Mechanical property measurements

All VGCF was graphitized prior to composite consolidation. Composites were molded in steel molds lined with fiberglass reinforced, non-porous Teflon release sheets. The finished composite panels were trimmed of resin flash and weighed to determine the fiber fraction. Thermal conductivity and thermal expansion measurements of the various polymer matrix composites are given in Table 6. Table 7 gives results from mechanical property measurements. 

Perhaps the most significant complication in the interpretation of nanoscale adhesion and mechanical properties measurements is the fact that the contact sizes are below the optical limit ( 1 t,im). Macroscopic adhesion studies and mechanical property measurements often rely on optical observations of the contact, and many of the contact mechanics models are formulated around direct measurement of the contact area or radius as a function of experimentally controlled parameters, such as load or displacement. In studies of colloids, scanning electron microscopy (SEM) has been used to view particle/surface contact sizes from the side to measure contact radius [3]. However, such a configuration is not easily employed in AFM and nanoindentation studies, and undesirable surface interactions from charging or contamination may arise. For adhesion studies (e.g. Johnson-Kendall-Roberts (JKR) [4] and probe-tack tests [5,6]), the probe/sample contact area is monitored as a function of load or displacement. This allows evaluation of load/area or even stress/strain response [7] as well as comparison to and development of contact mechanics theories. Area measurements are also important in traditional indentation experiments, where hardness is determined by measuring the residual contact area of the deformation optically [8J. For micro- and nanoscale studies, the dimensions of both the contact and residual deformation (if any) are below the optical limit. 

In this chapter, we overview basic techniques for making nanoscale adhesion and mechanical property measurements. Both quasi-static and dynamic measurements are addressed. In Section 2 of this chapter, we overview basic AFM instrumentation and techniques, while depth-sensing nanoindentation is overviewed in Section 3. Section 4 addresses recent advances in instrumentation and techniques... 

Depth-sensing nanoindentation is one of the primary tools for nanomechanical mechanical properties measurements. Major advantages to this technique over AFM include (1) simultaneous measurement of force and displacement (2) perpendicular tip-sample approach and (3) well-modeled mechanics for dynamic measurements. Also, the ability to quantitatively infer contact area during force-displacement measurements provides a very useful approach to explore adhesion mechanics and models. Disadvantages relative to AFM include lower force resolution, as well as far lower spatial resolution, both from the larger tip radii employed and a lack of sample positioning and imaging capabilities provided by piezoelectric scanners. 

Unertl, W.N., Implications of contact mechanics models for mechanical properties measurements using scanning force microscopy. J. Vac. Sci. Technol. A Vac. Surf. Films, 17(4), 1779-1786(1999). 

Asif, S.A.S., Colton, R.J. and Wahl, K.J., Nanoscale surface mechanical property measurements Force modulation techniques applied to nanoindentation. In Ovemey, R.M. and Frommer, J.E. (Eds.), Interfacial Properties on the Submicron Scale. ACS/Oxford Press, Oxford, 2001. 

The two mechanical properties measured most frequently using indentation techniques are the hardness, H, and the elastic modulus, E. A t5pical load-displacement curve of an elastic-plastic sample during and after indentation is presented in Fig. 30, which also serves to define some of the experimental quantities involved in the measurement. 

Mooney Viscometer studies at 100°C and 120°C show lower viscosity of the Al-hlled gums. Lower viscosity compounds require less energy input for extrusion. Comparative results on the dynamic mechanical properties, measured using a rubber process analyzer (RPA), show that at the... 

FIGURE 17.7 Results for the Bl through B8 and A2 and A3 sihca samples showing the Mooney viscosity at 100°C, and the d3mamic mechanical properties measured hy mhher process analyzer (RPA) during curing of the compounds. 

In this paper, we examine the relationship between radiation resistance and polymer structure using volatile product and mechanical property measurements. 

While producing samples more efficiently is one aspect which can lead to more efficient materials discovery efforts, efficient characterization is also needed. In his 1970 paper, [1] Hanak spoke to the issue of materials testing and evaluation. He discussed advances in the measurement of a number of chemical, physical and mechanical properties, measurements which must be tailored to the specific materials problem under investigation. Ultimately it was difficulties in characterization that limited the impact of these approaches. Computers were not yet commonly available, and automated sample evaluation methods remained to be developed. 

Tablet mechanical properties measured on samples prepared on an instrumented tablet press or compaction simulator are an excellent means to characterize excipients under dynamic conditions (8,9). Meaningful data analyses are best achieved if both tablet preparation and tablet property measurements are performed at carefully controlled conditions using standardized procedures. Such testing in the authors ...

Composite mechanical properties measured parallel to the fibers axis direction are not in general very sensitive to the interphase. The fiber itself is the major load bearing element in the composite and does not require much support from the matrix. 

Mechanical Properties. Measurement of the mechanical properties of diamond is complicated, and references should be consulted for the various qualifications (7,34). Table 1 compares the theoretical and experimental bulk modulus of diamond to that for cubic BN and for SiC (29) and compares the compressive strength of diamond to that for cemented WC, and the values for the modulus of elasticity E to those for cemented WC and cubic BN. 

This material also has a porous structure by virtue of its being made by etching a phase-separated borosilicate glass. PS chains have also been introduced into the pores of this type of glass [146], but the only results to date involve mechanical property measurements, and scattering investigations. 

A servo hydraulic dynamic fatigue machine can, clearly, be used for testing under constant strain as well as constant stress conditions and this would be preferable to the traditional mechanical instruments. Interestingly, a comparison has been made of dynamic mechanical properties measured on a new version of the Goodrich flexometer and a servo hydraulic tester48. 

R. Solasi et al., Mechanical response of 3-layreed MEA during RH and T variation based on mechanical properties measured under controlled T and RH, Proceedings of 4th International Conference on Fuel Cell Science, Engineering and Technology, Irvine, CA, 19-21 June 2006... 

Fatliquor affects mostly the mechanical properties, measured also by a collection of ASTM methods given in (25). In addition, the sounds emitted by leather when it is deformed are greatly suppressed by the presence of fat, supporting a method of assay by means of the acoustic emission test (27). 

R. G. Brown, K. E. Gilchrist, Some Physical and Mechanical Property Measurements on PFR Absorber Materials, U.K. AEA Report TRG-Memo-6322, November 1973. 

It is clear that structure-sensitive dynamic properties [low-cycle fatigue (LCF) and fracture toughness (Klc)] notably increase for the alloy with the nondendritic structure. One more proof of the advantage of the nondendritic structure are the results on mechanical properties measured in three directions of forgings from a 1933 grade alloy obtained from large-scale ingots of 845 mm in diameter (Table 16). 

This equation was used to estimate the interfacial adhesion in comparison with the acid-base properties of glass fibers in LDPE. The effect of surface treatment of glass beads on their interfacial adhesion to PET was also estimated from a mechanical property measurement. A mathematical model describing the adsorption of polymers on filler surfaces related coupling density to the average area available for coupling between rubber and filler surface. ... 

Changes during storage in the moisture permeability of cellulose acetate films used to effect controlled release (Fig. 173) were predicted from changes in mechanical properties of the films.705 The mechanical properties measured were relaxation time versus mechanical stress. 

The compound was made of scrap rubber from truck tires, essentially natural rubber, and sulfur. This compound is poor and vulcanization necessitates rather high pressure so as to compact the mixture. Nevertheless the final materials exhibit rather good mechanical properties measured either under static or dynamic conditions, as well as interesting qualities for absorption of impact noises [11]. 

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