Lap-shear bond strength

Furukawa N, Yamada Y, Kimura Y (1997) Lap shear bond strength of thermoplastic polyimides and copolyimides. High Perform Polym 9(1) 17... 

Table 7.2 shows the effect of sodium etching on several fluoropolymers by Tetra-Etch on the surface composition and lap shear bond strength. In general, the data for various fluoropolymers indicate an increase in the adhesive bond strength with increasing fluorine and chlorine content. Kinetics of treatment is more favorable to perfluorinated PTFE than PVF that contains one fluorine per monomer unit according to the data in Table 7.2. 

Evidently at this level of I p, the strength of specific interactions is insufficient to influence the lap-shear bond strength as measured by the chosen procedure. 

With adhesives, therefore, the same test method may be quoted for widely differing materials and the standards are written in such a way as to take account of this. For instance, BS 5350 Part C5, the lap shear bond strength test (see Shear tests), may be nsed to determine the bond strength of adhesives of widely different cohesive strengths on substrates of widely differing nature. 

Table 3.15 Typical lap-shear bond strengths (MPa), without and with plasma treatment ...

Lap-shear bond strengths of joints made fi-om steel substrates coated with a variety of oils and waxes ( 6 mg/cm ) and joined with room-temperature curing acrylic adhesive have been reported to be up to 15 MPa (Charnock 1985). Very little degradation was seen after 1,000 h of exposure at 40°C and 95% relative humidity. However, the shear strength dropped by roughly half when the joints were subjected to a 30 min bake at 200°C. Although the bond strengths do not approach those reported for Al or Ti adherends, they were adequate for the intended application. 

Next to the epoxy-nylons and epoxy-urethanes, the epoxy-polysulfide adhesives show the greatest lap shear tensile strength at temperatures below 0°C. Bonded etched steel substrates show a tensile shear strength of 2900 psi at room temperature, and this increases to 3400 psi when the temperature is reduced to -156°C. Epoxy-nylon and epoxy-polysulfide are the only adhesives that show an increase in strength as the temperature is significantly reduced. 

The key requirement for a well-configured adhesive joint (i.e. attaining optimum ultimate capacity) is to minimize any direct or induced peel stresses. Therefore, it should be arranged to transfer the applied load mainly in shear, since adhesively bonded joints can be strong in shear but are inevitably weak in peel (Hart-Smith, 2001). To this effect, peel stresses detract from the overall joint shear strength, hence were attributed as bad in the prelude to this section. Consequently, the double-lap shear bond configuration is... 

Polyimides of 6FDA and aUphatic diamines with good low temperature processkig and low moisture swelling are known to be useful as hot-melt adhesives (109). Aluminum strips bonded by this polymer (177°C/172 kPa (25 psi) for 15 min) exhibited a lap-shear strength of 53 MPa (7690 psi) at room temperature and 35 MPa (5090 psi) at 100°C. The heat- and moisture-resistant 6F-containing Pis useful ki electronic devices are prepared from... 

Fig. I. Comparison of unprimed and eleetroprimed single lap-shear adhesive joint strengths for steel coupons bonded with imidazole-cured epoxy [43].

Surface cleaning/etches. As with aluminum and titanium, the most critical test for bonded steel joints is durability in hostile (i.e., humid) environments. The fact that the problem is a serious one for steel was illustrated in a study [117] that compared solvent cleaned (smooth) 1010 cold-rolled steel surfaces with FPL aluminum (microrough) substrates. Although the dry lap-shear strengths were not markedly different, stressed lap-shear joints of steel adherends that were exposed to a humid environment failed in less than 30 days, whereas the aluminum joints lasted for more than 3000 days. 

There has been very little work done on the development of EB-curable epoxy adhesives. When undertaking this development work the authors had two objectives. The first objective was to develop a series of adhesives for bonding aluminum-to-aluminum (Al-Al) and composite-to-composite (C-C) with lap shear strengths of 30 MPa or greater at room temperature. The second objective was that the... 

An early study by Rudkin (1950) showed that substitution of OH groups with acetyl resulted in a significant decrease in bond strength between the wood and a UF resin in lap-joint tests. Vick and Rowell (1990) studied the adhesive bonding of acetylated yellow poplar, with 18 different thermoplastic and thermosetting adhesives. The effectiveness of the adhesives was examined by determination of bond shear strength (and wood failure) of 6 mm thick, bonded wood strips after conditioning at 27 °C and... 

ISO 1827 1991 Rubber, vulcanized or thermoplastic - Determination of modulus in shear or adhesion to rigid plates - Quadruple shear method ISO 1922 2001 Rigid cellular plastics - Determination of shear strength ISO 4587 2003 Adhesives - Determination of tensile lap-shear strength of rigid-to-rigid bonded assemblies... 

Corrosion Testing. Salt spray testing (ASTM-B-117-52,54) was used to determine durability of adhesive bond in corrosive environment. Lap shear samples were exposed to salt spray for 14 days and then immediately tested for lap shear strength. 

As a result, the miscibility between the PU network and the VMCC linear chains was greatly improved and both tensile and lap shear strength were enhanced compared to the materials without opposite charge groups in which only hydrogen bonding between carboxyl and urethane could form instead of ionic bonds. 

The degree of bonding analysis has been verified for both compression molding and online consolidation of thermoplastic composites. In these studies, composite test specimens were consolidated under controlled processing conditions. The most common types of tests performed to measure the interply bond strength were the interlaminar (short beam) shear test [21,25] or the lap shear test [12,21,26]. 

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