|Term||DefinitionThis property is a special property in this wiki.|
|AIM event||Application and Impact Mobilization Events (AIM).|
|CMC||Ceramic Matrix Composites (CMC).|
|DSC||Differential Scanning Calorimetry (DSC).|
|LCM||Liquid Composite Moulding (LCM), a family of infusion processes refers to processes that saturate a dry reinforcement that is on/in the mould by means of a pressure differential (injection pressure, vacuum, combination of both).|
|LRTM||Light Resin Transfer Moulding (LRTM) uses a semi rigid tool half (A side) that is similar to those used in VIP and a semi flexible tool half (B side) (typically made of thin fibreglass).|
|MMC||Metal Matrix Composites (MMC).|
|MRCC||Manufacturer's Recommended Cure Cycle (MRCC).|
|MSTE factory ontology||A systems level description of manufacturing problems relating to the physical factory and part producibility. The MSTE factory ontology consists of four classes: Material and process (M), Shape (S), Tooling and consumables (T) & Equipment (E); and the concept: The factory (F) consisting of the MSTE within the MSTEP approach.|
|MSTEP||Material and process (M), Shape (S), Tooling and consumables (T) & Equipment (E) - all have an interlinked effect on the Process step (P). (See MSTE factory ontology)|
|PMC||Polymer Matrix Composites (PMC).|
|RTM||Resin transfer moulding (RTM) involves loading a preform into a two (or more) piece, matched tool, closing it, and injecting resin under pressure (~15-100 psi, or ~1-7 bar). Well suited to small to medium sized parts, limited to large sizes due to injection pressure loads and tool cost.|
|SAMPE||The Society for the Advancement of Material and Process Engineering (SAMPE).|
|SME||Small and medium-sized enterprises (SME).|
|VARI||Vacuum assisted resin infusion (VARI) - also known as vacuum assisted resin transfer moulding (VARTM), vacuum infusion process (VIP) or often just resin infusion. VARI is a liquid composite moulding (LCM) closed mould process with a single side tool and vacuum bag where the resin is drawn through the preform using vacuum.|
|VARTM||Vacuum assisted resin transfer moulding (VARTM) - also known as vacuum assisted resin infusion (VARI), vacuum infusion process (VIP) or often just resin infusion. VARTM is a liquid composite moulding (LCM) closed mould process with a single side tool and vacuum bag where the resin is drawn through the preform using vacuum.|
|adhesive bonding||A joining process where a polymeric material (the adhesive) joins two separate structural pieces called adherends. Adhesive bonding is used instead of, or in parallel with mechanical means of joining such as riveting or bolting.|
|advanced manufacturing||The development and adoption of emerging innovation/technology that establishes new ways to manufacture existing products and enhance existing processes, manufacture new products from new advanced technologies, and develop cost-efficient ways of working (e.g. new business models, integrating all parts of the value chain).|
|amorphous||Literally "without structure", randomly coiled molecular polymer chains.|
|aramid fibre||Generic name for fibres composed of aromatic polyamide. Best known fibre is Kevlar, introduced by DuPont (USA) in early 1970s. Also, Technora (Japan), and Twaron (Europe). Originally developed to replace steel belts in radial tires, increased durability and increased strength.|
|areal weight||Areal weight (or fibre areal weight, AW ) refers to the mass/weight of fibre per unit area. (Typically in g/m2 gsm ) or ounces/yard2 (often just called ounces). Areal weight depends on tow size and fibre architecture (weaving, density, etc.).|
|balanced laminate||A laminate whose in-plane shear coupling stiffness is zero. This occurs if all plies in a laminate that are not oriented parallel or perpendicular to the primary laminate axis (i.e. non 0 or 90 degree plies) occur only in ±θ pairs that have the same thickness and elastic properties.|
|building block approach||An approach where risk is incrementally assessed in the scale-up of part size and complexity. Material and process (M&P) variabilities are evaluated at lower scales; While at higher scales, load paths and structural designs are verified. This approach involves three complementary engineering design activities:
|carbon fibre||Carbon fibres are composed of large aromatic sheets similar to those in graphite. These graphitic layers form the basic structural units in the shape of ribbons. The structure of carbon fibre ribbon is believed to be a columnar arrangement of disoriented graphite crystallites parallel to the ribbon length. The idealized tetragonal crystallites are stacked above one another, with slight disorientation between the crystals in the direction of fibre axis, trapping sharp needle like voids, where the boundaries between the stacks represent the disordered regions.|
|composite||Engineered materials (designed to have specific properties) made from two or more constituent materials with different physical or chemical properties. The constituents remain separate and distinct on a macroscopic level within the finished structure.|
|computational thinking||A problem solving process where computational skills (e.g. thinking logically, algorithmically, and recursively), can be used to express solutions in a manner than can be actioned effectively by human intervention or machine. (Same as simulation based thinking)|
|constituent materials||The individual materials that combine to form the composite material. The constituent materials are separate and distinct on a macroscopic level.|
|crystalline||Periodic 3-D, repeating array of molecules.|
|cure window||The allowable range of temperature, pressure, and vacuum values at specific times in the cure cycle. These limits are usually defined as process requirements.|
|deconvoluted||Separating a complex process involving several interacting phenomenon into several simple processes involving straightforward (easy to understand) phenomena.|
|degree of cure||Degree of cure (DOC) is an indication of how far the chemical curing reaction (crosslinking process) has advanced in a thermoset resin. DOC is defined with a number between 0 and 1 (or 0% and 100%) where 100% is a fully cured resin. It does not have to fully reach 100% for the resin to become solid or the part to be used. In some aerospace applications, resins are only cured to about 90%. Higher the degree of cure, higher the mechanical properties.|
|delamination||The failure mode characterized by a partial or full separation of adjacent laminae. Delamination is unique to laminated structures, and can be induced by impact load, fatigue load, and quasistatic load. (Also known as interlaminar separation)|
|design for manufacturing||Design for manufacturing (DFM) is the general engineering practice of designing parts with manufacturing in mind; typically with regard to the cost of manufacturing and the ease in which the part can be made.
Typically, a part that has good DFM characteristics will have good producibility and a robust process.(Same as "Design for manufacture" or "Design for manufacturability")
|development design cycle||The key design phases in new product development (NPD), particularly for complex engineering systems. This includes conceptual design, preliminary design (trade study), detail design, and production.|
|drapeability||Drapeability refers to how well a material conforms to a complex shape (non developable surface). Trade off: typically the more drapeable a fabric, the less dense the weave (lower Vf), and less stable during processing.|
|dry-spot||Areas or patches of fibre that are not fully wet out with resin. All LCM process are susceptible to flow induced dry spots.
Dry spots are typically caused by one or all of the following:
|effective heat transfer coefficient||The heat transfer coefficient applied to surface boundaries that include lumped bagside and/or toolside effects. These effects include bagging and consumables, tool size effects, tool substructure and heat transfer due to convection (e.g. airflow) and radiation (e.g. wall, rack effects).|
|factory cell||An individual station within a factory where a given set of tasks are accomplished (also known as a "work cell"). Some cells may directly add value to the product (e.g. deposition), while others may serve support roles that are critical to maintaining part quality (e.g. receiving, storage, inspection & shipping).|
|fibre architecture||Fibre architecture refers to how the fibre is assembled.
Most common architectures:
|fibre bed compaction||In an unconstrained state, fibre has loft (springiness), when it goes into a mould it must be compacted to obtain the desired Vf. As the compaction increases, the permeability decreases.|
|fibre washout||Fibre washout refers to the displacement of fibre by resin due to excessive shear stress. This can occur locally (i.e. in a small, contained region) or throughout the whole preform (i.e. sliding the preform and/or wrinkling it).|
|filament||A single unit of fibre reinforcement that cannot be separated further without breaking it. It often has a circular cross section that is formed by the dies used to create it or its precursor material. Many filaments are manufactured in parallel to produce a strand or tow. The number of filaments in a strand or tow is often references by how many thousands of filaments comprise the tow. e.g. an 18k tow is made up of ~18000 filaments.|
|flow and consolidation management||A central processing theme in the manufacturing cycle. This theme concerned with managing changes in the physical response of parts/tools when the resin is predominantly in a liquid phase (e.g. pre-gelation, pre-solidification) and the prevention of manufacturing defects.|
|flow front||Flow front refers to the leading edge of the resin as it is flowing into and through the fibre preform.|
|glass transition temperature||The glass transition temperature (Tg) is the temperature region where the polymer transitions from a hard, glassy material to a soft, rubbery material. It is one of the most important properties of any amorphous polymer.|
|graphene||Graphene is a one atom thick two dimensional honeycomb layer of bonded carbon atoms. When many graphene layers are stacked regularly in three dimensions and held together with weak forces, graphite is created.|
|heat of reaction||Polymerization of thermoset resins is an exothermic reaction and heat is generated during the curing process.
A thermosetting resin has the potential to release a certain amount of energy while curing. This is called the total heat of reaction, HR, with a unit of J/g (SI units).The heat of reaction during polymerization is measured using a Differential Scanning Calorimeter (DSC) equipment measuring much energy/heat comes out of the reaction for a small resin sample.
|knowledge||In the context of knowledge in practice, knowledge refers to the systematic use of science based knowledge in composites manufacturing practice.
There is a distinction between experience based knowledge and science based knowledge:
|knowledge in practice||A framework for formalizing effective and low risk science based composites manufacturing practice and the process of knowledge translation.|
|macroscopic flow||Resin flow in between fibre tows.|
|manufacturing outcomes||Outcomes represent the range of response/sensitivity to factory system attributes. Those that fail to satisfy manufacturing requirements are known as defects. Examples of manufacturing outcomes include process parameter outcomes, material structure outcomes, and material performance outcomes.|
|material deposition||The act of combining reinforcement fibre, resin to shape on a mould (tool).
There are three main methods to combine resin and fibre to deposit onto a tool (i.e. material deposition):
|material deposition management||A central processing theme in the manufacturing cycle. It includes the steps primarily involved in moving material into the correct position on the tool or with combining fibre, resin and other constituents in-situ on tools.|
|material equivalency||The commonality of material level properties at all scales of the ‘building block’ (coupon level to production scale structures) in terms of chemical–physical–mechanical states such as degree of cure/degree of crystallization, fibre volume fraction, residual stresses, etc.|
|material qualification||An engineering design activity that relates to the determination of material level properties that will be used in the structural design and certification.|
|matrix||The continuous material phase that binds the reinforcement together, maintains shape, transfers load, protects the reinforcement from environment and damage, and provides the composite support in compression.
|microscopic flow||Resin flow in between fibres.|
|modelling||The use of multiphysics models to predict the outcome of real-world scenarios. May be analytical (closed form, "hand calculations") or computational (implementation on computers is required due to the large number of calculations involved. e.g. finite element method, finite difference method)
Most often in composite materials engineering, modelling refers to either:
(same as "Simulation")
|objective function||A rubric used to provide a measure of performance that describes the producibility of a part. They may be quantitative or qualitative.
There are three objective functions in manufacturing:
Objective functions are typically minimized or maximized to achieve a certain optimal condition; but in the context of manufacturing, maintaining the value of an objective function or achieving a nominal (target) value is a common goal (e.g. maintaining quality while increasing rate is a common workflow to achieve business growth; producing a new part for a target cost is important to maintaining a business case)
|permeability||Permeability refers to the resistance to fluid flow through a porous material.
|practice||Any manufacturing and/or decision making activity that occurs during any stage of the development design cycle (e.g. conceptual design to production). In the context of Knowledge in Practice, practice refers to the systematic use of science based knowledge to reduce composites manufacturing risk, cost, and development time.|
|preform||‘Preform’ is the term for the fibre reinforcement. This is the stage between the raw material form after it is processed into an architecture (fabric, mat, etc.) and becoming a composite.|
|preforming||‘Preforming’ refers to the task of preparing the fibre.
|prepreg||Pre-impregnated (prepreg) material refers to fibre that is already combined with resin. It is the most common material form used in aerospace. During prepreg production, (e.g. fibres are run through a resin bath), prepreg is heated and partially cured to B Stage (< 5 % degree of cure). Thermoset prepregs (e.g. epoxy prepreg) have to be kept in a freezer at around -20 °C. At room temperature, the epoxy starts to cure.|
|processing themes||Key components of all composite manufacturing processes. Collectively, the four themes represent the time-temperature-pressure-vacuum history, which is traditionally used to define a manufacturing cycle.
The four processing themes are:
(Same as "Theme")
|producibility||The capability of the manufacturing process to produce parts of acceptable quality (e.g. meet engineering, manufacturing, regulatory requirements), repeatably and robustly.|
|production approval||An engineering design activity that ensures that the material qualification and structural certification steps are properly linked once the structure enters production.|
|racetracking||Racetracking is when resin takes the path of least resistance through a tool. This typically occurs at the outer edges of the reinforcement (between the fibre and tool). Depending on the severity, this can lead to dry spots (resin starved regions). Racetracking is not consistent and difficult to predict accurately (a ‘range’ of racetracking effects is predicted).|
|residual stress and dimensional control management||A central processing theme in the manufacturing cycle. This theme relates to management of internal stresses that occur as the material undergoes differential thermal and physical phase change volume changes and viscoelastic property development.|
|resin||For polymer matrix composites (PMCs), resin refers to the matrix; the continuous material phase that binds the reinforcement together, maintains shape, and transfers load. Resins are divided into two main groups: thermosets and thermoplastics.|
|risk||With regards to manufacturing, risk is the combination of the probability and consequences of undesirable manufacturing outcomes. Manufacturing risk can lead to technical issues, program/schedule delays, and cost overruns.|
|robust process||A process whose outcomes are relatively insensitive to variability of manufacturing parameters.|
|semi-crystalline||A portion of the molecular polymer chains tend to ‘fold up’ into densely packed regions called crystals.|
|simulation||The use of multiphysics models to predict the outcome of real-world scenarios. May be analytical (closed form, "hand calculations") or computational (implementation on computers is required due to the large number of calculations involved. e.g. finite element method, finite difference method)
Most often in composite materials engineering, simulation refers to either:
(same as "Modelling")
|simulation based thinking||A problem solving process where computational skills (e.g. thinking logically, algorithmically, and recursively), can be used to express solutions in a manner than can be actioned effectively by human intervention or machine. (Same as computational thinking)|
|sizing||Sizing or fibre sizing refers to a coating that is applied to fibre during manufacturing. Highly proprietary (formulation and process).
Sizing serves two functions:
|structural certification||An engineering design activity that relates to the acceptance of the as manufactured structure being able to sustain the necessary loads and other service conditions determined by engineering, manufacturing, and regulatory requirements.|
|theme||A key component of all composite manufacturing processes. Collectively, the four themes represent the time-temperature-pressure-vacuum history, which is traditionally used to define a manufacturing cycle.
The four processing themes are:
(Same as "Processing themes")
|thermal diffusivity||A quantitative measure of how a material will respond to transient thermal conditions. It is defined as the ratio of thermal conductivity to the volumetric heat capacity of the material (density times the specific heat capacity).
Materials with large thermal diffusivity have a high thermal conductivity relative to their capacity to store energy (heat capacity) and will rapidly distribute the thermal energy throughout its volume and rapidly change temperature to reach the new equilibrium temperature.Materials with small thermal diffusivity have a low thermal conductivity relative to their capacity to store energy (heat capacity) and will have a sluggish temperature response to a change in thermal conditions (large temperature lag). This is because it takes more energy per unit volume to change the temperature, and the low thermal conductivity means it takes longer to distribute the thermal energy throughout its volume.
|thermal management||A central processing theme in the manufacturing cycle. This theme is concerned with managing the thermal response of materials during storage and handling or parts/tools when they are subsequently heated.|
|thermal profiling||Experimental thermal profiling is a typical practice where part/tool temperatures and temperature rates are empirically measured using temperature measurement devices (typically thermocouples). This activity is performed to ensure that representative locations in the part of interest satisfy the cure window with respect to minimum/maximum heat up and cool down rates and length (duration) of temperature holds.|
|thermoplastic||A class of polymer, some common examples include polypropylene and polyethylene. They soften and melt upon heating (i.e. potentially recyclable), high viscosity when melted, therefore difficult to saturate fibres. Usually needs a lot of pressure and heat to process.|
|thermoset||Thermosets are a class of polymer that undergo polymerization and crosslinking during curing with the aid of a hardening agent and heating or promoter. Initially they behave like a viscous fluid. During curing, they change from viscous fluid to rubbery gel (viscoelastic material) and finally glassy solid.
If heated after curing, initially they become soft and rubbery at high temperatures. If further heated, they do not melt but decompose (burn)
Comes in two parts: part A (resin) and B (hardener). When mixed, curing reaction starts and is not reversible.Examples include epoxy or polyester.
|tow||A tow is a bundle or yarn of individual fibres. The tow size is inherent to the fibre manufacturing process (i.e. a tow is manufactured in one process, rather than each fibre individually then bundled together after).
Typically, smaller tows are better because they result in a more homogeneous material.
The larger the tow:
|uncertainty||A general term for the variability that affects the accuracy of a metric, statement or thought.
Modelling & simulation In modelling & simulation a distinction is made between uncertainty and error:
|uncertainty quantification||An emerging discipline that relates to the characterization of modelling and simulation uncertainties. There are four key aspects of uncertainty quantification (UQ) that can be used to manage uncertainty to establish an ‘evidence of credibility’ in a computational model:
|vacuum infusion process||Vacuum Infusion Process (VIP) involves placing a preform on a one sided tool, sealing a vacuum bag on top of it, and drawing resin through the preform with vacuum. Vacuum Infusion Process (VIP) - also known as vacuum assisted resin infusion (VARI), vacuum assisted resin transfer moulding (VARTM) or often just resin infusion. VIP is a liquid composite moulding (LCM) closed mould process with a single side tool and vacuum bag where the resin is drawn through the preform using vacuum.|
|validation||With regards to modelling & simulation, validation demonstrates the accuracy of a computational model — in the context of its intended use — to check that it represents the physics of the problem and the ‘reality of interest’ (needs are satisfied).|
|verification||With regards to modelling & simulation, verification confirms the implementation of a computational model to ensure that it represents the mathematical model and equations used to describe it (requirements are met).|
|viscosity||In composites processing, viscosity is an indicator of how easily the resin matrix will mix with the reinforcement and how well it will stay in place during processing. The lower the viscosity, the more easily resin flows. Resin viscosity ranges considerably across chemistries and formulations. By scientific definition, viscosity is a measure of a material’s resistance to deformation. For liquids, it is in response to imposed shear stresses.|
|volume fraction||Volume fraction of either matrix or fibres with respect to total composite volume (matrix + fibre).|
|weight fraction||Weight fraction of either matrix or fibres with respect to total composite weight (matrix + fibre).|
|workflows||A set of steps/procedures that are intended to provide guidance in manufacturing and/or decision making activities.
There are two types of workflows:
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.