The production process for polymer matrix composites has the potential to introduce variety of processing defects. Fibre misalignment can occur when fibres are laid up. Fibres in the same layer may be misaligned relative to each other or misalignment between layers. Foreign inclusions such as dirt and debris may contaminate the matrix or act as a local stress concentration in the finished product.
These defects can lead to delamination either during the production process or later on when the component is in service. The use of composite materials is constantly increasing in aviation, aerospace, energy wind turbines where reliable inspection methods must be applied frequently for safe operation. Among those, ultrasonic and thermographic methods are the most sucessfull and widely used [1]. Composite materials are highly anisotropic with a high amount of boundaries which lead to high noise levels which limits the detection accuracy.
With improved transducers and signal processing methods, modern C- scan methods have become very effective for composite testing. C-scan analysis provide information of the location and size of the inpurities, fibre layup-plan and misalignment, delaminations, impact damage, fiber fatigue damage, water filled cores, etc. There are also new ultrasonic methods evolving with guided ultrasonic waves [4].
Vacuum infusion VI is a widely used technique for production of large composite parts [6]. Typical mistake in vacuum infusion is the non-sealed vacuum membrane with a large impact on quality and in most cases, a waste of component and many hours of labour work.
The aim of our research is to study and detect the various artificial defects in glass fibre reinforced polymer composite using 4D C-scan technique.
Experimental setup 2. Defects were introduced by inserting round pieces of aluminium and PVC foil, placed between layers. Its popularity is partly due to the low cost of the tooling and the environmental safety [6].
On the other hand, the complex preparation procedure of VI could easily lead to defects such as air voids through non-sufficiently sealed spots. The VI mould layup is shown in figure 1. The layers were placed on a flat glass surface, coated with the release wax. Two sets were placed between voids clusters on random locations. The Al and PVC-foil were cut to circular shape with layers. Second row was placed between nd layer, rd, th and th layer consequently. The plate was cured at a room temperature.
In all cases scanning shall cover the whole testing volume. If individual sections of this volume cannot be covered in at least one scanning direction, or if the angles of incidence with the opposite surface do not meet the requirements of 6.
This may, in some cases, require removal of the weld reinforcement. Supplementary methods may require testing using twin crystal angle beam probes, creeping wave probes, further ultrasonic techniques or any other suitable method, for example, liquid penetrant, magnetic particle, radiographic testing. In selecting alternative or supplementary methods, due consideration should be given to the type of weld and probable orientation of any imperfections to be detected.
Alternatively, the width of the scanning surfaces may be smaller if equivalent coverage of the testing volume can be achieved by scanning from both the upper and the lower surface of the joint. Scanning surfaces shall be even and free from foreign matter likely to interfere with probe coupling e. Waviness of the test surface shall not result in a gap between the probe and test surfaces greater than 0,5 mm. These requirements shall be ensured by dressing if necessary.
Local variations in surface contour, e. This additional scanning is necessary to compensate for the reduced weld coverage that will occur with a gap of this dimension. In all cases, the maximum permitted gap on areas of the test surface from which the evaluation of indications is to be carried out shall be 0,5 mm.
Scanning surfaces and surfaces from which the sound beam is reflected may be assumed to be satisfactory if the surface roughness, Ra, is not greater than 6,3 4m for machined surfaces, or not greater than 12,5 4m for shotblasted surfaces. Where imperfections are found their influence on the proposed angle beam test shall be assessed and, if necessary, the techniques adjusted correspondingly.
When satisfactory coverage by ultrasonic testing is seriously affected, by agreement, other inspection methods e. Checks to confirm these settings shall be performed at least every 4 h and on completion of the testing. Checks shall also be carried out whenever a system parameter is changed or changes in the equivalent settings are suspected.
Suitable techniques are described in prEN If the differences are less than 2 dB, correction is not required. If the differences are greater than 2 dB but smaller than 12 dB, they shall be compensated for. When there are no apparent reasons for high correction values, the attenuation, at various locations on the test object, shall be measured and, where it is found to vary significantly, corrective actions considered.
This requirement may be relaxed subject to! To accommodate all of these requirements this standard specifies four testing levels A, B, C and D.
From testing level A to testing level C an increasing probability of detection will be achieved by an increasing testing coverage e. The testing level D may be agreed for special application using a written procedure which shall take into account the general requirements of this standard. In general the testing levels are related to quality levels e. EN The appropriate testing level may be specified by standards for testing of welds e.
EN , product standards or other documents. When EN is specified the recommended testing levels are as given in Table 5. It should be noted that the joint types shown are ideal examples only and where actual weld conditions or accessibility do not conform exactly with those shown, the testing technique shall be modified to satisfy the general requirements of this standard and the specific testing level required.
For these cases a written test procedure shall be prepared. For such imperfections specific testing techniques should be considered, particularly for welds in thicker materials.
Seams IV. Laps and Scabs V. Cracks VI. Lack of penetration VII. Cracks 2. Bursts 3. Flakes 4. Adhesive bonding uses adhesives to bond adjoining parts. Fusion welding 2. Compact joints and no need of additional plates 2.
Water or fluid tight joints 3. High corrosion resistance 4. Butt joint, lap joint, corner joint and edge joint. Disadvantages of Gas Welding. Arc Welding Equipment 1. C machine 2. Electrode and holder 3.
Cables and connectors 4. Earthing clamps 5. Chipping hammer 6. Wire brush 7. Helmet, safety goggles, hand gloves, apron etc. Arc Welding Types 1. Carbon arc welding 2. Shielded metal arc welding 3. Submerged arc welding 4. Gas tungsten arc welding 5.
Gas metal arc welding 6. Electroslag welding 7. Plasma arc welding 8. Flux cored arc welding 9. Friction 2. Ultrasonic 3. Diffusion 4. Explosive 5. Forge 6. Hammer 7. Most importantly, using the PipeWIZARD system requires only a single calibration block and limits the number of scans required to inspect a weld, saving time and money.
Some variations are apparent in the performance of different operators and companies and an on-the-job testing of operator competence has been proposed as this is such a crucial element of the operation. The detection of the external slots was more variable. A comparison of amplitude based AUT size values with destructive measures Ref. A plot of the RT lengths of the defects, also shown in figure 3, demonstrates that they were deliberately made to be short and so were more uktrasonic to detect by the AUT.
The two features were included into a set of other, real areas of porosity and the list fed back to each AUT contractor. Utilizing the wall thickness variation tool for welds in seamless pipes ensures that welds are inspected with a high degree of precision.
Copper cracking is generally misclassified when it is detected and so ppipeline be left unrepaired. Menu More Contact Us. Orders are processed as quickly as possible and shipped the next business day of the receipt. Particular attention was paid to the types of defect associated with mechanized welding such as copper pick-up, cold laps and other lack of fusion defects. The issues surrounding the accuracy of size evaluation and further work needed in this area is discussed.
This information was provided along with the calibration coupons to each company. Further work is needed to improve the detection girfh both copper and transverse defects.
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