numerical investigation of the stacking sequence and platelet meso-morphology.

Bearing performance and progressive failure analysis of bolted joint in 3D printed pseudo-woven CFRP composite with fibre steering

This study investigates the bearing failure process of 3D printed pseudo-woven carbon fibre reinforced polymer (CFRP) composite joints, with a particular focus on the damage mechanisms influenced by steered fibres. A multiscale finite element model employing LaRC05 failure criteria is developed and validated against the experimental load–displacement curves and micro-computed microtomography (CT) images of four distinct cases. The model clearly demonstrates the critical importance of maintaining fibre continuity around the bolt hole, as this significantly influences the ability to reduce stress concentrations caused by the direct bearing loads from the bolt. Moreover, the model reveals that fibre steering can substantially improve the composite joint’s performance. This enhancement is achieved by adjusting the level of shear-induced damage propagation in individual filaments. The results demonstrate the potential and capability of the model to capture individual filament behaviour for the failure analysis of 3D printed composites, achieving good correlations with experimental measurements and observations, in terms of failure modes and load-bearing capacities.

Dynamic Progressive Failure Analysis of 3D Five-directional Braided Composites under Transverse Compression Based on Macro-scale Heterogeneous Model

At present, there are few systematic researches on macro-scale heterogeneous modeling and numerical simulation of dynamic mechanical properties of 3-D braided composites. In this paper, the parametric virtual simulation model of 3D five-directional braided composites is realized in the way of “point-line-solid” based on the integrated design idea of process-structure-performance. And the impact compression numerical simulation of the material is carried out by using multi-scale analysis method. The effects of strain rate and braiding angle on transverse impact compression properties and fracture characteristics of composites is studies and verified by comparing the test results with the numerical simulation results systematically. The dynamic failure mechanism of the matrix and fiber bundles during the impact compression process is revealed. The results show that the macro-scale heterogeneous simulation model of 3D five-directional braided composites established is effective, and the numerical simulation results agree well with the test results. The matrix fracture and shear failure of fiber bundles are presented simultaneously under transverse impact compression. The failure of fiber bundles and matrix mainly concentrates on two main fracture shear planes. And the included angle between the fracture shear planes and the vertical direction is consistent with the corresponding internal braiding angle of specimens.

Multiscale modelling of CFRP composites exposed to thermo-mechanical loading from fire

Carbon fibre reinforced polymers (CFRP) are prone to structural damage during extreme events such as fire. Typically, modelling the effect of fire on CFRP structures is carried out through mesoscale analysis to predict overall structural performance. In this study, Finite Element (FE) modelling has been conducted to investigate the effects of fire on CFRP specimens at both meso- and micro-scales. The mesoscale analysis informs the microscale analysis to examine the effects of fire on each constituent of the material. A comparison of thermal analysis at the meso- and micro-scales reveals less than a 6% difference in the predicted nodal temperature. For the first time, fire-induced progressive failure analysis has been conducted on the fibres, matrix, and fibre/matrix interface of representative plies within the composite laminates. Fibre breakage, matrix cracking, and interface debonding were accurately captured using representative volume element (RVE) models under thermo-mechanical loading, showing qualitatively excellent agreement with experimental data.

Progressive failure analysis of woven and non‐woven CFRP composite/steel bolted joints

AbstractDue to recent advancements in textile fabrication, woven fabric reinforcements are used in composite structures as an alternative to traditional unidirectional fiber reinforcing layups. In this paper, experimental work was performed to study the behavior of multiple bolt‐lapped joints under uniaxial tension. Different bolt numbers, composite layups, and fabric configurations were studied. Single‐ and double‐lap configurations were used to investigate the effect of secondary stresses. It was found that the P‐δ curves of lapped joints exhibit four primary stages: a linear elastic stage, followed by a nonlinear hardening stage, then linear hardening leading up to the peak, and finally a softening stage. For double‐lapped non‐woven joints, the curves encompass only the first three stages; however, for woven composites, the last stage is very small. In addition, among the laminates, the non‐woven laminate sustains the highest normalized failure load, except in the staggered case, where the quasi‐isotropic woven laminate exhibits higher strength. Conversely, the bidirectional woven laminate demonstrates the lowest loads and the highest deformation.Highlights A study compared bolted joint performance of woven and uni‐based composites. Lapped joints with different bolt arrangements were experimentally studied. P‐δ curves showed elastic, nonlinear, linear hardening, and softening stages. Woven laminates showed higher displacements compared to non‐woven laminates. Secondary bending induced additional stress with less impact on woven samples. Bearing failure predominated, with variations in extent of bearing damage.

Multi-scale analysis of ultimate bearing capacity in composite hull joints: failure mechanism and numerical simulation

ABSTRACT Progressive failure analysis method is the main method to analyse the ultimate bearing capacity and failure mode of composite structures. Multi-scale method can effectively reduce the dependence of damage mode and stiffness degradation analysis on material parameters. Based on the multi-scale method, from micro-scale to mesoscale and then to macro-scale, the equivalent modulus and equivalent strength of fibre bundles, single-layer laminates and multi-directional laminates were predicted respectively, and the prediction method of ultimate bearing capacity of large-scale composite structures from material level to structure level was constructed. The mechanical properties of standard composite materials and the ultimate bearing capacity of full-scale composite joints were tested respectively, and the ultimate bearing capacity and failure mode of L-joints were predicted by numerical method. The results show that the numerical simulation method based on multi-scale can accurately predict the ultimate bearing capacity and failure mode of large-scale joints of the hull.

Limit states of thin-walled composite structures with closed sections under axial compression

The subjects of the study were thin-walled composite columns with closed cross sections manufactured using the autoclave technique. The composite profiles were characterized by the fact that they had a constant height and arrangement of laminate layers, however, varied cross-sectional shapes. The study was conducted using several interdisciplinary experimental research methods and advanced numerical simulations. In the course of the research, both forms of structural stability loss were registered, and damage to composite structures was assessed. In the course of the research, the influence of the shape of the cross-section on the stability and load-carrying capacity of the structure was evaluated. A measurable effect of the conducted research was the determination of the structure's post-buckling equilibrium paths, which made it possible to determine the structure's behavior in the full range of loading. In addition, the author's numerical models developed enabled validation of parallel experimental studies. The developed numerical models were based on a failure criterion known as progressive failure analysis - which allowed a thorough assessment of the failure mechanism of the composite material.

Progressive failure analysis of laminar composites under compression using smeared crack-band damage model and full layerwise theory

This paper presents an original finite element (FE) model that integrates the smeared crack band (SCB) approach and full layerwise plate theory (FLWT). The model enhances the computational efficiency of progressive failure analysis (PFA) of laminar composites in compression, by utilizing the layerwise approach which reduces a 3D model to a 2D one. The model distributes damage throughout the FE domain, with fracture mechanisms represented by material stiffness degradation controlled by damage variables (based on equivalent strains specifically defined for each failure mode). Mesh dependency issues are addressed by scaling fracture energy using a characteristic element length, and failure initiation and modes are determined using the 3D Hashin failure criterion.Accurately describing lamina response in fiber direction under compression requires linear-brittle softening with a stress plateau. The study showed that a model considering 30 % of residual stress accurately predicts maximum stress regardless of mesh refinement, demonstrating results’ minor dependence from the selected element size.The model accuracy has been confirmed by comparing the obtained results against experimental and benchmark data from the literature. The size effect study demonstrated a decrease in maximum stress of the open-hole laminates in compression with increasing specimen in-plane size. This trend is consistent with experimental and reference numerical observations, confirming the model accuracy and applicability even for relatively coarse meshes. Therefore, computational efficiency is improved, with preserved accuracy of conventional solid finite element models.

Data-driven integration of synthetic representative volume elements and machine learning for improved microstructure-property linkage and material performance in ceramics

Ceramic materials, characterized by their heat resistance, dielectric properties, and mechanical performance, are often compromised by brittleness due to microstructural inclusions. These inclusions, such as defects, secondary phases, and pores, are critically analyzed for their impact on material strength and fracture properties. In this study, the linkage between microstructure and properties in ceramic materials is explored through a methodological approach that combines experimental observations with physics-based and machine learning models. A data-driven approach has been employed, utilizing synthetic Representative Volume Elements (RVEs) derived from X-ray computed tomography scans of ceramics. The methodology involves an automated finite element (FE) simulation process for progressive failure analysis under uniaxial compression and tension. The analysis is conducted using statistical, data-driven, and machine learning techniques, including principal component analysis and k-means clustering, to assess the microstructural features' impact on material performance. The study focuses on the use of RVEs for accurately capturing essential microstructural characteristics and addresses the challenges in developing synthetic models and the limitations of simulation capabilities. The study's findings reveal that less uniform inclusion distribution and a higher standard deviation in inclusion size correlate to lower mechanical performance. By applying data-driven methods, this research contributes to the optimization of material performance and the establishment of structure-property relationships, with a particular emphasis on the influence of inclusions and defects on the mechanical behavior of ceramic materials.

Determination and Verification of Repair Tolerance of Patch Repaired T700SC/EC240A Composite Laminates Based on Progressive Failure Analysis Method

Determination and Verification of Repair Tolerance of Patch Repaired T700SC/EC240A Composite Laminates Based on Progressive Failure Analysis Method

Path-Dependent Progressive Failure Analysis for 3D-Printed Continuous Carbon Fibre Reinforced Composites

In order to predict the damage behaviours of 3D-printed continuous carbon fibre (CCF) reinforced composites, when additional short carbon fibre (SCF) composite components are employed for continuous printing or special functionality, a novel path-dependent progressive failure (PDPF) numerical approach is developed. First, a progressive failure model using Hashin failure criteria with continuum damage mechanics to account for the damage initiation and evaluation of 3D-printed CCF reinforced polyamide (PA) composites is developed, based on actual fibre placement trajectories with physical measurements of 3D-printed CCF/PA constituents. Meanwhile, an elastic-plastic model is employed to predict the plastic damage behaviours of SCF/PA parts. Then, the accuracy of the PDPF model was validated so as to study 3D-printed CCF/PA composites with either negative Poisson’s ratio or high stiffness. The results demonstrate that the proposed PDPF model can achieve higher prediction accuracies in mechanical properties of these 3D-printed CCF/PA composites. Mechanism analyses show that the stress distribution is generally aggregated in the CCF areas along the fibre placement paths, and the shear damage and matrix tensile/compressive damage are the key damage modes. This study provides a new approach with valuable information for characterising complex 3D-printed continuous fibre-matrix composites with variable mechanical properties and multiple constituents.

Study on the Properties and Fatigue Characteristics of Glass Fiber Composites Due to Porosity

A study was conducted on the changes in mechanical properties and fatigue failure characteristics due to voids, one of the fabrication defects in composite materials. This study was primarily based on glass fiber fabrics applied to wind turbine blades and their material properties were predicted through micro and meso modeling of composite materials by simulating random defects including voids. As the wind turbine blades become larger, various defects develop. The fundamental changes in the materials’ properties due to voids were predicted through homogenization methods and Representative Volume Element (RVE), and the failure properties were obtained through progressive failure analysis by applying virtual coupons according to ASTM D3090 and ASTM D6641. The progressive failure was identified using the Matzenmiller–Lubliner–Taylor (MLT) failure condition, and the fatigue failure characteristics were assessed through the Tsai–Hill 3D load.

Progressive failure and quantitative stability analysis of rock slope with cross-type discrete fracture network using spring-based smoothed particle hydrodynamics method

The propagation and coalescence of discontinuous cross-type joints are often the primary drivers of rock slope failures. Due to the inherent randomness of these joints, identifying suitable methods to accurately characterize progressive failure and quantitatively assess the stability of slopes with cross-type joints is particularly challenging. To address this, a Discrete Fracture Network-Spring Based-Smoothed Particle Hydrodynamics (DFN-SB-SPH) method is proposed, which considers cross-type DFN generation, rock matrix heterogeneity, cracking, block contact, and deposition within a unified SPH framework. In this approach, damage and contact of blocks are achieved by introducing a fracture sign to enhance the kernel function and applying Newton's law to the damaged particles to realize the point to point contact. A uniaxial compression test on rock samples with double fissures is carried out to verify the accuracy of the proposed method. The influence of joint density, geometric parameters (i.e., trace length, dominate dip angle) of cross joints, and rock mass heterogeneity on the failure characteristics of RSCD are investigated. The results revealed that the DFN-SB-SPH model possesses robust capabilities for crack tracking, mass movement, and contact slipping along fracture surfaces. Moreover, DFN generation, heterogeneous characterization, shear and tensile fractures within a single SPH framework without mesh distortion are realized. Five typical failure modes calculated by DFN-SB-SPH are primarily determined by the combination of joint dip angles and trace lengths. Furthermore, the dip angle, trace length, joint density, and rock mass heterogeneity significantly alter the stability of RSCD with sensitivity coefficients for factor safety of 27.7 %, 44.6 %, 72.9 % and 35.0 %, respectively. Higher dominant dip angles (above 60°) lead to significantly longer run-out distances for RSCD compared to lower angles (below 30°) once instability occurs. The sudden rise in major principal stress at the slope's top and toe, along with the shift of tensile stress concentration towards the middle, predicts the stages of crack propagation and sliding in slope failure.

On the experimental determination and prediction of damage evolution in composites via cyclic testing

This study introduces a novel approach to obtaining and predicting damage evolution laws using quasi-static cyclic testing within the framework of continuum damage mechanics. To achieve this, a comprehensive set of characterization and parameter identification tests was performed. Carbon-epoxy specimens were manufactured using the filament-winding technique, and these laminates were tested using a universal testing machine. Digital image correlation was employed in all experiments to capture strain fields, and an alternative method utilizing the combined loading compression device is presented to obtain mechanical properties. Once the material was characterized, cyclic tests were conducted, including [Formula: see text], [Formula: see text], and [Formula: see text] tensile tests, and shear v-notch tests. These aim to determine damage evolution laws for both conditions, pure and coupled stress states. From these tests, values for damage onset and threshold were obtained and used to define four new parameters. These parameters permit the estimation of degradation relationships for any arbitrary orientation without requiring additional tests. This approach was tested as the proof-of-concept within the positive range of transverse tension and in-plane shear stress domain. The obtained results are promising, justifying its extension to other failure mechanisms. While acknowledging its limitations, this new approach holds potential for implementation in the analysis of progressive failure in fiber-reinforced composite materials, possibly in conjunction with established failure criteria and computational tools, mainly in the finite element method domain.

Effects of translaminar edge crack and fiber angle on fracture toughness and crack propagation behaviors of laminated carbon fiber composites

Abstract In this study, the translaminar fracture toughness of carbon fiber laminated composites with different layer sequences was investigated experimentally and numerically for different crack directions. In the numerical study, first of all, the critical stress intensity factor was determined by using the M-integral method. Three-dimensional model and M-integral analysis were achieved in the ANSYS finite element package program. The non-local stress fracture criterion was used to in order to find failure curves of the materials. Then, in order to find the crack propagation directions numerically, the solid model was transferred to the LS-DYNA program and progressive failure analysis was performed. Fracture toughness decreased by 9.92 % with the change of crack angle from 15° to 90°. As the fiber angle changed from 0° to 45°, it decreased by 9.17 %. The biggest error between the experimental and numerical study results was found at α = 45°, with a rate of 12.3 %.

Compressive failure analysis of composite honeycomb sandwich panels with impact damage and stepped-scarf repairs

Composite honeycomb sandwich panels (CHSPs) have been widely used in the aerospace industry owing to their lightweight and superior mechanical properties. However, these CHSPs are susceptible to impact damage, leading to a significant reduction in compressive strength and potentially jeopardize aircraft safety. It is crucial to investigate repair methods for CHSPs with impact damage. This paper aims to evaluate the repair performance of CHSPs with impact damage through an analysis of their compressive failure behaviors. To accomplish this, both experimental tests and advanced numerical models are employed. The numerical models for the intact, damaged and stepped-scarf repaired CHSPs are established using the progressive failure analysis model, cohesive zone model and sandwich plate theory. A good agreement is observed between the experimental results and numerical predictions of compressive failure behaviors. Moreover, the validated numerical models are successfully utilized for determining optimum repair parameters by parametric analysis of the repaired CHSPs. The establishment of these numerical models offers an accurate and cost-effective evaluation of repair performance for CHSPs with impact damage, highlighting the novelty and main contribution of this paper.

Experimental and numerical studies on compressive failure behaviors of stepped-scarf repaired composite stiffened panels

Composite materials have been widely used in aerospace and other fields due to their superior mechanical properties. The repair of composite structures has received increasing attention in recent decades. In this work, the compressive failure behaviors of intact, defective and stepped-scarf repaired composite stiffened panels are analyzed experimentally and numerically. The evaluation of repair schemes of composite stiffened panels based on finite element (FE) analysis is investigated by comparison with experimental results. The maximum absolute value of error in load-carrying capacity between the numerical and experimental results does not exceed 3.65%. Progressive failure analysis model and cohesive zone model are utilized to reveal the damage evolution of multilayered composites and adhesive film. The failure modes obtained from FE analysis are in good agreement with the experimental observations. Moreover, the influence of the stepped-scarf ratio and repair patch angle deviation on the compressive strength is investigated to determine optimum repair parameters based on the established FE models. On the basis of the conducted studies, the results provide valuable insights into the evaluation and validation of repair schemes for composite stiffened panels with high accuracy and cost-effectiveness.

Progressive failure analysis of z-pin reinforced composite pi joints

A finite element model of a z-pin reinforced composite pi joint has been developed and correlated against experimental results. A smeared cohesive zone modeling approach was implemented to represent the effect of z-pinning in an efficient and scalable manner. In the smeared approach, cohesive properties governing the traction–separation response of the z-pin reinforced areas were defined to account for the effective fracture toughness caused by z-pinning in an averaged sense. The crack band method was used to account for diffuse damage and failure in the weave of the pi preform. The damage in the preform developed due to delamination suppression caused by the z-pinning. The numerical model was calibrated using experimental data from pristine and defective z-pinned pi joints subjected to pull-off and side-bend loading. Comparisons of experimental and numerical results show good agreement in terms of structural response, critical loads, and failure modes.

Progressive Failure Analysis of Carbon Fiber Reinforced Polymer Composite with a Circular Notch by Varying Fiber Orientation

Progressive failure for Carbon Fiber Reinforced Polymer (CFRP) was computationally studied and analyzed using Hashin’s failure criteria. It was an interactive failure criterion having 4 separate modes of failure. 8 layers of plies were oriented at specific stacking sequences to create different laminates with dimensions being specified using the ASTM D5766 standard. A total of 7 types of laminate were modeled and simulated to predict the failure for each type under tensile loading. A circular notch was added in the center for the concentration of stress. The damage to the fiber and matrix propagated and failed the structure. Contour plot analyses showed failure progression of fibers and matrix around the circular notch. Results show that matrix failure most predominant and critical type of failure for most laminates. From the stress vs. strain curves, it was seen that the [0/90]4 cross-ply laminate showed the highest open-hole tensile strength.