What is Dynamic Mechanical Analysis (DMA)

Dynamic Mechanical Analysis (DMA)

The viscoelastic properties of materials, most frequently polymers, are studied and characterized using the testing approach known as dynamic mechanical analysis (DMA). DMA involves applying different forces or stresses to a material and measuring the resulting deformation or strain, generally when the material goes through a controlled temperature or frequency shift.

Dynamic Mechanical Analysis (DMA) is a technique used to examine the viscoelastic behaviour of solid-like materials by analyzing their response to specific sinusoidal stress or strain. This method evaluates the material’s deformation or flow properties as a function of time and temperature. Primary values include the storage and loss moduli E’ and E”, as well as the loss or damping factor tan. DMA tests can be used to infer physical, mechanical, and long-term material behaviour.

DMA scales include environmental parameters like temperature or relative humidity, as well as mechanical stress amplitude and frequency. An “amplitude sweep” is used to determine the linear viscoelastic (LVE) range of a material, with elastic deformation predominating. The frequency sweep provides information on time-dependent material behaviour in the nondestructive deformation range.

Elevated temperatures are determined by DMA measurements with a temperature ramp, particularly for polymers. These measurements are usually conducted at a fixed frequency and subject to stress or strain. Permeating dampness affects the mechanical properties of a sample, with temperature and frequency typically held constant. Changing the deformation slightly can improve the observed curve’s precision, but maintaining a low-risk environment is crucial.

DMA is a method used to study the behaviour of materials over an extended period of time, allowing for a better understanding of their properties in both liquid and solid forms. It is particularly useful in studying resin curing reactions, as it helps to understand how substances behave at different temperatures. Different methods exist for calculating thermal transition temperatures, such as the top of the tan graph, the E” curve’s highest point, a method based on E’-curve steps, and the E’-curve inflexion point technique.

DMA systems can evaluate various types of materials, including strain, compression, and types of load needed, with linear and rotary drives used for stress, bending, and compression tests. The oscillatory nature of DMA measurements results in complex moduli, which can be translated between tests if the Poisson’s ratio of the studied material is known.

DMA systems can test a wide variety of materials, from very low-modulus materials to fiber-reinforced polymers. Choosing the right material category for an application can help identify previously unrecognized options. By understanding the material’s expected mechanical properties, product designers can make informed decisions about their application and test requirements.

DMA is a technique used to study the viscoelasticity of polymers, which is a combination of viscous and elastic responses. It helps understand the relationship between stress and strain, storage modulus (E’), loss modulus (E”), and tan delta (tan δ), which represents the damping behaviour of a material. DMA can be applied to determine the glass transition temperature (Tg), study secondary transitions, compare materials, evaluate additive effects, and understand material ageing and stability. The process involves sample preparation, mounting, testing, and data analysis. The resulting data provides insights into the material’s behaviour under different conditions and can help in understanding the effects of additives or fillers on the material’s mechanical properties.

Video 01: Dynamic Mechanical Analysis (DMA) – online training course