# Dynamic Mechanical Analysis (DMA)

Dynamic Mechanical Analysis (DMA) is a material characterization technique where a small deformation is applied to a sample in a cyclic manner. This allows measurement of the materials response to stress, temperature, frequency or time. The term is also used to refer to the analyzer that performs the test.

How it works. DMA applies a sinusoidal deformation to a sample of known geometry. The sample can be subjected by a controlled stress or a controlled strain. For a known stress, the sample will then deform a certain amount. How much it deforms is related to its stiffness. A force motor is used to generate the sinusoidal wave and this is transmitted to the sample via a drive shaft. DMA measures stiffness and damping, these are reported as modulus and tan delta. Because of a sinusoidal force, the modulus can be expressed as an in-phase component, the storage modulus (E’), and an out of phase component, the loss modulus (E”). The complex modulus (E*) is a measure of the overall resistance of a material to deformation. The storage modulus is the measure of the sample’s elastic behavior. The ratio of the loss to the storage is the tan delta and is often called damping. It is a measure of the energy dissipation of a material.

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## Key Attributes

• Temperature range: -150 to 600 °C;
• Modulus range : 103 — 3×1012 Pa;
• Frequency range: 2×10-3 to 80 Hz;
• Maximum force: 35 N;
• Minimum pre-tension (for Tensile): 0.001 N;
• Tan delta range: 0.0001 to 10 rad;
• Dynamic sample deformation: +/-0.5 to 1,500 µm;
• Tools: Parallel plates (8 mm, 15 mm, 25 mm), Fiber and Film, Three-Point Bending.

## Strengths

• Non-destructive measuring method;
• Clear physical meaning;
• Mechanical properties measurement of wide variety samples (thin films, fibers, elastomers, solid polymers, polymer melts, composites, ceramics, metals, foams);
• Simple sample preparation;
• Wide range of test tools is available for testing a variety of materials.

## Limitations

• Sample size depends on motor/transducer force and displacement ranges, sample compliance and stiffness, size of the test tool;
• Sample stiffness must be within the operational range of the instrument;
• Mechanical limitations in the high normal force region.

## Applications

• Viscoelastic material properties, such as various moduli (E’, E”) and the loss factor tan (?);
• Temperatures that characterize the viscoelastic properties;
• Measurement of damping, creep compliance, and stress relaxation behavior;
• The glass transition temperature, in particular (for which DMA is the most sensitive method);
• The frequency-dependent mechanical properties of materials.