Strain gauges for low elastic materials (plastic, wood, gypsum)

Strain gauges for low-modulus materials

Measuring strain on plastics, wood and gypsum requires careful consideration of the mechanical properties of the test material. Compared with many metals, these materials have a lower modulus of elasticity, which means that a conventional strain gauge may locally influence the deformation being measured.

Althen offers GF Series strain gauges for plastics, LF Series gauges for wood and gypsum, and PFLW/PLW Series gauges for longer-term measurements on wood. These product families address different requirements for gauge stiffness, measuring length and installation.

Why does strain gauge stiffness matter?

A strain gauge must follow the deformation of the test material without significantly restricting it. On relatively compliant materials, a stiff gauge backing or measuring grid can locally reinforce the surface and introduce measurement errors.

Specially designed low-modulus strain gauges help reduce this stiffening effect. The GF and LF Series use measuring grid designs intended to limit their influence on the test specimen.

When should you use strain gauges for low-modulus materials?

Typical applications include:

• Tensile, compression and bending tests on plastic components.
• Mechanical testing of wood and wood-based materials.
• Strain measurements on gypsum specimens and components.
• Product development and material characterization.
• Longer-term strain measurements on wood, using suitable gauges and installation methods.

What should you consider when selecting a strain gauge?

• Material stiffness: Select a gauge designed to minimize local reinforcement of the specimen.
• Expected strain: Check the strain limit of the specific gauge model against the expected deformation.
• Gauge length and configuration: Choose a suitable measuring length and single-axis or multi-axis arrangement for the test objective.
• Bonding: Confirm that the adhesive is compatible with the material surface and does not adversely affect the specimen.
• Temperature effects: Consider thermal expansion, temperature compensation and self-heating caused by bridge excitation.
• Moisture and measurement duration: Wood and gypsum can be sensitive to moisture. Consider humidity, dimensional changes and long-term stability when planning the installation.

Always consult the individual product datasheet for operating temperature, strain limits, compatible adhesives and measurement configurations.