Degree Of Debonding Research Articles

Analysis of Debonding Failures of the Screen and Case during Tablet Drop

In recent years, due to the increasingly powerful functions of tablets, more and more people have used tablets. The failure of the screen caused by debonding failure between the screen and the case of the tablet due to drops will affect the normal use of the tablet. However, there have been few studies on the debonding methods of the screen and the case of the tablet, as well as the factors influencing the debonding between the screen and the case of the tablet. Numerical analysis software was used in this paper to simulate the iPad Air (Air) drop process, and the cohesive zone model and tiebreak contact were used to simulate the debonding process between the screen and case of the Air tablet, respectively. When the results are compared to the experiments, the results show that the cohesive zone model is superior. The effects of various rounded corner radii, drop postures in the XY plane, materials of the outer case, and strain rates of PC/ABS on the localized debonding between the outer case and outer glass of the Air during the drop process were investigated. The degree of debonding between the Air model’s outer case and outer glass is defined by t, which is the ratio of the area of the deleted cohesive elements to the total area of the cohesive elements. The results show that the rounded corner radius and the strain rate of PC/ABS have less influence on t; the t of the Air model dropped at 45° in the XY plane is 37.7% of that dropped at 0° and 90°; and the t of the Air model with glass as the outer case material is 48% of that with aluminum alloy as the outer case material. These studies serve as a foundation for tablet design and material selection.

Bond strength of silicone to polyurethane following immersion of silicone in cleaning solutions

Statement of problem The use of polyurethane liners beneath silicone facial prostheses is recommended to improve the effectiveness of water-based adhesives, reduce bacterial colonization, and allow very thin margins. Patients using silicone prostheses with a polyurethane lining often observe different degrees of debonding which may lead to failure of the prosthesis. Aggressive cleaning may be associated with debonding of the silicone to polyurethane. Purpose The purpose of this investigation was to determine the effect on bond strength of soaking specimens of silicone to polyurethane in hot or room-temperature soapy water. Material and methods Specimens of silicone to primed polyurethane were divided into 3 groups of 16 specimens for testing: control (no soak), room-temperature soapy water soak, and hot soapy water soak. The soaked specimens were placed in soapy water at different temperatures for 1825 minutes to simulate 1 year of a 5 min/day cleaning cycle. One examiner performed the assessment of T-peel strength (N/mm) for all specimens. Each specimen was attached to an adhesive testing machine and separated in tension at the crosshead speed of 25.4 mm/min. Data were analyzed with a 1-way ANOVA followed by post hoc pairwise testing using the Tukey test (α=.05). Results A significant difference in bonding strength between the 3 groups was found ( P<.001), with post hoc tests indicating that the control group bonding strength (6.06 ± 1.84 N/mm) was significantly higher than both room-temperature water soapy soak (3.93 ± 1.84 N/mm; P=.005) and the hot soapy water soak group values (2.49 ± 1.75 N/mm; P<.001). However, there was no significant difference found between the hot and room-temperature soapy soak values. Conclusion Within the limitations of this study, soaking in hot or room-temperature soapy water produced a significant reduction of bond strength of silicone to polyurethane.

The effect of particle–matrix adhesion on the mechanical behavior of glass filled epoxies: Part 1. A study on yield behavior and cohesive strength

Basic properties of glass filled epoxy such as yield behavior and cohesive strength, which are important in understanding toughening mechanism, are studied using compression tests and double notch 4 point bending (DN-4PB) tests. Three different glass reinforcements, large glass spheres, small glass spheres, and glass fibers, were treated by different methods and used at different volume fractions ranging from 10 to 30 vol%. The effect of different surface treatments and moisture exposure on the yield behavior is studied. It was found that in all types of formulation the yield stress decreased after moisture exposure and that the yield stress was dependent on the surface treatment both before and after moisture exposure. No treatment and treatment of glass reinforcements with aminopropyltrimethoxysilane coupling agent resulted in relatively higher yield stress. Close observation of microstructure by transmission OM showed that the degree of debonding in the specimens for compression tests was quite dependent on the surface treatment after moisture exposure. The decrease in cohesive strength of the neat specimens were observed after moisture exposure.

Stress Transfer Function for Interface Assessment in Composites with Plasma Copolymer Functionalized Carbon Fibres

Radio-frequency-induced plasma copolymerization of acrylic acid/1,7-octadiene was used to produce a range of functionalized plasma copolymer coatings with controlled degree of adhesion. The single-fibre fragmentation test was used to characterize the adhesion of plasma copolymer coated fibres to epoxy resin. The cumulative stress transfer function (CSTF) and Kelly-Tyson approaches were used to evaluate the degree of adhesion. By continuous monitoring of the fragmentation process, it was found that the mechanical performance of a composite material could be evaluated using the CSTF methodology at strain well below saturation. The degree of debonding was a good measure of relative interface/interphase adhesive strength. The trend in the CSTF is consistent with the propagation of interfacial debonds during the test. For a completely debonded fibre a normalized CSTF value, referred as stress transfer efficiency (STE), was found to provide a more consistent analysis that was able to differentiate between fibres with similar degrees of debonding. The calculated values of interfacial shear strength (IFSS) were only valid for a fully debonded fibre (1,7-octadiene plasma homopolymer coating) where the assumption of a constant shear stress, as in the Kelly-Tyson model, applied. However, IFSS did not provide the same ranking. Where debonding does not occur, the stress transfer efficiency also provides a sensitive measure of the interface/interphase performance. Improved adhesion over the untreated-unsized carbon fibre was observed for both of the plasma copolymer-coated and commercially treated carbon fibres. Since there is a concentration dependence of carboxyl groups on adhesion, the mechanism appears to relate to covalent bond formation with the epoxy group. Plasma copolymer coatings on carbon fibres also causes an increased tensile strength and Weibull modulus.

The friction and wear characteristics of plasma-sprayed ZrO2-Cr2O3-CaF2 from room temperature to 800°C

The friction and wear characteristics of low-pressure plasma-sprayed (LPPS) ZrO2-Cr2O3-CaF2 from room temperature to 800°C were studied by using a high-temperature reciprocating wear tester. At room temperature, friction of ZrO2-Cr2O3-CaF2 composite coating against Al2O3 sphere was quite high, and exhibited a decrease trend with the increase of load from 30 N to 80 N. At 700°C, the composite exhibited the lowest friction and wear among all selected temperature conditions. Brittle fracture and delamination with large wear sheets were considered as the dominant wear mechanism at room temperature. At 400°C, microfracture dropping become more dominated. However, plastic deformation, formation of CaF2 lubrication films and particle removal of Cr2O3 appeared as the main wear mechanisms at elevated temperatures. CaF2 acting as an effective lubricant at 600°C and 700°C reduced the friction and wear of the composite. Cr2O3 particles played a very important role on controlling the size and type of microcracks and preventing or deflecting the microcrack propagation during 700°C test. Cr2O3 particles also acted as hard barriers to resist the scratching and high-temperature deformation of ZrO2-CaF2 matrix without increasing the friction. To a great extent, wear mainly depended on the degree of debonding and removal of Cr2O3 particles at 700°C.

界面はく離損傷を有する繊維強化複合材料の波動電ぱ特性 （第２報） 繊維強化複合材料の超音波伝ぱ速度と減衰係数に及ぼす界面はく離の影響 繊維方向に偏向したせん断波の散乱解析に基づく検討

Waves propagating in fiber-reinforced composite materials exhibit dispersion and attenuation due to wave scattering by fibers. In the present study, the overall characteristics of ultrasonic transverse waves propagating in a composite material with fiber-matrix interface debonding are examined via scattering analysis. The study is concerned with shear waves polarized parallel with unidirectionally reinforced fibers which are randomly distributed in an elastic matrix. The scattered wave generated by a single fiber embedded in an infinite matrix with various degrees of debonding is computed by two-dimensional boundary element analysis for several incidence angles of the plane waves in a wide frequency range. The results are used to determine the effective complex wave number for the composite, accounting also for statistical nature of the interface debonding. The attenuation coefficient and the phase velocity of the composite can be readily obtained from the complex wave number as a function of the frequency and a damage parameter characterizing the extent of interface debonding. Numerical illustrations are provided for a composite made of titanium alloy reinforced with silicon-carbide fibers. The dependence of the phase velocity and the attenuation coefficient on the frequency, the extent of debonding and the propagation direction is discussed in detail. The apparent decrease in effective composite density due to debonding is also explored through comparison between the static-limit velocity and the corresponding effective shear modulus.

Modified null field method for P- and SV-wave scattering from a partially debonded fiber

The modified null field approach to elastic P- and SV-wave scattering (in plane strain) from a partially debonded fiber has been developed. The debonded region on the fiber surface is subjected to traction free boundary conditions, whereas the fiber is assumed to be in welded contact with the host medium elsewhere. Additional null field equations for an elliptical extension of the actual surface of the scatterer are introduced which require additional expansions for the field in the region between the extended mathematical boundary and the actual boundary of the scatterer. The numerical accuracy of the modified null field method has been tested for the case of a perfectly bonded fiber for P- and SV-wave incidence. Scattering cross-section plots are presented for different degrees of debonding.