Model 3421 extensometers measure shear strain of foam and honeycomb sandwich cores, as well as rigid cellular plastics. These extensometers can be used to measure shear modulus, 2% offset shear strength, and stress-strain curves prior to specimen failure. The extensometer may be used to measure strain through specimen failure with specimen fixturing to limit out-of-plane expansion. The Model 3421 may also be used for sandwich core shear fatigue testing. The Model 3421 is applicable for testing to the following standards:

ASTM C273

Shear Properties of Sandwich Core Materials

ASTM C394

Shear Fatigue of Sandwich Core Materials

ISO 1922

Rigid cellular plastics — Determination of shear strength

DIN 53294

Testing of sandwiches; shear test

EN 12090

Determination of Shear Behavior of Thermal Insulation Products (single specimen test only) The extensometer mounts to the test specimen’s loading plates. It attaches to the specimen in seconds and can be used with tension or compression test fixture loading. The extensometer is adjustable to work with a range of specimen thicknesses and widths, and includes a built-in scale for setting it to the specimen width. To use the extensometer, the test operator clips it onto the specimen by squeezing two pads, placing the extensometer against the side of the specimen, and releasing the pads. The extensometer is self-supporting and no further adjustments are necessary. It is removed before failure by unclipping. Model 3421 extensometers are strain gaged devices, making them compatible with any electronics designed for strain gaged transducers. Most often they are connected to a test machine controller and Epsilon will equip the extensometer with a compatible connector wired to plug directly into the controller. For systems lacking the required electronics, Epsilon can provide a variety of solutions for signal conditioning and connection to data acquisition systems, chart recorders, or other equipment.

Excitation:

5 to 10 VDC recommended, 12 VDC or VAC max.

Output:

2 to 4 mV/V

Linearity:

±5.0 mm/±0.200” measuring range:
≤0.005 mm for displacement values <0.5 mm
≤1.0% of reading for displacement values ≥0.5 mm ±2.5 mm/±0.100” measuring range:
≤0.001 mm for displacement values <0.25 mm
≤0.4% of reading for displacement values ≥0.25 mm

Temperature Range:

Standard (-ST) is -40 °C to +100 °C (-40 °F to 210 °F)

Cable:

Integral, ultra-flexible cable, 2.5 m (8 ft) standard

Specimen Size:

Thickness (including core and both loading plates): 20–75 mm (0.8–3.0 inches); width: 40 mm (1.5 inches) minimum, 50-150 mm (2-6 inches) typical