Dynamic Mechanical Analyzer (DMA) - A344
| Dynamic Mechanical Analyzer (DMA) | |
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| Dynamic Mechanical Analyzer, TA Instruments | |
| Document Type | Article |
| Document Identifier | 344 |
| Themes | |
| Relevant Class |
Equipment |
| Tags | |
| Factory Cells | |
| Prerequisites | |
Introduction[edit | edit source]
A Dynamic Mechanical Analyzer is an instrument that can apply forces to a small sample and measure the resulting displacement. These forces can be applied dynamically. DMAs also feature an environmental chamber to control the temperature of the sample and ambient humidity.
Equipment Demonstration[edit | edit source]
The video below provides an introduction to the Dynamic Mechanical Analyzer instrument. It outlines it's uses, parts of the instrument, and how to obtain the glass transition temperature (Tg) of a material.
Features[edit | edit source]
A DMA uses various electromechanical components to apply loads and record displacement. They are optimized to produce precise measurements at relatively small forces in displacement compared to other testing equipment. A linear motor is typically used to apply forces to the sample. A linear motor is similar to a regular motor in that it uses precise electrical currents to produce forces, but it produces linear translations instead of rotation in conjunction with the linear motor.
The position of the force applicator is measured precisely by a method that is typically proprietary to manufacturers. To hold the sample and apply loads, a fixturing system is needed. There are a variety of sample fixtures available. Some examples being three point bend, dual cantilever, tension, and compressive fixtures. These are typically made of steel or stainless steel for high stiffness and temperature stability.
An environmental chamber can be used to control the temperature of the sample. Electric heating elements and fast flowing air are used to heat up the sample with quick response and minimal thermal gradients. The sample can also be cooled in the same fashion using an external air cooling device or a liquid nitrogen supply. The relative humidity can also be controlled inside the chamber. Systems are also available that can submerge the sample in a liquid while it is being tested.
Uses and Test Types[edit | edit source]
DMAs have multiple uses in material characterization. A common use is determining the glass transition temperature (Tg) of polymers. This can be done by observing the elastic properties of the sample while increasing the temperature. It is common to study the effects of different processing parameters on the Tg of the final material. Moisture content, recycled material content, processing temperature, and degree of cure for thermosetting polymers are some examples of material characteristics that can have an effect on the Tg of the final material.
A DMA can be used to characterize the material properties of viscoelastic materials like plastics and rubbers over a range of temperatures. This can be useful data for component design with viscoelastic materials that are subject to stress and high or low temperature. Creep sand stress relaxation are two characteristics that DMA cna be especially useful to study. A DMA can also be used to measure the elastic properties of the thermosetting polymer while it is curing. The results can be used to design manufacturing processes involving resins and adhesives.
Analysis of Results[edit | edit source]
The data collected in the activity shown in the video above is provided below as a CSV files:
| DMA Dataset |
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Combining Instruments[edit | edit source]
Related pages
| Page type | Links |
|---|---|
| Introduction to Composites Articles | |
| Foundational Knowledge Articles | |
| Foundational Knowledge Method Documents | |
| Foundational Knowledge Worked Examples | |
| Systems Knowledge Articles | |
| Systems Knowledge Method Documents | |
| Systems Knowledge Worked Examples | |
| Systems Catalogue Articles | |
| Systems Catalogue Objects – Material | |
| Systems Catalogue Objects – Shape | |
| Systems Catalogue Objects – Tooling and consumables | |
| Systems Catalogue Objects – Equipment | |
| Practice Documents | |
| Case Studies | |
| Perspectives Articles |
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| About | Help |
Welcome
Welcome to the CKN Knowledge in Practice Centre (KPC). The KPC is a resource for learning and applying scientific knowledge to the practice of composites manufacturing. As you navigate around the KPC, refer back to the information on this right-hand pane as a resource for understanding the intricacies of composites processing and why the KPC is laid out in the way that it is. The following video explains the KPC approach:
Understanding Composites Processing
The Knowledge in Practice Centre (KPC) is centered around a structured method of thinking about composite material manufacturing. From the top down, the heirarchy consists of:
- The factory
- Factory cells and/or the factory layout
- Process steps (embodied in the factory process flow) consisting of:
The way that the material, shape, tooling & consumables and equipment (abbreviated as MSTE) interact with each other during a process step is critical to the outcome of the manufacturing step, and ultimately critical to the quality of the finished part. The interactions between MSTE during a process step can be numerous and complex, but the Knowledge in Practice Centre aims to make you aware of these interactions, understand how one parameter affects another, and understand how to analyze the problem using a systems based approach. Using this approach, the factory can then be developed with a complete understanding and control of all interactions.
Interrelationship of Function, Shape, Material & Process
Design for manufacturing is critical to ensuring the producibility of a part. Trouble arises when it is considered too late or not at all in the design process. Conversely, process design (controlling the interactions between shape, material, tooling & consumables and equipment to achieve a desired outcome) must always consider the shape and material of the part. Ashby has developed and popularized the approach linking design (function) to the choice of material and shape, which influence the process selected and vice versa, as shown below:
Within the Knowledge in Practice Centre the same methodology is applied but the process is more fully defined by also explicitly calling out the equipment and tooling & consumables. Note that in common usage, a process which consists of many steps can be arbitrarily defined by just one step, e.g. "spray-up". Though convenient, this can be misleading.
Workflows
The KPC's Practice and Case Study volumes consist of three types of workflows:
- Development - Analyzing the interactions between MSTE in the process steps to make decisions on processing parameters and understanding how the process steps and factory cells fit within the factory.
- Troubleshooting - Guiding you to possible causes of processing issues affecting either cost, rate or quality and directing you to the most appropriate development workflow to improve the process
- Optimization - An expansion on the development workflows where a larger number of options are considered to achieve the best mixture of cost, rate & quality for your application.
