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16. A surface replica image showing a matrix crack arrested by fiber/matrix debonding. From Gamstedt and Talreja (1999).
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This chapter summarizes part of the six lectures, pertaining to fatigue of composite materials, presented at the session, “Modern Trends in Composite Laminates Mechanics” at CISM in Udine. The summary provided here is of introductory nature aimed at a reader who is not an expert in the subject. Ample references are given to help the reader pursue t...
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Citations
... Fatigue damage in metal materials includes dislocations, slips, microcracks, and other damage caused by microplasticity, 7 while fatigue damage in FRP mainly includes matrix cracking, fiber breakage, and fiber/matrix interface debonding. 8 Many researchers have proposed fatigue models based on experimental research to study the evolution of fatigue damage in FRP materials. Degrieck et al 9 classified these fatigue models into three types: a) fatigue life model, b) macro-phenomenological model, and c) progressive damage model. ...
... Substituting the failure condition, S x ¼ 1 ð Þ¼S cr and Δσ ¼ S cr e cr into Equation (8) gives: ...
In this study, tension‐tension fatigue tests were conducted to investigate the residual stiffness degradation of carbon fiber‐reinforced polymer (CFRP) tendons. Different stress levels were used in the tests, and measurements of residual stiffness and the number of loading cycles were taken. Based on experimental data for CFRP tendons, a quantitative residual stiffness model was developed by modifying Yao's model. This model is applicable to various stress levels. To assess its accuracy and applicability, the predicted results of this model were compared with those of cited models from other researchers. The findings revealed a three‐stage degradation of residual stiffness in CFRP tendons under different stress levels. Furthermore, it was observed that the proportion of fatigue life accounted for by Stage III decreased with smaller stress ranges, while the proportion accounted for by Stage II increased. The proposed quantitative residual stiffness model was verified using both experimental and cited data.
... The first is based on Stress-Life (S-N) curves, and the other two approaches use macroscopic measurable properties to describe the gradual degradation of the specimen, being established as phenomenological models. The use of stiffness as the damage metric has some advantages as it shows a higher sensitivity to damage progression, has less dispersion in comparison to the residual strength approaches and can be measured using non-destructive methods [10][11]. Some studies used stiffness degradation as a damage parameter to describe the fatigue damage of composite materials and the authors found that the proposed damage function can model the experimental data very well [12][13][14]. ...
The stacking sequence of composite joints, especially the ply orientation at the substrate/adhesive interface, plays an important role in their fracture behavior. However, few works are available on this subject, especially under fatigue loading conditions. This study addresses the stacking sequence effect on the fracture and fatigue behavior of adhesively bonded glass-fiber reinforced polymers. Two layups were considered: [0°/90°/90°/0°]s and [-45°/90°/45°/0°]s2. Single-lap shear (SLS) specimens bonded with a two-component epoxy-based adhesive system (SikaPower ® 880) were subjected to quasi-static and fatigue testing. Quasi-static tensile tests were executed with the aim of obtaining the load-displacement curves and their respective average fracture ultimate load (Pu). Fatigue tests were performed considering a maximum load (Pmax) equal to 40% of Pu. The evolution of the specimen stiffness (E= P/) as a function of the number of cycles (N) was recorded during the SLS fatigue/fracture tests. The fatigue tests considered a sinusoidal waveform with a load ratio (R) of 0.1. Fractographic analyses were conducted using a Zeiss Smartzoom 5 digital microscope. The failure mechanisms of both stacking sequences were compared and correlated with the fracture strength, stiffness, and fatigue life results. Both stacking configurations exhibit fiber tear failure under fatigue loading. However, the bidirectional lay-up presented more intra-laminar failure than the quasi-isotropic laminate. The stiffness degradation model used, proved to be accurate to describe the fatigue damage evolution of the SLS, being able to characterize the fatigue life. This information can be used as a guideline in the selection of the best composite joint configuration for high-performance engineering applications.
... However, the above literature analysis is not comprehensive enough. Later, scholar Talreja [98] conducted an in-depth discussion. The scholar further found through fatigue loading tests that in general, the stress conditions of FRP composites under fatigue state can be divided into three categories: under high stress level controlled by FRP fiber fracture and under moderate stress by fiber/resin interface The bond strength is determined by the fatigue elongation failure mode at low stress. ...
The performance deterioration of steel anchors caused by steel corrosion is becoming more serious in slope anchorage applications. Therefore, the fiber reinforced plastic (FRP) composites have become a substitute material for traditional anchorage structures due to their advantages of low price, lightweight, high strength, and corrosion resistance. Numerous studies have proven that FRP anchors have better anchoring capacity than traditional steel anchors in practical engineering and are not as susceptible to environmental influences. This review mainly introduced the mechanical properties of FRP, focuses on the current research progress and innovation of FRP anchor in anchorage engineering, then provides a basis for the design of FRP anchor. In this study, the failure characteristics and problem of insufficient bonding strength of the first interface of FRP anchor anchoring slope were discussed, and the improvement was introduced. It will be conducive to the extension and application of FRP composites as structural materials in civil engineering. A detailed introduction is also given to biomaterials, which are mainly derived from nature and which will not only reduce waste disposal problems and environmental pollution but will also replace conventional applications. Finally, there will be an important reference and value for the development of green and sustainable engineering structures.
... From this starting point, several published papers are available that try to establish a sound correlation between the damage and fatigue behavior of composite plates. The first approach to this problem was from the aeronautical field [24,25], stating that, unlike metals, fatigue in composites develops in stages, each distinguished by a set of cracks. Experimental investigations into the damage development and residual strengths of open-hole specimens in fatigue were conducted and a model developed [26][27][28]. ...
Fiber reinforced composites are widely used in the production of parts for load bearing structures. It is generally recognized that composites can be affected both by monotonic and cyclic loading. For assembly purposes, drilling is needed, but holes can act as stress concentration notches, leading to damage propagation and failure. In this work, a batch of carbon/epoxy plates is drilled by different drill geometries, while thrust force is monitored and the hole’s surrounding region is inspected. Based on radiographic images, the area and other features of the damaged region are computed for damage assessment. Finally, the specimens are subjected to Bearing Fatigue tests. Cyclic loading causes ovality of the holes and the loss of nearly 10% of the bearing net strength. These results can help to establish an association between the damaged region and the material’s fatigue resistance, as larger damage extension and deformation by cyclic stress contribute to the loss of load carrying capacity of parts.
... But in most cases it is only valid till the operation reaches the selected number of cycles. [4][5]. ...
This paper's goal is to introduce the third step of the EFOP-3.6.1-16-2016-00014. project on the Faculty of Engineering, University of Szeged. In this period the production technology of composite material was chosen and a fatigue test machine was developed and tested. The paper shortly describes the composite materials and summarizes the theory of fatigue than it presents the process of the development with several prototypes of fatigue test machine, some of which were manufactured and tested. Initially a shaker played the key role in the first two conceptions and finally a crank mechanism became as the best solution. The main solved problems during the development were selection of bearings and solving the partly dynamic balancing of the moving parts.
... How the changes in fiber and matrix properties affect the S-N fatigue behavior of a composite can be approximately illustrated by Fig. 8, which was also conceptually constructed by Talreja. 7 Since the vertical location of Region-I, along the strain axis, is determined by fiber failure strain, ε f , this band can be raised/ lowered to relatively higher or lower strain levels using stiffer fibers having a higher or lower failure strain than that of the matrix. This means that with stiffer fibers, the strain range of Region-II will be relatively extended. ...
... The fatigue strength and its degradation behavior can be well described in terms of the conceptual framework, developed by Talreja,7 and described in Sect. 6 in this review. ...
A concise review of fatigue of fiber-reinforced composites, covering fatigue life and damage development and how the properties of constituents, orientations and other parameters affect fatigue life, is presented. The subject broadly covers polymer, metal, and ceramic matrix composites, by including specific examples of fatigue data from literature. Studies of composite fatigue have mostly evolved over the last 60 years, largely driven by aerospace applications of composites. The field is very vast in terms of accumulated technical literature and fatigue data. Therefore, only some iconic examples, each with good experimental data, have been considered in this review to illustrate the behavior and the trends as clearly as possible. First, the general nature of tensile deformation of fiber composites under various combinations of fiber and matrix failure strains are reviewed to provide a background with which the more complicated fatigue behavior can be easily understood. Second, examples of S–N fatigue data of glass (GFRP) and carbon (CFRP) fiber-reinforced plastics are provided, illustrating the effects of reinforcement, constituent properties, temperature, and orientation effects on fatigue failure. These analyses are also modeled by S–N curve calculations using exponential S–N fatigue constitutive equations proposed by author. These calculations helped to easily rationalize the trends in S–N data, as influenced by strength and failure strains of fiber and matrix. Next, stiffness degradation behavior in fiber composites are reviewed, with specific examples including CFRP (polymer matrix) and SiC/SiC (ceramic matrix) composites. The nature of stiffness degradation is also modeled using a semi-empirical equation that relates the fractional remaining stiffness to fractional remaining fatigue life in the composite. Finally, a few examples of fatigue behavior of laminated composites that are typically used in real-world applications are reviewed.
... Additionally, the military industry is looking for materials with specific properties. Therefore, it is extremely important to determine the strength of these materials, both for static and dynamic loads, including fatigue loads [10][11][12][13][14][15]. Aside from the traditionally determined parameters for construction materials, such as Young's modulus, Poisson's ratio or fatigue limits, it is important to determine other parameters related, for example, to the dissipation of deformation energy and vibration damping. ...
Composite materials (fiber reinforced plastics, FRPs) are successfully utilized in the production of various mechanical devices, including land vehicles, marine vessels, and aircrafts. They are primarily used for the production of body parts and hulls. Due to their importance, certain requirements relating to the mechanical properties of the materials used must be met for such applications. One aspect of the passive safety of vehicles is the effects of a possible collision with another object. The behavior of the structure in such a case can be determined based on the coefficient of restitution, which is a measure of energy dissipation after an impact. This paper presents the results of measuring the value of the coefficient of restitution for the selected composite materials, utilizing various reinforcement materials including different types of fibers and wooden veneer. The selected materials included glass, carbon, Kevlar fibers, and veneer from exotic wood in an epoxy resin matrix. The tested samples were made using various methods in order to understand the influence of the technology on the value of the coefficient. The authors determined the coefficient values utilizing two methods based on the measurement of two different physical quantities. In the first case, the height of the rebound of the ram was measured using a fast digital camera; in the second case, the time between successive rebounds of the tool was measured, determined based on the signal from the acceleration sensor. The authors compared the results of the coefficient values obtained using these methods and examined the relationship between the rebound energy and the value of the coefficient of restitution. The results have been discussed, and some conclusions have been made. Among other things, it seems that both methods of measurement are interchangeable with regard to lower impact velocities corresponding to lower heights (up to 300 mm) of the drop of the ram used in the tests.
... Those parameters can depend not only on the properties of constituent layers but also on their layup. Therefore, significantly more data are needed for fatigue composite structure characterization than in the case of metallic structures [41]. Additionally, composites are vulnerable even to low-energy impacts, which can introduce in the structure the so-called Barely Visible Impact Damage (BVID) [42]. ...
The capabilities of ceramic PZT transducers, allowing for elastic wave excitation in a broad frequency spectrum, made them particularly suitable for the Structural Health Monitoring field. In this paper, the approach to detecting impact damage in composite structures based on harmonic excitation of PZT sensor in the so-called pitch–catch PZT network setup is studied. In particular, the repeatability of damage indication for similar configuration of two independent PZT networks is analyzed, and the possibility of damage indication for different localization of sensing paths between pairs of PZT sensors with respect to damage locations is investigated. The approach allowed for differentiation between paths sensitive to the transmission mode of elastic wave interaction and sensitive reflection mode. In addition, a new universal Bayesian approach to SHM data classification is provided in the paper. The defined Bayesian classifier is based on asymptotic properties of Maximum Likelihood estimators and Principal Component Analysis for orthogonal data transformation. Properties of the defined algorithm are compared to the standard nearest-neighbor classifier based on the acquired experimental data. It was shown in the paper that the proposed approach is characterized by lower false-positive indications in comparison with the nearest-neighbor algorithm.
... Details of the procedure are given in [30]. The S-N curve giving the best fit with the experimental data had a slope of 0.1, the same as usually measured for this type of material using standard coupon data [10,11,[39][40][41][42][43]. However, the origin of the local S-N curve had to be greater than for typically obtained S-N curves to match the experimental data. ...
A progressive FEA mechanical fatigue degradation model for composites was developed and implemented using a UMAT user material subroutine in Abaqus. Numerical results were compared to experimental strain field data from high frequency digital image correlation (DIC) of split disk fatigue testing of pressure vessel cut outs with holes. The model correctly predicted the onset and evolution of damage in the matrix as well as the onset of fiber failure. The model uses progressive failure analysis based on the maximum strain failure criterion, the cycle jump method, and Miner’s sum damage accumulation rule. A parameter study on matrix properties was needed to capture the scatter in strain fields observed experimentally by DIC. S-N curve for the matrix material had to be lowered by 0% to 60% to capture the experimental scatter. The onset of local fiber failure had to be described by local S-N curves measured by DIC having 2.5 times greater strain than that of S-N curves found from standard coupon testing.
... Details of the procedure are given in [30]. The S-N curve giving the best fit with the experimental data had a slope of 0.1, the same as usually measured for this type of material using standard coupon data [31,32,33,10,34,35,36,37]. However, the origin of the local S-N curve had to be greater than for typically obtained S-N curves to match the experimental data. ...
A progressive FEA fatigue degradation model for composites was developed and implemented using a UMAT user material subroutine in Abaqus. Numerical results were compared to experimental strain field data from high frequency Digital Image Correlation (DIC) of split disk fatigue testing of pressure vessel cut outs with holes. The model correctly predicted the onset and evolution of damage in the matrix as well as the onset of fiber failure. The model use progressive failure analysis based on the maximum strain failure criterion, the cycle jump method and Miner sum damage accumulation rule. A parameter study on matrix properties was needed to capture the scatter in strain fields observed experimentally by DIC. S-N curve for the matrix material had to be lowered by 0% to 60% to capture the experimental scatter. The onset of local fiber failure had to be described by local S-N curves measured by DIC having 2.5 times greater strain than that of S-N curves found from standard coupon testing.
