FORM 2
THE PATENTS ACT 1970
[39 OF 1970]
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
[See section 10 and rule 13]
“A METHOD FOR MANUFACTURING CYLINDRICAL PARTS AND A SYSTEM
THEREOF”
NAME AND ADDRESS OF THE APPLICANT:
RELIANCE INDUSTRIES LIMITED, having address at 3rd Floor, Maker Chamber-IV, 222,
Nariman Point, Mumbai – 400021, Maharashtra, India.
Nationality: INDIAN
The following specification particularly describes the invention and the manner in which it is to be performed.

TECHNICAL FIELD
Present disclosure generally relates to manufacturing. Particularly, but not exclusively, the present disclosure relates to manufacturing of composite enclosed parts. Further, embodiments of the disclosure disclose a method and a system for manufacturing reinforced polymer cylindrical parts using vacuum infusion technique.
BACKGROUND
Cylindrical parts find a wide range of industrial applications such as aircraft fuselages, casings, pipes, pressure vessels, storage tanks for storing fuels, chemicals, gaseous and liquidous components, and so on. Manufacturing composite material based cylindrical parts have been gaining increasing popularity these days owing to several inherent advantages such as high strength to weight ratio, flexibility with respect to orientation of base and reinforcing materials [fibers] based on desired mechanical/structural characteristics, and so on. The cylindrical parts such as pressure vessels, boilers, storage tanks, etc., also make use of dished ends which serve as closures for enclosing one or more openings. A dished part, also known as a dished head or tank head, acts as a pressure element which is intended to sustain large fluidic pressures.. Throughout the disclosure, the terms “dished part” and “dished end” may be used interchangeably. Apart from dished ends, the cylindrical parts also contain baffle plates as partitions to separate one section of the cylinder from the other. For a cylindrical part, both axial and circumferential properties are considered while performing thickness calculations. Axial properties are mainly required for assessment of axial strength and hoop/circumferential properties are required for assessment of hoop and flexural strength.
Fiber reinforced cylindrical parts are manufactured by various known manufacturing techniques of which filament winding process is an extensively deployed technique. Filament winding (FW) is a fabrication technique which can be employed for manufacturing both open and closed end cylindrical structures. Filament winding involves winding strands or filaments of fiber rovings under tension over a rotating mandrel. The filaments or fiber rovings, conventionally were immersed in a resin bath so that these filaments or rovings are impregnated with resin as they pass on towards the mandrel for getting wound. The process may be continuous or discontinuous. In a

discontinuous process, 2 axis machines are involved in laying fibre, fiberglass cloth or a veil in a continuous hoop pattern onto the rotating mandrel. Continuous process, on the other hand, use multi-axes machines which provide customizability with respect to the angle of lay-up. Dished ends and baffles plates, unlike the cylindrical parts, are conventionally manufactured using hand lamination process which involves saturation of reinforcement material made from glass, carbon, or aramid fibres with a cold-curing resin. Brushes or rollers are used for applying resin over the fibers. The reinforcement material (mats) is placed onto a mould along with a mould release agent, which are also accompanied by a first coat of resin layer. The material is built up layer by layer until the required thickness is reached which is followed by curing of the resin.
Conventionally, Filament winding process is automated where variables such as resin content, wind angle, tow or bandwidth of winding, thickness of the fiber bundle, speed of mandrel, curing time, etc., are all computer controlled without the need of human intervention. The roving feed is usually traversed in longitudinal directions to obtain a predetermined geometric pattern as well thickness. Due to impregnation of resin prior to winding, curing takes place once the winding is complete. The mandrel is then either removed or collapsed or sometimes even left within the cylindrical part depending on the requirement. Despite being preferred technique for fabricating fiber reinforced cylindrical parts, Filament winding technique or process faces a number of shortcomings. One of the shortcomings is the higher cycle time and therefore, reduced productivity. One reason for this is the impregnated resin may have longer curing time characteristics so that the curing starts only when all the layers of rovings or filaments are wound onto the mandrel to desired shape and size. Another limitation is that the Filament winding process may be accompanied with quality issues and improper surface finish. The FW process can be accompanied with sandwiching CSM/UD mat which is a manual process that can result in non-uniform tension and uneven overlap between two layers while winding. For instance, there could be formation of voids, air bubbles, pinholes, white lines, dislocations, patches and so on. Poor surface finish and internal defects may lead to rework which is undesired from resource allocation, capital and lead time perspectives. The internal defects may also lead to variation in thickness and mechanical properties. Another shortcoming is that the structural layer of the end product comprises both rovings as well as fabric to meet the directional properties. This necessitates the need for time-to-time human intervention, thereby restricting the possibility of fully automating

the Filament winding process. Hand lamination process employed in manufacturing dished ends also face similar shortcomings, where several quality related issues may be observed along with high cycle times required for manufacturing. Quality issues may be with respect to poor surface finish, non-uniform thickness, uneven mechanical properties, and so on. Hand lamination process could also turn out to be expensive since resin ratio is in the range of about 70% and resins available are very expensive.
The present disclosure is intended to overcome one or more above stated limitations.
SUMMARY
One or more shortcomings of the conventional manufacturing methods and systems are overcome, and additional advantages are provided through the present disclosure. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.
In one non-limiting embodiment of the present disclosure, a method for manufacturing a composite cylindrical part is disclosed. The method includes feeding, by one or more spools, veil of a first fabric towards a rotating mandrel, such that one or more layers of the first fabric are wound on the rotating mandrel to form a stack of base layer. The method then includes optionally laying at least one core layer on the base layer. Further, the method includes winding, by the rotating mandrel, one or more layers of a second fabric over the at least one core layer to form a stack of top layer, where the base layer, the at least one core layer and the top layer constitute a composite structure. The method then includes placing the composite structure in a vacuum infusion set up, and then, infusing resin under vacuum over the composite structure. Then, the method includes curing the infused resin to obtain the composite cylindrical part.
In an embodiment, the method includes adjusting at least one of pitch, width and thickness of the base layer and the top layer during the winding by linearly moving at least one of the mandrel and the one or more spools.

In an embodiment, the method includes winding the veil of the first fabric on the rotating mandrel at a preset angle relative to an axis of a first shaft of the rotating mandrel.
In an embodiment, the method includes infusing the resin under vacuum through a plurality of inlet ports and expending the resin from a plurality of outlet ports, the plurality of inlet and outlet ports being defined in the vacuum infusion set up.
In an embodiment, the method includes continuously rotating the mandrel until the resin reaches a gel point to prevent accumulation of the resin at one or more lower sections due to gravity.
In an embodiment, the method includes winding a plurality of fabric layers over the base layer and the top layer without sandwiching the at least one core layer between the base layer and the top layer.
In an embodiment, the method includes infusing the resin onto the base layer and subsequently curing the resin infused onto the base layer prior to laying the at least one core layer and/or the top layer.
In an embodiment, the method includes covering the composite structure with a peel ply and a knitted type of non-structural fabric, and then vacuum bagging the composite structure covered with the peel ply and the knitted type of non-structural fabric prior to infusing the resin under vacuum.
In an embodiment, the method includes channeling flow of the resin through the non-structural fabric to wet the composite structure from above, under vacuum. Further, the method includes closing the plurality of inlet and outlet ports when the composite structure is completely impregnated with the resin.
In an embodiment, the method includes forming a seam between free ends of the base layer, the top layer and/or the plurality of fabric layers after winding on the mandrel. Further, the seam is formed by a zip arrangement followed by reinforcing the seam by one or more adhesive tapes.
In an embodiment, the method includes regulating, by a control unit, at least one of speed of the mandrel, speed of the one or more spools, longitudinal position of the mandrel, longitudinal

position of the one or more spools, feed rate, and variables associated with the vacuum infusion process.
In an embodiment of the present disclosure, the method includes manufacturing composite dished parts and/or baffles with respect to a cylindrical shell part using the vacuum infusion process. The method involves placing one or more hemispherical or elliptical shell parts in a vacuum infusion set up, and then, infusing resin under vacuum over one or more longitudinal sections of the cylindrical shell parts to form the dished parts and baffles with the one or more longitudinal sections of the cylindrical shell part. Then, the method includes curing the infused resin to obtain the composite dished parts and/or baffles.
In an embodiment, the method includes defining cavities corresponding to one or more baffles at one or more longitudinal intersections of a plurality of cylindrical shell parts. The one or more cavities define a contour of each of concave and convex baffles of uniform thickness positioned at the one or more longitudinal intersections of a pair of cylindrical shell parts for performing the vacuum infusion of the resin. This is followed by infusing the resin under vacuum infusion technique to fill the cavities and joining spaces formed at the one or more longitudinal intersections, to form the one or more baffles adjoining the plurality of cylindrical shell parts.
In an embodiment, the method includes forming a dished end at an opening defined in the cylindrical shell parts. The dished end includes concave and convex dished end parts of uniform thickness that need to be formed at the opening of the cylindrical shell parts. The method involves infusing the resin under vacuum infusion technique to fill spaces corresponding to the concave and convex dished ends at the opening in the cylindrical shell parts.
In an embodiment, the method includes covering a stack of fibers with a peel ply and a knitted type of non-structural fabric, and then vacuum bagging the stack of fibers covered with the peel ply and the knitted type of non-structural fabric prior to infusing the resin under vacuum.
In an embodiment, the method includes curing the resin infused under vacuum during the vacuum infusion process.

In another non-limiting embodiment, a system for manufacturing a composite cylindrical part is disclosed. The system includes one or more spools, each adapted to feed a veil of fabric to a rotating mandrel. The rotating mandrel receives a first fabric layer from one or more spools to form a stack of a base layer. The mandrel is then adapted to optionally receive at least one core layer on the base layer. Further, the mandrel is adapted to receive one or more layers of a second fabric over the at least one core layer to form a stack, where the base layer and the top layer constitute a composite structure with the optional core layer sandwiched therebetween. The system also includes a vacuum infusion section where the composite structure is impregnated with resin infused under vacuum, followed by curing the resin to form the composite cylindrical part. Further, the system includes a control unit communicatively interfaced with actuators associated with each of the mandrel, the one or more spools, and the vacuum infusion set up.
In an embodiment, each actuator is configured to impart at least one of linear displacement and rotary motions to the mandrel and the one or more spools.
In an embodiment, the vacuum infusion section of the system includes a plurality of inlet ports and a plurality of outlet ports which assist in simultaneous infusion and expending of the resin. Further, each of the plurality of inlet ports and the outlet ports comprise a valve operatively associated with the control unit to selectively allow or restrict flow of the resin.
In an embodiment, the vacuum infusion section of the system includes a plurality of flow channels, each configured to channel flow of the resin through a non-structural fabric to wet the composite structure from above, under vacuum.
In an embodiment, the vacuum infusion section of the system includes one or more vacuum pumps, each configured to apply vacuum to the plurality of flow channels to aid infusion of the resin over the composite structure.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following description.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The novel features and characteristics of the disclosure are set forth in the appended description. The disclosure itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following description of an illustrative embodiment when read in conjunction with the accompanying drawings. One or more embodiments are now described, by way of example only, with reference to the accompanying drawings wherein like reference numerals represent like elements and in which:
FIG. 1 illustrates a schematic perspective view of a system for manufacturing a composite cylindrical part, in accordance with an embodiment of the present disclosure;
FIG. 2 illustrates a schematic front view of a mandrel and a spool of FIG. 1 employed for winding of a veil of fabric;
FIG. 3 illustrates a schematic sectional view of the mandrel taken along section S-S in FIG. 1;
FIGS. 4A and 4B illustrate schematic sectional front view and sectional side view respectively of the mandrel showing the laid up base layer, the at least one core layer and the top layer of the composite structure, according to some embodiments of the present disclosure;
FIG. 5 illustrates a flowchart depicting a method for manufacturing a composite cylindrical part, according to an embodiment of the present disclosure; and
FIGS. 6A and 6B illustrate schematic perspective views of the mandrel of FIG. 2 showing a seam formed by zip arrangement and one or more adhesive tapes, according to an embodiment of the present disclosure;
FIG. 7 illustrates a perspective view of a plurality of cylindrical sections whose openings are concealed by dished ends and longitudinal intersections are joined by baffle plates using vacuum infusion process, in accordance with an embodiment of the present disclosure; and
FIGS. 8 and 9 are sectional views showing an exemplary baffle and a dished end manufactured by vacuum infusion process, according to some embodiments of the disclosure.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the systems and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DESCRIPTION
While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.
It is to be noted that a person skilled in the art would be motivated from the present disclosure and modify configuration of the system of the present disclosure for the purpose of manufacturing a composite cylindrical part. However, such modification(s) should be construed within the scope of the instant disclosure. Accordingly, the drawings show only those specific details that are pertinent to understand the embodiments of the present disclosure so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
The terms “comprises”, “comprising”, “includes”, “including” or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a method or a system, that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such a method or a system. In other words, one or more elements in the method or the system preceded by “comprises… a” does not, without more constraints, preclude the existence of other elements or additional elements in the method or the system.
In the following description of the embodiments of the disclosure, reference is made to the accompanying figures that form a part hereof, and in which are shown, by way of illustration, specific embodiments in which the disclosure may be practiced. These embodiments are described

in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that, changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
FIGS. 1 and 2 illustrate an exemplary system (10) for manufacturing a composite cylindrical part, according to some embodiments of the present disclosure. FIG. 1 illustrates a perspective view while FIG. 2 illustrates a front view with some components omitted. The term “composite” herein above and throughout the specification refers to a combination of two or more materials having different properties, including but not limited to physical and chemical properties. The composite material discussed in accordance with embodiments of the present disclosure includes fiber reinforced composite materials such as fiber reinforced polymers (FRPs), although other forms may be employed. The system (10) is intended to produce a cylindrical part which finds applications in various sectors, such as but not limiting to aerospace, artilleries, oil and energy, chemical industries, power drives, and so on. The system (10) and the method disclosed in embodiments of the present disclosure may be extended to manufacturing of non-cylindrical [open or closed] sections such as airfoils, conical, ellipsoidal, spherical, and polygon shapes like hexagon, octagon, etc.
The system (10), as shown, includes a mandrel (11) or a rotary drum which may be rotated, for example, using a rotary actuator like an electric motor. Throughout the disclosure, the terms “mandrel” and “rotating mandrel” may be used interchangeably. The mandrel (11) may include one or more first shafts (13) at which rotary power may be applied. The first shaft (13) may be coupled to one or more rotary actuators [not shown] to receive drive power through any of the transmission units, such as, but not limiting to gear drives, belts, chains. The axis of rotation of the first shaft (13) and therefore, the mandrel (11) is represented by A-A. Further, the direction of rotation of the mandrel (11) is represented by numeral (MD) with arrow pointing towards the reader. The direction of rotation may also be reversed i.e., along (-MD) depending on the application. In an embodiment, the mandrel (11) may be manufactured by metallic materials such as steel, aluminium, etc., although other materials such as wood, polymers and so on. In another embodiment, the mandrel (11) may be hollow with closed ends. The system (10) further includes one or more spools (15), each adapted to feed a veil of base material such as fabric (14) towards

the rotating mandrel (11) under tension. In an embodiment, the fabric may be strands, fiber rovings or any other material having good tensile [stretchability] characteristics alongside other mechanical and structural properties. For example, the fiber rovings may be glass fiber rovings, carbon fiber rovings, aramid fiber rovings or any other class of fiber composites. In an embodiment, the veil of fabric (14) may have strands oriented in transverse directions say X and Y directions which are transverse to each other, so that the fabric appears as a mesh formed of horizontal and vertical fiber strands. In an embodiment, the spool (15) may be optionally coupled to a rotary actuator similar to the mandrel (11), the rotary actuator adapted to aid rotation of the spool (15) relative to the mandrel (11). The spool (15) may have a second shaft (16) which may receive drive power from the rotary actuator for rotation. Further, the one or more spools (15) may have these fabrics or fiber rovings or strands wound onto them in a large number of windings. Although a single spool (15) is shown, it should not be construed as a limitation, as any number of spools may be placed relative to the mandrel (11) in any desired orientation [normal, angular, etc.,] depending on the nature of composite structure required. For example, two different spools having veils of two different fabric materials may be wound simultaneously or in a predefined sequence on the mandrel (11) at different orientations, for example, +45 degrees and -45 degrees. The tension in the veil of fabric (14) relative to the spool (15) and the mandrel (11) may be set as to ensure proper winding on the mandrel (11). In an embodiment, at least one of the mandrel (11) and the spool (15), apart from rotating, may undergo linear translation [reciprocation] along the axis A-A and B-B respectively to ensure that the veil of fabric (14) is uniformly wound over length of the mandrel (11). This feature, alongside forming a stack of fabric layers one above the other though partial or full overlap, also facilitates winding of fabric veils at different orientations on the mandrel (11). For this purpose, separate rotary and linear actuators [not shown] may be coupled to the shafts, or an integrated rotary-linear actuator [not shown] may be employed.
In an embodiment as shown in FIG. 1, the rotary and linear actuators or the rotary-linear actuators may be operatively interfaced with a control unit (100) to control parameters, including but not limited to rotational speeds, relative positions of the mandrel (11) and the one or more spools (15), feed rate, and so on. The feed direction is depicted by numeral (FD) while the linear translation of the spool (15) and/or the mandrel is depicted by double headed arrow referenced by (LD). The direction of rotation of spool (15) is depicted by (SD) which according to this embodiment is same

as rotation direction (MD) of the mandrel (11). The wound-up fabric layer is depicted by numeral (12). In an embodiment, the spool (15) may feed a first fabric layer [depicted by numeral (12)] for winding over the mandrel (11) to form a stack of a base layer [better shown in FIG. 3 by numeral (12A) as well as in FIG. 4A, 4B by numeral (42)]. In an embodiment, the veil of fabric (14) [or fibers] is wound at an angle of 89 degrees to achieve circumferential/hoop properties, and may be provided with CSM/UD mat to attain desired axial strength. In another embodiment, an engineered fabric [material] comprising glass in both hoop and axial direction as per requirement may be used in addition to adjusting [monitoring] specific width, thickness, and pitch of winding during the process. This is crucial to build the desired thickness in one go during layup for the subsequent vacuum infusion process. This is also beneficial in eliminating most of the defects like voids, air bubbles, pinholes, white lines, dislocations, patches.
FIG. 3 illustrates a sectional view of the mandrel (11, 41) showing the first fabric layer (12A) laid up as base layer on the mandrel (11). FIG. 3 also illustrates a magnified view of two subsequent layers (12X) and (12Y) laid adjacent to each other in partially overlapping configuration. Reference is also made to FIGS. 4A and 4B with FIG. 3 which illustrate sectional front and side views of the mandrel (11) laid up with number of fabric layers. The mandrel (11, 41) as illustrated in FIGS. 1 and 2, after receiving and winding the base layer (12, 12A, 42) is adapted to optionally receive at least one core layer (43) on or over the base layer (12, 12A, 42). The at least one core layer (43) may be intended to reinforce the base layer (12, 12A, 42) and subsequent layers laid on top of the core layer (43), so that the core layer (43) may function as core of any composite part. In an embodiment, the core layer (43) may be vacuum infusion compatible, which will be explained later. Further, the core layer (43) may be selected from one or more materials which assist in increasing overall section thickness, thereby improving the section modulus and flexural modulus, alongside improving other mechanical properties. In an embodiment, the density of material used as the core layer (43) may be significantly lesser than the fabric base layer (12, 12A, 42) and the subsequent layers (44). This may be beneficial in attaining weight effectiveness i.e., strength to weight ratio compared to winding just the fabric layers.
Further, as shown in FIG. 4A and 4B, the core layer (43) may receive a further fabric layer i.e., a second fabric layer (44) which may form the top layer (44). The top layer (44) and the base layer (42) together with the sandwiched core layer (43) may constitute the composite structure, which

in embodiments of the present disclosure, may be a cylindrical [shell] part. The base layer (42) and the top layer (44) may be formed by winding the veil of fabric layer received from the one or more spools (15), while the core layer (43) may be laid or formed by any of the known techniques, such as a lay-up process. In an embodiment, the base layer (42) and the top layer (44) may have different compositions and may have different orientations of the fiber strands. In another embodiment, the base layer (42) and the top layer (44) may be wound at different angles, pitches [overlaps], widths, and for different thicknesses depending on the requirement. For instance, the base and top layers may have fibers oriented in opposite directions, say +45 degrees and -45 degrees. In yet another embodiment, the core layer (43) may be optional i.e., may or may not be sandwiched between the fabric layers so that a plurality of fabric stacks layers may be wound to form a stack which constitute composite structure. Once the fabric layers with or without the core layer (43) is formed, the mandrel (11, 41) may be placed in a vacuum infusion section/set-up where the composite structure may be impregnated with resin infused under vacuum. This may be followed by curing the resin to form the composite cylindrical part as the end product. In an embodiment as shown in FIG. 3, at least one of pitch (P), width (W) and thickness (T) of the base layer (42) and the top layer (44) may be adjusted during the winding by linearly moving at least one of the mandrel (11, 41) and the one or more spools (15). Adjusting the width (W) to desired width requirement ensures continuous winding over the mandrel (11, 41) without the need for any human intervention. Further, adjustment of pitch (P) is crucial to ensure desired directional properties of the composite structure and to minimize the wastage. Monitoring the pitch (P) is also essential for building desired thickness in one pass of fabric layer(s) winding. For instance, for the base layer (42), the first fabric layer is wound on the mandrel (11, 41) with a specific pitch (P) so that the thickness (T) may build in a single pass. Similarly, to the top layer (44), the second fabric layer is wound on the mandrel (11, 41) with a specific pitch (P) so that the thickness (T) may build in a single pass. In an embodiment, the first fabric layer and the second fabric layer may be same and may be fed by a single spool (15).
Now, reference is made to FIG. 5 which illustrates a flowchart outlining the method embodiment of the present disclosure. Reference is also made to FIGS. 1-4 outlined in the previous paragraphs. The second phase of manufacturing the cylindrical part i.e., vacuum infusion process is described herewith. Once the composite structure is formed as described above, the composite structure

having fibre stack with or without the core layer (43) is covered with peel ply [not shown] and a knitted type of non-structural fabric [not shown]. The composite structure covered with peel ply and the non-structural fabric is then vacuum bagged. Once this is done, vacuum may be applied until desired vacuum pressure is achieved and maintained. This may be followed by allowing the resin to flow towards the covered composite structure. The resin distribution over the covered composite structure may be aided by channeling the resin flow through a plurality of channels defined in the vacuum infusion set-up. The incoming resin percolates or penetrates through the non-structural fabric, and thereby wets the composite structure from all the directions. In an embodiment, the vacuum infusion may be accompanied with infusing the resin under vacuum through a plurality of inlet ports [not shown], and expending the resin from a plurality of outlet ports [not shown], with the plurality of inlet and outlet ports being defined in the vacuum infusion set up. Once the composite structure is completely impregnated with resin, both the inlet and outlet ports may be closed to facilitate curing of the resin under vacuum conditions. In an embodiment, resin infusion may take place in different phases. For instance, the vacuum infusion may include infusing the resin onto the base layer (42), and immediately curing the resin infused onto the base layer (42) prior to laying the at least one core layer (43) and/or the top layer (44). Once the resin impregnated base layer (42) is cured, the core layer (43) may be optionally placed, which may be followed by laying/winding the top layer (44) thereon, which again will be infused and cured with resin. In an embodiment, the mandrel (11, 41) may be continuously rotated until the resin reaches a gel point [partially cured state] to prevent accumulation of the resin [by dripping] at one or more lower sections of the vacuum infusion set up under the influence of gravity. Once the curing is complete, the mandrel (11, 41) may either be separated or allowed to remain inside the composite structure depending on the requirement. The steps described above are illustrated in the flowchart shown in FIG. 5. In an embodiment, each of the plurality of inlet ports and the outlet ports comprise a valve [not shown] operatively associated with the control unit (100) to selectively allow or restrict flow of the resin. Further, the vacuum infusion section of the system (10) may include one or more vacuum pumps [not shown], each configured to apply vacuum to the plurality of flow channels in the set-up to aid infusion of the resin over the composite structure.
FIGS. 6A and 6B illustrate schematic perspective views of the mandrel (61) showing a seam (65) formed by zip arrangement (63) and one or more adhesive tapes (64A, 64B). The seam (65) may

be established between free ends of the base layer (42), the top layer (44) and/or the plurality of fabric layers after winding on the mandrel (61). The seam (65) may be formed by the zip arrangement (63) followed by reinforcing the seam (65) by one or more adhesive tapes (64A, 64B) as shown. Once the seam (65) is formed, the composite structure (62) together with the mandrel (61) may be placed in the vacuum infusion set-up for resin infusion and curing. In an embodiment, the seam (65) may be reinforced by any other joining means. In an embodiment, the fabric material is glass fabric mat CSM.
The system (10) and the method of the present disclosure may have several advantages. The same are elucidated below along with statistical data. One advantage is the consistency in mechanical properties of the manufactured cylindrical part due to better control over the process. Table 1 below shows flexural modulus of the cylindrical part manufactured by the system (10) and the method of the present disclosure, as compared to conventional Filament Winding.

Method of Present disclosure Coefficient of Variance 4.4

Range/Mean 26.4%
Conventional Filament Winding Coefficient of Variance 6

Range/Mean 36.2%
Table 1
As coefficient of variance and ratio of Range to mean is less in method and system of present disclosure compared to conventional filament winding, which shows the method, and the system of the present disclosure is more consistent.
Another advantage is reduction in thickness and weight of the composite cylindrical part. For example, in a sample case of 2500mm diameter, 41% of material saving may be achieved by the method and the system of the present disclosure when compared to the conventional filament winding technique. Yet another advantage is consistent thickness of the composite cylindrical part with enhanced surface finish and negligible internal defects. A still another advantage is that the reduction in cycle time for manufacturing since only one type of fabric may be used, and also due to continuous winding of fabric over mandrel which leads to building of thickness in a single pass.

Further advantages include reduced manpower and human intervention, ease of handling and assembly.
In an embodiment of the disclosure, the method of the present disclosure involves manufacturing composite dished-ends and baffles by vacuum infusion process. Baffles and dished ends used in cylindrical shell parts are conventionally manufactured using hand lay-up process which has some drawbacks associated with the quality, properties, and surface finish. These drawbacks may be addressed by forming the dished ends and baffles by vacuum infusion process in the vacuum infusion process described in the above paragraphs. The vacuum infusion process may be performed with or without sandwiching core material like in the case of composite cylindrical part described above. The vacuum infusion process may be performed in a single vacuum infusion facility where the composite cylindrical parts are initially produced using the process described with reference to FIGS. 1-6 above. Once cylindrical parts are cured, it may be subjected to a further vacuum infusion for forming the dished ends and baffles.
The method steps involved in manufacturing composite dished ends and baffles with respect to the cylindrical shell part using vacuum infusion involves placing one or more cylindrical shell parts in a vacuum infusion set up. This may be followed by infusing resin under vacuum over one or more longitudinal sections of the cylindrical shell parts to form the dished parts and baffles with the one or more longitudinal sections of the cylindrical shell part. Then, the method includes curing the infused resin to obtain the composite dished parts and/or baffles.
With respect to forming composite baffles, the method includes defining cavities (C) corresponding to one or more baffles at one or more longitudinal intersections of a plurality of cylindrical shell parts. The one or more cavities (C) define a contour of each of concave and convex baffles of uniform thickness positioned at the one or more longitudinal intersections of a pair of cylindrical shell parts for performing the vacuum infusion of the resin. This is followed by infusing the resin under vacuum infusion technique to fill the cavities (C) and joining spaces formed at the one or more longitudinal intersections, to form the one or more baffles adjoining the plurality of cylindrical shell parts. In an embodiment, the baffles may adjoin partitions that separate the cylindrical shell parts into a plurality of cylindrical sections.

Similarly, for the dished ends, the vacuum infusion step includes forming a dished end at an opening defined in the cylindrical shell parts. The dished end includes concave and convex dished end parts of uniform thickness that need to be formed at the opening of the cylindrical shell parts. The method involves infusing the resin under vacuum infusion technique to fill spaces corresponding to the concave and convex dished ends at the opening in the cylindrical shell parts.
The vacuum infusion steps detailed above may include laying up fabrics as a dry stack of materials relative to the longitudinal sections of the cylindrical shell parts so as to define cavities (C) and channels. The fibre stack is then covered with peel ply and a knitted type of non-structural fabric. The whole dry stack is then vacuum bagged and check for leakages through the bag is made. Once bag leaks have been eliminated, resin is allowed to flow into the laminate i.e., dry stack of fabric. The resin distribution over the whole laminate is aided by resin flowing easily through the non-structural fabric and wetting the fabric out from above. Measures are taken to ensure that the baffles and dished ends have constant thickness throughout their respective longitudinal dimensions. The part i.e., baffles or dished ends is then left under vacuum to cure as per resin curing cycle. Once the part is completely cured, part is de-molded and post processed.
The stack of fibers which form the dry stack may or may not have the core material sandwiched therebetween. In an embodiment, the core material may be selected from one or more vacuum infusion compatible materials so that quality of composite part may be improved. In another embodiment, like the setup of composite cylindrical part described above, the vacuum infusion setup for manufacturing dished-ends and baffles also include multiple inlet and outlet parts for simultaneous resin infusion and removal. In an embodiment, the design i.e., shape, size and structure of the dished-end and baffles may be flexible to make the dished-ends and baffles compatible with the composite cylindrical parts discussed previously. In an embodiment, composite baffles and dished ends may be manufactured using GFRP, CFRP or hybrid materials. FIG. 7 shows a perspective view of an exemplary cylindrical shell part (70) having dished ends (72) and baffles defining the partition (74). FIGS. 8 and 9 show the cross-sections of baffles (71) and the dished ends (72) respectively, having uniform thickness (T) throughout the length, manufactured using vacuum infusion technique.

Table 2 shown below depicts comparison of statistical properties of the vacuum infusion process and the conventional hand lamination process, both being employed to manufacture dished-ends and/or baffles.

Method of Present disclosure Coefficient of Variance 4.82

Range/Mean 14%
Conventional Hand lamination Coefficient of Variance 6.93

Range/Mean 19%
Table 1
As coefficient of variance and ratio of Range to mean is lesser in method and system of present disclosure compared to conventional hand lamination process, the vacuum infusion method and the system of the present disclosure is more consistent compared to conventional hand lamination process.
The method and the system employed in manufacturing composite dished ends and baffles may provide several benefits. One advantage is that design (Shape, Size, thickness) of the dished end / baffles may be modified to eliminate all processing constraints of vacuum infusion process, and therefore, to minimize production complexity as well as the cycle time. Another advantage is that the thickness as well as layup sequence for the part may be optimized to achieve maximum mechanical performance at minimum weight. Apart from these, other advantages like improved surface finish and consistency in mechanical properties may be attained due to better control over the vacuum infusion process. Other advantages like reduced lead time, reduced manpower, ease of handling/assembly may also be realized.
EQUIVALENTS
With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting.
Reference numerals:

Part Numeral
System 10
Mandrel 11, 41, 61
Wound up layer 12
First shaft 13
Veil of fabric 14
Spool 15
Second shaft 16
Base layer 12, 12A, 12X, 12Y, 42, 62
Core layer 43
Top layer 44
Zip arrangement 63
Adhesive tapes 64A, 64B
Seam 65
Cylindrical shell part 70
Baffles 71
Dished ends 72
Uniform thickness T
Cavities/channels C
A-A Mandrel axis
B-B Spool axis
Feed direction FD
Linear translation direction LD

Mandrel rotation direction MD
Spool rotation direction SD
Section S-S
Pitch P
Width W
Thickness T
Control unit 100

WE CLAIM:
1. A method for manufacturing a composite cylindrical part, the method comprising:
forming at least one base layer (12, 12A, 12X, 12Y, 42, 62) by winding veil and one or more layers of a first fabric (12A) received from one or more spools (15) over a rotating mandrel (11, 41, 61);
forming at least one top layer (44) over the base layer (12, 12A, 12X, 12Y, 42, 62) by winding one or more layers of a second fabric received from the one or more spool (15) over the rotating mandrel (11, 41, 61),
forming of at least one core layer (43) over the base layer (12, 12A, 12X, 12Y, 42, 62) by winding at least one material received from the one or more spools (15) over the rotating mandrel (11, 41, 61),
wherein, the at least one base layer (12, 12A, 12X, 12Y, 42, 62), the at least one core layer (43) and the at least one top layer (44) form a composite structure;
infusing resin over the composite structure in a vacuum infusion setup; and
curing the infused resin over the composite structure to obtain the composite cylindrical part.
2. The method as claimed in claim 1, wherein the method comprises adjusting at least one of pitch (P), width (W), and thickness (T) of the base layer (12, 12A, 12X, 12Y, 42, 62) and the top layer (44) through linear movement of the at least one of the rotating mandrel (11, 41, 61), and one or more spools (15).
3. The method as claimed in claim 1, wherein winding the veil of the first fabric on the rotating mandrel (11, 41, 61) happens at a preset angle relative to an axis (A-A) of a first shaft (13) of the rotating mandrel (11, 41, 61).
4. The method as claimed in claim 1, wherein vacuum infusion setup comprises a plurality of inlet ports and outlet ports and the infusion of the resin is facilitated through the plurality of inlet ports and expansion of the resin is facilitated through the plurality of outlet ports.
5. The method as claimed in claim 1, wherein the method comprises continuous rotation of the mandrel (11, 41, 61) till the resin reaches a gel point.

6. The method as claimed in claim 1 comprises forming at least one core layer (43) over the base layer (12, 12A, 12X, 12Y, 42, 62) by winding at least one material received from the at least one spool (15) over the rotating mandrel (11, 41, 61).
7. The method as claimed in claim 1 comprises winding a plurality of fabric layers over the base layer (12, 12A, 12X, 12Y, 42, 62) and the top layer (44) without winding of the at least one core layer (43).
8. The method as claimed in claim 1, wherein the infusion and the curing of the resin on the base layer (12, 12A, 12X, 12Y, 42, 62) happens prior to laying of the at least one core layer (43) and the top layer (44).
9. The method as claimed in claim 1 comprises covering the composite structure with a peel
ply and a knitted type of non-structural fabric, and then vacuum bagging the composite
structure covered with the peel ply and the knitted type of non-structural fabric prior to the
infusion of the resin.
10. The method as claimed in claim 1 comprises channeling flow of the resin through the non-structural fabric to wet the composite structure from above, under the vacuum.
11. The method as claimed in claim 10 comprises closing of the plurality of inlet ports and outlet ports being facilitated when the composite structure is completely impregnated with the resin.
12. The method as claimed in claim 1 comprises forming a seam (65) between free ends of the base layer (12, 12A, 12X, 12Y, 42, 62), the top layer (44) and the plurality of fabric layers after winding on the mandrel (11, 41, 61).
13. The method as claimed in claim 12, wherein the seam (65) is formed by a zip arrangement (63) followed by reinforcing the seam by one or more adhesive tapes (64A, 64B).
14. The method as claimed in claim 1 comprises regulating by a control unit, at least one of speed of the mandrel (11, 41, 61), speed of the one or more spools (15), longitudinal

position of the mandrel (11, 41, 61), longitudinal position of the one or more spools (15), feed rate, and variables associated with the vacuum infusion process.
15. The method as claimed in claim 1 comprises manufacturing composite dished parts (72)
and baffles (71) with respect to a cylindrical shell part (70) using the vacuum infusion
process, the manufacturing of composite dished parts (72) and baffles (71) comprises:
placing one or more hemispherical or ellipsoidal shell parts (70) in a vacuum infusion setup;
infusing the resin under vacuum over one or more longitudinal sections of the cylindrical shell part (70) to form the dished parts (72) and the baffles (71); and
curing the infused resin to obtain the composite dished parts (72) and the baffles (71).
16. The method as claimed in claim 15 comprises defining cavities (C) corresponding to one or more baffles at the one or more longitudinal intersections of the plurality of cylindrical shell parts (70).
17. The method as claimed in claim 16, wherein the cavities (C) being filled by infusion of the resin under the vacuum infusion process and joining spaces being formed at the one or more longitudinal intersections, to form the one or more baffles (71) adjoining the plurality of cylindrical shell parts (70).
18. The method as claimed in claim 15 comprises forming a dished end (72) at an opening defined in the cylindrical shell parts (70).
19. The method as claimed in claim 18, wherein the dished end (72) comprises concave and convex dished end parts (72) configured to be formed at opening of the cylindrical shell parts (70).
20. The method as claimed in claim 19, wherein spaces corresponding to the concave and convex dished ends (72) at the opening in the cylindrical shell parts (70) being filled with the infusion of the resin under the vacuum infusion setup.

21. The method as claimed in claim 15 comprises covering a stack of fibers with a peel ply and a knitted type of non-structural fabric, and then vacuum bagging the stack of fibers covered with the peel ply and the knitted type of non-structural fabric prior to infusing the resin under vacuum.
22. A system for manufacturing a composite cylindrical part comprising:
one or more spools (15) adaptable to feed a veil of fabric (14) to a rotating mandrel (11, 41, 61), the rotating mandrel (11, 41, 61) is configured to receive a first fabric layer (12A) from one or more spools (15) to form a stack of a base layer (12, 12A, 12X, 12Y, 42, 62), the rotating mandrel (11, 41, 61) receives one or more layers of a second fabric over an at least one core layer to form a stack of top layer (44), wherein the base layer (12, 12A, 12X, 12Y, 42, 62) and the top layer (44) constitute a composite structure with an optional at least one core layer (43) positioned therebetween;
vacuum infusion section configured to impregnate the composite structure with the infusion of resin under vacuum; and
a control unit communicatively interfaced with actuators associated with each of the rotating mandrel (11, 41, 61), one or more spools (15), and the vacuum infusion setup.
23. The system as claimed in claim 22, wherein each actuator being configured to impart at least one of linear displacement and rotary motions to the mandrel (11, 41, 61) and the one or more spools (15).
24. The system as claimed in claim 22 comprises a plurality of inlet ports and a plurality of outlet ports, wherein each of the plurality of inlet ports and the outlet ports comprise a valve operatively associated with the control unit to selectively allow or restrict flow of the resin.
25. The system as claimed in claim 22, wherein the vacuum infusion section comprises a plurality of flow channels, each configured to channel flow of the resin through a non-structural fabric to wet the composite structure from above, under vacuum.
26. The system as claimed in claim 22, wherein the vacuum infusion section comprises one or more vacuum pumps, each configured to apply vacuum to the plurality of flow channels.