Shear Strength Measurement

The mechanical properties of adhesive joints are primarily determined by applying an in-plane shear stress to the assemblies. Fig. 23 shows the single lap shear configuration recommended in ASTM D 1002, Federal Specification MMM-A 132 and Federal Test Method Standard No. 175. 

E 104 glass fabric carrier coated with Larc TPI polyamic acid precursor 

This can be illustrated by the first adhesive reported by Hergenrother and prepared by coating a solution of poljrphenylquinoxaline 16 (Tg = 318 °C) on a fiber-glass fabric to achieve, after 

Hergenrother published additional results to compare the adhesive properties of polyphenylquinoxalines 16, 17 (Tg = 290 °C) and a polymer (Tg = 285 °C) synthesized by reacting 4,4 -carbonylbis(l,2-benzenediamine) with (1,4-phenylene)-1,1 -bis [2-phenyl-1,2-ethanedione] 12 

The high melt viscosity of Larc-TPI at 350 °C (10 Pas) prohibits its use as an adhesive for bonding metallic or laminate skins on core honeycombs to make high-strength sandwich structures. The work of Chow et al. discussed in Section 9.3.2.2 demonstrates that file melt viscosity of the poly(isoimide) 

The lap-shear strength values listed in Table 9.3 show that Larc-IA exhibits the best adhesive properties up to 204 °C before and after thermal aging at that temperature but Larc-TPI remains better when adhesion is measured at 232 °C. 

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Fig. 2. Results of interfacial shear strength measurements of the same fiber/matrix systems using four different micro-mechanical tests during a round-robin program involving 12 different laboratories, (a) Results for untreated, unsized carbon fibers, (b) Results for carbon fibers with the standard level of surface treatment. Redrawn from ref. [13].

In the 90° direction, the fiber-matrix interphase is a controlling factor in the flexural strength. Here a 35% increase in flexural strength is measured in direct proportion to the increase in interfacial shear strength measured with the ITS tests. The transverse tensile strength of the fiber-matrix interphase is greater for the finished fiber than for the bare fiber. Apparently the lower toughness of the... 

In light of these qualifications, it can only be said that the maximum measured value of 10 kg/mni seems reasonable. It also compares favorably with shear strength measurements derived from epoxy-bonded, lap-shear tests (9). 

Grosseau-Poussard, J.L., Moine, P. and Brendle, M., Shear Strength Measurements of Parallel MoSjThin Films, Thin Solid Films, 307,163, (1997). 

Multipoint BET analysis showed that the surface area and average pore diameter of quartz are about two times higher than that of dolomite. These results are important especially in the random packing on the filtration and the compaction behavior of the cakes in shear strength measurements. 

S =1. These cakes were then dried for a definite time in the open atmosphere in the laboratory to obtain partially saturated cakes. The required time to reach a definite saturation degree was determined experimentally. The shear strength measurements of the produced cakes were made then using a Fischer test apparatus (6,7) shawn in Fig. 1. All experiments (production and the shear strength measurements of the cakes) have been done at room temperature. 

Figure 1. Fischer test apparatus used in the shear strength measurements.

All minerals subjected to the shear strength measurement have been compressed for half an hour at varying pressures to obtain a stable cake height. This compression time (half an hour) has been chosen according to the typical compression kinetics of Ti02 as an example given in Fig.2. As it is seen in Fig.2, the cakes have reached to a constant height in 3-5 minutes by compression at 4-20 bar and therefore to make sure 30 minutes has been taken as the compression time in each experiment. 

Shear strength—measures changes in shear strength by pulling lap shear samples on an Instron. The load at which samples pull apart is designated as the failure load. 

The shear strength measurement was conducted with an Instron tensile test machine of the constant-rate-of-crosshead movement type. A shear tool described in ASTM D732 was used. The samples were run at a crosshead speed of 0.05 In/mln. 

During the period after World War 11 to the late 1960s, the field of marine geotechnology rapidly developed. These developments involved the following areas (1) shear strength measurements, (2) submarine slope stability, (3) Lake Maracaibo, (4) the Mississippi Delta,... 

Moore, D.G., and Richards, A.R 1962. Conversion of "relative shear strength" measurements by Arrhenius on east Pacific cores to conventional units of shear strength. Geotechnique 12 55-59. Murray, J., and Renard, A.E. 1891. Report on deep sea sediments based on the specimens collected during the voyage of HMS challenger reports. Government Printer, London. 

Richards, A.F., and Parker, H.W. 1968. Surface coring for shear strength measurements. In Civil Engineering in the Oceans, American Society of Civil Engineers, New York, pp. 445-489. 

Boyce, R.E. 1977. Deep sea drilling project procedures for shear strength measurement of clayey sediment using modified Wykeham Farrance laboratory vane apparatus. In Initial Reports of the Deep Sea Drilling Project, Baker, P.F., Dalziel, I.W.D. etal., eds., U.S. Government Printing Office, Vol. 36, pp. 1059-1068. 

In addition, for carbon fiber-reinforced con sites, the 90° flex modulus of 1M7/I.30E (6% wt. in epoxy)/Epon 862/W shows a 19% increase conqiared with IM7/Epon 862/W (control), while there is a 12% increase of the modulus for 6% I.30E/Epon 862/W nanoconqiosite con ared with neat Epon 862/W polymer. The interlaminar shear strength measured using 0°, 4-point flex mechanical tests... 

Figure 14. Effect of surface oxygen content on interfadal shear strength measured on single fiber AU and HMU indcate no commercial surface treatment AS and HMS indicate commercial surface treatment. Temperatures indicate heat treatment for removal of oxygen. (Reprinted with permission from Ref. 94. Copyright 1982 Gordon and Breach Sdence Publications.)...

Table 9.1 Sisal fiber/polyester interfacial shear strength measured by single fiber pullout test. Reproduced with kind permission of the publishers of [38]...

In addition, variation in the chemical, physical, or morphological nature of the fiber along its length will affect the results of interfacial shear strength measurements, which only consider very small secticms. 

Figure 2.16 compares the relative co-axial shear strength (measured on the Collar and Pin test specimens described in MoD DTD 5628, Method H) of a number of adhesives with a resistance to disassembly similar to related press-fitted collar and pin components. The strength of the bonded joints is considerably in excess of the resistance to movement displayed by friction- fitted assemblies. 

Figure 28 Lap-shear strength versus ageing time in air at 177°C for Ti/Ti specimens bonded with polyimide oligomers 51. Curves (a-c) are lap-shear strength values measured at 25°C for oligomers with n = 3,2 and 1, respectively, whereas curves (a -c ) refer to lap-shear strengths measured at 177°C in the same order of molecular weights.

Figure 30 Variation of the lap-shear strength as a fnnction of the ageing time in flowing air for TU-2 titanium alloy bonded with polyimide precursors 30. Assemblies aged at 260°C lap-shear strength measnred at room temperature (a) and at 260°C (b). Assemblies aged at 300°C lap-shear strength measured at room temperature (c) and at 300°C (d).

BAIR S. and WINER W.O. "Shear Strength Measurements of Lubricants at High Pressure",Trans. A.S.M.E.,Journal of Lubrication Technology,vol 101,p251-257,1979. 

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