On the use of lock-in thermography to monitor delamination growth in composite panels under compression

2014 ◽  
Vol 21 (4) ◽  
pp. 485-492 ◽  
Author(s):  
Cinzia Toscano ◽  
Aniello Riccio ◽  
FrancescoPaolo Camerlingo ◽  
Carosena Meola
Keyword(s):  
Composite Structures ◽  
Mechanical Test ◽  
Compressive Loading ◽  
Composite Panel ◽  
Reinforced Polymer ◽  
Catastrophic Failures ◽  
Load Carrying ◽  
Lock In ◽  
Delamination Propagation

AbstractThe success of composites in automotive, aerospace, and naval applications is mainly related to their aptitude to be tailored to obtain a final product that perfectly fulfills the design requirements. However, during both manufacturing processes and maintenance, some flaws, like delaminations (which may escape simple visual inspection), may be induced in composite structures. The presence of delaminations is of major concern for the load-carrying capability of carbon fiber-reinforced polymer panels. Indeed, delaminations can strongly affect the structural strength and may grow under in-service loads, leading sometimes to catastrophic failures. The aim of this work is to explore the use of lock-in thermography for the monitoring of delamination propagation in composite structures when subjected to generic multiaxial loading conditions. A stiffened composite panel with an embedded skin delamination subjected to compressive loading was taken as a benchmark to assess experimentally the effectiveness of lock-in thermography for monitoring the delamination propagation in situ during the compressive mechanical test. The delamination size as a function of the applied load, observed by lock-in thermography during the execution of the compressive test, was used to validate the results of preliminary numerical computations.

Square Short Wood Columns Strengthened with FRP Sheets under Compressive Load

2012 ◽  
Vol 256-259 ◽  
pp. 1008-1011
Author(s):  
Yan Mei Zhu ◽  
Shu Cheng Yuan ◽  
Min Hou ◽  
Qing Yuan Wang
Keyword(s):  
Ultimate Strength ◽  
Failure Modes ◽  
Compressive Loading ◽  
Compressive Load ◽  
Fiber Reinforced Polymer ◽  
Test Results ◽  
Reinforced Polymer ◽  
Load Carrying ◽  
Strength And Stiffness ◽  
Wood Columns

This paper presents the experimental results of the wood columns externally strengthened with fiber reinforced polymer (FRP) subjected to axial compressive loading. In total, 14 square short wood columns were made, which were reinforced by FRP in two reinforcing arrangements. The main parameters studied in the test were (1) the strengthening materials, i.e. carbon FRP (CFRP), basalt FRP (BFRP) and aramid FRP (AFRP); (2) the reinforcing arrangements, i.e. the full wrapping of FRP and the partial reinforcing arrangement; (3) the layers of FRP sheets applied, i.e. one, two and three. The ultimate strength, load-axial displacements curves, load-strain relationships, and the failure modes of all the columns were presented. The test results show that both types of the reinforcing arrangements could increase the ultimate strength and stiffness of the columns tested greatly. The columns strengthened with two layers of FRP sheets gave higher load carrying capacities when compared to the columns strengthened with one or three layers of FRP sheets. The result confirms that the more layers of FRP sheets, the higher of load carrying capacity; however, the adverse results were shown when three layers of FRP sheets applied. Finally, the result also showed that the full wrapping reinforcing arrangement is more effective than the partial one in enhancing the stiffness.

scholarly journals Fast 4D On-the-Fly Tomography for Observation of Advanced Pore Morphology (APM) Foam Elements Subjected to Compressive Loading

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7256
Author(s):  
Michal Vopalensky ◽  
Petr Koudelka ◽  
Jan Sleichrt ◽  
Ivana Kumpova ◽  
Matej Borovinsek ◽  
...  
Keyword(s):  
Dynamic Testing ◽  
Mechanical Test ◽  
Compressive Loading ◽  
Time Lapse ◽  
3D Models ◽  
Pore Morphology ◽  
X Ray ◽  
Maximum Parameters ◽  
3D Information

Observation of dynamic testing by means of X-ray computed tomography (CT) and in-situ loading devices has proven its importance in material analysis already, yielding detailed 3D information on the internal structure of the object of interest and its changes during the experiment. However, the acquisition of the tomographic projections is, in general, a time-consuming task. The standard method for such experiments is the time-lapse CT, where the loading is suspended for the CT scan. On the other hand, modern X-ray tubes and detectors allow for shorter exposure times with an acceptable image quality. Consequently, the experiment can be designed in a way so that the mechanical test is running continuously, as well as the rotational platform, and the radiographic projections are taken one after another in a fast, free-running mode. Performing this so-called on-the-fly CT, the time for the experiment can be reduced substantially, compared to the time-lapse CT. In this paper, the advanced pore morphology (APM) foam elements were used as the test objects for in-situ X-ray microtomography experiments, during which series of CT scans were acquired, each with the duration of 12 s. The contrast-to-noise ratio and the full-width-half-maximum parameters are used for the quality assessment of the resultant 3D models. A comparison to the 3D models obtained by time-lapse CT is provided.

scholarly journals Vibration Parameters for Impact Detection of Composite Panel: A Neural Network Based Approach

2021 ◽  
Vol 5 (7) ◽  
pp. 185
Author(s):  
Maurizio Arena ◽  
Massimo Viscardi
Keyword(s):  
Composite Structures ◽  
Fiber Reinforced Polymer ◽  
Composite Panel ◽  
Impact Detection ◽  
Reinforced Polymer ◽  
Modal Parameters Identification ◽  
Useful Life ◽  
Vibration Parameters ◽  
The Impact ◽  
A Current

The need for reliable methodologies for structural monitoring is certainly a current line of research in many engineering sectors. The detection of the impact on composite materials is in fact a recent subject of study, aimed at safeguarding the mechanical integrity and improving the useful life of structural components. In such a context, the work deals with evaluation of the use of neural algorithms for localizing the position of the impacts on composite structures. Starting from FE (finite element) simulations, representative of the dynamic response of a CFRP (Carbon Fiber Reinforced Polymer) panel as a benchmark, the approach has been finally validated experimentally by modal parameters identification.

POSTBUCKLING DEGRADATION FE ANALYSIS OF STIFFENED COMPOSITE PANELS

2010 ◽  
Vol 10 (04) ◽  
pp. 645-668 ◽  
Author(s):  
J. ANSÓTEGUI ARAICO ◽  
I. ORTIZ DE ZARATE ALBERDI ◽  
F. REBOLLO ARRIBAS
Keyword(s):  
Composite Structures ◽  
Compressive Loading ◽  
Composite Panels ◽  
Adhesively Bonded ◽  
Interface Failure ◽  
Damage Propagation ◽  
Adhesive Interface ◽  
Stiffened Composite Panels ◽  
Load Carrying ◽  
Current Design

The capability of a commercial industrial tool, ABAQUS, to simulate the critical damage mechanisms in stiffened composite panels has been evaluated. The analysis and conclusions are supported by experimental results. The focus is on skin–stringer separation during compressive loading. Results show that the advanced degradation modeling capabilities present in commercial codes today may lead to an accurate characterization of the deep postbuckling range behavior and the collapse of stiffened composite panels. Compared to current design practice, where the first indication of ply failure or the onset of damage propagation is taken as the failure load, the methods used here provide a way to exploit the reserves in composite structures. It is concluded that implementing degradation mechanisms (composite ply and adhesive interface degradation) presents a significant improvement to simulate accurately the deep postbuckling states and collapse for stiffened composite panels with adhesively bonded stringers. The nature of the final loss of load-carrying capacity for this type of structures, by composite ply and adhesive interface failure, driven by postbuckling deformation, makes this simulation approach essential.

Large deformation bending responses of nanotube-reinforced polymer composite panel structure: Numerical and experimental analyses

2018 ◽  
Vol 233 (5) ◽  
pp. 1695-1704 ◽  
Author(s):  
Kulmani Mehar ◽  
Subrata K Panda ◽  
Trupti R Mahapatra
Keyword(s):  
Finite Element ◽  
Large Deformation ◽  
Polymer Composite ◽  
Composite Structures ◽  
Kinematic Model ◽  
Element Model ◽  
Higher Order ◽  
Composite Panel ◽  
Numerical Examples ◽  
Reinforced Polymer

The large deformation deflection responses of randomly oriented multi-walled carbon nanotube-reinforced polymer composite structures were examined theoretically using a novel higher order shear deformation kinematic model. Moreover, the excess geometrical distortion within the structure is incorporated via the full geometrically nonlinear strain–deformation relations (Green–Lagrange strain) including all of the nonlinear higher order terms to achieve the generality. The randomly oriented nanotube-reinforced polymer composite properties were evaluated computationally via Mori–Tanaka scheme for the theoretical analysis purpose. The deflection responses were evaluated numerically using an original MATLAB program with the help of the direct iterative method and finite element steps. The performance of the currently developed numerical model was verified by solving various numerical examples for the convergence and subsequent comparison purpose. Also, the deflection values were evaluated experimentally and compared with the current numerical results using the experimentally obtained elastic properties. Finally, the generality and the applicability of the currently developed higher order nonlinear finite element model is revealed by solving various numerical examples.

Non-Destructive Testing of Thermoplastic Carbon Composite Structures

2020 ◽  
Vol 2020 (1) ◽  
pp. 34-52
Author(s):  
Rafał Szymański
Keyword(s):  
Composite Structures ◽  
Ultrasonic Method ◽  
Composite Panel ◽  
Aviation Industry ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Pulse Technique ◽  
Thermoplastic Matrix ◽  
The Subject ◽  
Non Destructive

AbstractThe article is in line with the contemporary interests of companies from the aviation industry. It describes thermoplastic material and inspection techniques used in leading aviation companies. The subject matter of non-destructive testing currently used in aircraft inspections of composite structures is approximated and each of the methods used is briefly described. The characteristics of carbon preimpregnates in thermoplastic matrix are also presented, as well as types of thermoplastic materials and examples of their application in surface ship construction. The advantages, disadvantages and limitations for these materials are listed. The focus was put on the explanation of the ultrasonic method, which is the most commonly used method during the inspection of composite structures at the production and exploitation stage. Describing the ultrasonic method, the focus was put on echo pulse technique and the use of modern Phased Array heads. Incompatibilities most frequently occurring and detected in composite materials with thermosetting and thermoplastic matrix were listed and described. A thermoplastic flat composite panel made of carbon pre-impregnate in a high-temperature matrix (over 300°C), which was the subject of the study, was described. The results of non-destructive testing (ultrasonic method) of thermoplastic panel were presented and conclusions were drawn.

scholarly journals Ferromagnetic soft catheter robots for minimally invasive bioprinting

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Cheng Zhou ◽  
Youzhou Yang ◽  
Jiaxin Wang ◽  
Qingyang Wu ◽  
Zhuozhi Gu ◽  
...  
Keyword(s):  
Minimally Invasive ◽  
The Body ◽  
Magnetic Actuation ◽  
Internal Organs ◽  
Planar Surfaces ◽  
Reinforced Polymer ◽  
Direct Fabrication ◽  
Digitally Controlled

AbstractIn vivo bioprinting has recently emerged as a direct fabrication technique to create artificial tissues and medical devices on target sites within the body, enabling advanced clinical strategies. However, existing in vivo bioprinting methods are often limited to applications near the skin or require open surgery for printing on internal organs. Here, we report a ferromagnetic soft catheter robot (FSCR) system capable of in situ computer-controlled bioprinting in a minimally invasive manner based on magnetic actuation. The FSCR is designed by dispersing ferromagnetic particles in a fiber-reinforced polymer matrix. This design results in stable ink extrusion and allows for printing various materials with different rheological properties and functionalities. A superimposed magnetic field drives the FSCR to achieve digitally controlled printing with high accuracy. We demonstrate printing multiple patterns on planar surfaces, and considering the non-planar surface of natural organs, we then develop an in situ printing strategy for curved surfaces and demonstrate minimally invasive in vivo bioprinting of hydrogels in a rat model. Our catheter robot will permit intelligent and minimally invasive bio-fabrication.

Probability-based diagnostic imaging with corrected weight distribution for damage detection of stiffened composite panel

2021 ◽  
pp. 147592172110339
Author(s):  
Guoqiang Liu ◽  
Binwen Wang ◽  
Li Wang ◽  
Yu Yang ◽  
Xiaguang Wang
Keyword(s):  
Distribution Function ◽  
Diagnostic Imaging ◽  
Weight Distribution ◽  
Composite Structures ◽  
Damage Identification ◽  
Guided Wave ◽  
Composite Panel ◽  
Damage Localization ◽  
Localization Accuracy ◽  
Direct Interpretation

Due to no requirement for direct interpretation of the guided wave signal, probability-based diagnostic imaging (PDI) algorithm is especially suitable for damage identification of complex composite structures. However, the weight distribution function of PDI algorithm is relatively inaccurate. It can reduce the damage localization accuracy. In order to improve the damage localization accuracy, an improved PDI algorithm is proposed. In the proposed algorithm, the weight distribution function is corrected by the acquired relative distances from defects to all actuator–sensor pairs and the reduction of the weight distribution areas. The validity of the proposed algorithm is assessed by identifying damages at different locations on a stiffened composite panel. The results show that the proposed algorithm can identify damage of a stiffened composite panel accurately.

Numerical Limit Analysis of Slab Bridges with Construction Joints

2018 ◽  
Author(s):  
Thomas Westergaard Jensen ◽  
Linh Cao Hoang
Keyword(s):  
Carrying Capacity ◽  
Limit Analysis ◽  
Concrete Slabs ◽  
Load Carrying Capacity ◽  
Layer Model ◽  
Yield Criteria ◽  
Reinforced Concrete Slabs ◽  
Load Carrying ◽  
Construction Joints

The conic yield criteria for reinforced concrete slabs in bending are often used when evaluating the load‐carrying capacity of slab bridges. In the last decades, the yield criteria combined with numerical limit analysis have shown to be efficient methods to determine the load carrying capacity of slabs. However, the yield criteria overestimate the torsion capacity of slabs with high reinforcement ratios and it cannot handle slabs with construction joints. In this paper, numerical limit analysis with the conic yield criteria are compared with yield criteria based on an optimized layer model. The analysis show an increasing overestimation of the load carrying capacity for increasing reinforcement degrees. Furthermore, yield criteria, which combine the conic yield criteria with an extra linear criterion due to friction, are presented for slab bridges with construction joints. The yield criteria for slabs with construction joints are used, in combination with limit analysis, to evaluate a bridge constructed of pre‐cast overturned T‐beams and in‐situ concrete. The analysis show that the load carrying capacity is overestimated, when the construction joints are not considered in the yield criteria.

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