scholarly journals Damage detection in laminar thermoplastic composite materials by means of embedded optical fibers

2006 ◽  
Vol 60 (7-8) ◽  
pp. 176-179
Author(s):  
Aleksandar Kojovic ◽  
Irena Zivkovic ◽  
Ljiljana Brajovic ◽  
Dragan Mitrakovic ◽  
Radoslav Aleksic
Keyword(s):  
Composite Materials ◽  
Optical Fiber ◽  
Real Time ◽  
Optical Fibers ◽  
Impact Damage ◽  
Experimental Testing ◽  
Low Energy ◽  
Thermoplastic Composite ◽  
Woven Fabric ◽  
The Impact

This paper investigates the possibility of applying optical fibers as sensors for investigating low energy impact damage in laminar thermoplastic composite materials, in real time. Impact toughness testing by a Charpy impact pendulum with different loads was conducted in order to determine the method for comparative measurement of the resulting damage in the material. For that purpose intensity-based optical fibers were built in to specimens of composite materials with Kevlar 129 (the DuPont registered trade-mark for poly(p-phenylene terephthalamide)) woven fabric as reinforcement and thermoplastic PVB (poly(vinyl butyral)) as the matrix. In some specimens part of the layers of Kevlar was replaced with metal mesh (50% or 33% of the layers). Experimental testing was conducted in order to observe and analyze the response of the material under multiple low-energy impacts. Light from the light-emitting diode (LED) was launched to the embedded optical fiber and was propagated to the phototransistor-based photo detector. During each impact, the signal level, which is proportional to the light intensity in the optical fiber, drops and then slowly recovers. The obtained signals were analyzed to determine the appropriate method for real time damage monitoring. The major part of the damage occurs during impact. The damage reflects as a local, temporary release of strain in the optical fiber and an increase of the signal level. The obtained results show that intensity-based optical fibers could be used for measuring the damage in laminar thermoplastic composite materials. The acquired optical fiber signals depend on the type of material, but the same set of rules (relatively different, depending on the type of material) could be specified. Using real time measurement of the signal during impact and appropriate analysis enables quantitative evaluation of the impact damage in the material. Existing methods in most cases use just the intensity of the signal before and after the impact, as the measure of damage. This method could be used to monitor the damage in real time, giving warnings before fatal damage occurs.

Low Energy Impact Damage Detection in Laminar Thermoplastic Composite Materials by Means of Embedded Optical Fibers

2005 ◽  
Vol 494 ◽  
pp. 481-486
Author(s):  
A. Kojović ◽  
I. Živković ◽  
Lj. Brajović ◽  
D. Mitraković ◽  
R. Aleksić
Keyword(s):  
Composite Materials ◽  
Optical Fibers ◽  
Impact Damage ◽  
Charpy Impact ◽  
Optical Signal ◽  
Low Energy ◽  
Thermoplastic Composite ◽  
Woven Fabric ◽  
Energy Impact ◽  
The Impact

The possibility of applying optical fibers as sensors for investigation of real time low energy impact damage in laminar thermoplastic composite materials has been studied. For that purpose intensity based optical fibers were embedded in composite material specimens. Kevlar 129 (DuPont’s registered trade-mark for poly (p-phenylene terephthalamide)) woven fabric was used as reinforcement. Impact toughness testing by the Charpy impact pendulum was conducted in order to investigate low energy impacts. Transient intensity of optical signal during the impact, were compared with material crack initiation energy and crack propagation energy. Following this approach, development of damage in material was monitored. Obtained results show that intensity based optical fibers could be used as detectors for material damage appearance, and also, for level evaluation of its degradation caused by low energy impacts.

Transverse Impact and Tensile Behavior of the Three-Dimensional Woven Fabric Reinforced Thermoplastic Composites

2010 ◽  
Vol 129-131 ◽  
pp. 1238-1243 ◽  
Author(s):  
Wei Gou Dong ◽  
Hai Ling Song
Keyword(s):  
Composite Materials ◽  
Damage Tolerance ◽  
Three Dimensional ◽  
Thermoplastic Composite ◽  
Woven Fabric ◽  
Thermoplastic Composites ◽  
Two Dimensional ◽  
Energy Impact ◽  
Commingled Yarns ◽  
The Impact

Two forms of perform were prepared by a Glass fiber/Polypropylene fiber commingled yarn. One was a three-dimensional woven fabric with an angle-interlock structure, and another was a two-dimensional plain woven fabric laminate. The three-dimensional woven fabric reinforced thermoplastic composites(3-DWRC) and two-dimensional woven fabric reinforced thermoplastic composites(2-DWRC) were fabricated by hot-press process. The Impact and tensile performances of both 3-DWRC and 2-DWRC were examined. Compared to the 2-DWRC, the 3-DWRC have better impact properties, the energy required to initiate cracks, the threshold force of the first oscillation and maximum load increased by 41.90%, 54.41%, 38.75% respectively under the low-energy impact conditions. The tensile tests shown that the 3-DWRC presented batter fracture toughness than the 2-DWRC. The use of thermoplastic composites is growing rapidly because of their excellent properties, a high toughness and damage tolerance, short processing cycles, and the ability to be reprocessed. But thermoplastic materials usually have a difficulty to impregnate between reinforcing fibers, due to high melt polymer viscosity. It is a technology innovation that the commingled yarns composed of reinforced fibers and thermoplastic fibers are used as prepreg for thermoplastic composite materials. Because thermoplastic fiber and reinforced fiber are closely combined, which reduces distances of resin’s infiltration, this can effectively overcome the difficulties of resin’s impregnation. The commingled yarns can be woven and knitted, and can facilitate the processing of complex structural composites. Three-dimensional fabrics reinforced composites are ideal materials with excellent integrity because it is linked with yarns between layers. Its shearing strength between layers, damage tolerance and reliability are better than the two-dimensional fabric laminated composites. At present, the researches of thermoplastic materials with two-dimensional fabric reinforced structure made from commingled yarns are much more, such as manufacturing technology, material properties ,effects of process conditions on properties, relationship between structures and properties, and so on [1-8]. However, only a few studies appear in literature on the structure-property relationships of three-dimensional fabric reinforced thermoplastic composite materials made of commingled yarns [9-10]. Byun, Hyung Joon et al. [9] undertook the impact test and the tensile test on 3-D woven thermoplastic composite materials and 2-D plain woven laminate which is made by CF/PEEK mixed yarn. Dong Weiguo and Huang Gu[10] studied the porosity, tensile and bending properties on 3-D woven thermoplastic composites which make from core-spun yarn containing glass fibers and polypropylene fibers. The aim of this study was to investigate the impact behavior of and tensile properties of 3-D woven fabric thermoplastic composites made by a GF/PP commingled yarns. Attempts was made to identify the damage mode of the 3-D woven fabric thermoplastic composites under the low energy impact and tensile conditions.

FBGs Real-Time Impact Damage Monitoring System of GFRP Beam Based on CC-LSL Algorithm

2018 ◽  
Vol 18 (05) ◽  
pp. 1850075 ◽  
Author(s):  
E. Vorathin ◽  
Z. M. Hafizi ◽  
S. A. Che Ghani ◽  
J. P. Siregar ◽  
K. S. Lim
Keyword(s):  
Composite Materials ◽  
Real Time ◽  
Monitoring System ◽  
Cross Correlation ◽  
Impact Damage ◽  
Dynamic Strain ◽  
Internal Damage ◽  
Measuring Device ◽  
Glass Fiber Reinforced ◽  
The Impact

Glass-fiber reinforced polymer (GFRP) composite materials have an undisputed dominance over conventional metallic materials. However, susceptibility to barely visible or invisible internal damage due to impact has increased the demand for these composite materials in robust real-time structural health monitoring (SHM) system since they are capable of localizing the source of impact. Thus, in this paper, an in situ FBG sensor was embedded in a GFRP beam, providing an online real-time monitoring system and with the knowledge of cross-correlation linear source location (CC-LSL) algorithm, the impact location was capable of being determined in a split second. The consistency of cross-correlation function in providing repeatable results for all trials estimated a consistent time difference for all the impact points. The CC-LSL algorithm also revealed that the highest percentage of error was only 4.21% away from the actual hit. In the meantime, FBGs also showed good results as a dynamic strain measuring device in capturing frequency response at certain orientations compared to the AE sensor.

Experimental investigation on a fully thermoplastic composite subjected to repeated impacts

2019 ◽  
Vol 233 (19-20) ◽  
pp. 6985-7002
Author(s):  
S Boria ◽  
A Scattina ◽  
G Belingardi
Keyword(s):  
Composite Laminates ◽  
Mechanical Performance ◽  
Impact Damage ◽  
Energy Levels ◽  
Thermoplastic Composite ◽  
Thermoplastic Composites ◽  
Low Velocity ◽  
Repeated Impacts ◽  
Structural Parts ◽  
The Impact

In the last years, the spread of composite laminates into the engineering sectors was observed; the main reason lies in higher values of strength/weight and stiffness/weight ratios with respect to conventional materials. Firstly, the attention was focused on fibres reinforced with thermosetting matrix. Then, the necessity to move towards low density and recyclable solutions has implied the development of composites made with thermoplastic matrix. Even if the first application of thermoplastic composites can be found into no structural parts, the replacement of metallic structural parts with such material in areas potentially subjected to impact has become worthy of investigation. Depending on the field of application and on the design geometry, in fact, some components can be subjected to repeated impacts at localized sites either during fabrication, activities of routine maintenance or during service conditions. When composite material was adopted, even though the impact damage associated to the single impact event can be slight, the accumulation of the damage over time may seriously weaken the mechanical performance of the structure. In this overview, the capability of energy absorption of a new composite completely made of thermoplastic material was investigated. This material was able to combine two conflicting requirements: the recyclability and the lightweight. In particular, repeated impacts at low velocity, on self-reinforced laminates made of polypropylene (PP), were conducted by experimental drop dart tests. Repeated impacts up to the perforation or up to 40 times were performed. In the analysis, three different energy levels and three different values of the laminate thicknesses were considered in order to analyse the damage behaviour under various experimental configurations. A visual observation of the impacted specimens was done, in order to evaluate the damage progression. Moreover, the trend of the peak force interchanged between specimen and dart and the evolution of both the absorbed energy and of the bending stiffness with the impacts number were studied. The results pointed out that the maximum load and the stiffness of the specimens tended to grow increasing the number of the repeated impacts. Such trend is opposite compared to the previous results obtained by other researchers using thermosetting composites.

scholarly journals Bird-Strike Resistance of Composite Laminates with Different Materials

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 129 ◽  
Author(s):  
Yadong Zhou ◽  
Youchao Sun ◽  
Tianlin Huang
Keyword(s):  
Composite Materials ◽  
Composite Laminates ◽  
Impact Damage ◽  
Dynamic Properties ◽  
Dynamic Structure ◽  
Strength Properties ◽  
Bird Strike ◽  
Particle Hydrodynamics ◽  
Bird Impact ◽  
The Impact

To obtain some basic laws for bird-strike resistance of composite materials in aeronautical application, the high-velocity impact behaviors of composite laminates with different materials were studied by numerical methods. The smoothed particle hydrodynamics (SPH) and finite element method (FEM) coupling models were validated from various perspectives, and the numerical results were comparatively investigated. Results show that the different composite materials have relatively little effect on projectile deformations during the bird impact. However, the impact-damage distributions can be significantly different for different composite materials. The strength parameters and fracture energy parameters play different roles in different damage modes. Lastly, modal frequency was tentatively used to explain the damage behavior of the composite laminates, for it can manifest the mass and stiffness characteristics of a dynamic structure. The dynamic properties and strength properties jointly determine the impact-damage resistance of composite laminates under bird strike. Future optimization study can be considered from these two aspects.

In-situ observation of damage evolution in polycarbonate subjected to hypervelocity impact

2019 ◽  
Author(s):  
Nobuaki Kawai ◽  
Mikio Nagano ◽  
Sunao Hasegawa ◽  
Eiichi Sato
Keyword(s):  
Real Time ◽  
Stress Wave ◽  
Damage Evolution ◽  
Impact Damage ◽  
Hypervelocity Impact ◽  
The Other ◽  
Impact Event ◽  
Real Time Imaging ◽  
The Impact ◽  
Impact Events

Abstract In the fields of space engineering and planetary science, hypervelocity impact phenomena have been studied as they relate to the space debris problem and planetary impact. With regard to hypervelocity-impact-induced damage, many studies focus on the evaluation of impact-damage geometry and morphology, for example, to construct the ballistic limit equations and/or penetrating equations for space structures, and to predict the size and shape of crater and fragments generated by planetary impact [1-4]. While the final state or late stage of an impact event are of primal interest, damage accumulation at early stages affect the overall outcome of the impact event. The understanding of hypervelocity-impact-damage processes lead to improvement of material-response models for hypervelocity impact and higher fidelity simulations of hypervelocity impact events. Under such a background, we have performed real-time imaging of hypervelocity-impact events on transparent materials to investigate the impact-damage formation and evolution processes [5-7]. In our previous work, the stress-wave-propagation behavior and damage evolution were observed by means of a transmitted light shadowgraph. In these measurements, the shape of the longitudinal-stress-wave front, crater and spall fracture were successfully visualized. On the other hand, these shadowgraph images provide little information about damage microstructure. The shadowgraph has difficulty in visualizing ramped waves, such as the release wave, and also for the shear wave which is not accompanied by the change of volumetric strain. Those play important role in initiating damage. This occurs because the intensity of the shadowgraph image depends on the second spatial derivative of the refractive index. In this study, we try two types of real-time imaging of impact events. One is imaging by using scattered light on the impacted target to visualize the microstructure of the impact-induced damage, the other is a shadowgraph using polarized light to visualize propagation of the impact-induced stress field.

scholarly journals Long-Range Distributed Solar Irradiance Sensing Using Optical Fibers

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 908 ◽  
Author(s):  
Regina Magalhães ◽  
Luis Costa ◽  
Sonia Martin-Lopez ◽  
Miguel Gonzalez-Herraez ◽  
Alejandro F. Braña ◽  
...  
Keyword(s):  
Solar Energy ◽  
Optical Fiber ◽  
Real Time ◽  
Long Range ◽  
Optical Fibers ◽  
Solar Irradiance ◽  
High Sensitivity ◽  
Ground Level ◽  
Solar Simulator ◽  
Distributed Sensor

Until recently, the amount of solar irradiance reaching the Earth surface was considered to be a steady value over the years. However, there is increasing observational evidence showing that this quantity undergoes substantial variations over time, which need to be addressed in different scenarios ranging from climate change to solar energy applications. With the growing interest in developing solar energy technology with enhanced efficiency and optimized management, the monitoring of solar irradiance at the ground level is now considered to be a fundamental input in the pursuit of that goal. Here, we propose the first fiber-based distributed sensor able of monitoring ground solar irradiance in real time, with meter scale spatial resolutions over distances of several tens of kilometers (up to 100 km). The technique is based on an optical fiber reflectometry technique (CP-ϕOTDR), which enables real time and long-range high-sensitivity bolometric measurements of solar radiance with a single optical fiber cable and a single interrogator unit. The method is explained and analyzed theoretically. A validation of the method is proposed using a solar simulator irradiating standard optical fibers, where we demonstrate the ability to detect and quantify solar irradiance with less than a 0.1 W/m2 resolution.

Evaluation of repeated low energy impact damage in carbon–epoxy composite materials

2005 ◽  
Vol 67 (3) ◽  
pp. 307-315 ◽  
Author(s):  
W.A. de Morais ◽  
S.N. Monteiro ◽  
J.R.M. d'Almeida
Keyword(s):  
Composite Materials ◽  
Epoxy Composite ◽  
Impact Damage ◽  
Low Energy ◽  
Energy Impact
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