Abstract:
A method and apparatus for manufacturing composite articles such as laminate ballistic protection and structural reinforcements. The method involves placing a composite assembly in a sealable membrane system, e.g. a vacuum bag and placing the vacuum bag in a pressure vessel to apply heat and pressure to the composite assembly, thereby manufacturing a composite article. The apparatus comprises: a pressure vessel; a source of processing liquid to apply isostatic pressure to the vacuum bag; processing liquid heating, cooling, pressurising and circulating means; and a control system to control the heating, cooling and pressurising means. The sealable membrane system may preferably comprise: a sealable membrane to separate the composite article from the processing liquid and maintain the composite article below atmospheric pressure; and a membrane to cushion the composite article and resist adhesion of the article to other membranes. The processing liquid is preferably silicone oil.

Description:
[0001]    The present invention relates to the manufacturing process of composite articles. The composite articles are constructed from a multilayer stack of materials that are consolidated through the application of concurrent pressure and thermal cycling. The composite articles may provide ballistic protection and or structural reinforcement, with the multilayer stack including, but not limited to, monolithic ceramics, adhesive membranes and monolayers containing reinforcing fibres and matrix material. 
       BACKGROUND OF THE INVENTION 
       [0002]    Articles resilient to projectiles, commonly referred to as armour, are constructed from specialised materials using various methods to impede perforation by projectiles such as bullets and fragments. 
         [0003]    Articles of ballistic personal protective equipment (PPE), commonly referred to as body armour, include helmets and vests that contain ‘soft’ flexible armour inserts and ‘hard’ rigid armour inserts: Armour is also used to protect occupants and equipment in land, sea and air vehicles. 
         [0004]    Rigid armour inserts, known as Small Arms Protective Inserts (SAPIs), are engineered to protect against high-velocity rifle projectiles and share similarities in materials used and construction techniques with helmets and vehicle armour. Whilst SAPIs are available in many levels of protection, two basic configurations exist. 
         [0005]    The first is a 100% fibre based composite SAPI designed to protect against ‘soft’ lead filled Full Metal Jacket (FMJ) projectiles (an example of this is USA NIJ 0101.04 level III—6 strikes of 7.62×51 mm NATO FMJ). The second is a layered SAPI containing a ceramic strike-face to protect against Armour Piercing (AP) projectiles that contain ‘hard’ penetrators (an example of this is USA NIJ 0101.04 level IV—1 strike of 30.06 M2 AP). 
         [0006]    100% fibre based composite SAPIs can be manufactured from material such as para-aramid (for example Kevlar® or Twaron®) or ultra high molecular weight polyethylene (UHMWPE) when combined with a suitable resin matrix system. Materials are commercially available pre-impregnated (often referred to as ‘pre-preg’) with resin matrix (such as Dyneema® HB products and Spectra Shield®) to simplify this stage. 
         [0007]    A traditional 100% fibre based composite SAPI manufacturing technique is commonly referred to as ‘high-pressure axial pressing’ requiring ‘pre-preg’ material, such as Dyneema® HB product, to be cut into the desired shape and stacked. The stack is then positioned between a matching pair of metallic dies attached within the axial press and compressed concurrently with the application of heat (from electric heating elements or the circulation of hot oil through the metallic dies) to comply with predetermined pressure and thermal cycles. Compression is halted only once the material has cooled sufficiently. If desired, the SAPI is covered using a fabric, adhered with contact adhesive. 
         [0008]    It is known that for this type of armour, consolidation under higher pressure equates to higher ballistic performance. DSM, manufacturers of Dyneema® HB products, specify that their material must be consolidated with an axial pressure of at least 180 bar, but preferably 350 bar for a performance increase of approximately 10%. This means that to make a single 10″×12″ SAPI, at least a 140 ton press, but preferably a 270 ton press is required. Thus, if a square meter of armour is required, a 3,570 ton press is needed to consolidate the material at 350 bar. Such presses are expensive and uncommon. Since presses exert pressure in an axial manner, consolidating articles shaped other than flat generate pressure gradients and inconsistent levels of consolidation. Flatter shapes minimise this effect, however items like helmets suffer greatly from uneven consolidation. 
         [0009]    Air entrapment within axially pressed SAPIs is an issue. It is common to require between 50-200 ‘pre-preg’ plies to manufacture a SAPI that meets USA NIJ 0101.04 level III standard. When the ‘pre-preg’ is stacked and pressed, air is trapped between the layers and compressed, only to appear as bubbles that indicate areas of delamination when removed from the press. To counter this, pressure must be ramped up incrementally, however this is not ideal and extends cycle time. 
         [0010]    A major cost associated with conventionally pressing SAPIs is tooling. Rigid metallic matched die sets are required for all geometries to be manufactured. If a press is large enough to process multiple SAPIs, then multiple tooling sets are required. In addition to the die sets, cooling and heating platens are also required. The production speed for this type of SAPI is slow, since the material has to reach a consistent temperature throughout but not have localised ‘hot spots’ that would permanently damage the material. A typical cycle time is approximately 45 minutes per USA NIJ 0101.04 level III standard SAPI. 
         [0011]    A traditional method of manufacturing a layered SAPI containing a ceramic strike-face is to bond a monolithic ceramic tile to the front face of an axially pressed 100% fibre based composite. ‘backing’. A resin or elastomeric compound is usually used as the adhesive material and the assembly is clamped whilst curing in an evacuated bag. The evacuated bag provides an even clamping force of near atmospheric pressure. If desired, the layered SAPI is covered using a fabric, adhered with contact adhesive. 
         [0012]    This type of layered SAPI is time consuming to manufacture and can suffer significant through-thickness inconsistency. Typically all kiln fired ceramics exhibit warping, in some circumstances by more than 3 mm. Since the 100% fibre based composite ‘backing’ is shaped by precision machined dies and flexes minimally, the discrepancy in geometry between the ceramic tile and the ‘backing’ is filled by excess bonding adhesive. This adds weight and reduces ballistic performance. 
         [0013]    Another traditional method of manufacturing a layered SAPI is a batch-type process that employs an autoclave. Industrial autoclaves are pressure vessels used to process parts and materials which require exposure to elevated pressure and temperature. Typically a stack of ‘pre-preg’ material is placed behind a ceramic tile with an intervening layer of adhesive film or composite. The assembly is then wrapped with a plastic release film and placed in a heat sealable vacuum bag. The bag is then evacuated and sealed. This process overcomes the air entrapment issues encountered during axial pressing and clamps the assembly together to allow handling without any alignment shift. The filled vacuum bags are loaded within an autoclave, which is pressurised, typically 6 to 20 bars, using air or an inert gas and heated to comply with predetermined pressure and thermal cycles. Following sufficient time at elevated temperature, the autoclave is cooled whilst maintaining pressure. Pressure is released when the temperature has reduced adequately. If desired, the layered SAPI is covered using a fabric, adhered with contact adhesive. 
         [0014]    The major deficiency of this procedure is low composite consolidation pressure. Autoclaves are pneumatic (gas filled) rather than hydraulic (liquid filled) devices, and are subjected to stringent safety regulations. The typical working pressures that autoclaves use generally range from 6-20 bar, which is well below the minimal (180 bar) and desired (350 bar) consolidation pressures suggested by DSM, manufacturers of Dyneema® HB products. To compensate for this low-pressure consolidation, extra composite is used to achieve ballistic performance; however this increases cost, weight and thickness. 
       OBJECT OF THE INVENTION 
       [0015]    It is an object of the present invention to overcome, or at least substantially ameliorate, the disadvantages and shortcomings of the prior art. 
         [0016]    A further object of the invention is to decrease production time of composite articles. 
         [0017]    A further object of the invention is to increase composite article efficacy through enhanced ballistic performance and/or reduced weight. 
       SUMMARY OF THE INVENTION 
       [0018]    According to the embodiments of the present invention, although this should not be seen as limiting the invention in any way, there is provided a programmable system and/or methods of exercising pressure and thermal cycling for the purpose of composite article consolidation, the system (apparatus) including:
       a processing fluid contained within a closed processing liquid filled circuit;   a composite article processing volume having:
           an opening to facilitate loading and unloading;   processing liquid circulation processing porting to allow the inward and outward passage of processing fluid within the closed processing liquid filled circuit.   
           a processing fluid pressurisation system having means to increase or decrease pressure within the closed processing fluid filled circuit;   an external processing fluid circulation system fluidly connected to the closed processing liquid filled circuit;   an external processing fluid heating system fluidly connected to the closed processing liquid filled circuit;   an external processing fluid cooling system fluidly connected to the closed processing liquid filled circuit;   a process control system including:
           means to control the processing fluid heating system and the processing fluid cooling system;   means to control the processing fluid pressurisation system;   
           a composite article preparation system including:
           a sealable membrane to separate the composite article and the processing fluid;   a sealable membrane to maintain the composite article in a pressure below atmospheric pressure prior to the application of external processing fluid pressure;   a membrane to cushion the composite article;   a membrane to resist adhesion of other membranes to the external surface of the composite article;   
               
 
         [0035]    In preference, the processing fluid circulation system includes a circulation device to circulate processing fluid at elevated pressure. 
         [0036]    In preference, the processing fluid heater system includes a heating device to heat the processing fluid. 
         [0037]    In preference, the processing fluid cooling system includes a cooling device to cool the processing fluid. 
         [0038]    In preference, the processing fluid is silicone oil. 
         [0039]    In preference, the composite article processing volume is a metallic structure. 
         [0040]    In preference, the composite article processing volume is cylindrical with an opening at one end. 
         [0041]    In preference, the processing fluid pressurisation system utilizes hydraulic-over-hydraulic or air-over-hydraulic pumping technology. 
         [0042]    In preference, the processing fluid circulation system utilizes hydraulic-over-hydraulic or air-over-hydraulic pumping technology. 
         [0043]    In preference, the processing fluid heater system uses electric resistive elements shielded from high pressure by metallic tubing. 
         [0044]    In preference, the processing fluid cooling system is an assembly largely of finned metallic tubing. 
         [0045]    In preference, the fluid is a liquid. 
         [0046]    In preference, the sealable membrane that isolates the composite article from processing fluid is the sealable membrane that maintains the composite article in a pressure below atmospheric prior to the application of external processing fluid pressure; and is a heat-sealable plastic bag. 
         [0047]    In preference, the membrane that cushions the composite article is the membrane that opposes unwanted adhesion to the composite article, and is silicone sheeting or polytetrafluoroethylene coated material. 
         [0048]    The present invention can also be used to consolidate finished or green-body composite articles from mixtures or slurries. Finished articles are bound by a matrix that acts to bond reinforcements such as particles, fibres and nanotubes following pressure and thermal cycling. Green-body composites are bound by a matrix following pressure and thermal cycling with sufficient strength to allow additional processing such as high-temperature sintering. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0049]    The accompanying drawings, which are incorporated into and constitute part of this specification, illustrate one or more embodiments and, together with the description of the invention, serve to explain the principles and implementations of the invention. In the drawings: 
           [0050]      FIG. 1 . illustrates a basic block diagram for the inventive composite article manufacturing system. 
           [0051]      FIG. 2 . illustrates a composition of raw materials assembled to manufacture a Small Arms Protective Insert (SAPI). 
           [0052]      FIG. 3 . illustrates a composition of raw materials prepared to manufacture a Small Arms Protective Insert (SAPI). 
           [0053]      FIG. 4 . illustrates a composite article processing volume. 
           [0054]      FIG. 5 . illustrates a processing liquid heating system. 
           [0055]      FIG. 6 . illustrates a processing liquid cooling system. 
           [0056]      FIG. 7 . illustrates a processing liquid pressurisation system. 
           [0057]      FIG. 8 . illustrates a processing liquid circulation system. 
           [0058]      FIG. 9 . illustrates a process control system. 
           [0059]      FIG. 10 . illustrates a typical predetermined pressure cycle. 
           [0060]      FIG. 11 . illustrates a typical predetermined thermal cycle. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0061]    Embodiments are described herein in the context of a process for the manufacture of composite articles. Those of ordinary skill in the art will realise that the following detailed description is illustrative only and is not intended to be in any way limiting. Other embodiments of the present invention will readily suggest themselves to such skilled persons having the benefit of this disclosure. Reference will now be made in detail to implementations of embodiments of the present invention as illustrated in the accompanying drawings. The same reference indicators will be used throughout the drawings and the following detailed description to refer to the same or like parts. 
       General Description of the Inventive System and Process 
       [0062]      FIG. 1  illustrates a basic block diagram for the inventive composite article manufacturing system, generally numbered  100 , including a composite article processing volume  101 , a processing liquid storage tank  102 , a processing liquid transfer pump system  103 , a processing liquid pressurisation system  104 , a processing liquid circulation system  105 , a processing liquid heating system  106 , a processing liquid cooling system  107 , a processing liquid  108  and a process control system  109 . 
         [0063]    To manufacture a Small Arms Protective Insert (SAPI), a composition of raw materials is assembled as illustrated in  FIG. 2 , generically numbered  200 . The assembly of raw materials  200  could typically contain, but is not limited to, a monolithic ceramic tile  201 , one or more layers of resin pre-impregnated (pre-preg) fibres  202  positioned forward of the monolithic ceramic tile  201 , one or more layers of pre-preg fibres or an adhesive film  203  positioned behind on the ceramic  201  and in front of a substantial stack of backing layers of pre-preg fibres  204 . The layers of materials are rigidly connected temporarily with adhesive tape  205  or hot-melt adhesive. Surrounding the connected stack of materials is a membrane of stretched, coloured, porous covering fabric  206 . Surrounding the covering fabric  206  is a layer of sealing membrane  207 . 
         [0064]    Within a SAPI the hard, frangible monolithic ceramic tile  201  functions to fragment and erode projectiles upon impact. Typical ceramic materials include Silicone Carbide, Boron Carbide and Aluminium Oxide. The one or more layers of pre-preg fibres  202  positioned forward on the ceramic function as a spall-face to support and retain the monolithic ceramic tile  201  during and after projectile impact. Typical spall-face materials include epoxy or phenolic resin reinforced para-aramid or glass fibres. 
         [0065]    The one or more layers of pre-preg fibres  203 , referred to as a stiffening membrane, or an adhesive film  203  positioned behind the monolithic ceramic tile  201 , function to thoroughly bond the substantial stack of backing  204  to the monolithic ceramic tile  201 . Typical thin film adhesives include polyurethanes and polyolefins, and typical stiffening membranes include epoxy or phenolic resin reinforced para-aramid, glass or carbon fibres. 
         [0066]    The membrane of stretched, coloured, porous covering fabric  206  functions as a SAPI covering. It can be applied by stretching, clamping and heat-fusing front and rear membranes around the circumference of the SAPI. Stretching the covering  206  during application minimises weight and ensures geometric conformity. Typical materials for the covering  206  include fabrics comprised of nylon (90%) and elastane (10%). The layer of adhesive film  207  functions to bond and seal the covering fabric  206  to the layers of materials temporarily rigidly connected with adhesive tape  205 . The sealing membrane  207  is selected to be compatible with the specific concurrent pressure and thermal cycling of the process and to provide the desired environmental protection to the SAPI. Typical sealing membranes include polyurethanes and polyolefins. 
         [0067]    Prior to processing a SAPI the assembly of raw materials  200  is prepared as illustrated in  FIG. 3 . The assembly of raw materials  200  is placed within a plastic bag  302  that is lined with a silicone membrane  301 . The silicone membrane  301  functions to cushion and protect the plastic bag  302  from the assembly of raw materials  200  and oppose adhesion of the layer of adhesive film  207  to the plastic bag  302 . The plastic bag  302  is then placed within a vacuum chamber  304  that contains heat-sealing bars  303 . The chamber  304  is evacuated and after a period of time the plastic bag  302  is sealed by the heat-sealing bars  303 . 
         [0068]    The chamber  304  is then equalised to atmospheric pressure and the sealed plastic bag  302  removed. This method of preparing the assembly of raw materials  200  for processing removes atmosphere from within the plastic bag  302  and allows assembly of raw materials  200  without compression of the outer surfaces of the plastic bag  302  that limits the efficiency of atmosphere removal. The removal of atmosphere from within the plastic bag  302  is essential to achieve effective consolidation during processing. The plastic bag  302  is sealed to isolate the assembly of raw materials  200  from processing liquid  108  and maintains the removal of atmosphere from within the plastic bag  302 . 
         [0069]    Processing a SAPI occurs in the inventive composite article manufacturing system, generally numbered  100 . The closed plastic bag  302  is positioned within the processing volume  101  that is subsequently sealed. Processing liquid  108  is transferred from the processing liquid storage tank  102  by the processing liquid transfer pump system  103  to fill the composite article processing volume  101 , processing liquid heating system  106 , processing liquid cooling system  107 , processing liquid pressurisation system  104 , processing liquid circulation system  105  and all associated piping. 
         [0070]    The processing liquid storage tank  102  and processing liquid transfer pump system  103  are then isolated allowing the processing liquid pressurisation system  104 , controlled by the process control system  109 , to increase processing liquid  108  ambient pressure, typically to 100 bar. The processing liquid circulation system  105  is then activated to circulate the pressurised processing liquid  108  through the composite article processing volume  101  and processing liquid heating system  106 . The processing liquid heating system  106  is then activated and controlled by the process control system  109  to attain and maintain a desired processing liquid  108  temperature, typically 125° C. The processing liquid pressurisation system  104  accounts for thermal expansion of the processing liquid  108 . Following thermal heating and dwell periods, the process control system  109  switches processing liquid  108  circulation to include the processing liquid cooling system  107  and exclude the processing liquid heating system  106 . 
         [0071]    The processing liquid pressurisation system  104  accounts for thermal contraction of the processing liquid  108 . The process control system  109  stops the processing liquid circulation system  105  when processing liquid  108  has reduced to a desired temperature, typically 45° C., and then controls the processing liquid pressurisation system  104  to reduce processing liquid  108  ambient pressure to atmospheric pressure. The processing liquid storage tank  102  and processing liquid transfer pump system  103  are connected and the processing liquid transfer pump system  103  used to transfer all processing liquid  108  to the processing liquid storage tank  102 . The processing volume  101  is opened and the sealed plastic bag  302  removed, opened and the contents removed. The silicone membrane  301  is separated from the assembly of raw materials  200 , now a finished, SAPI, consolidated by the concurrent pressure and thermal cycling. 
         [0072]    The processing liquid  108  is a medium that has minimal compressibility, minimal toxicity and reactiveness, high boiling point, practical viscosity and high thermal conductivity. The composite article manufacturing system, generally numbered  100 , employs non-reactive polydimethylsiloxane (silicone oil) as the processing liquid  108 , sourced as ‘WACKER® AK100’ from Wacker Chemie AG, Germany. ‘WACKER® AK100’ is a clear, odourless and colourless liquid with a viscosity of approximately 100 mm 2 /s to room temperature and a flash point exceeding 275° C. (ISO 2592). The manufacturer&#39;s Australian MSDS specifies the material as a non-hazardous substance (according to the criteria of NOHSC) and a non-dangerous good (according to the ADG Code). ‘WACKER® AK100’ has been found to provide almost no lubricity and suffer a substantial reduction in viscosity at elevated temperature. 
         [0073]    The composite article processing volume  101 , illustrated in  FIG. 4 , is a pressure vessel capable of withstanding an internal pressure at elevated temperature, practically shaped with an opening to facilitate loading and unloading. The composite article manufacturing system, generally numbered  100 , employs a composite article processing volume  101  of welded metallic construction that is engineered to function with a safe maximum operating internal pressure of 100 bar and a maximum operating temperature of 150° C. 
         [0074]    The composite article processing volume  101  must be engineered in a manner compliant with relevant standards, in Australia AS1210. Preferably, the composite article processing volume  101  is cylindrical with tubular length substantially longer than diameter, orientated with tubular length horizontal and physically constrained with structural supports  408 . 
         [0075]    The composite article processing volume  101  has an opening  401  at one end of the cylindrical section that is manually operated and when opened provides unrestricted access to the full internal diameter. Such openings are referred to as ‘quick-opening closures’ within industry and are available in standard configurations. The composite article processing volume  101  has an external layer of thermal insulation  407  to minimise heat loss and maximise process efficiency. The composite article processing volume  101  has external porting for processing liquid  108  circulation inlet  402 , circulation outlet  403 , sensor feed-thru  404 , venting for filling and emptying  405  and emergency pressure release  406 . 
         [0076]    The processing liquid heating system  106 , illustrated in  FIG. 5 , is an assembly of electric heater elements  501  and a pressure vessel  502  capable of withstanding an internal pressure at elevated temperature that is engineered similarly to the composite article processing volume  101 . The processing liquid heating system  106  is similar to articles referred to within industry as ‘flanged immersion heaters’. The pressure vessel  502  is cylindrical with tubular length substantially longer than diameter, orientated with tubular length horizontal and physically constrained with structural supports  508 . The pressure vessel  502  has an open flanged end  503  and a closed end  504  and has external porting for processing liquid  108  consisting of circulation inlet  505  and circulation outlet  506 . The processing liquid heating system  106  has an external layer of thermal insulation  507  to minimise heat loss and maximise process efficiency. 
         [0077]    The assembly of electric heater elements  501  consists of many electrically resistive heater elements  501  contained within metallic tubes  509  that are attached to a flange  511  that connects to the pressure vessel  502 . The metallic tubes  509  act to shield the electrically resistive heater elements  501  from pressure and are thermally coupled with a thermally conductive medium  510 . The inventive system uses commercially available metallic hydraulic tubing to shield the electrically resistive heater elements  501  from pressure and a unique composite of high temperature anti-seize compound and graphite powder as the thermally conductive medium  510 . The metallic tubes  509  form a seal with the flange  511  utilising multiple o-rings  512  and are secured with the retainer plate  513 . 
         [0078]    The assembly of electric heater elements  501  is additionally aligned and supported by baffles  514  spaced along the length of the assembly and secured by a rod  515  that passes through the centre of the pressure vessel  502  and is anchored to the flange  511 . The baffles  514  are orientated to disturb the circulation of processing liquid  108  in operation. Industrial ‘flanged immersion heaters’ such as the inventive processing liquid heating system  106  are uncommon due to the high operating pressure. 
         [0079]    The processing liquid cooling system  107 , illustrated in  FIG. 6 , is an assembly of finned tubing  601  contained within ducting  602  that supports the cooling air flow devices  603 . The assembly of finned tubing  601  can be divided into numerous groups, each plumbed in parallel, reducing the magnitude of backpressure the processing liquid cooling system  107  imposes during circulation. The finned tubing  601  is manufactured from commercially available metallic hydraulic tubing with the addition of external protrusions to increase surface area. These external protrusions may be sheet-metal discs or a wire-form, soldered to the tube to maximise heat transfer. During operation, the cooling air flow devices  603  mounted on one side of the assembly of finned tubing  601  causes a pressure gradient that forces air to pass through the processing liquid cooling system  107  and exchange heat energy. Industrial radiators such as the inventive processing liquid cooling system  107  are uncommon due to the high operating pressure. 
         [0080]    The processing liquid pressurisation system  104 , illustrated in  FIG. 7 , is an assembly of a hydraulic power system  701 , a hydraulic driver cylinder  702 , a hydraulic driven cylinder  703 , a pressure release gate  704  and various valving. In operation the processing liquid pressurisation system  104  is controlled by the process control system  109 , to increase or decrease ambient processing liquid  108  system pressure. When functioning to decrease ambient processing liquid  108  system pressure release gate  704  is opened and processing liquid  108  returns to the processing liquid storage tank  102 . A restrictive orifice may be included to retard the rate of processing liquid  108  flow. When functioning to increase ambient processing liquid  108  system pressure the hydraulic power system  701  powers the hydraulic driver cylinder  702  which oscillates back and forth along its full stroke, controlled by a magnetic switching. 
         [0081]    The hydraulic driver cylinder  702  ram is attached to the hydraulic driven cylinder  703  ram and mimics its action. The hydraulic driven cylinder  703  has inlet and exit porting at both cylinder ends, each governed by one-way valves. Inlet porting is coupled to the processing liquid storage tank  102  with one-way valves  705  allowing only processing liquid  108  flow from the processing liquid storage tank  102  when motion of the hydraulic driven cylinder  703  ram generates low pressure. 
         [0082]    One-way valves  705  disallow return of processing liquid  108  to the processing liquid storage tank  102 . Outlet porting is coupled to the composite article processing volume  101 , with one-way valves  706  allowing only flow of processing liquid  108  to the composite article processing volume  101  when motion of the hydraulic driven cylinder  703  ram generates a pressure exceeding the ambient processing liquid  108  system pressure. One-way valves  706  disallow flow of processing liquid  108  from the composite article processing volume  101 . 
         [0083]    This inventive processing liquid pressurisation system  104  isolates the processing liquid  108  from the hydraulic power system  701  and generates processing liquid  108  pressure with a ‘positive displacement’ pumping technique; that is, the fluid added to increase pressure is directly proportional to cylinder displacement and not a pressure differential that changes with viscosity. No parts of the processing liquid pressurisation system  104  that contact processing liquid  108  utilise rotational shaft seals or metal-on-metal bearing surfaces. This eliminates inevitable wear and seal failure problems caused by poor lubricity and substantial reductions in viscosity at elevated to temperature of the processing liquid  108  in combination with elevated pressure. Industrial fluid pressurisation systems such as the inventive processing liquid pressurisation system  104  are uncommon due to the unique requirements. 
         [0084]    The processing liquid circulation system  105 , illustrated in  FIG. 8 , is an assembly of a hydraulic power system  701 , a hydraulic driver cylinder  802 , a hydraulic driven cylinder  803  and various valving. In operation the processing liquid circulation system  105  is controlled by the process control system  109  to circulate pressurised processing liquid  108 . When functioning to circulate pressurised processing liquid  108  the hydraulic power system  701  powers the hydraulic driver cylinder  802  which oscillates back and forth along its full stroke, controlled by magnetic switching. The hydraulic driver cylinder  802  ram is attached to the hydraulic driven cylinder  803  ram and mimics its action. The hydraulic driver cylinder  802  has an additional ram  806  protruding from its other end to balance static pressure loading and limit the force required of the hydraulic driver cylinder  802  to a magnitude sufficient to overcome processing liquid  108  circulation backpressure and frictional sealing loads only. This makes feasible an advantageous increase in hydraulic driven cylinder  803  diameter relative to the hydraulic driver cylinder  802 . 
         [0085]    The hydraulic driven cylinder  803  has inlet and exit porting at both cylinder ends, each governed by one-way valves  804 . Inlet porting is coupled to the composite article processing volume  101  with one-way valves  804  allowing only processing liquid  108  flow from the composite article processing volume  101  when motion of the hydraulic driven cylinder  803  ram generates low pressure. One-way valves  804  disallow return of processing liquid  108  to the composite article processing volume  101 . Outlet porting is coupled to either the processing liquid heating system  106 , or processing liquid cooling system  107 , with one-way valves  804  allowing only flow of processing liquid  108  to processing liquid heating system  106 , or processing liquid cooling system  107 , when motion of the hydraulic driven cylinder  803  ram generates a pressure exceeding the ambient processing liquid  108  system pressure. 
         [0086]    One-way valves  804  disallow flow of processing liquid  108  from the processing liquid heating system  106 , or processing liquid cooling system  107 . All seals within the hydraulic driven cylinder  803  are constructed from high-temperature material, such as viton fluoroelastomers, to ensure service at elevated process temperature and pressure. This inventive processing liquid circulation system  105  isolates the processing liquid  108  from the hydraulic power system  701  and generates processing liquid  108  circulation with a ‘positive displacement’ pumping technique; that is, the fluid circulation is directly proportional to cylinder displacement and not a pressure differential that changes with viscosity. 
         [0087]    No parts of the processing liquid circulation system  105  that contact processing liquid  108  utilise rotational shaft seals or metal-on-metal bearing surfaces. This eliminates inevitable wear and seal failure problems caused by poor lubricity and substantial reductions in viscosity at elevated temperature of the processing liquid  108  in combination with elevated pressure. Industrial fluid circulation systems such as the inventive processing liquid circulation system  105  are uncommon due to the unique requirements. 
         [0088]    The process control system  109 , illustrated in  FIG. 9 , is an assembly of thermal sensing devices  903 , pressure sensing devices  904 , electrical current sensing devices  905 , electrical voltage sensing devices  906 , fluid level sensing devices  907 , valving  908 , electrically operated switches  909 , manually operated switches  910 , control hardware  901  and software  902 . In operation the process control system  109  employs closed loop pressure and thermal control to navigate predetermined pressure and thermal cycles. A typical predetermined pressure cycle is illustrated in  FIG. 10 , with pressure graduated on the vertical, or y-axis, and elapsed time on the horizontal, or x-axis. 
         [0089]    A typical predetermined thermal cycle is illustrated in  FIG. 11 , with temperature graduated on the vertical, or y-axis, and elapsed time on the horizontal, or x-axis. In operation the thermal sensing devices  903  function to accurately measure processing liquid  108  temperatures, ambient air temperatures and temperatures within regions of interest in the inventive composite article manufacturing system, generally numbered  100 . Suitable thermal sensing devices  903  include thermocouples and platinum resistance thermometers, known as RTD sensors. 
         [0090]    In operation the pressure sensing devices  904  function to accurately measure processing liquid  108  pressures. Suitable pressure sensing devices  904  output an analogue signal that deviates in a known manner at elevated temperature. In operation the electrical current sensing devices  905  and electrical voltage sensing devices  906  function to measure the electrical power load of electric motors and the processing liquid heating system  106 . This enables power consumption monitoring and fault detection. In operation the fluid level sensing devices  907  function to accurately measure the quantity of processing liquid  108 , within the processing liquid storage tank  102 . 
         [0091]    This enables fluid loss monitoring and leak detection. In operation the valving  908  functions to control the passage of processing liquid  108  in the inventive composite article manufacturing system, generally numbered  100 . The valving  908  is preferably actuated electrically or pneumatically and must be capable of functioning at maximum processing liquid  108  temperature. 
         [0092]    In operation the electrically operated switches  909  are activated by the control hardware  901  to switch valving  908 , the processing liquid transfer pump system  103 , the processing liquid pressurisation system  104 , the processing liquid circulation system  105 , the processing liquid heating system  106  and the processing liquid cooling system  107 . Manually operated switches  910  are included to override the control hardware  901  when required.