Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/28—Shaping operations therefor
  • B29C70/54—Component parts, details or accessories; Auxiliary operations, e.g. feeding or storage of prepregs or SMC after impregnation or during ageing
  • B29C70/546—Measures for feeding or distributing the matrix material in the reinforcing structure
  • B29C70/548—Measures for feeding or distributing the matrix material in the reinforcing structure using distribution constructions, e.g. channels incorporated in or associated with the mould
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/06—Fibrous reinforcements only
  • B29C70/10—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres
  • B29C70/12—Fibrous reinforcements only characterised by the structure of fibrous reinforcements, e.g. hollow fibres using fibres of short length, e.g. in the form of a mat
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/04—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising reinforcements only, e.g. self-reinforcing plastics
  • B29C70/28—Shaping operations therefor
  • B29C70/40—Shaping or impregnating by compression not applied
  • B29C70/42—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles
  • B29C70/44—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using isostatic pressure, e.g. pressure difference-moulding, vacuum bag-moulding, autoclave-moulding or expanding rubber-moulding
  • B29C70/443—Shaping or impregnating by compression not applied for producing articles of definite length, i.e. discrete articles using isostatic pressure, e.g. pressure difference-moulding, vacuum bag-moulding, autoclave-moulding or expanding rubber-moulding and impregnating by vacuum or injection
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
  • C08J5/047—Reinforcing macromolecular compounds with loose or coherent fibrous material with mixed fibrous material
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4209—Inorganic fibres
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4209—Inorganic fibres
  • D04H1/4242—Carbon fibres
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/42—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
  • D04H1/4382—Stretched reticular film fibres; Composite fibres; Mixed fibres; Ultrafine fibres; Fibres for artificial leather
  • D04H1/43835—Mixed fibres, e.g. at least two chemically different fibres or fibre blends
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/54—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving
  • D04H1/558—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by welding together the fibres, e.g. by partially melting or dissolving in combination with mechanical or physical treatments other than embossing
• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/58—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by applying, incorporating or activating chemical or thermoplastic bonding agents, e.g. adhesives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2363/00—Characterised by the use of epoxy resins; Derivatives of epoxy resins
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
  • C08J5/0405—Reinforcing macromolecular compounds with loose or coherent fibrous material with inorganic fibres
  • C08J5/042—Reinforcing macromolecular compounds with loose or coherent fibrous material with inorganic fibres with carbon fibres

Definitions

• the present invention relates to the production of composites for the structural use characterized by the utilization of fibers (optionally recycled) with three-dimensional geometry.
• the invention relates to new materials and new processes aimed at producing such materials useful for light, strong and low cost structures, to be used in the automobile, rail and ship transport and in general for all those industrial applications where light and very resistant structures are required.
• a composite material is a heterogeneous material, that consists of two or more phases with different physical properties, wherein said properties are better than those of the phases that constitute it.
• the different steps in the composite are constituted of different materials, such as in the case of carbon fiber and epoxy resin composites.
• the different phases are made of the same material, such as SiC/SiC and self-reinforced polypropylene (SRPP).
• the single materials forming the composites are called constituents, and according to their function, they are called matrix and reinforcement (or charge).
• the matrix is the polymeric part (for example the resin), while the reinforcement are the fibers.
• the matrix consists of a continuous homogeneous phase, which has the task of:
• the matrixes are polymeric, because they guarantee low density (and therefore lightness of the final material): however, they have the inconvenience to drastically reduce the performance when the temperature rises.
• epoxy resins can be used (as a matrix) (the same used in some adhesives and polyesters) or the phenolic resins, optionally added with other polymers (such as PVB), which contribute to improve the mechanical characteristics (such as flexibility) of the composite material while maintaining adhesion to the reinforcement.
• PVB polymer matrix composite materials
• the reinforcement is represented by a dispersed phase, which is in fact dispersed in various ways within the matrix and has the task of ensuring rigidity and mechanical strength, taking on itself most of the external load.
• the composite materials are divided in:
• structured composites for example sandwich panels, laminated composite materials and aluminum composite panels.
• the reinforcement consists of "particles", which (unlike the fibers) can be considered to be equiaxial.
• the chemical-physical properties of the particle composite materials depend on the geometry of the particle system, that is: size and shape of the particles;
• Fiber-reinforced composites can in turn be classified in:
• discontinuous (or short) fiber composites arranged randomly.
• Composite materials with a fibrous dispersed step have a marked anisotropy. Said anisotropy does not occur (or at least very negligibly) in particle composites, to the extent that said particles are equiaxial.
• the anisotropy if under control may constitute an advantage: the material is reinforced in those directions where it is known that it will be loaded and therefore the performances are optimized (as in the case of continuous fiber composites). If, however, it is due to phenomena more difficult to control (for example plastic flow of the material in a mold, as in the case of short fiber composites) it becomes problematic, because the orientation of the directions of maximum reinforcement hardly coincides with the desired one.
• the reinforcement can for example consist of:
• carbon fiber consisting of graphitic carbon and amorphous carbon
• ceramic fibers for example silicon carbide or alumina
• aramid fiber like Kevlar
• the polymeric composite materials for structural uses consist of two phases: a thermosetting or thermoplastic polymer matrix and fibers of different nature with high tensile strength and low density.
• the matrix has the function of impregnating and holding the fibers together, allowing the shaping of the material, in relation to the component to be made, and of transferring to the fibers the stresses applied to the component during use.
• the adhesion between the fibers and the matrix must be very high.
• Fiber-reinforced polymeric composites are a class of materials widely used in the aerospace sector, as they are characterized by lightness and high specific structural strength (ratio between strength and density), which allows to reduce energy consumption and/or to increase the useful load of the aircraft.
• thermosetting matrix reinforced with carbon fibers are particularly studied for the high performance they offer.
• the diffusion on other means of transport on land and sea is currently limited by the high cost of carbon fibers and the production technologies of composite products, which are generally not very flexible and in any case can be automated only for some product geometries.
• the present invention relates to polymeric composites for structural uses comprising inorganic or synthetic fibers, preferably from waste recycling, having three-dimensional geometry. Furthermore, the present invention relates to a method for the preparation of said composite materials.
• the composite materials according to the present invention are useful in the automotive, aeronautical, railway, naval fields and, in general, for all those industrial uses where light and resistant structures are required.
• the composite material object of the present invention is prepared using a process called infusion.
• Infusion is a technique for creating composites, which involves laying the reinforcement fibers on the dry mold, i.e. without resin, and subsequently adding resin to the mold by depression.
• an area with a lower pressure than the surrounding atmospheric one is created inside the mold, capable of attracting the resin, for which flow channels have been set up, going from the resin storage tanks to the mold.
• This depression commonly called “vacuum”
• vacuum bag is obtained by covering the mold with a plastic film, commonly called “vacuum bag”, effectively connected to the mold to avoid air infiltration. The air is sucked from the area between the vacuum bag and the mold by means of an electromechanical pump and suction ducts.
• the vacuum bag will adhere strongly to the mold by squeezing the fibers and creating the depression necessary to make the resin flow.
• the resin Once the resin begins to flow into the mold, it must be able to travel the entire surface of the mold, that is, impregnating all the fibers, in less time than the curing time.
• the resin must remain in the liquid state throughout the infusion process to allow complete impregnation of all areas; only at this point the catalysing process of the resin can begin which then passes to the solid state with an exothermic reaction.
• the resin passes from the storage tanks to the mold through suitably sized and positioned tubes. Once inside the mold, however, the resin must be able to flow easily and therefore resin diffusion methods must be provided which vary according to the type of infusion adopted.
• the fibers are cut through a cutting unit (rotary cutter), in order to obtain fibers of a size between 1-600 mm; preferably 15-300 mm; most preferably 30-60 mm in length.
• a cutting unit rotary cutter
• Said fibers are selected from the group comprising: carbon, glass, ceramic, aramid, basalt fibers; carbon fibers are preferred; carbon fiber sheets from aerospace industry waste are highly preferred.
• the fibers are collected in a carding machine that allows the opening the bundle of fibers and untangle them.
• the untangled fibers are subjected to a step called "enzymic step" in which, thanks to a pneumatic conveying system, the fibers are transported in a hopper in which, with the help of specific nozzles, an emulsifying product is nebulized with the dual objective to favour the sliding of the fibers and to reduce the electrostatic charge.
• emulsifying product it is meant a substance capable of stabilizing an emulsion, acting as a surfactant or stabilizer.
• a resinoid substance/primer is applied, useful for promoting the adhesion of the fibers to the matrix.
• This step is particularly important, because it allows to safeguard the mechanical properties of the fibers and makes them more wettable.
• auxiliary support fibers selected from the group comprising: natural fibers, such as cotton or flax; organic polyester fibers (PES); polyestereketone fibers (PEEK); inorganic glass, metal and/or aramid fibers; wherein said auxiliary support fibers are present in a dose of 0.5-50%, preferably 1-10%; most preferably 5% of the total composition.
• the auxiliary support fibers allow homogeneous reinforcement and guarantee specific functional properties.
• the fibers thus obtained/treated of the previous steps feed a carding machine, preferably aerodynamic carding, in which the fibers are untangled, air-formed and distributed according to a partially parallel orientation.
• a carding machine preferably aerodynamic carding, in which the fibers are untangled, air-formed and distributed according to a partially parallel orientation.
• the veil of fibers is subsequently layered and joined together with other veils to create a fabric with a flat textile structure having the desired thickness and weight.
• the different layers of veils are heated until the fibers are thermally welded to each other due to the effect of heating, thus obtaining a non-woven fabric.
• the non-woven fabric of the previous step is passed through rollers, obtaining a non-woven felt (three-dimensional mat) whose physical and mechanical properties vary according to the application needs in terms of weight, thickness, grammage, percentage of fibers, auxiliary additives and degree of fiber orientation.
• This STEP is the one described above.
• the molds can be made of wood, epoxy boards, metal or composite material. Generally, metal or composite material molds are used to produce numerous components, while wooden molds are used for the production of prototypes.
• the mold is assembled, if composed of several parts, and covered with a release product to facilitate the detachment of the finished product when the lamination is finished.
• the felt i.e. the three-dimensional mat obtained at the end of STEP 1
• reinforcement material is cut to obtain reinforcement shapes that adapt to the mold made and prepared during STEPS 2 and 3.
• Such reinforcement material (the felt) on the mold is carried out dry, facilitating its positioning on said mold and allowing the use of high grammage reinforcement material. Said positioning provides for the placing of several layers of reinforcing material allowing to make a laminate.
• STEP 6 optional - Covering the mold If the positioning of the reinforcement materials of step 5 continues over time, it is advisable to cover the mold with plastic sheeting between one working session and the next, to avoid that residues of fibers or dust settle on the reinforcement material.
• the mold must be covered with the infusion auxiliaries, i.e. tools that allow the flow of the resin inside the laminate and therefore the execution of the infusion process.
• the infusion network consists of pipes, fittings, valves, couplings and traps that allow vacuum suction and resin injection into the vacuum bag.
• the resin infusion channels generally consist of tubes that start from the storage tanks and arrive at the article.
• the next step consists in laying out the vacuum bag, which is placed above all the layers previously described.
• the vacuum bag consists of an air-impermeable plastic film, which is spread over the mold and fixed along its entire perimeter to prevent the entry of air.
• the vacuum bag must then be shaped, placed on top of the mold and cut along the perimeter. Finally, the perimeter of the vacuum bag must be fixed to the flange of the mold outside the suction lines.
• creation of the vacuum can be carried out, using a pumping station consisting of one or more pumps to allow the air present between the vacuum bag and the mold to flow.
• the resin must first be poured into the containers and then added to the catalyst and any additives, such as accelerators or retarders.
• the temperature range within which the infusion can be carried out ranges from 16° C to 32° C.
• the stop taps of the infusion lines must be opened to allow the resin to begin to flow to the mold.
• the infusion can be said to be completed when all the areas have been reached by the resin; at this point it is noted that the resin begins to enter the suction lines and at the same time the pressure value undergoes a sudden drop.
• auxiliary support fibers used during STEP 1 are selected from the group comprising: natural fibers, such as cotton or flax; organic polyester fibers (PES); polyestereketone fibers (PEEK); inorganic glass, metal and/or aramid fibers;
• the fibers have a filiform structure having a completely random positioning
• the perimeter flange of the mold has a size of at least 150mm.
• the value of depression for the realization of the vacuum varies from 0.4 bar to 0.65 bar, a very preferable value is 0.55 bar;
• the temperature range within which the infusion can be carried out ranges from 16 °C to 32 °C;
• the infusion period depends on the propagation speed of the resin, and wherein said propagation speed is affected by:
• the resin used in STEP 12 is selected from the group comprising: epoxy resin and/or epoxy-vinylester resin.
• the composite material obtained at the end of the procedure described above was subjected to physico- mechanical tests, such as tensile tests with strain gauge, bending, Flat-top cylinder Indenter for Mechanical Characterization (FIMEC) and modal analysis, to evaluate its mechanical strength.
• physico- mechanical tests such as tensile tests with strain gauge, bending, Flat-top cylinder Indenter for Mechanical Characterization (FIMEC) and modal analysis, to evaluate its mechanical strength.
• Figure 1 shows the felt (three-dimensional mat) obtained through the working of carbon fiber, in which the fibers are oriented according to a three-dimensional and random architecture.
• Figure 2 shows a functional scheme of the infusion system comprising:
• Figure 3 shows the composite material obtained at the end of the process of the present invention.
• Figure 4 shows in a graph the result of the tensile tests in the same infusion direction as the resin on 4-layer panels.
• Figure 5 shows in a graph the result of the tensile tests in the 45° direction with respect to the infusion direction of the resin on 4-layer panels.
• Figure 6 shows in a graph the result of the tensile tests in the 90° direction with respect to the infusion direction of the resin on 4-layer panels
• Figure 7 shows in a graph the result of the bending tests in the same infusion direction as the resin on 4- layer panels.
• Figure 8 shows in a graph the result of the bending tests in the 45° direction with respect to the infusion direction of the resin on 4-layer panels.
• Figure 9 shows in a graph the result of the bending tests in the 90° direction with respect to the infusion direction of the resin on 4-layer panels.
• the recycled carbon fibers were collected to be cut through a cutting unit (rotary cutter) so as to obtain a homogeneous size of the fibers, having a length of 45 mm.
• a resinoid substance/primer useful to promote the adhesiveness of the fibers to the matrix was applied, to protect the mechanical properties of the carbon fibers and to make them more wettable.
• the mass of carbon fibers was mixed, through a mixing unit, for 5% of the total composition, with flax fibers.
• the fibers thus obtained were processed with an aerodynamic carding machine, in which the fibers were untangled, air-formed and distributed according to a partially parallel orientation. Following aerodynamic carding, a veil of fibers oriented according to a three-dimensional and one-way architecture was obtained (see Figure 1).
• the veil of fibers was subsequently stratified and joined together with three other veils of fibers to create a non-woven fabric with a flat textile structure.
• the four fiber veils were heated by thermal means. Due to the heating effect, the fibers that formed the veils were welded to each other, resulting in a non-woven fabric.
• the non-woven fabric was passed through rollers, obtaining a non-woven felt (three-dimensional mat) having a 1 mm thickness.
• a panel made of composite material was made, using 4 200 g layers of carbon fibers felt worked as described in Example 1.
• the sizes of each single layer of felt were as follows: 300 mm x 185 mm and 1 mm thickness.
• Said layers were oriented at a 0°/90°/0°/90° to obtain an almost isotropic laminate.
• the panel was found to have a mass of 283 g.
• Thickness 4.5 mm
• Example 2 Using the process of Example 2, ten panels of the four-layer composite material according to the present invention were prepared.
• Tables 1 and 2 report the mean values obtained by characterizing the 10 panels of composite material obtained with the process of the present invention.
• Tables 3 and 4 report the mean values obtained by characterizing 10 panels of composite materials made of the classic carbon fiber sheets. Table 3 - Tensile tests in the 0°, 45° and 90° directions of a composite material made with classic carbon fiber sheets.
• Said layers were oriented at 0°/90°/0°/90° to obtain an almost isotropic laminate.
• Said panel had a mass of 283 g.
• the results were aimed at verifying the operating elastic constants through correlation with the corresponding modal analysis performed numerically, on the Finite Element model (FE) of the same panel.
• FE Finite Element model
• the responses and excitations were directly acquired, in the form of transfer functions in the frequency domain, acceleration/force, through the multichannel analyzer "GenRad 2515 C.A.T. System” with appropriate windows on the impact signal of the instrumented hammer and the accelerometer response, performing an average of 5 useful hits for each point of acquisition.
• the "coherence” function controlled on all acquisition points in the selected acquisition field, between 0 and 1,000 Hz, always had values equal to, or close to, "1", which indicated an excellent correlation in the transfer between the excitation and response energy, with good linearity and, in general, absence of effects unrelated to the desired excitation in the transfer functions.
• the modal analysis, with the acquired functions, were performed using the computer integrated in the G.R. 2515 system, using the analysis software "Modal Plus” (SDRC).
• the panel was placed horizontally on a layer of polyurethane foam shaped in cusps. This solution was sufficient to approximate a free-free mass condition, in which the rigid modes of the same on the support occurred at a much lower frequency than that of the first elastic mode of the structure, ensuring non interference.
• the panel was ideally divided into 15 points of acquisition of the response to excitation, equally spaced in 2 directions, X (long side) and Y (short side).
• the impact technique was used as excitation, using a PCB instrumented hammer, with nominal 100 N/Volt load cell, while the 15 point response was acquired with an ICP 303A3 piezoelectric accelerometer, of PCB, fixed, from time to time, by means of a "Petro Wax” adhesive from PCB ("beeswax" synthetic). For each point an average on 5 hits considered valid was performed.
• the response accelerometer was previously calibrated against a reference accelerometer PCB 302A07 (100 mV/G), via schaker B-K 4809, driven by a B-K 2706 amplifier with sinusoidal input at 160 Hz (1,000 rad/s) by Pintek 3200 generator, at an acceleration of 1 Grms, equal to 1.41 peak-peak.
• the calibrated elastic constants of the 4-layer panel which most reduced the deviations on the calculated natural frequencies compared to the experimental ones, were the following:

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Textile Engineering (AREA)
• Mechanical Engineering (AREA)
• Composite Materials (AREA)
• Inorganic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Reinforced Plastic Materials (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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• 2019
  • 2019-02-06 IT IT102019000001681A patent/IT201900001681A1/it unknown
• 2020
  • 2020-02-06 WO PCT/EP2020/052951 patent/WO2020161220A1/en unknown
  • 2020-02-06 EP EP20705125.1A patent/EP3921144A1/de active Pending

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