COMPOSITE PRODUCT MANUFACTURING SYSTEM AND METHOD

A method of manufacture of a composite material is provided. The method includes providing a deformable body having substrate and matrix materials on a surface of a first tool. The substrate material is loosely bound by the matrix material and may include a composite pre-form. The relative movement between the first tool and a second tool is controlled so as to apply pressure to the body between opposing surfaces of the first and second tools and thereby debulk and/or consolidate said body. The first or second tool includes a plurality of individually controllable tool elements, the temperature and/or displacement of said elements being controlled to generate a desired profile in said body. An adaptive debulking system and tool are also disclosed.

DETAILED DESCRIPTION OF THE INVENTION

The present invention derives from the understanding that the consolidation process for composite product production is not purely a machine dependent parameter. Accordingly it has been determined that, because corresponding composite lay-ups can differ both between products and due to input material variation, each lay-up should be debulked/consolidated in a bespoke manner in order to achieve a consistent end product. The inventor(s) has determined that the viscoelastic creep/recovery response of the resin determines the degree of debulking and the conformity of the composite to a desired net shape. The profile of the product can change over the debulk period. Accordingly the consolidation pressure applied to the composite preform, including the rate of application thereof, as well as the temperature state of the material can all be adjusted over different areas of the preform to achieve the desired profile of the end product.

Certain aspects of the invention therefore concern the provision of an adaptive tool, or feedback-loop controlled, moulding operation which comprises of a surface mapping of the composite lay-up in order to determine any adjustments to be made to the tool in order to achieve a desired profile of the preform and/or end product.

Turning now toFIG. 1, there is shown a first stage in the process, in which a composite material preform10has been deposited on a tool12or mandrel. The preform10comprises a substrate which is pre-impregnated with matrix material.

In this embodiment the tool has a contoured tool surface14shaped to apply a desired profile to a surface of the composite product to be produced. Various profiles, including curved surfaces and sharper edges, and/or other complex geometries, can be formed using a correspondingly shaped tool as will be understood by the person skilled in this field.

The preform10for the composite material to be produced is deposited on the tool surface14by laying down successive plies16of composite material. Each layer or ply16comprises a conventional arrangement of fibres, which is pre-saturated or impregnated with a conventional matrix material, such as an expoxy resin or other suitable polymer. The first layer16is laid upon surface14and the subsequent layers are laid down sequentially, each upon the last, in order to build up a stack of layers within the matrix material. Each layer substantially follows the contour of the previous layer such that the outermost layer substantially follows the profile of the underlying tool surface14.

After a stack of layers16have been deposited as shown inFIG. 1, it is necessary to consolidate the stack before adding more plies.

The next stage in accordance with one example of the invention is to determine the surface geometry or topology of the as-laid fibre preform prior to consolidation. This may be achieved using a number of different conventional non-contact scanning or probe devices, comprising, for example, laser scanning, optical measuring, non contact based, ultrasonic or proximity based surface or volumetric based measurement. In one example, position feedback from the ply laying head can also provide basic dimensional data, for example in order to indicate whether consolidation is necessary.

An example of the inspection device is shown inFIG. 2, which shows two measurement devices18,20arranged to scan the surface22of the preform10on the tool12. The first18and second20measurement devices (e.g. scanning heads) determine the variations in the surface height in orthogonal directions. The first head18is arranged to traverse or scan the surface in the direction indicated by arrow A, whilst the second head20traverses or scans the surface in the direction indicated by arrow B. Such a two-directional scanning system may be used particularly for components with curved surfaces.

Other measurement/scanning methods may be used as be realised by the person skilled in the art.

The surface measurement/topology data is typically acquired and/or stored with reference to a datum feature. Such a datum feature may comprise one or more predetermined locations on the tool surface14such that all measurements are taken with reference to a known fixed point. The measurements are typically acquired electronically.

The measurement data24is fed to a data store which typically forms a part of a data management and/or processing system26as shown inFIG. 3. The system may comprise one or more processors arranged to receive various data inputs, including the measured surface geometric data24, and to process those inputs in order to determine a suitable control output28for debulking/consolidation of the preform material10.

From the measured data24, the processing system26is able to construct a 3-dimensional surface profile or model for the measured surface22.

The processing system26also receives or accesses a predetermined surface profile or model28from a data store which is accessible to the data processing system26. The predetermined surface profile is indicative of an ideal or desired surface profile, either before or after debulking has taken place. Typically the desired surface profile is the surface profile after debulking and may be a nominal surface profile, for example captured using CAD software.

The processing system26determines the difference between the desired surface profile and the measured surface profile. Thus the processing system can determine the degree or amount by which the measured surface profile must be modified in order to achieve the desired surface. Such data may be stored as a series or array of two-dimensional locations in an arbitrary plane and a height value (or variation) at each of said locations. The plane may be a horizontal plane or some other plane (e.g. a section through, or else a plane above or below the pre-form) sufficient to encompass or accommodate a major dimension (e.g. a length and/or width dimension rather than a depth dimension) of the preform10. Ideally the plane is not orthogonal to the surface22but is substantially aligned therewith as far as possible.

The data processing system26may have one or more modules of computer-readable code, such as software, comprising one or more algorithms to determine suitable displacement, pressure and/or temperature parameters to apply over regions of the surface22in order to achieve the desired surface profile. The software typically also determines a length of time over which to apply the determined parameters and/or a rate at which those parameters should be changed over time in order to achieve the desired surface. In some embodiments, the discrepancy between the measured and nominal surfaces alone is sufficient to allow the processing system26to determine a suitable control signal output30. In such an embodiment the algorithms or control laws may assume that consistent materials are used such that the surface height variation correlates to a defined displacement, pressure and temperature in the debulking tool.

However the viscoelastic creep/recovery response of a resin is highly non-linear. When coupled with multiple degrees of freedom of operational parameters, it will be appreciated that a more suitable method of determining the suitable control parameters may involve interrogation of a material properties data store32. The data store may comprise records of material properties or behaviour under varying processing conditions, which may be derived, for example, from empirical data. In this manner, multiple different materials can be accommodates, such that the system/tool can be used for varying different product materials and configurations.

The material data store32may also receive materials measurement data, e.g. dimensional data, as an input, such as thickness, areal weight, etc.

The data processing system may also access a data store34or algorithms for converting the determined processing parameters into control signals3Q for the debulking tool. A database may additionally or alternatively be maintained which correlates the various operational parameters over suitable ranges, such as temperatures, deformation rates, applied pressures and times, an example of which for one actuator is shown inFIG. 8.

In this embodiment, the processing system26may take the form of a computer which derives the appropriate control parameters and produces a debulking control definition for transmission to a debulking tool controller38as shown inFIG. 4, for example over a network connection. However in other embodiments, the processing system26and debulking tool controller38could be one and the same.

The debulking tool40in the example shown inFIGS. 4 and 5comprises an adaptive debulking hood56having an array of elements42. Each element comprises an actuator44as shown inFIG. 5which is individually controllable by the controller38. The elements42are arranged as a two-dimensional matrix or array which is sufficient in size to accommodate the area of the pre-form in plan.

The location of the elements42within the array may be fixed. However the elements42are actuatable in a direction substantially perpendicular to the plane or surface of the array, i.e. in the direction C indicated inFIGS. 4 and 5. In other examples, such as for a curved tool, the direction C may be different for each actuator.

Each element has one or more sensors associated therewith, typically incorporated in the actuator assembly44or elsewhere in the hood56, which can be used to determine a current operational state of the element. The sensor readings can then be fed back to the controller38during operation in order to allow actuation of each element according to a closed feedback loop. The sensors may comprise any, or any combination, of conventional position, displacement, pressure and/or temperature sensors.

InFIG. 5there is shown a preferred embodiment in which the position and temperature of each element can be independently controlled. In this embodiment, each element comprises a linear actuator44arranged to move relative to an intermediate thin walled member or structure46. The member46is an intermediate contact member for contacting applying a contact pressure to the pre-form in the manner of a caul plate. However in this example, the intermediate member is resiliently deformable or otherwise compliant such that movements of the actuators44can deform the caul plate and thereby modify the surface profile thereof. In one embodiment, the caul plate may be formed as a substantially flat or planar member which is deformed from its at-rest condition into a desired surface profile for the pre-form. Alternatively, the caul plate may be formed of a more resilient material which defines a desired or average surface profile for the pre-form. Thus the actuators in use may only need to deform the caul plate by smaller amounts in order to achieve a bespoke, adapted surface for individual pre-forms in use.

In the example of a curved tool, the thin walled member46may be similar in shape to the consolidated preform surface22′.

One example of a flexible caul plate46is shown inFIG. 6, which is formed as a series or network of individual plate portions47and a plurality of linkage portions49therebetween. The linkages49are flexible to allow controlled flexing of the caul plate between the plate portions47, which are relatively stiffer than the linkages.

The plate portions47can be tailored for a specific desired geometry and the linkages may be formed so as to offer a consistent or varying resilience between different portions47. Such a configuration may offer flexion of the caul plate within predefined limits. The vicinity of any deformations may be controlled to occur at discrete points by virtue of the flexible linkage joint system. The caul plate may comprise an outer or peripheral frame51, which may support the plate portions47, for example via further linkages or ties49a. Conventional caul plate and/or stiffener materials may be used.

Interposed between each actuator and the intermediate member46is a bearing member48, through which a load may be applied to the intermediate member. The bearing member may be a resilient member, comprising, for example, an elastomer. This allows the adaptable caul46to move without locking or bending the actuator mechanism.

A heater arrangement50is provided adjacent, typically in contact with, the intermediate member46so as to allow heat transfer between the tool and the pre-form. The heater may comprise an array of individual heaters corresponding to the array of elements. Alternatively the heater may comprise a common heater structure, of which individual portions or regions corresponding to the individual elements42can be selectively heated.

In the embodiment ofFIG. 5, the heater is provided by a heater mat structure50located between the actuator44and the intermediate member46. Individual portions or zones of the heater mat structure50are individually controllable to increase or decrease the temperature thereof, for example by resistive heating elements in the mat.

In any embodiment, the heater may be integrated within the tool. It is not essential that the heaters and actuators are aligned in a one-to-one relationship, although such an arrangement may be beneficial to allow correlation of temperature and pressure application to the pre-form in use. Corresponding measurement of the temperatures in the actuators/elements/hood are made to allow full control, for example by monitoring resistance of the heater elements or the use of a heat flux sensor within the intermediate member46.

In one embodiment it has been found that a high temperature or low heat flux transfer for one or a group of actuators can be indicative of the intermediate layer46not being in contact with the component (e.g. that a void is present or that an actuator/mechanism has failed to operate correctly). Thus a signal or alert can be output to indicate such a determination and/or allow corrective action to be implemented via the tool40.

In the examples ofFIGS. 4 and 5, the tool comprises a displacement actuation system, a pressure control system and a temperature control system. Each of those sub-systems may be individually controllable in accordance with the control input received from the controller38. In this regard, the system comprises a distribution control interface or manifold52to allow dissemination of different control signals to the individual elements, such as the heater and/or actuator of each element. A series of wired or wireless connections54may be established between the relevant components and the interface52for this purpose.

Using the above-described system an adaptive tool can be provided having a bank of underlying actuators and heaters selectively actuatable via a series of connected/disconnected members to change the shape of the pre-form. The heat, applied force/pressure and the rate of actuation are all controlled by the data processing system26(either directly or indirectly via debulk controller38) as dictated by the control law such that the tool can apply variations in temperature and pressure, for example at different rate, over different portions of the tool to effect changes to the moulding of the final composite component to be formed from the pre-form. The tool allows the compaction pressure/temperature to be applied in any sequence as deemed by the control law to achieve the desired quality of the part.

In use, as shown inFIG. 7, the pre-form10on the lay-up tool12, after scanning is placed adjacent the intermediate member or caul plate46of the adaptive tool arrangement56described above. The pre-form10is typically uncured at this point. The lay-up tool and the adaptive tool56form opposing portions of the debulking tool used to modify the pre-form. The desired settings for the adaptive tool56are determined and the corresponding parameters for the actuators44and/or heaters50are set.

The lay-up tool12and the adaptive hood56are then brought together, typically for a predetermined length of time, such that the pre-form is sandwiched between the opposing surfaces14,46of the tool parts. The position and applied pressure of either/both of the lay-up tool12and adaptive hood56is controlled over that time. The relative orientation of those parts may be controlled by mechanical actuators58on the fixtures of the tools, i.e. to control global tool positioning and/or applied pressure. The controller described above may receive position/pressure readings for those actuators58and adjust them accordingly.

The controller operates the adaptive debulking hood in the manner described above. The preform can thus be deformed to a varying degree over its surface in contact with the adaptive tool surface. A vacuum may optionally be drawn between the opposing tool surfaces14and46during the consolidation process.

It is to be noted that the operational parameters for the adaptive tool56may have initial set values which may be fixed or else which may change according to a predetermined schedule during processing. Additionally or alternatively, variations in the operational parameters may be made by the controller (i.e. in a transient manner) in response to sensor readings during operation. For example, pressure and/or temperature readings may be fed to the controller and the pressure/temperature at different locations and/or the overall pressure/temperature profile may be compared to desired or predicted settings.

An example of such a profile for one of the actuators/elements42is shown inFIG. 8. As can be seen changes in pressure/temperature/displacement can be implemented in sequence (i.e. individually controlled) according to an adaptive method of control. Thus in response to sensing of varying conditions in different regions of the substrate the individual elements can be actively adjusted. For example temperature and/or pressure increases may be delayed or accelerated in one zone (i.e. for one or more elements) relative to another so as to allow adjustment in the substrate profile, whilst delaying curing. Also it is possible that pressure/displacement may be increased or decreased for one or more elements, whilst maintaining a constant temperature or adjusting the temperature in a contrasting manner. Conversely, temperature may be increased or decreased whilst maintaining a constant displacement/pressure (e.g. to accelerate curing once a desired profile is achieved). In this manner the interplay between temperature/displacement/pressure control provides far greater freedom in order to more accurately achieve a desired substrate profile or fibre volume fraction in response to variations in input substrate layups.

Regardless of whether the adaptive debulk tool56is controllable only initially before operation, or else is responsive to sensed variations during operation, the tool can offer improved conformity to a desired component geometry, which accommodates variations in the pre-form due to the laying-up process.

The tool of the present invention is typically used to undertake a partial or initial cure for the pre-form only. According to any aspect of the invention, any of the element control/actuation steps (e.g. for consolidation) may be performed during curing.

A component output from the adaptive tool will typically be cured sufficiently such that its geometry is rigid and defined such that the component can then be taken through final cure either in the tool or by transferring the partially cured component to a conventional autoclave. The full cure is typically undertaken by heating the entire component to a predetermined temperature, in contrast to zoned temperature variations which are allowed by a tool according to the present invention. The full cure temperature is typically higher than the consolidation/zoned heating temperature.

At the end of the debulking process the preform is consolidated and achieves a CAD nominal surface topology and may then be subjected to further processing i.e. additional layup. At the end of the lay up process the preform can be reconsolidated following the process step described above and then subjected to final cure operation.

Embodiments of the invention may be summarised as an intelligent morphing tool which responds to the variation in an input condition of a deformable/uncured composite component and produces a defined output by means of an adaptive array of actuators for a component contact surface.

Thus the invention is capable of determining and implementing a deviation in an adaptable composite processing tool to enable deformation of an input composite material as dictated by the geometry of the input material. This differs from conventional global tool setting parameters to allow zoned parameter correction for unacceptable tolerances in preforms during processing thereof. The invention allows feedback and consolidation of the consolidation process to accommodate input material variation. The output (i.e. control adjustments) can provide feedback for the layup system to ensure target fibre-volume fractions are achieved. The present invention can reduce scrap rate as well as being able to control the consolidation of a simple or a highly complex part in a manner which can minimise distortion in components after cure.

The proposed system can also be applied in the process of adaptive drape forming, diaphragm forming vacuum forming or in other specialised areas wherever the shell/tool manipulation is required.

Examples of components to which the invention can be applied include composite aerofoils, vanes, stators, cowling, etc for fluid flow machines, such as gas turbine engines, pumps or the like. The invention may have application for other bulky shaped parts aerospace, marine, automotive or other engineering fields.

Whilst the examples of the invention relate to polymer composites having a fibre substrate, typically comprising long or short glass or carbon fibres, the invention is not so limited and may encompass other composites. Other matrix materials than the resin/polymer materials described above may be used, such as silicon carbide (SiC) and ceramics. Although it is advantageous in some embodiments to use a pre-impregnated substrate, the invention can be performed on dry fibre substrates with a binder. The invention may encompass ceramic matrix composites or the like.

The invention may find particular benefit in allowing prototype product designs to be taken forward into production more quickly.