Patent Publication Number: US-2023159723-A1

Title: Thermoplastic composition, consolidated laminate structure, and method for manufacturing thereof

Description:
PRIORITY 
     The present application is a continuation-in-part of, and claims priority from, U.S. Ser. No. 17/530,978, filed on Nov. 19, 2021, which is titled “THERMOPLASTIC FILMS AND METHODS FOR COATING THERMOPLASTIC SUBSTRATES WITH THERMOSET MATERIALS,” the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present application relates to the field of thermoplastic structures, in particular polyaryletherketone-based thermoplastic structures. 
     BACKGROUND 
     The process of finishing polyaryletherketone-based thermoplastic structural components with a thermoset material presents challenges, specifically with respect to medium and large-scale components, particularly those used in airstream applications. Current surface treatment techniques include the need for mechanically treating substrate surfaces using techniques such as sand blasting, grit blasting, plasma treatment, and other techniques that roughen substrate surfaces prior to bonding with a finishing material. 
     Furthermore, implementation of polyaryletherketone-based thermoplastic structural components into medium to large scale components is restricted by a technology gap in electromagnetic effects (EME) protection. Expanded copper is one approach for addressing EME. However, this approach can present challenges with regards to finishing quality and induction welding while adding extra process steps during manufacturing. 
     Accordingly, those skilled in the art continue with research and development in the field of thermoplastic structures, in particular polyaryletherketone-based thermoplastic structures. 
     SUMMARY 
     In one embodiment, a thermoplastic composition includes a thermoplastic polymer and electrically conductive particles dispersed in the thermoplastic polymer. 
     In another embodiment, a consolidated laminate structure includes a thermoplastic substrate and a thermoplastic composition consolidated with the thermoplastic substrate to define a receiving surface. The thermoplastic composition includes a thermoplastic polymer and electrically conductive particles dispersed in the thermoplastic polymer. 
     In yet another embodiment, a method for manufacturing a consolidated laminate structure includes applying a thermoplastic composition to a first major surface of a thermoplastic substrate. The thermoplastic composition includes a thermoplastic polymer and electrically conductive particles dispersed in the thermoplastic polymer. The method further includes co-consolidating the thermoplastic composition with the thermoplastic substrate to define a receiving surface. 
     Other embodiments of the disclosed thermoplastic compositions, consolidated laminate structures, and methods for manufacturing thereof, will become apparent from the following detailed description, the accompanying drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a method for forming a thermoplastic film according to the present description; 
         FIG.  2    is a schematic diagram of a thermoplastic film according to the present description; 
         FIG.  3    is a schematic diagram of another thermoplastic film according to the present description; 
         FIG.  4    is a cross sectional schematic of a laminate structure prior to consolidation according to the present description; 
         FIG.  5    is a cross sectional schematic of the laminate structure of  FIG.  4    after consolidation; 
         FIG.  6    is a cross sectional schematic of the laminate structure of  FIG.  5    with an additional coating; 
         FIG.  7    is a cross sectional schematic of the laminate structure of  FIG.  6    with an additional coating; 
         FIG.  8    is a schematic diagram relating to a method for method for induction welding according to the present description; 
         FIG.  9    is a flow diagram of a method for manufacturing a consolidated laminate structure according to the present description; 
         FIG.  10    is a block diagram of aircraft production and illustrative methodology; and 
         FIG.  11    is a schematic illustration of an aircraft. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed are thermoplastic compositions and methods for modifying a receiving surface of a consolidated laminate structure. The thermoplastic compositions and methods improve an electrical conductivity of a consolidated laminate structure, which may provide for EME protection for an aircraft comprising the consolidated laminate structure. 
     The thermoplastic compositions and methods may also facilitate induction welding of a consolidated laminate structure with another structure. 
     The thermoplastic compositions and methods may also improve compatibility of a consolidated laminate structure and a thermoset coating, such as an epoxy-based primer. The disclosed thermoplastic compositions and methods may account for threshold adhesive properties with the thermoset coating and miscibility of the components of the compositions. The result is a modified surface of the thermoplastic composite material to enhance compatibility to a thermoset coating. 
     Referring to  FIG.  1   , disclosed is a thermoplastic composition  1 . The thermoplastic composition  1  includes a thermoplastic polymer  10  and electrically conductive particles  13  dispersed in the thermoplastic polymer  10 . The thermoplastic polymer  10  may include, for example, a first thermoplastic polymer  11  in admixture with a second thermoplastic polymer  12 . The thermoplastic composition  1  may be manufactured by, for example, combining and blending the thermoplastic polymer  10  and the electrically conductive particles  13  in an extruder E and extruding the resulting thermoplastic composition  1  into a coating, such as a film  2 . 
     The thermoplastic polymer  10  may be selected based upon desired material properties. For example, a film  2  of the thermoplastic composition  1  may be mixed with a thermoplastic substrate material during a consolidation process and may be coated with a thermoset coating. The thermoplastic polymer  10  of the thermoplastic composition  1  may be selected based upon material properties such as miscibility with the thermoplastic substrate material and threshold adhesive properties that align with the mating thermoset coating. Thus, the underlying thermoplastic substrate may be made from a polyaryletherketone polymer or other material not having threshold adhesive properties with thermoset coatings and the surface of the thermoplastic substrate may be modified by consolidation with the thermoplastic composition  1  of the present description to enhance compatibility of the thermoplastic substrate with the thermoset coating. 
     In one aspect, the thermoplastic polymer may include a semi-crystalline thermoplastic polymer material. In another aspect, the thermoplastic polymer may include a polyaryletherketone polymer. The polyaryletherketone polymer may be in the form of a semi-crystalline material belonging to the family of polyaryletherketone (PAEK) polymers. The polyaryletherketone polymer may be in the form of a film, plastic pellets, powder, etc. The polyaryletherketone polymer may include polyether ether ketone. In another example, the polyaryletherketone polymer includes polyether ketone ketone. In yet another example, the polyaryletherketone polymer includes a blend of at least two polyaryletherketones. For example, the polyaryletherketone polymer may include a blend of polyether ketone ketone and polyether ether ketone. Polyaryletherketone polymers provide for miscibility with a thermoplastic substrate formed from thermoplastic polyaryletherketone polymers. 
     In an aspect, the thermoplastic polymer may include an amorphous thermoplastic polymer. In another aspect, the thermoplastic polymer may include polyetherimide. In another aspect, the thermoplastic polymer may include amorphous polyetherimide. Polyetherimide is miscible with polyaryletherketone polymers and provides adhesive properties that align with the mating thermoset coating and is compatible with aerospace grade paints and coatings and stable at processing temperatures of at least about 350° C. 
     In another aspect, the thermoplastic polymer may include a polyaryletherketone polymer in admixture with polyetherimide. The thermoplastic composition  1  may include a ratio of the polyetherimide to the polyaryletherketone polymer. In one example, the ratio of the polyetherimide to the polyaryletherketone polymer is between about 5:95 and about 50:50. In another example, the ratio of the polyetherimide to the polyaryletherketone polymer is between about 10:90 and about 50:50. In yet another example, the ratio of the polyetherimide to the polyaryletherketone polymer is between about 20:80 and about 50:50. 
     The thermoplastic composition  1  may have a high or low melting temperature based on respective melting and softening temperatures of constituents of the thermoplastic composition  1 . In one example, the melting temperature of the polyaryletherketone polymer is about 250° C. to about 350° C. In another example, the melting temperature of the polyaryletherketone polymer is at least about 300° C. 
     The thermoplastic composition  1  may have a degree of crystallinity based on respective crystallinity of constituents of the thermoplastic composition  1 . In an aspect, a degree of crystallinity of the thermoplastic composition  1  may range from about 1 percent to about 30 percent. In an aspect, a degree of crystallinity of the thermoplastic composition  1  may range from about 2 percent to about 15 percent. In an aspect, a degree of crystallinity of the thermoplastic composition  1  may range from about 3 percent to about 10 percent. 
     The thermoplastic composition  1  may include additional additives. In one example, the thermoplastic composition  1  includes a heat stabilizer. In another example, the thermoplastic composition  1  includes a nucleating agent. 
     The electrically conductive particles  13  may have an amount, composition, shape, and size selected to achieve desired electrical properties. 
     The amount of electrically conductive particles may be selected to achieve desired electrical properties. In an aspect, the amount of electrically conductive particles may be more than a minimum amount sufficient to achieve a percolating network. In an aspect, the amount of electrically conductive particles may be less than a maximum amount sufficient to enable induction welding. For example, the amount of electrically conductive particles may be added in amount needed to meet the EME requirements, but is not too conductive to significantly affect the induction welding process. 
     The amount of electrically conductive particles may depend on a composition, shape, and size of the electrically conductive particles. In an aspect, the amount of electrically conductive particles in the thermoplastic composition is in a range from about 0.1 to about 90 percent by weight. In another aspect, the amount of electrically conductive particles in the thermoplastic composition is in a range from about 0.5 to about 75 percent by weight. In another aspect, the amount of electrically conductive particles in the thermoplastic composition is in a range from about 1 to about 50 percent by weight. 
     The electrically conductive particles may be composed of any electrically conductive material having compatibility with the other components of the thermoplastic composition  1 . In an example, the electrically conductive particles may include metal-based electrically conductive particles, such as nickel-based electrically conductive particles, copper-based electrically conductive particles, iron-based electrically conductive particles, chromium-based electrically conductive particles, or cobalt-based electrically conductive particles, or combinations thereof. In another example, the electrically conductive particles may include carbon-based electrically conductive particles, such as carbon nanotubes. In yet another example, the electrically conductive particles may include metal coated graphite, such as nickel coated graphite. 
     The electrically conductive particles may have a shape selected to achieve desired electrical properties. In an example, the electrically conductive particles may include spherical-shaped electrically conductive particles. In another example, the electrically conductive particles may include platelet-shaped electrically conductive particles. In another example, the electrically conductive particles may include rod-shaped electrically conductive particles. 
     The electrically conductive particles may have a size selected to achieve desired electrical properties. In an example, the electrically conductive particles may include nano scale electrically conductive particles. In another example, the electrically conductive particles may include micro scale electrically conductive particles. 
     Referring to  FIGS.  1  to  3   , the thermoplastic composition  1  may be extruded into a film  2 . The film  2  includes a thermoplastic polymer  20  and electrically conductive particles  23  dispersed in the thermoplastic polymer  20 . The thermoplastic polymer  20  may include, for example, a first thermoplastic polymer  21  in admixture with a second thermoplastic polymer  22 . The thermoplastic film  2  may be manufactured by, for example, combining and blending the thermoplastic polymer  10  (which may include the first thermoplastic polymer  11  in admixture with the second thermoplastic polymer  12 ) and the electrically conductive particles  13  in an extruder E and extruding the above-described thermoplastic composition  1  into a film  2 . In one example, the film  120  has a thickness of about 1 mil to about 15 mil. 
     Referring to  FIGS.  2  and  3   , the first thermoplastic polymer  21  is preferably a semi-crystalline thermoplastic polymer material such as a polyaryletherketone polymer, and the second thermoplastic polymer  22  is preferably an amorphous thermoplastic polymer such as polyetherimide.  FIG.  2    shows that the electrically conductive particles  13  are present in amount such that the electrically conductive particles  13  are isolated.  FIG.  3    shows that the electrically conductive particles  13  are present in amount such that the electrically conductive particles  13  form a percolating network. The percolation threshold is the concentration at which there are enough electrically conductive particles in the matrix to form a semi-continuous network of electrically conductive particles. At this threshold, the conductivity begins to increase exponentially due to the inter-connectivity of the particles which can transfer and disperse the incoming electromagnetic energy more efficiently. Prior to this threshold, the particles are discontinuous and relatively isolated from each other. The percolation threshold will be unique vary based on the nature of the electrically conductive particles  13 , including the size and shape. 
       FIG.  4    illustrates a laminate structure  30  including a thermoplastic substrate  31  and the thermoplastic composition  1  in the form of a film  2  positioned on the thermoplastic substrate  31  to define a receiving surface  36 . The thermoplastic substrate  31  includes a thermoplastic polymer. In one example, the thermoplastic polymer of the thermoplastic substrate  31  includes a polyaryletherketone polymer. The thermoplastic substrate  31  may be formed of multiple plies  32 ,  33 ,  34  of laminate (e.g., at least two plies, such as 5 or more plies) in a stacked configuration and having a first major surface  35  for receiving the film  2  thereon. The multiple plies  32 ,  33 ,  34  of laminate may include a polymer from the family of polyaryletherketone (PAEK) polymers. In one example, the multiple plies  32 ,  33 ,  34  of laminate include polyether ketone ketone. The thermoplastic substrate  31  may be a thermoplastic fiber composite substrate, and may include a thermoplastic polymer and a fiber material, such as carbon fiber. In an aspect, each of the multiple plies  32 ,  33 ,  34  may include a thermoplastic polymer and a fiber material, such as carbon fiber. 
     Referring to  FIG.  5   , the laminate structure  30  may be co-consolidated into a consolidated laminate structure  40  having a receiving surface  46  corresponding to the receiving surface  36  of the film  2  of  FIG.  4   . The consolidated laminate structure  40  includes a thermoplastic substrate  41  corresponding to thermoplastic substrate  31  consolidated with the thermoplastic composition  1 , the thermoplastic composition  1  defining the receiving surface  46 . The thermoplastic composition includes a thermoplastic polymer as described above. For example, the thermoplastic composition may include a polyaryletherketone polymer in admixture with polyetherimide. 
     Referring to  FIG.  6   , the consolidated laminate structure  40  may further include a thermoset material  50  applied to the receiving surface  46 . In one example, the thermoset material  50  is in the form of a thermoset coating. In one example, the thermoset material  50  may include an epoxy. In another example, the thermoset material  50  may be a primer, such as a paint primer. Additionally, the consolidated laminate structure  40  may further include a top coat  60  applied to the thermoset material  50  or primer, see  FIG.  7   . In one example, the top coat  60  includes polyurethane. 
     The consolidated laminate structure as described above may form an exterior component of an aircraft body of an aircraft and the thermoplastic composition including the electrically conductive particles dispersed in the thermoplastic polymer may facilitate for EME protection of the exterior component. In particular, the consolidated laminate structure may be incorporated into external applications such as fuselage skins, wing skins, horizontal stabilizer skins, vertical stabilizer skins, control surfaces, chine structures, etc. Inadequate EME solutions has been a main reason programs have been reluctant to consider thermoplastic composites for the aforementioned applications. Additionally, by avoiding the use of expanded copper foil, the consolidated laminate structure can enable another added benefit from a weight savings perspective, wherein the electrically conductive particles of the present description can yield adequate conductivity at a fraction of the weight introduced by conventional expanded copper foil. 
     In an aspect, the consolidated laminate structure may provide for a customizable solution for addressing EME at various locations of the aircraft. In this regards, the amount of electrically conductive particles dispersed in the thermoplastic polymer may selectively vary according to the position of the consolidated laminate structure. Thus, an added benefit of being able to precisely control the conductivity of the surfacing film will be to vary the electrically conductive particle loading based on different structures on an aircraft. Some structures are more prone to EME effects or have a requirement for higher electrical conductivity. Those structures may be loaded with more electrically conductive particles to make the structure more electrically conductive. On the other hand, there are some structures on an aircraft with less EME susceptibility or with a lower electrical conductivity requirement. Those structures can be loaded with less electrically conductive particles. By having this variability, it is possible to save weight on the aircraft by adding extra electrically conductive particles in areas which they are needed the most. 
     The consolidated laminate structure as described above may be used in a method for induction welding. Referring to  FIG.  8   , the method includes positioning a consolidated laminate structure  40  adjacent to another structure  70 , and passing an electromagnetic current through the consolidated laminate structure  40  to melt at least a portion of the thermoplastic polymer thereof and thereby join the consolidated laminate structure and the another structure. The electrically conductive particles dispersed in the thermoplastic polymer may facilitate heating of the thermoplastic composition by induction heating to melt at least a portion thereof. Upon solidification of the melted thermoplastic composition, the consolidated laminate structure  40  is joined to the structure  70 . One key joining techniques for PAEK thermoplastic composites is induction welding. Induction welding passes an electromagnetic current through the composite laminate. As it does so, this current interacts with the inherent conductive nature of the carbon fiber in the composite to generate heat which quickly melts the PAEK thermoplastic and therefore joins the two structures. 
     Referring to  FIG.  9   , disclosed is a method  600  for manufacturing a consolidated laminate structure  30 . The method  600  includes applying the thermoplastic composition  1  to the first major surface  35  of the thermoplastic substrate  31 . In one example, the thermoplastic substrate is a layered structure including multiple plies  32 ,  33 ,  34  of thermoplastic material. The thermoplastic composition  1  of the method  600  includes the thermoplastic polymer  20  and electrically conductive particles  23  dispersed in the thermoplastic polymer  20 . In one example, the thermoplastic composition  1  includes a polyaryletherketone polymer in admixture with a polyetherimide. 
     Still referring to  FIG.  9   , the method  600  further includes co-consolidating  640  the thermoplastic composition  1  with the thermoplastic substrate  31  to define a receiving surface  36 . In one or more examples, the co-consolidating  640  is performed at a temperature of about 275° C. to about 400° C. In another example, the co-consolidating  640  is performed at a temperature of about 330° C. to 400° C. In yet another example, the co-consolidating  640  is performed at a temperature of at least 340° C. The co-consolidating  640  may include any means including compression molding or stamp forming. 
     The method  600  may further include applying  650  a thermoset material  50  such as a thermoset coating, to the receiving surface  46 . In one example, the thermoset material  50  of the method  600  includes an epoxy. In another example, the thermoset material  50  of the method  600  is a primer, such as a paint primer. Referring to  FIG.  7   , the method  600  may further include applying a top coat  60  to the thermoset material  50 . In one example, the top coat  60  includes polyurethane. 
     Still referring to  FIG.  9   , the method  600  may further include, prior to the applying  630 , extruding  620  the thermoplastic composition  1 . The extruding  620  may include extruding  620  the thermoplastic composition  1  to yield a thermoplastic film  2 . 
     The method  600  may further include, prior to the applying  630 , arranging  610  multiple plies  32 ,  33 ,  34  of laminate in a stacked configuration to yield the thermoplastic substrate  31 . The arranging  610  may be performed by any suitable means of arranging plies of laminate. The multiple plies  32 ,  33 ,  34  of laminate may include, for example, at least one of polyether ether ketone and polyether ketone ketone, or a blend thereof. 
     Referring to  FIG.  10    and  FIG.  11   , the disclosed consolidated laminate structure, thermoplastic composition and method will be used in the context of aircraft manufacturing and service including material procurement (block  1106 ), production, component and subassembly manufacturing (block  1108 ), and certification and delivery (block  1112 ) of aircraft  1102 . 
     Examples of the subject matter disclosed herein may be described in the context of aircraft manufacturing and illustrative method  1100  as shown in  FIG.  10    and aircraft  1102  as shown in  FIG.  11   . In one or more examples, the consolidated laminate structure  100  comprises a stringer assembly used in aircraft manufacturing. During pre-production, illustrative method  1100  may include specification and design (block  1104 ) of aircraft  1102  and material procurement (block  1106 ). During production, component and subassembly manufacturing (block  1108 ) and system integration (block  1110 ) of aircraft  1102  may take place. Thereafter, aircraft  1102  may go through certification and delivery (block  1112 ) to be placed in service (block  1114 ). While in service, aircraft  1102  may be scheduled for routine maintenance and service (block  1116 ). Routine maintenance and service may include modification, reconfiguration, refurbishment, etc. of one or more systems of aircraft  1102 . 
     Each of the processes of illustrative method  1100  may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include, without limitation, any number of aircraft manufacturers and major-system subcontractors; a third party may include, without limitation, any number of vendors, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on. 
     As shown in  FIG.  11   , aircraft  1102  produced by illustrative method  1100  may include airframe  1118  with a plurality of high-level systems  1120  and interior  1122 . Examples of high-level systems  1120  include one or more of propulsion system  1124 , electrical system  1126 , hydraulic system  1128 , and environmental system  1130 . Any number of other systems may be included. Although an aerospace example is shown, the principles disclosed herein may be applied to other industries, such as the automotive industry. Accordingly, in addition to aircraft  1102 , the principles disclosed herein may apply to other vehicles, e.g., land vehicles, marine vehicles, space vehicles, etc. 
     Apparatus(es) and method(s) shown or described herein may be employed during any one or more of the stages of the manufacturing and illustrative method  1100 . For example, components or subassemblies corresponding to component and subassembly manufacturing (block  1108 ) may be fabricated or manufactured in a manner similar to components or subassemblies produced while aircraft  1102  is in service (block  1114 ). Also, one or more examples of the apparatus(es), method(s), or combination thereof may be utilized during production stages component and subassembly manufacturing (block  1108 ) and system integration (block  1110 ), for example, by substantially expediting assembly of or reducing the cost of aircraft  1102 . Similarly, one or more examples of the apparatus or method realizations, or a combination thereof, may be utilized, for example and without limitation, while aircraft  1102  is in service (block  1114 ) and/or during maintenance and service (block  1116 ). 
     Different examples of the composition(s), structure(s) and method(s) disclosed herein include a variety of components, features, and functionalities. It should be understood that the various examples of composition(s), structure(s) and method(s), disclosed herein, may include any of the components, features, and functionalities of any of the other examples of the composition(s), structure(s) and method(s) disclosed herein in any combination. 
     Many modifications of examples, set forth herein, will come to mind of one skilled in the art, having the benefit of the teachings, presented in the foregoing descriptions and the associated drawings. 
     Therefore, it is to be understood that the subject matter, disclosed herein, is not to be limited to the specific examples illustrated and that modifications and other examples are intended to be included within the scope of the appended claims. Moreover, although the foregoing description and the associated drawings describe examples of the subject matter, disclosed herein, in the context of certain illustrative combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative implementations without departing from the scope of the appended claims. Accordingly, parenthetical reference numerals in the appended claims are presented for illustrative purposes only and are not intended to limit the scope of the claimed subject matter to the specific examples provided herein. 
     Although various embodiments of the disclosed thermoplastic compositions, consolidated laminate structures, and methods for manufacturing thereof, have been shown and described, modifications may occur to those skilled in the art upon reading the specification. The present application includes such modifications and is limited only by the scope of the claims.