Fatigue damage analysis of composite materials using thermography-based techniques (original) (raw)
Related papers
Journal of Composites Technology and Research, 1994
A mechanical test technique was developed to assist in quantifying the accumulation of damage in composite materials during thermomechanical fatigue (TM_ cycling. This was accomplished by incorporating definitive elastic mechanical property measurements into an ongoing load-controlled TMF test without disturbing the test specimen or significantly altering the test conditions. The technique allows two fundamental composite properties consisting of the isothermal elastic static moduli and the macroscopic coefficient of thermal expansion (CTE) to be measured and collected as functions of the TMF cycles. The specific implementation was incorporated into the commonly employed idealized in-phase and out-of-phase TMF cycles. However, the techniques discussed could be easily implemented into any form of load-controlled TMF mission cycle. By quantifying the degradations of these properties, tremendous insights are gained concerning the progression of macroscopic composite damage and often times the progression of damage within a given constituent. This information should also be useful for the characterization and essential for the verification of analytical damage modeling methodologies. Several examples utilizing this test technique are given for three different fiber lay-ups of titanium metal matrix composites.
A review of thermographic techniques for damage investigation in composites
Frattura ed Integrità Strutturale
The aim of this work is a review of scientific results in the literature, related to the application of thermographic techniques to composite materials. Thermography is the analysis of the surface temperature of a body by infrared rays detection via a thermal-camera. The use of this technique is mainly based on the modification of the surface temperature of a material, when it is stimulated by means of a thermal or mechanical external source. The presence of defects, in fact, induces a localized variation in its temperature distribution and, then, the measured values of the surface temperature can be used to localize and evaluate the dimensions and the evolution of defects. In the past, many applications of thermography were proposed on homogeneous materials, but only recently this technique has also been extended to composites. In this work several applications of thermography to fibres reinforced plastics are presented. Thermographic measurements are performed on the surface of the specimens, while undergoing static and dynamic tensile loading. The joint analysis of thermal and mechanical data allows one to assess the damage evolution and to study the damage phenomenon from both mechanical and energetic viewpoints. In particular, one of the main issues is to obtain information about the fatigue behaviour of composite materials, by following an approach successfully applied to homogenous materials. This approach is based on the application of infrared thermography on specimens subjected to static or stepwise dynamic loadings and on the definition of a damage stress, D , that is correlated to the fatigue strength of the material. A wide series of experimental fatigue tests has been carried out to verify if the value of the damage stress, D , is correlated with the fatigue strength of the material. The agreement between the different values is good, showing the reliability of the presented thermographic techniques, to the study of composite damage and their fatigue behaviour.
A review of thermographic techniques for damage investigation in composites.PDF
The aim of this work is a review of scientific results in the literature, related to the application of thermographic techniques to composite materials. Thermography is the analysis of the surface temperature of a body by infrared rays detection via a thermal-camera. The use of this technique is mainly based on the modification of the surface temperature of a material, when it is stimulated by means of a thermal or mechanical external source. The presence of defects, in fact, induces a localized variation in its temperature distribution and, then, the measured values of the surface temperature can be used to localize and evaluate the dimensions and the evolution of defects. In the past, many applications of thermography were proposed on homogeneous materials, but only recently this technique has also been extended to composites. In this work several applications of thermography to fibres reinforced plastics are presented. Thermographic measurements are performed on the surface of the specimens, while undergoing static and dynamic tensile loading. The joint analysis of thermal and mechanical data allows one to assess the damage evolution and to study the damage phenomenon from both mechanical and energetic viewpoints. In particular, one of the main issues is to obtain information about the fatigue behaviour of composite materials, by following an approach successfully applied to homogenous materials. This approach is based on the application of infrared thermography on specimens subjected to static or stepwise dynamic loadings and on the definition of a damage stress, D , that is correlated to the fatigue strength of the material. A wide series of experimental fatigue tests has been carried out to verify if the value of the damage stress, D , is correlated with the fatigue strength of the material. The agreement between the different values is good, showing the reliability of the presented thermographic techniques, to the study of composite damage and their fatigue behaviour.
Composites Part B: Engineering, 2017
Standards and conventional procedures used for analysing fatigue damage in composite materials involve high experimental campaign costs due to time-consuming tests. This aspect becomes relevant for large structures where the cost of experimental setup tends to rise according to structure dimensions. In this regard, in recent years, efforts to produce fatigue characterisation of materials have made use of several experimental techniques, i.e. thermographic techniques. Most of these, however, refer to Standard specimens and laboratory equipment and setup. Through the use of Thermography, in this work a new procedure has been developed which is capable of monitoring damage in GFRP composite material. The analysis of thermal signal in the frequency domain allows for the isolation of indexes which are related to the thermoelastic and dissipative heat sources. In particular, the phase of thermoelastic signal, associated with intrinsic dissipation processes occurring in the material, has been used to localize and assess the damaged areas in a quantitative manner. Moreover, the thermoelastic phase analysis leads to an evaluation of the endurance limit of composites. In fact, by comparing the results with those provided by the standard test methods, the
Damage assessment of composite materials by means of thermographic analyses
Composites Part B: Engineering, 2013
Composite materials are largely used for structural applications, thanks to their high strength-to-weight ratios. However, it is difficult to make accurate estimations on their mechanical behavior, as it is affected by several factors, involved both in the manufacturing process and in the experimental testing. In this study, GFRP laminates, with different stacking sequences, are tested under static loading conditions. During testing, thermal analyses are also performed by means of a thermal camera, obtaining an energetic parameter (i.e. the temperature) useful for the evaluation of damage. The thermographic method allows both qualitative and quantitative analyses to be performed in a relatively short time. Besides thermal analyses, damage is also assessed by means of static tests, interrupted at different load levels, and followed by stiffness reduction measurements and microscopic analyses, allowing for a comparison of the obtained results.
Damage evolution and infrared thermography in woven composite laminates under fatigue loading
International Journal of Fatigue, 2006
An analytical model based on cumulative damage has been used for predicting the damage evolution in composite materials. The model is verified with experimental data from a carbon/epoxy composite fatigued under tension-tension load. Fatigue tests of specimens have been monitored with an infra-red thermography system. By analysing the temperature of the external surface during the application of cyclic loading, it is possible to evaluate the damage evolution. The model agrees well with the experimental data, and it can be used to predict the evolution of damage in composites.
Degradation Assessment of Industrial Composites Using Thermography
Procedia CIRP, 2015
Thermographic inspection is a relatively new technique for Non-Destructive Testing (NDT) which has been gathering increasing interest due to its relatively low cost hardware and extremely fast data acquisition properties. This technique is especially promising in the area of rapid automated damage detection and quantification. In collaboration with a major industry partner from the aerospace sector advanced thermographybased NDT software for impact damaged composites is introduced. The software is based on correlation analysis of time-temperature profiles in combination with an image enhancement process. The prototype software is aiming to a) better visualise the damages in a relatively easy-to-use way and b) automatically and quantitatively measure the properties of the degradation. Knowing that degradation properties play an important role in the identification of degradation types, tests and results on specimens which were artificially damaged have been performed and analyzed.
A new rapid thermographic method to assess the fatigue limit in GFRP composites
Composites Part B: Engineering, 2016
Conventional procedures and methods used for obtaining the fatigue performance of materials represent a critical aspect of mechanical characterization because of time consuming tests with a high number of specimens. In the last few years, great efforts have been made to develop a number of methods aimed at reducing testing time and, subsequently, the cost of the experimental campaign. In the process, thermographic methods have shown to be a useful tool for the rapid evaluation of fatigue damage and fatigue limit. This work deals with a new procedure for the evaluation of fatigue limit and the monitoring of damage in GFRP material by means of thermography. Although damage mechanisms in composite materials are difficult to understand, the proposed procedure allows us to obtain a number of parameters providing information relating to the onset of failure phenomena. It is worth noting that the reported procedure provides results in good agreement with those attained by the standard test methods.
Continuum Mechanics and Thermodynamics, 2019
This paper combines the infrared thermography and the computed laminography techniques to better understand the mechanisms of damage under fatigue for a short fibre-reinforced thermoplastic material. Depending on the experimental technique used, the measurement implies a "homogenization" of the values deduced over a prescribed volume. The real volume contributing to the thermal fields and thus the dissipated energy evaluated from thermography cannot be easily determined. The laminography technique provides precious insights for the determination of the dissipation fields, by providing a clearer view of the in-depth notch front profile as well as the local fibre orientation and by giving an idea of the volume change induced by porosity. In turn, the latter may affect the physical (thermal) constants used in the determination of the dissipated energy.
Thermographic diagnosis of fatigue degradation of epoxy-glass composites
2007
AbstrAct Purpose: The purpose of this paper was to describe results of application of thermography to evaluate the degree of fatigue degradation of epoxy-glass composites. Design/methodology/approach: Samples of epoxy-glass composite were subjected to fatigue degradation. During fatigue test, after defined number of cycles, samples were heated using infra-red heater and at the opposite side temperature increase was evaluated with thermovision camera. Findings: Analysis of achieved results allowed to elaborate relation between number of fatigue cycles and the degree of fatigue degradation. Such relation may be applied in diagnostic procedures. Research limitations/implications: Performed tests were of preliminary character and results will be applied to prepare research programme on thermographic testing of composites. Practical implications: Results of such tests may be applied in the future in diagnostic procedures to nondestructive evaluation of the degree of fatigue degradation of high performance polymer composites. Originality/value: Thermographic methods are applied up till now to non-destructive flaws detection. Proposed in the paper method may be applied to evaluate the degree of thermal and fatigue degradation in composites without any macroscopic flaws.