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  Novel thick laminate fabrication methodUSPTO Application #: 20060172645Title: Novel thick laminate fabrication method Abstract: The invention is a processing technique which allows Fiber Reinforced Polymer laminates of any arbitrary thickness to be manufactured. Thick laminates processed in this fashion will not exhibit adverse process induced residual stresses which serve to reduce or limit laminate operability, performance and service life. This invention provides a means by which conventional processing problems associated with very thick laminate construction can be avoided, thereby ensuring a high degree of thick laminate part quality and performance (end of abstract) Agent: Mark Rodgers - Santa Barbara, CA, US Inventor: D. Erich Weerth USPTO Applicaton #: 20060172645 - Class: 442229000 (USPTO) Related Patent Categories: Fabric (woven, Knitted, Or Nonwoven Textile Or Cloth, Etc.), Woven Fabric (i.e., Woven Strand Or Strip Material), Including A Free Metal Or Alloy Constituent, Metal Or Metal-coated Strand The Patent Description & Claims data below is from USPTO Patent Application 20060172645. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] Not Applicable FEDERALLY SPONSORED RESEARCH [0002] Not Applicable SEQUENCE LISTING [0003] Not Applicable BACKGROUND OF THE INVENTION [0004] The invention relates to producing thick composite laminates, and specifically to addressing process problems associated with thick laminate manufacture. [0005] Fiber reinforced polymer (FRP) matrix construction has been widely used in the aerospace industry for quite some time because it exhibits a much higher specific strength (i.e. strength divided by density) compared to isotropic metals. The weight savings associated with FRP construction offers significant structural performance advantages as well as ballistic protection advantages in defense as well as commercial applications. [0006] As structural performance and ballistic threat requirements continue to increase, the need for thicker and thicker FRP construction mounts. Where aerospace applications have successfully used thin FRP laminates, other applications in civil engineering, transportation and ballistic protection have pushed the FRP processing envelope toward thicker and thicker laminates. [0007] Thick laminate construction exceeding two inches in thickness has typically been difficult to accomplish in a repeatable, high quality fashion. Fabrication problems associated with the use of thermoset resin systems such as epoxy, polyester and vinyl ester resins are prevalent in the fabrication of thick laminates. This is primarily due to the high exothermic reaction of the resin matrix as polymerization occurs during curing of laminates using reinforcing fibers exhibiting low thermal conductivity. Laminates fabricated using low thermal conductivity fibers such as E-Glass and S-2 Glass prevent an exothermic reaction from properly dissipating the heat generated from the exotherm. [0008] Consequently, in the case of thick glass fiber reinforced laminate construction, the high fiber volume fraction impedes adequate heat transfer during evolution of the exothermic reaction created during polymerization of the resin. The internal heat generated by the exothermic reaction of the resin develops thermal stresses in the FRP laminate during the curing process. These thermal stresses are of sufficient magnitude to cause the laminate to crack before the laminate becomes fully cured. The thicker the laminate the higher the thermal gradients that are developed during the curing process. It is these high tensile process induced residual stresses which adversely affect laminate quality and performance. [0009] Thick panels of composite materials are becoming vital for defense as well as commercial applications, particularly as such panels are well suited for explosive resistant applications that are extremely relevant in an age of global terrorism. Thus there is a critical need to fabricate very thick, as thick as 20 inches or more, glass fiber reinforced laminates without the formation of interlaminar flaws, air voids or excessive tensile residual stresses, all of which impair design functionality, service life, performance and fitness for purpose. It is the object of this invention to provide a means by which all the aforementioned problems associated with very thick laminate construction can be avoided, thereby ensuring a high degree of laminate quality and performance. BRIEF SUMMARY OF THE INVENTION [0010] The invention is a method of producing a thick laminate assembly of Fiber Reinforced Polymer (FRP) panels. The method includes placing an electric heating element on a surface of a pre-cured first panel such that the heating element can be controlled external to the laminate assembly, covering the surface of the first panel and electric heating element with thermoset resin and placing a second pre-cured panel on top of the first panel. The electric heating element is used as the heat source to cure the thermoset resin, thereby bonding the two panels together into a laminate assembly. [0011] In one version, the method includes bonding additional panels to the laminate assembly until an assembly of desired total thickness is achieved, using an electric heating element as the heat source for curing the thermoset resin used to bond additional panels to the assembly. The panels may be added sequentially or the entire assembly can be set-up and cured simultaneously. [0012] In one embodiment, the electrical resistance element is at least one heating wire laid over a surface area of the panel in a serpentine pattern, such that both ends of the wire can be accessed external to the panels. In one version, the turns of the pattern are within the surface area of the panel. In another version, the turns are around pins external to the surface area of the panel. [0013] In one aspect, the method includes a step of sealing the joint line between panels when the resin is heated to a point of minimum viscosity. In a further aspect, the assembly is vacuum bagged during the curing process. [0014] In one aspect, the method includes at least one thermocouple placed between the panels to monitor temperature during the cure cycle. In one version, two thermocouples are installed at opposite diagonal corners of the panel. [0015] In another embodiment, the invention is a method of producing a laminate assembly of Fiber Reinforced Polymer (FRP) panels including placing an electric heating element on a surface of a first panel such that the heating element can be controlled external to the laminate assembly, placing a film adhesive with the heating element, and placing a second panel on top of the first panel. The electric heating element is used as the heat source to heat the film adhesive, thereby bonding the two panels together into a laminate assembly. In one version, the film adhesive is a single layer woven fabric, pre-impregnated with thermoset resin and partially cured. The film adhesive implementation supports the various embodiments, aspects, and versions of the above implementation employing the resin. [0016] The invention also includes an adhesive film for joining panels together including; a single layer woven fabric, pre-impregnated with thermoset resin and partially cured, and at least one heating wire. The wire is woven in a serpentine pattern into the fabric which constitutes the film adhesive layer, such that the wire can be accessed on both ends external to the fabric, and the wire, resin and fabric are packaged as one unit which can be placed between panels to be joined. In one version the film adhesive layer includes at least one thermocouple mounted on the fabric with connections external to the film. BRIEF DESCRIPTION OF THE DRAWINGS [0017] The following detailed description of the invention will be better understood by referring to the accompanying drawings. [0018] FIG. 1 illustrates the heating element on a single pre-cured panel. Continue reading... Full patent description for Novel thick laminate fabrication method Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Novel thick laminate fabrication method patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Novel thick laminate fabrication method or other areas of interest. ### Previous Patent Application: a mat with yarns made of alkali-resistant glass Next Patent Application: Warp knit fabric with steric structure Industry Class: Fabric (woven, knitted, or nonwoven textile or cloth, etc.) ### FreshPatents.com Support Thank you for viewing the Novel thick laminate fabrication method patent info. 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