Microtensile testing

Lin M-T, El-Deiry P, Chromik RR, Barbosa N, Brown WL, Delph TJ, Vinci RP. Temperature-dependent microtensile testing of thin film materials for application to microelectromechanical system. Microsyst Technol 2006 12(10-11) p 1045-1051. 

In microtensile testing, the coated substrate in the shape of a tensile coupon is uniax-ially strained in a universal mechanical testing device (Fig. 6.3) and the surface can be viewed in a scanning electron microscope or with an optical microscope (Agrawal and Raj, 1989,1990 Ignat, 1996 LateUa et al., 2007 Roest et al., 2011). Typically, brittle... 

Figure 6.3 Schematic of a coated tensile test specimen pulled during microtensile testing.

Free standing thin film of 99.99% pure Ag with strong 111 texture microtensile test at 20 ° C at strain rate of 1.1x10 0.2% offset yield strength. 5.8 5.8 ev270... 

Thermal Air Aging forced air oven 165 3650 3 Turns from a light tan to dark brown due to processing aids 50 >50 Malar Ausimont Specimen Compression molded microtensile test bars... 

P. S. R. Sreekanth, and S. Kanagaraj. Assessment of Surface and Bulk Properties of UHMWPE/MWCNT Nanocomposites using Nanoindentation and Microtensile Testing. Journal of Mechanical Behavior of Biomedical Materials 18,140-151 (2013). 

Fig. 4.21 a Microtensile testing platform for mechanical characterisation of single electrospun nanofibre and b set-up of MEMS-based tensile tester. Reproduced from Refs. [231, 232] respectively... 

Changes in piopeities <15% aie consideied insignificant test peifomied on 250—1250-)J.m microtensile bars tensile strength, elongation, and weight gain deterniined within 24 h after termination of exposure. 

Microtensile samples were conditioned overnight (22 "C, 60% RH) and tested on an Instron at a crosshead speed of 5.1 mm/min. 

D 1708 Test method for Tensile Properties of Plastics by Use of Microtensile Specimens... 

The mechanical properties of the bulk PET and its nanocomposites were measured by tensile testing on injection-molded microtensile dogbones (ASTM-D638, Type IV) and by dynamic mechanical analysis (DMA) on injection-molded bars. 

Hexafluoropropylene content of the terpolymer improved its stress crack resistance at elevated temperatures. A microtensile bar of the polymer was punched out of a molded plaque and placed in an air oven at 200°C. This specimen was bent 180° in a brass channel. The results of the tests are presented in Table 5.58 showing the positive impact of 5% HFP content on the stress crack resistance of the TFE/Et copoly-mer/terpolymer. 

Tensile strength of the membrane was determined using Ingstron Microtensile machine. The samples with 1.4 cm in width, 2.8 cm in length and 0.015 cm thickness were used in this test. 

Immersions of polymer microtensile specimens in solutions of metal ions or lipid emulsions at elevated temperatures for 16 weeks have been reported [32]. Temperatures of 37, 70, and 90°C are recommended with sampling monthly to establish trends. For pacemaker leads, the solutions should include all the metals found within the device, a base, and an acid. For example, aqueous solutions of 1 M AgNOs or 0.1 M C0CI2 (acetylacetanoate) can assess oxidation. Immersion in 1 N acetic acid. Ringer s solution, and 1.0 N HCl can assess hydrolytic resistance. Immersion in 20% intralipid (soybean) emulsion can assess the propensity to absorb lipids. However, in our experience, none of the above in vitro tests appear to be reliably predictive of performance in pacemaker lead insulation. Why The in vivo environment cannot be duplicated in vitro. For example, the oxidation state of an ion varies as a function of what it is dissolved in. Distilled water containing a metal ion does not represent the environment within a lead. This accelerated test predicts that Ag+ will oxidize and degrade polyether polyurethanes while Co will not. Multiple in vivo studies clearly demonstrate exactly the opposite [14, 33]. Traces of cobalt will degrade the polymer in vivo whereas silver will not. 

Clearly one can implant microtensile specimens in animals such as rats or rabbits for several years, characterizing the materials as a function of periodic explant time. However, thin samples tend to curl or fold in vivo, affecting the reliability of the test. This can be dealt with by using thicker samples, but the rate of measurable degradation decreases as the thickness increases. Thus, we have abandoned this form of testing since it rarely gives the necessary answers in a reasonable implant time. It is more appropriate to implant the devices or subassemblies and remove characterization samples from them. 

Tefzel DuPont Specimen 0.25-1.3 mm microtensile bars, tested within 24 hrs after exposure... 

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