Thermal behaviour - A232
|Foundational knowledge article|
The thermal history of an uncured composite material plays a critical role in how the material properties evolve, how the material can be handled during the various stages of manufacturing, including the thermal cure step, and how the final microstructure and properties of the composite are created. The following pages provide KPC users with an understanding of the foundational topics in processing science.
The foundational knowledge volume contains pages for the following thermal behaviour topics:
- Basics of heat transfer
- Thermal phase transformation of polymers
- Curing of thermosetting polymers
- Melt and crystallization of thermoplastic polymers
- Chemical degradation of polymers
- Physical aging of polymers
By visiting the links provided, you can explore the topics and learn more.
Basics of Heat Transfer[edit | edit source]
Heat transfer is the physics process responsible for the redistribution of thermal heat energy between systems. For composites, this includes the redistribution of heat both within the laminate itself, and between the laminate body and its surrounding environment. The heat transfer process has important roles in both the composite manufacturing process and the operational service of the composite material.
Thermal Phase Transformation of Polymers[edit | edit source]
Polymers go through several distinct phase transition points at particular temperatures. These transitions induce changes to their specific volume, mechanical properties, and physical behaviour.
Curing of Thermosetting Polymers[edit | edit source]
For thermosetting polymers, the manufacturing process step of curing is necessary to transform the viscous polymer resin into a rigid solid. During this process, chemical reactions take place that result in the formation of molecular bonds that set the polymer into shape.
Melt and Crystallization of Thermoplastic Polymers[edit | edit source]
During processing into a composite matrix, thermoplastics are heated to melt flow and impregnate the reinforcement fibres. The polymer is then cooled to solidify. During this solidification process, molecular re-arrangement of the polymer chains, referred to as crystallization, is occurring that give the polymer its solid-state material characteristics.
Chemical Degradation of Polymers[edit | edit source]
With exposure to elevated temperatures beyond their temperature stability limit, polymers can begin to chemically degrade. Material damage can involve both oxidation, and the breaking of covalent bonds within the polymer. The temperature limit at which degradation begins represents the ultimate temperature at which the polymer may be processed and used, although practically – the service temperature of the polymer may be lower for mechanical property reasons such as softening and loss of suitable stiffness.
Physical Aging of Polymers[edit | edit source]
Physical aging is the volumetric relaxation of a polymer that results in the stiffening of the polymer. It is separate from chemical aging, which is the result of chemical degradation. Physical aging occurs when a polymer is in a meta-stable non-equilibrium state and attempts to progress towards its natural equilibrium state. It is a phenomena commonly experienced by thermoplastics when they are rapidly cooled from an elevated temperature during their shape manufacturing process.
Explore this area further
- Thermal behaviour - A232
|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|
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.
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.