Numerical Simulation of Failure of Composite Coatings due to Thermal and Hygroscopic Stresses

Abstract

Due to the higher thermal and moisture expansions of epoxy coatings than the rigid substrate, these coatings suffer from high thermal and hygroscopic stresses, leading to coating/substrate interfacial crack growth. Herein, a parametric study was conducted systematically on epoxy coatings incorporated with fillers, in order to understand their effects on coating/substrate interface delamination caused by thermal and hygroscopic stresses. A finite element model (FEM) was developed to determine an indicator J-integral value (Ji), in comparison with a critical JC value to interpret the obtained interface delamination experimental results. FE simulations showed that interfacial pre-cracks located at coating edges were more serious than those at the centre. Once delamination was triggered by thermal shock or moisture absorption, it propagated rapidly along the coating/substrate interface. However, by adding suitable micro-/nano-fillers to the coating the thermal and hygroscopic stresses give lower Ji values, so that delamination crack growth can be effectively controlled. The simulation results demonstrate that the incorporation of fillers with lower Young’s modulus, lower thermal expansion and moisture absorption coefficients, smaller size for soft fillers, larger size for rigid fillers, and suitable aspect ratios for rod-shape fillers to the coatings, are more effective against interface delamination. Hence, useful guidelines for improving the design of epoxy composite coatings against delamination growth can be obtained for different engineering applications.

Resistance of PVD Coatings to Erosive and Wear Processes: A Review

“…Hardness of the coating can be in the range from 5 GPa for Ti 11 Mg 29 Gd 2 N 58 coating to 45 GPa for CrCN/CrN coating with 1 µm thick layer of tetrahedral carbon [10,11]. However, this method also allows producing reflective coatings, e.g., Nb 2 O 5 /SiO 2 coating, with a hardness even lower than 1 GPa [12]. Coatings of high hardness are mainly used 2 of 34 for anti-wear applications, as protective coatings for tools and knives [13,14], and for anti-erosion applications [15][16][17].…”

Effect of Hydrothermal Environment on Mechanical Properties and Electrical Response Behavior of Continuous Carbon Fiber/Epoxy Composite Plates

“…CFRP has good, long-lasting performance, in general, but it is still sensitive to humidity and heat [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. With the addition of humidity, heat, and other factors, the mechanical and thermal properties of the material could be reduced, which affects its life.…”

“…The permeation behavior of water and gas through the polymer/aluminum coating has also been investigated to achieve a detailed understanding of its mechanical performance under thermal and/or hygroscopic stresses [ 27 ]. Recently, the effects of epoxy composite coatings on interface delamination due to thermal and hygroscopic stresses have also been analyzed using FE simulations and compared with experimental results [ 28 ]. It was suggested that the interfacial debonding or failure originated from the thermal or hygroscopic stress that tends to take place due to the mismatch in thermal or moisture expansion between the epoxy resin matrix and the fiber reinforcements [ 17 , 28 ].…”

“…Recently, the effects of epoxy composite coatings on interface delamination due to thermal and hygroscopic stresses have also been analyzed using FE simulations and compared with experimental results [ 28 ]. It was suggested that the interfacial debonding or failure originated from the thermal or hygroscopic stress that tends to take place due to the mismatch in thermal or moisture expansion between the epoxy resin matrix and the fiber reinforcements [ 17 , 28 ]. Hence, it is essential to reveal the effect of such environmental changes on both the epoxy resin matrix and the fiber/epoxy interface of the CFRE used in building structures, especially those in road and bridge structures in coastal areas.…”

A New Grating Thermography for Nondestructive Detection of Cracks in Coatings: Fundamental Principle

“…Therefore, these methods require a relatively long time to detect all the cracks in coatings. Currently, the detection of surface cracks in coatings is still a research hot spot in the nondestructive testing field [10][11][12][13][14][15][16].…”