Glass epoxy bond

A model developed by Bell Labs researchers (Ref 22) in the late 1970s (Ref 23) details the mechanism by which CAR formation and growth occurs. The first step is a physical degradation of the glass/epoxy bond. Moisture absorption then creates an aqueous medium along the separated glass/epoxy interface that provides an electrochemical pathway and facilitates the transport of corrosion products. 

FRACTURE MECHANICS TESTS TO CHARACTERIZE BONDED GLASS/EPOXY COMPOSITES ... 

Fracture Mechanics Tests to Characterize Bonded Glass/Epoxy Composites... 

Fracture mechanics characterisation tests have been performed to determine the mixed mode fracture envelope of an epoxy bonded glass/epoxy composite. Analysis of lap shear, and L-stiffener geometries has shown that for this relatively brittle adhesive reasonable first estimations of failure loads can be obtained for both cracked and uncracked specimens. An image analysis technique has been developed which enables failure mechanisms to be... 

Davies et al. Failure of bonded glass/epoxy composite joints, Proc. Structural Adhesives in Engineering (SAE6), Bristol, June 2001. 

Ducept F, Davies P, Gamby D Mixed mode failure criteria for a glass/epoxy composite and an adhesively bonded composite/composite joint, Int. Journal of Adhesion Adhesives, 20, 3, 2000 p233-244. 

In his test, a thin film of adhesive on a glass microscope slide or a metal coupon is cured and soaked in hot water until the film can be loosened with a razor blade. There is usually a sharp transition between samples that exhibited cohesive failure in the polymer and those which exhibited more of an interfacial failure. Since the diffusion of water into the interface is very rapid in this test, the time to failure is dependent only on interfacial properties and may differ dramatically between unmodified epoxy bonds and epoxy bonds primed with an appropriate silane coupling agent. The time to debond in the hot water for various silane primers differed by several thousandfold when used with a given epoxy. In parallel tests, a thick film of epoxy adhesive on nonsilaned aluminum coupon showed about the same degree of failure after 2h in 70°C water as a silaned joint exhibited after more than 150 days (3600 h) under the same conditions. 

For the production of base materials for circuit boards with higher performance (e.g., glass/epoxy or graphite/cyanate ester combinations) and of multilayer boards, the laminating resin acts as adhesive or special bonding prepregs must be used. The requirements for the resins, which act as adhesive, depend on both the processing conditions and the desired properties of the final circuit board and are similar to those described above. 

Glass is efficiently bonded with UV-aerobic acrylics, and replaces epoxies, anaerobics, or heat-fusing techniques. A manufacturer of pressed glass stemware required an adhesive that would resist repeated exposures to detergent and water while providing a faster cure rate than an epoxy bonding process. A transparent UV acrylic was developed that cured a 2-mil gap completely in 2.5 seconds under a 250-watt mercury lamp. It did not discolor on aging and was moisture resistant (Fig. 2). 

Chen et al recently reported the fabrication and characterization of a high power self-breathing PEMFC with optimally designed wet KOH etched flow-fields and electrodes [49]. Ni/Cu/Au layers are used for current collecting, the 1.5 /im-thick in-between layer instead of a thick Au layer allowing to reduce the fabrication cost. The MEA is composed of a classical Nafion -1135 membrane with Pt-alloy sprayed carbon paper on both sides. The two silicon electrodes are sandwiched and pressed at RT with the MEA, and then sealed with epoxy. A base-chip formed by drilled Pyrex glass anodically bonded with KOH eched silicon acted both as H2 inlet/outlet manifolds and as a support for a... 

Ducept et al., [13] studied mixed mode failure criteria for a glass/epoxy composite and an adhesively bonded composite joint. In their study, the initiation failure point detected by acoustic signal and by the non-linearity point on the load/displacement curve and found good correspondence. Magalhaes et al., [14] studied the application of acoustic emission to investigate the creep behavior of composite bonded lap shear joints. 

The term prepreg is used for the non-conducting semi-cured layers of FR4 which are used to separate the conducting layers of a multiplayer printed circuit board. Printed circuit broad laminates comprise a layer of prepreg bonded between sheets of copper foil. The Japanese NEC company is understood to be marketing a self-extinguishing reinforced glass-epoxy resin for PCB. 

All kinds of sheet or board material could be used as stiffener materials for the flexible circuits however, several materials are conunouly used.Typical stiffener materials for the traditional flexible circuits are listed in Table 61.19. Paper phenol boards and glass-epoxy boards are employed for relatively thick requirements. Polyimide films and polyester films are employed for relatively thin requirements. Aluminum plates and stainless steel plates are commonly used as the Stiffener materials of flexible circuits. A specialty of the metal stiffeners is their forming capabilities after they are bonded on flexible circuits. Paper phenol and polyester are not available for thermo setting adhesives because of the low heat resistance. 

On the exterior of the vehicles, rubber profiles around windows and doors and the trunk lid are "lap bonded with cyanoacrylate adhesives because continuously extruded profiles cannot be used for sharp comers. To obtain effective sealing and better sliding in the case of sliding windows, these profiles are flocked by means of polyurethane-based flocking adhesives. The lenses of headlamps are joined to the housing by polyamide or polyurethane hot-melt adhesives and epoxy resins. The layers of laminated safety glass are bonded with a film based on poly(vinyl butyral). 

Exposure to water at 88°C has a more drastic effect on glass/epoxy than aramid/epoxy. The greater reduction in shear strength (and hence bond strength) of the glass system and its immediate degradation, compared with a one hour incubation period for the aramid system, indicates that the two fibre composites have differing mechanisms of bond deterioration. 

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