Dual cantilever bending

The late 1970s saw Polymer Laboratories develop their DMTA using dual cantilever bending, which works well for most small. samples from -150 C to the onset of melt. Shear, tensile, torsion, and simple compression options followed, as did the complementary Di-clectric Thermal Analyser (DETA), and computers were used from 1982 to both control and analyze the data. Seiko Instruments copied this and tried to patent it. and others such as Netzsch, Perkin-Elmer, and TA Instruments looked very closely at this before launching their own. For comparative data and fast thermal scans they all can give good data, but for absolute modulus numbers most systems need to consider the frame compliance, sample end corrections, and relative dimensions, and hence only a limited range of sample dimensions can be used for accurate measurement of modulus in a particular mode of deformation. 

Figure 15 (a) Optical fiber coating run in dual cantilever bending with notched clamp. Total thickness 150 microns. Cure of the coating can be seen between run I and run 2. (b) Peaks due to ionhopping in glass. 

Different clamping geometries are used to accommodate particular specimens (Figure 8). Single or dual cantilever bending modes are the most common for materials which can be formed into bars. Shear measurements are used for soft, thick samples. Films and fibres are usually mounted in tension with loading arranged so that the sample is... 

Netzsch DMA 242 C The DMA 242 C can determine viscoelastic properties over a wide modulus range with the common types of deformation geometries three-point bending, single- and dual-cantilever bending, compression/pene-tration, shear, and tension. Netzsch also offers a series of special sample holders, such as those designed, for example, for extremely stiff composite materials and metals. A stainless-steel container is available to facilitate measurements with the sample in various media (the immersion test—option). 

Deformation modes three-point bending single/dual-cantilever bending shear compression/penetration tension... 

Geometry options single-cantilever bending 1.0-17.5 mm dual-cantilever bending 2.0-35.0mm three-point bending 20.0-45.0mm Tension <10 mm compression unlimited, <10 mm Shear 10-mm-diameter plate TMA-mode measurement range 1000 pm... 

An example of a frequency-multiplexed DMTA scan is shown in Figure 7.16. The sample is measured in dual cantilever-bending geometry with small strain amplitude so that the requirements of theory are met. As the temperature is scanned, the on-board processor clocks around the selected frequencies continuously. Each data point is recorded with the instantaneous temperature. The curves shown in Figure 7.16 are generated and software can convert them to three-dimensional plots (see later), and, by interpolation between data points, any frequency-plane or temperature-plane slice can be accessed. 

Dual cantilever bending, 1Hz E (initial) 4 E"(initial) 0 E (150C1632hr) 4E"(1S0C1632hr)... 

Figure 19 A schematic diagram of the PL-DMTA head the dual-cantilever bending mode is illustrated in this case...

Figure 4.5 Schematic of available sample geometries, (a) Top left - single cantilever bending (b) top right-dual cantilever bending (c) middle left - tension (d) middle right - compression (e) bottom left-three-point bending (f) bottom right - shear. Note that for these definitions the sample length, /, is always taken as the distance between the fixed clamp and the driveshaft clamp.

Evaluation of the molded samples was performed using a Polymer Laboratories DMTA operating in the bending mode. The samples were evaluated in the dual cantilever... 

Single- and dual-cantilever clamps Three-point bending clamp Shear sandwich clamp... 

Figure 1 Common mechanical deformation modes compression, tension, shear, torsion, bending single cantilever, dual cantilever, three point bending)...

Modern instruments can handle many different sample types such as bars, films, fibres, coatings, pellets, rods, and cylinders. Different sample types are handled using the six measuring systems available three-point bending, parallel plate, dual cantilever, single cantilever, fibre tension, and film extension. 

Figure 5.8 DMTA testing heads for various modes (a) dual cantilever (b) three-point bend (c) tension (d) compression (e) shear sandwich (showing two specimens). Photographs by TA Instruments, Delaware USA...

Figure 5.50. DMA sample geometries for solids and liquids for solids—dual cantilever, tension, single cantilever, three-point bending or flexure, compression for liquids— cone-plate flow, torsional flow the rheometers that measure liquid-state properties also measure the properties of solid samples in torsional shear (courtesy of TA Instruments).

Figure 6.9 DMTA testing heads for various modes (a) dual cantilever, (b) three-point bend, (c) tension, (d) compression and (e) shear sandwich (showing two specimens). Photographs by TA Instruments, Delaware USA. (Reproduced from Hillier, K.W. and Kolsky, H. (1949) An investigation of the dynamic elastic properties of some high polymers. Proc. Phys. Soc. B, 62, 111. Copyright (1949) Institute of Physics.)...

Dynamic mechanical properties of the irradiated wood was measured using a Pyris Diamond DMA, manufactured by PerkinElmer Life Sciences, Norwalk, CT equipped with a controlled hquid nitrogen cooling accessory. The materials were analyzed in bending mode with the dual cantilever beam fixture for the instrument. 

TA Instruments dynamic mechanical analyzers are used over a temperature range from -150 to 600°C (-238 to 1112°F) to measure deformations for shear, tension, compression, three-point bending, and dual/single cantilever [3]. They include an optical encoder. DMA instrumentation is more sensitive than differential scanning calorimetry for measuring smaller transition regions. The company s DSC instruments measure heat... 

Figure 13 Forced vibration bending in the (a) dual- and (b) single-cantilever modes...

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