scholarly journals An Energy-Based Concept for Yielding of Multidirectional FRP Composite Structures Using a Mesoscale Lamina Damage Model

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 157 ◽  
Author(s):  
Seyed Rahimian Koloor ◽  
Atefeh Karimzadeh ◽  
Noorfaizal Yidris ◽  
Michal Petrů ◽  
Majid Ayatollahi ◽  
...  
Keyword(s):  
Yield Point ◽  
Composite Structures ◽  
Failure Modes ◽  
Initial Slope ◽  
Dissipation Energy ◽  
Fiber Failure ◽  
Damage Initiation ◽  
Frp Composite ◽  
Structural Applications ◽  
Evolution Curve

Composite structures are made of multidirectional (MD) fiber-reinforced polymer (FRP) composite laminates, which fail due to multiple damages in matrix, interface, and fiber constituents at different scales. The yield point of a unidirectional FRP composite is assumed as the lamina strength limit representing the damage initiation phenomena, while yielding of MD composites in structural applications are not quantified due to the complexity of the sequence of damage evolutions in different laminas dependent on their angle and specification. This paper proposes a new method to identify the yield point of MD composite structures based on the evolution of the damage dissipation energy (DDE). Such a characteristic evolution curve is computed using a validated finite element model with a mesoscale damage-based constitutive model that accounts for different matrix and fiber failure modes in angle lamina. The yield point of composite structures is identified to correspond to a 5% increase in the initial slope of the DDE evolution curve. The yield points of three antisymmetric MD FRP composite structures under flexural loading conditions are established based on Hashin unidirectional (UD) criteria and the energy-based criterion. It is shown that the new energy concept provides a significantly larger safe limit of yield for MD composite structures compared to UD criteria, in which the accumulation of energy dissipated due to all damage modes is less than 5% of the fracture energy required for the structural rupture.

Failure Analysis of Composite Structures Using Multiscale Technique

2020 ◽  
Vol 995 ◽  
pp. 209-213
Author(s):  
Young W. Kwon
Keyword(s):  
Composite Structures ◽  
Failure Modes ◽  
Cell Model ◽  
Fibrous Composite ◽  
Failure Criteria ◽  
Multiscale Approach ◽  
Interface Failure ◽  
Fiber Failure ◽  
Strain Rate Effects ◽  
Constituent Material

Failure analyses of laminated fibrous composite structures were conducted using the failure criteria based on a multiscale approach. The failure criteria used the stresses and strains in the fiber and matrix materials, respectively, rather than those smeared values at the lamina level. The failure modes and their respective failure criteria consist of fiber failure, matrix failure and their interface failure explicitly. In order to determine the stresses and strains at the constituent material level (i.e. fiber and matrix materials), analytical expressions were derived using a unit-cell model. This model was used for the multiscale approach for both upscaling and downscaling processes. The failure criteria are applicable to both quasi-static loading as well as dynamic loading with strain rate effects.

Integrally-Stiffened Composite Damage Tolerance Evaluated by Computational Simulation

2001 ◽  
Author(s):  
Christos C. Chamis ◽  
Levon Minnetyan
Keyword(s):  
Material Properties ◽  
Composite Structures ◽  
Failure Modes ◽  
Damage Tolerance ◽  
Epoxy Composite ◽  
Computational Simulation ◽  
Computer Code ◽  
Simulation Design ◽  
Damage Initiation ◽  
Composite Damage

Abstract An integrally stiffened graphite/epoxy composite rotorcraft structure is evaluated via computational simulation. A computer code that scales up constituent micromechanics level material properties to the structure level and accounts for all possible failure modes is used for the simulation of composite degradation under loading. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulation. Design implications with regard to defect and damage tolerance of integrally stiffened composite structures are examined. A procedure is outlined regarding the use of this type of information for setting quality acceptance criteria, design allowables, damage tolerance, and retirement-for-cause criteria.

Sensing of Damage in Glass Fiber Composites by Adding Carbon Nanotubes

2013 ◽  
Vol 330 ◽  
pp. 68-76 ◽  
Author(s):  
Li Min Gao ◽  
Xin Lin Qing
Keyword(s):  
Carbon Nanotubes ◽  
Glass Fiber ◽  
Composite Structures ◽  
Fiber Composites ◽  
Damage Initiation ◽  
Micro Scale ◽  
Glass Fiber Composites ◽  
Specific Strength ◽  
Fiber Reinforced Polymer Composites ◽  
Structural Applications

Advanced fiber-reinforced polymer composites are known to possess outstanding specific strength and stiffness and their use in structural applications continues to expand. Most structural composites are susceptible to the formation of micro-scale damage in polymer matrix under adverse conditions which has significant implications on the durability and performance of fiber composites. Thus, it is imperative to detect the initiation and evolution of damage in composites long before their catastrophic failure. In this report, our recent research in sensing of micro-crack in matrix in situ and in real time for glass fiber composites was reviewed. Carbon nanotubes were dispersed into glass fiber composites by three roll mill technique. A resistance parameter was utilized to quantitatively characterize damage initiation and propagation. Damage mechanisms and development were investigated under tension, fatigue loadings. This research demonstrates the feasibility and benefits of electrical resistance measurements in the sensing of micro-scale damage for fiber composites using carbon nanotubes and offers the potential for in-service health monitoring of composite structures.

Progressive damage simulation of open-hole composite laminates under compression based on different failure criteria

2016 ◽  
Vol 51 (9) ◽  
pp. 1239-1251 ◽  
Author(s):  
Song Zhou ◽  
Yi Sun ◽  
Boyang Chen ◽  
Tong-Earn Tay
Keyword(s):  
Composite Structures ◽  
Damage Mechanics ◽  
Failure Modes ◽  
Failure Criteria ◽  
Strength Prediction ◽  
Progressive Damage ◽  
Cohesive Elements ◽  
Damage Initiation ◽  
Open Hole ◽  
Matrix Damage

The strength prediction of open-hole fibre-reinforced composite laminate under compression is very important in the design of composite structures. The modelling of fibre, matrix damage and delamination plays an important role in the understanding of the damage mechanics of laminate under open-hole compression. In this article, a progressive damage model for open-hole compression that is based on continuum shell elements and cohesive elements is established to model in-plane damage and delamination, respectively. The damage mechanics of sublaminate-scaled laminates with ply sequence [45/0/−45/90]ms and ply-level-scaled laminates with ply sequence [45n/0n/−45n/90n]s are investigated by our proposed model. The Tsai-Wu and Hoffman failure criteria are employed for the determination of matrix damage initiation. Compared with the experiments, the numerical results using the Tsai-Wu criterion exhibit better accuracy regarding open-hole compression strength prediction and failure modes simulation.

Axial and Lateral Impact Prediction of Composite Structures Using Explicit Finite Element Analysis

2002 ◽  
Author(s):  
Ari G. Caliskan
Keyword(s):  
Composite Materials ◽  
Composite Structures ◽  
Impact Analysis ◽  
Failure Modes ◽  
Basic Material ◽  
Lateral Impact ◽  
Absorption Mechanism ◽  
Element Analysis ◽  
Plane Shear ◽  
Structural Applications

The use of composite materials in the automotive industry is growing since these materials exhibit high stiffness, strength and low weight. As such, analytical capabilities must be developed in order for these materials to be used in more structural applications. Previous work in the area of crush performance has concentrated on experimental and empirical studies that have qualitatively characterized the crush process. These studies have shown that the crush process in composite materials is complex, and is dominated by fiber/matrix microcracking, which is the main energy absorption mechanism. In this study, the crush performance of a set of tubular composite structures were modeled using the explicit code RADIOSS™. Unlike many of the other commercially available codes, the composite material model within RADIOSS uses material input parameters that can be easily extracted from basic material test. These tests would include a 0° and 90° tensile and compressive test, as well as an in-plane shear test. The model can also accommodate strain rate effects. As the structure is loaded, the stresses within each element and ply are calculated. Using a Tsai-Wu failure criterion, the material fracture is simulated by removing a failed ply within a given element. As a consequence, the material degradation within and ahead of the crush front is simulated. The results of the study showed that the steady state crush load could be predicted accurately. However, the exact failure mode with the crushed structure was not as accurately represented in the model. In addition, two other case studies one being a 3-point bending on a hexagonal section and composite sandwich plate impact analysis were also performed. The results showed good agreement with experiments in both load levels and failure modes.

scholarly journals Compressive behaviours of octet-truss lattices

2020 ◽  
Vol 234 (16) ◽  
pp. 3257-3269 ◽  
Author(s):  
Yifan Li ◽  
Huaiyuan Gu ◽  
Martyn Pavier ◽  
Harry Coules
Keyword(s):  
Failure Modes ◽  
Density Ratio ◽  
Three Dimensional ◽  
Compressive Load ◽  
High Strength ◽  
Detailed Comparison ◽  
Compressive Response ◽  
Beam Elements ◽  
Structural Applications ◽  
Octet Truss

Octet-truss lattice structures can be used for lightweight structural applications due to their high strength-to-density ratio. In this research, octet-truss lattice specimens were fabricated by stereolithography additive manufacturing with a photopolymer resin. The mechanical properties of this structure have been examined in three orthogonal orientations under the compressive load. Detailed comparison and description were carried out on deformation mechanisms and failure modes in different lattice orientations. Finite element models using both beam elements and three-dimensional solid elements were used to simulate the compressive response of this structure. Both the load reaction and collapse modes obtained in simulations were compared with test results. Our results indicate that three-dimensional continuum element models are required to accurately capture the behaviour of real trusses, taking into account the effects of finite-sized beams and joints.

scholarly journals Structural Damage Identification of Composite Rotors Based on Fully Connected Neural Networks and Convolutional Neural Networks

Sensors ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 2005
Author(s):  
Veronika Scholz ◽  
Peter Winkler ◽  
Andreas Hornig ◽  
Maik Gude ◽  
Angelos Filippatos
Keyword(s):  
Neural Networks ◽  
Convolutional Neural Networks ◽  
Composite Structures ◽  
Damage Identification ◽  
Vibration Response ◽  
Damage Initiation ◽  
Matrix Cracks ◽  
Operational Life ◽  
Multiple Data Sets ◽  
Fully Connected

Damage identification of composite structures is a major ongoing challenge for a secure operational life-cycle due to the complex, gradual damage behaviour of composite materials. Especially for composite rotors in aero-engines and wind-turbines, a cost-intensive maintenance service has to be performed in order to avoid critical failure. A major advantage of composite structures is that they are able to safely operate after damage initiation and under ongoing damage propagation. Therefore, a robust, efficient diagnostic damage identification method would allow monitoring the damage process with intervention occurring only when necessary. This study investigates the structural vibration response of composite rotors by applying machine learning methods and the ability to identify, localise and quantify the present damage. To this end, multiple fully connected neural networks and convolutional neural networks were trained on vibration response spectra from damaged composite rotors with barely visible damage, mostly matrix cracks and local delaminations using dimensionality reduction and data augmentation. A databank containing 720 simulated test cases with different damage states is used as a basis for the generation of multiple data sets. The trained models are tested using k-fold cross validation and they are evaluated based on the sensitivity, specificity and accuracy. Convolutional neural networks perform slightly better providing a performance accuracy of up to 99.3% for the damage localisation and quantification.

Fiber Composite Strength Modeling With Extension to Life Prediction

2005 ◽  
Vol 128 (1) ◽  
pp. 41-49
Author(s):  
Edward M. Wu ◽  
John L. Kardos
Keyword(s):  
Composite Structures ◽  
Life Prediction ◽  
Failure Modes ◽  
Fiber Composite ◽  
Probability Model ◽  
Load Sharing ◽  
Local Load ◽  
Statistical Parameters ◽  
Composite Strength ◽  
Fiber Manufacturing

This paper focuses on the probability modeling of fiber composite strength, wherein the failure modes are dominated by fiber tensile failures. The probability model is the tri-modal local load-sharing model, which is the Phoenix-Harlow local load-sharing model with the filament failure model extended from one mode to three modes. This model results in increased efficiency in the determination of fiber statistical parameters and in lower cost when applied to (i) quality control in materials (fiber) manufacturing, (ii) materials (fiber) selection and comparison, (iii) accounting for the effect of size scaling in design, and (iv) qualification and certification of critical composite structures that are too large and expensive to test statistically. In addition, possible extensions to proof testing and time-dependent life prediction are discussed and preliminary data are presented.

Self Healing of Epoxy Composite for Aircraft's Structural Applications

2008 ◽  
Vol 136 ◽  
pp. 39-44 ◽  
Author(s):  
Willy C.K. Tan ◽  
J.C. Kiew ◽  
K.Y. Siow ◽  
Z.R. Sim ◽  
H.S. Poh ◽  
...  
Keyword(s):  
Composite Structures ◽  
Polymeric Materials ◽  
Hollow Fibre ◽  
The Body ◽  
Strength Increase ◽  
Self Healing ◽  
Structural Applications ◽  
Self Repair ◽  
Repair Systems ◽  
Point Bend

When one cut himself, it's amazing to watch how quickly the body acts to mend the wound. Immediately, the body works to pull the skin around the cut back together. The concept of repair by bleeding of enclosed functional agents serves as the biomimetric inspiration of synthetic self repair systems. Such synthetic self repair systems are based on advancement in polymeric materials; the process of human thrombosis is the inspiration for the application of self healing fibres within the composite materials. Preliminary results based on flexural 3 point bend test on prepared samples have shown the healed hollow fibre laminate has a healed strength increase of 47.6% compared to the damaged baseline laminate. These results gave us confidence that there is a great potential to adopt such self healing mechanism on actual composite parts like in aircraft’s composite structures.

scholarly journals Investigating the Effect of Interface Morphology in Adhesively Bonded Composite Wavy-Lap Joints

2021 ◽  
Vol 5 (1) ◽  
pp. 32
Author(s):  
Roya Akrami ◽  
Shahwaiz Anjum ◽  
Sakineh Fotouhi ◽  
Joel Boaretto ◽  
Felipe Vannucchi de Camargo ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Composite Structures ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Tensile Load ◽  
Lap Joints ◽  
Load Level ◽  
Displacement Curve ◽  
Interface Morphology ◽  
Angle Variation

Joints and interfaces are one of the key aspects of the design and production of composite structures. This paper investigates the effect of adhesive–adherend interface morphology on the mechanical behavior of wavy-lap joints with the aim to improve the mechanical performance. Intentional deviation from a flat joint plane was introduced in different bond angles (0°, 60°, 90° and 120°) and the joints were subjected to a quasi-static tensile load. Comparisons were made regarding the mechanical behavior of the conventional flat joint and the wavy joints. The visible failure modes that occurred within each of the joint configurations was also highlighted and explained. Load vs. displacement graphs were produced and compared, as well as the failure modes discussed both visually and qualitatively. It was observed that distinct interface morphologies result in variation in the load–displacement curve and damage types. The wavy-lap joints experience a considerably higher displacement due to the additional bending in the joint area, and the initial damage starts occurring at a higher displacement. However, the load level had its maximum value for the single-lap joints. Our findings provide insight for the development of different interface morphology angle variation to optimize the joints behavior, which is widely observed in some biological systems to improve their performance.

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