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Coating Defects and Inspection
Published in Karan Sotoodeh, Coating Application for Piping, Valves and Actuators in Offshore Oil and Gas Industry, 2023
Coating delamination refers to paint peeling off the substrate or undercoat. Delamination occurs due to loss of coating adhesion and the subsequent separation and lifting of the paint from the substrate, or a poorly bonded undercoat. The remedy action is to sandblast or mechanically remove the loose paint, clean and roughen the smooth surface and recoat it. Figure 4.15 illustrates the delamination of coating from a substrate. Delamination destroys coating strength and durability as well as coating appearance. The main causes of delamination are surface contamination and poor surface preparation. Poor application of coating on a metal surface is another cause of delamination.
Advancements in Post-Processing of Metal Additive Manufactured Components
Published in Pankaj Agarwal, Lokesh Bajpai, Chandra Pal Singh, Kapil Gupta, J. Paulo Davim, Manufacturing and Industrial Engineering, 2021
A. N. Jinoop, C. P. Paul, K. S. Bindra
Cracking is generally microscopic and is eliminated by tailoring processing conditions or post-processing. Delamination is a macroscopic defect by which a layer becomes fully or partly separated from the remaining layers due to the higher residual stresses or incomplete bonding with the previously-built layer. It cannot be eliminated by using post-processing techniques. Residual stresses generated during MAM can also result in distortion in the built components and deviations from the required dimensions (Sames et al. 2016).
Detection of structural defects in wind turbine blades employing guided waves and machine learning methods
Published in C. Guedes Soares, Developments in Renewable Energies Offshore, 2020
P. Sanchez Granados, C.Q. Gómez Muñoz, F.P. García Márquez
The resulting ultrasonic signals have been analysed to detect delamination. Due to the complexity of the analysis of these ultrasonic signals in composite materials, detection has been carried out by training different classifiers. The classifier that best suits this case study was the Ensemble Classifier model with 87.7% of accuracy.Even though the DT model has been discarded, DT model has been found to work well for areas between delamination’s, so it can be used to combine it with the EC model and improve delamination detection.
Longitudinal-torsional complex-mode ultrasonic actuator for vibration-assisted drilling of CFRP
Published in Machining Science and Technology, 2022
Chen Zhang, Xiaoxue Wang, Vadim V. Silberschmidt
Hole-exit defects mainly include exit delamination and burrs, as shown in Figure 17. Delamination is the main damage mode when drilling carbon-fiber laminates. Its main reason is reduction of stiffness of CFRP during hole formation, so when the cutting edge of the drill bit contacts the CFRP uncut part, it is easy to cause separation between the cut and uncut parts. Delamination reduces structural integrity, leads to poor tolerance in assembly, and increases the possibility of performance degradation. In contrast, the main reason for the formation of burrs is insufficient sharpness of the cutting edge of the drill to cut carbon fibers at the hole exit with the cutting lip increasing the engagement with the CFRP material. Such insufficient sharpness can accelerate the tool wear and increase the drilling force. Thus, separation between the cut and uncut parts for CFRP becomes more obvious.
A simplified modal-based method to quantify delamination in carbon fibre-reinforced plastic beam
Published in Nondestructive Testing and Evaluation, 2019
Mehdi Khammassi, Rizwan Wali, Abdulaziz Al-Mutory, Arslan Yousaf, Sadok Sassi, Mohamed Gharib
Delamination is essentially the separation of layers inside any composite structure. This separation causes a reduction in stiffness of the structure and may consequently reduce its modal frequencies. During a vibration-based application to measure the change in the natural frequency of composite laminates, the type, brand and location(s) of the sensors usually have a vital effect on the success of data acquisition. Many contact-based sensors (e.g., accelerometers, strain gauges) have disadvantages because they are surface-mounted and include wire connections for long-term monitoring. The unwanted effect of the sensor’s mass is another issue for monitoring lightweight composites. Indeed, for a system with a single degree of freedom, where the mass is and the stiffness is , if the attached sensor has an extra mass :
Temperature effects on the mode II delamination propagation behavior of aerospace-grade CFRP multidirectional laminates
Published in Mechanics of Advanced Materials and Structures, 2022
Yu Gong, Linfeng Jiang, Hansong Zhang, Ziming Wang, Ning Hu
Composites are widely used in advanced aircraft structures to achieve the goal of weight reduction and fuel efficiency improvement because of their high specific strength, high specific stiffness and easy integral manufacturing [1]. Composite laminates are one of the most commonly used structural configurations. However, delamination is prone to occur owing to weak interlaminar mechanical properties [2]. The initiation and growth of delamination will result in a significant reduction on the structural stiffness and strength, and even lead to catastrophic failure [3, 4]. Therefore, the studies on delamination are of important engineering significance and practical value and are also the focus of damage tolerance design and analysis of aircraft composite structures [5, 6].