A Methodology for Characterizing the Interfacial Fracture Toughness of Sandwich Structures using High Speed Infrared Thermography (original) (raw)
Related papers
Measure of fracture toughness in composite structures using Infrared Thermography
HAL (Le Centre pour la Communication Scientifique Directe), 2014
Fracture toughness is one of the most important properties of any material for a lot of design applications involving damage and crack growth. Unfortunately its value can be difficult to evaluate with standard methods such as "compliance" method. In this work, two special cases have been studied and infrared thermography has been used to overcome the limitations of conventional methods. Damage of compressive fiber failure in unidirectional composite laminate has been chosen due to its difficulty to evaluate toughness. The infrared thermography has been used to follow compressive failure mode developing during an indentation test and a compression after impact test, and to evaluate the fracture toughness of compressive fiber failure.
Composites Part A: Applied Science and Manufacturing, 2013
This work deals with the issue of damage growth in thin woven composite laminates subjected to tensile loading. The conducted tensile tests were monitored on-line with an infrared camera, and tested specimens were analysed using Scanning Electron Microscopy (SEM). Combined with SEM micrographs, observation of heat source fields enabled us to assess the damage sequence. Transverse weft cracking was confirmed to be the main damage mode and fiber breakage was the final damage leading to failure. For cracks which induce little variation of specimen stiffness, the classic ''Compliance method'' could not be used to compute energy release rate. Hence, we present here a new procedure based on the estimation of heat source fields to calculate the energy release rate associated with transverse weft cracking. The results are then compared to those computed with a simple 3D inverse model of the heat diffusion problem and those presented in the literature.
Advances in Crack Characterization by Lock-In Infrared Thermography
International Journal of Thermophysics, 2014
Detecting cracks in a nondestructive way is a challenge that has been addressed for decades but which is not completely solved yet. For the last years, infrared thermography has been the preferred photothermal technique to detect cracks, because of its capability to record surface temperature images. In this work, a discontinuous Galerkin (DG) finite element method has been developed to simulate the temperature evolution of an opaque sample with inner cracks characterized by their thermal contact resistance. DG methods are natural tools to tackle physical problems with discontinuous solutions where classical finite element methods fail. Discontinuous finite elements allow calculation of the surface temperature modification due to the presence of cracks of any size, shape, and thickness. Lock-in infrared thermography measurements, performed on calibrated vertical cracks in metallic samples, confirm the validity of the model.
Non-destructive evaluation of sandwich plates by an ultrasonic IR thermographic method
Proceedings of the 2016 International Conference on Quantitative InfraRed Thermography, 2016
The paper presents the possibility of using an ultrasonic IR thermographic method to detect internal defects in composite types of sandwich panels with metal sheets. Experimental results indicate that this method may in many cases be effective in detecting defects that weaken the structure of sandwich panels. The results also show the limitations of using this method to sandwich panels and the materials used in them.
Infrared thermography study of the fatigue crack propagation.PDF
The work is devoted to the experimental study of heat dissipation process caused by fatigue crack propagation. To investigate a spatial and time temperature evolution at the crack tip set of experiments was carried out using specimens with pre-grown centered fatigue crack. An original mathematical algorithm for experimental data treatment was developed to obtain a power of heat source caused by plastic deformation at crack tip. The algorithm includes spatial-time filtration and relative motion compensation procedures. Based on the results of mathematical data treatment, we proposed a way to estimate the values of J-integral and stress intensity factor for cracks with pronounced the plastic zone.
Infrared Thermography for Inline Monitoring of Glass/Epoxy under Impact and Quasi-Static Bending
Applied Sciences
The scope of this work is to show the potential of infrared thermography to collect important information to be exploited for the characterization of new composite materials. An infrared imaging device can be included in most mechanical test setups for the in-line monitoring of samples undergoing either impact or quasi-static bending, or else fatigue tests. As an important assertion, the use of infrared thermography allows for fast inspection of relatively large surfaces in a remote way without any alteration of the inspected part and without safety-at-work concerns.
Damage of woven composite under translaminar cracking tests using infrared thermography
Composite Structures
The aim of this work is to increase the study of the notch translaminar propagation of the woven structures, using the InfraRed Thermography (IRT). A test of notch propagation under quasi-static traction was developed and used to study the failure phenomena on two different draping sequences. For each study, a local estimation of dissipated energies, associated with different damages, is carried out using the measurement of the surface temperature field. The study of heat source fields combined with micrographic observations allowed to define the matrix microcracking as the predominant damage phenomenon in crack tip. The critical energy release rate, obtained using IRT, corresponds to critical energy release rate reported in the literature for translaminar rupture of laminates. Furthermore, when brittle cracking develops in a thermosetting matrix laminate, the majority of irreversible mechanical energy (>90%) is dissipated as heat. In the case of brittle cracking, the developed method proves to be an efficient alternative technique for the local measure of energy release rate, even in cases where the variations in stiffness due to cracking phenomena remain low.
Proceedings
Mechanical stresses of materials are generally coupled with temperature variations and then, monitoring such variations can help gaining information about the material behavior under the applied loads. This can be accomplished with an infrared imaging device, which can be advantageously exploited to sense the thermal radiation associated with mechanical stresses and to obtain a legible explicative temperature map. In the present paper, glass/epoxy is used as material case study to show that thermal signatures visualized during the load application can be decoded into knowledge, which can contribute to the material characterization. In particular, glass/epoxy specimens are subjected to three types of tests: cantilever beam alternate bending, quasi-static bending and low velocity impact. Thermal images are acquired in time sequence during each test and after post-processed and analyzed. It is possible to get data about the damage initiation and its evolution under either quasi-static ...
Components made of short glass fiber reinforced thermoplastics are increasingly used in the automotive industry in order to reduce the price and weight of the vehicule. These components are frequently submitted to fatigue loadings during their service conditions. Therefore, a good conception towards the fatigue phenomenon is mandatory. One preliminary need is to model correctly the non linear behavior of such material, which is clearly not an easy task due to the numerous dissipation mechanisms involved and the strong anisotropy induced by the injection process. In this study, we present some results on injected samples with a specific geometrical accident leading to a stress concentration factor Kt=2.5. A specific thermomechanical characterization is done using an infrared camera. Several key informations can be extracted from these experimental data: temperature variations, heat sources, crack initiation localization, crack propagation (detection of the crack vicinity), etc.These data are then compared to numerical simulations involving the simulation of the injection step and finite element analysis using an anisotropic elasto-viscoplastic model. The heat sources obtained with the model are compared the experimental ones. A very good agreement between the experimental data and the numerical ones is found which illustrate the relevancy of the model to capture some key thermomechanical properties of these materials, which is obviously a key element in the fatigue life prediction.