#### Definition

Dynamic Mechanical Analysis yields information on the mechanic properties under a small, mostly sinusoidal dynamic load as a function of temperature, time and/or frequency.

An applied mechanic load, i.e. tension or deformation, results in a corresponding response signal – deformation or tension - regarding amplitude and phase shift.

This results in a complex modulus called E*, G* and K* depending on the deformation type.

- E*: Complex elasticity modulus
- G*: Complex shear modulus
- K*: Complex compression modulus

#### Functional Principle

Dynamic Mechanical Analysis measures the visco-elastic properties of mostly polymer materials during a controlled temperature and/or frequency program.

During the test, a sinusoidal force (stress σ) is applied to the sample (Input). This results in a sinusoidal deformation (strain ε) (Output).

Certain materials, such as polymers, exhibit visco-elastic behavior; i.e., they show both elastic (such as an ideal spring) and viscous properties (such as an ideal dashpot). This visco-elastic behavior causes shifting of the corresponding stress and strain curves. The deviation is the phase shift δ.

The response signal (strain, ε) is split into an “in-phase” and an “out-of-phase” part by means of Fourier Transformation.

The results of this mathematical operation are the storage modulus E'(related to the reversible, “in-phase” response) and the loss modulus E''(related to the irreversible, “out-of-phase” response).

The loss factor tanδ is the ratio between the loss modulus and the storage modulus (tanδ = E''/E').

Generally, the storage modulus (E') refers to the material’s stiffness whereas the loss modulus (E'') is a measure for the oscillation energy transformed into heat. tanδ characterizes the mechanical damping or internal friction of a visco-elastic system.

For many decades, steel was the primary material used in the automotive industry. In more recent years, a shift toward electric motors has increased the popularity of lighter metals. Technological advancements make it necessary to continuously seek lighter and lighter materials, but without sacrificing the required stiffness over a broad temperature range. The key to reducing vehicular weight has been found in the use of fiber-reinforced polymers.

#### Application Literature

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Adhesives & Sealants Inorganics Metals & Alloys Organics Polymers