This invention pertains to the development of a specialized core material intended for use in both closed and open mold systems. It includes a detailed method for creating this core material, as well as the formation of a laminate that incorporates the core material. Furthermore, it covers the process for fabricating shaped articles using the laminate, the characteristics of these shaped articles, and the various applications for which they can be employed.

The core material developed in this invention comprises at least one fibrous web, which contains an integrated foam structure. This foam structure is composed of multiple members that are arranged within the fibrous web. The members are separated from each other by channels, which are designed to be permeable to resin and a binder. Additionally, these channels incorporate a network of electrically conductive material. This design facilitates the distribution of resin and binder throughout the foam structure, ensuring robust bonding and enhanced electrical conductivity in the final composite material.

Description

The invention pertains to a core material designed for both closed and open mould systems. It encompasses a method for producing this core material, a laminate that incorporates the core material, a procedure for creating a shaped article using this core material, the shaped article itself, and the applications of the said shaped article.

The core material described in the invention is applicable to the production of fiber-reinforced plastic materials and is suitable for use in both open and closed mould systems. Fiber-reinforced plastics are commonly utilized to manufacture various shaped articles, including automotive and industrial parts such as tanks, bathtubs, road signs, cladding panels, boats, caravans, nacelles, and rotor blades. Incorporating a fibrous web into a resin material generally enhances the material’s strength, stiffness, fatigue life, fracture toughness, environmental resistance, and temperature stability, while also reducing its weight and manufacturing costs.

The use of core materials in fiber-reinforced plastics has been a well-established practice for decades. This approach primarily aims to reduce the amount of resin needed, thereby achieving cost and weight savings. Additionally, it seeks to enhance certain mechanical properties of the material, such as bending stiffness. For example, patents EP-A-1 010 793 and WO-A-2004/028776 describe the incorporation of micro-spheres within a fibrous web for reinforcing objects made with such webs. Although WO-A-2004/028776 mentions the inclusion of metal fibers, it refers specifically to fibers within the web itself and not to a distinct layer of electrically conductive material.

WO-A-92/22420 details a method for creating a composite material in which a web is impregnated with a curable resin, and a porous layer is applied to the web material. The bonding of this porous layer occurs after the resin has cured. However, WO-A-92/22420 does not disclose a flexible core material that includes a web with an attached electrically conducting layer.

These existing fibre-reinforced materials, however, lack the capability to shield against electromagnetic interference (EMI), which can be crucial for certain applications.

Electromagnetic interference (EMI) is the vulnerability of electronic devices to external electromagnetic fields. These fields can cause current fluctuations in the devices, leading to issues such as unexpected switching in microprocessor units and semiconductor chips. This problem is especially pronounced in applications with a high concentration of electronic components, which are particularly prone to electromagnetic interference.

A widely recognized environmental source of electromagnetic interference is lightning. The damage is not limited to the initial lightning strike; the static electrical fields that persist after the strike can also have adverse effects. This is particularly concerning in applications that are prone to lightning strikes and contain a high concentration of advanced electronics, such as aircraft and wind turbine nacelles. In these scenarios, effective electromagnetic interference shielding is highly desirable雷电是

Another disadvantage of static electrical fields is their propensity to attract dust and other particles. This issue becomes particularly problematic when the affected object or article is in motion, as it can lead to undesirable friction. For instance, in the case of wind turbine blades, the attraction and accumulation of dirt due to static electrical fields can significantly decrease the turbine’s efficiency.

The potential damage from electromagnetic interference (EMI) can be mitigated by incorporating a continuous conductive shield around sensitive electronic systems. One common solution is the use of a Faraday cage, where the conducting material’s electrical charges redistribute themselves to cancel out external electromagnetic effects within the cage’s interior.

One effective method for providing a composite article with a continuous conductive shield involves embedding a conductive metal wire mesh within the composite article during its fabrication. This approach creates a conductive layer while utilizing standard composite parts fabrication processes. The article can be fabricated by initially placing a metal wire mesh onto a composite laminate built-up in a mold. During the molding process, resin flows into the voids of the mesh under uniform pressure, effectively integrating the structure and providing the necessary conductive shield.

However, this process necessitates careful handling of the metal wire mesh, which proves to be quite challenging in practice. Often, the metal wire mesh tears, shifts, or pierces crucial layers required for the production process, such as puncturing the plastic bag used in vacuum injection molding. Consequently, the metal wire meshes traditionally employed in these composite materials are relatively thick to prevent tearing. However, using thick metal meshes increases the production costs of the composite materials.

The objective of the invention is to provide a core material that addresses the aforementioned disadvantages.

The inventors discovered that this objective can be achieved by creating a core material with a continuous conductive shield.

Thus, the invention, in its first aspect, pertains to a material suitable for use in closed or open mould systems, comprising:

At least one woven or nonwoven fibrous web containing a foam structure within the web, with the foam structure being formed of multiple members separated by resin-permeable channels.

A binder and a layer of electrically conductive material, which has properties that provide shielding from electromagnetic radiation.

The electrically conductive layer is ideally a separate component. This layer can be affixed to the fibrous web using a binder or attached through gluing with a low-melting material and subsequent heating to create a melt-bonded connection. Mechanical attachment methods, such as stitching, are also viable.

This core material excels in applications requiring electromagnetic shielding. It offers exceptional drapability, compression resistance, and suitable permeability. Its inherent flexibility allows it to be easily shaped as needed before resin application.

The network can be realized as a wire mesh made of electrically conductive material or by incorporating electrically conductive fibers into the fibrous web. Another method involves creating the network through vacuum deposition techniques such as sputtering. Preferably, the network takes the form of a wire mesh.

The wire mesh can have a thickness of 500 μm or less, ideally 200 μm or less, such as 100 μm or less, or even 50 μm or less. Typically, the wire mesh will be at least 5 μm thick, such as 10 μm or more. Therefore, the invention allows the use of very thin wire meshes, reducing both cost and weight of the final product.

Mesh size can vary based on application needs, generally ranging from 10-1000 μm, such as 20-500 μm or 50-200 μm.

The electrically conductive material is typically metal, with copper, aluminum, and stainless steel being preferred. Depending on the application, different metals may be used; for example, copper offers high conductivity, while aluminum is lighter and more cost-effective. Electrically conductive materials can also be produced using carbon fibers.。

The conductivity of the core material of the invention ranges from 35·10^6 to 63·10^6 S/m at 20°C, preferably from 37·10^6 to 60·10^6 S/m at 20°C.

When the core material includes an electrically conductive wire mesh, the fibrous web with the foam structure acts as an electrical insulator between the wire mesh and an electrically conductive article it is applied to. This is particularly beneficial in applications using electrically conductive carbon for its mechanical properties, where unwanted currents could negatively affect the carbon’s performance.

The core material can be easily cut to size and, due to its drapability, can be bent and formed as needed. In some cases, the inclusion of the electrically conductive network even enhances the material’s formability compared to core materials without such a network.

The electrically conductive network within the core material can also be used to apply an electrical current for localized heating. For example, during the post-curing process of an article within a mold, the network allows precise heat application to specific areas. This capability enables effective post-curing while the article remains in the mold, offering a significant advantage in manufacturing.

Similarly, the core material of the invention can be incorporated into a mold wall to facilitate mold heating.

Moreover, the mechanical properties of the core material can be tailored and enhanced through the electrically conductive network, depending on the application. For example, incorporating copper into the network may enhance the impact resistance and toughness of the final product.

The distribution of members and channels within the core material can be either regular, with a pattern repeat of less than 1 cm or even less than 0.5 cm, or irregular, as described in WO-A-2004/028776.

The permeability of the core material to resin can be selected across a wide range, depending on the desired application, particularly concerning the resin’s penetration time. Excellent results have been achieved with core materials having an in-plane permeability of at least 1·10−9 m² for resin, providing highly satisfactory flow properties. For even better resin flow, the permeability is preferably at least 1.5·10−9 m², and more preferably more than 5·10−9 m².

The permeability is primarily provided by the channels formed by areas without members. Permeability (k) is defined here according to Darcy’s law for steady flow as follows:

(Here you would include the relevant formula or continuation of the definition as needed.)

q = k · A η · Δ   p Δ   x ,

wherein q is the resin flow in m3/s, A is the total surface of the cross section through which the resin flows in m2, η is the viscosity of the resin in Ns/m2, Δp is the pressure difference in N/m2, and Δx is the distance over which the pressure difference exists and the resin flows in m. The permeability is defined in the plane of the material, i.e. not perpendicular to the material, but parallel to the upper and lower surface thereof.

Drapability is defined as the core material’s ability to conform to a contoured surface, particularly a mold. Specifically, a core material is considered drapable if it can bend around a corner with a radius of 10 mm or less without substantial irreversible deformation. This feature enables the material to drape well in the mold, allowing for the production of smoothly shaped products. Ideally, the core material exhibits drapability that permits bending around a corner with a radius of only 5 mm or less.

Compression resistance is defined as the ability to withstand forces that tend to crush or buckle the material. This is measured by determining the height of the material before and during the application of a 1 bar pressure perpendicular to the plane of the material. The compression resistance is calculated as follows:

100  % × height   of   the   material   at   1   bar   pressure height   of   the   material   at   no   pressure .

The compression resistance can be tailored across a wide spectrum, depending on the application’s requirements and the desired characteristics. Excellent results have been observed with a core material exhibiting a compression resistance of at least 40% at 1 bar pressure. For applications in closed mold systems, it is highly preferable for the compression resistance to be at least 60% at 1 bar pressure, with 70% or more being even more desirable. Such high resistance is particularly beneficial as it minimizes the risk of channels being compressed, thus ensuring efficient resin flow during processing in a closed mold. Consequently, a core material with a compression resistance exceeding 75%, and ideally reaching at least 80%, 90%, or even 95% at 1 bar pressure, is highly preferred.

Under certain circumstances, one might opt for a core material with relatively low compression resistance, such as around 50% or less.

Specifically, for core materials suitable for hand lay-up or spray-up systems, a relatively low compression resistance is generally sufficient, particularly a resistance of 30% at 1 bar or more.

When prioritizing surface quality while aiming to limit resin usage and/or the final composite’s weight, one might choose materials with relatively lightweight members, such as a microsphere foam structure; materials with relatively large members, in the range of 1-3 mm; materials with narrow channels between the members, less than 1 mm; and/or a relatively low free volume, in the range of 40-60 vol.%.

If surface quality is paramount and weight or cost savings are less critical, selecting a core material with relatively small members, in the range of 0.5-2 mm (or 0.5-1.5 mm for non-irregular patterns), a high degree of irregularity in the member pattern, and a resin with low shrinkage after curing, such as epoxy resin, would be ideal.

If high drapability and surface quality are desired, selecting core materials with relatively wide channels, averaging 0.5-2 mm in diameter (or 0.5-0.75 mm for non-irregular patterns), combined with small members, averaging less than 1 mm in diameter, a high degree of irregularity, and a flexible fiber material such as polyester fibers with an acrylate binder, is ideal.

The members form “isles” within or upon the web, largely surrounded by channels through which resin can flow. These channels are mostly free of web material or fibers, although some fiber material may be present to ensure consistency of the core material. The material content in the channels should be low enough to provide sufficient permeability for adequate resin penetration, preferably with a permeability of at least 1·10−9 m².

The members typically consist of a closed-cell foam structure, potentially from a material usable as a binder. They can also include or be formed from micro-spheres, which will be discussed later. These members significantly contribute to the compression resistance of the core material and are generally impenetrable to resin, having a permeability substantially less than 1·10−9 m².

The members can have various shapes, with good results achieved using core materials where most members have circular, ellipsoidal, or polygonal cross-sections parallel to the material plane. Preferred polygonal cross-sections include triangular, tetragonal, pentagonal, hexagonal, heptagonal, or octagonal shapes, with combinations also being possible.

An irregular distribution can be achieved using uniformly shaped members of varying or identical dimensions. Excellent results have been observed with core materials where most, if not all, members exhibit a circular or ellipsoidal cross-section parallel to the material plane.

Alternatively, irregular distribution can be attained by incorporating a variety of differently shaped members. Outstanding results have been noted in core materials where the majority, and preferably all, members display a polygonal cross-section parallel to the material plane. These differently shaped members are ideally selected from triangles, tetragons, pentagons, and hexagons.

Exceptional surface quality is achieved with core materials featuring an irregular pattern, where most, and preferably all, members have a diameter of less than 3 mm, as defined by the diameter of the enveloping circle in the material plane. Preferably, the majority of members, and ideally all, have a diameter of less than 2.5 mm, with particularly good results seen when the majority have a diameter of less than 1.5 mm.

The lower limit of the diameter is not particularly critical; typically, most members will have a minimum diameter of about 0.2 mm, and for practical reasons, generally at least about 0.5 mm. Aside from surface quality, the diameter of the members also impacts the extent to which resin usage is restricted in a closed mould system.

The thickness of the core material can vary greatly, typically ranging between 1 and 4 mm, with a preferred range of 1.5 to 3 mm, although both thicker and thinner versions can be produced according to the invention.

Ideally, the fibrous web containing a foam structure has a free volume of less than 80 vol.%, more preferably between 50-70 vol.%. The free volume refers to the portion of the material that can be penetrated by resin, with the remaining volume composed of the members and some fibres.

A preferred web consists of at least 20 wt.% fibres, with up to 80 wt.% binder material, which may be foamed. The closed-cell foam structure forming the members can be created from (optionally expandable) micro-spheres introduced into the web using a foamed binder material.

Excellent results have been achieved with core materials containing micro-spheres with an activation temperature of at least 120°C, where the free volume in the web is at most 80 vol.%. The web can be bonded mechanically, physically, or chemically.

A much-preferred core material includes at least 30 wt.% fibres and up to 70 wt.% binder material, potentially also containing expandable micro-spheres. Typically, the amount of expandable micro-spheres is less than 15 wt.%, preferably between 1-10 wt.% based on the total weight of the core material.

The micro-spheres are preferably expandable and more desirably have an activation temperature of at least 120°C.

Exceptional results have been achieved with core materials incorporating expanded thermoplastic micro-spheres, such as those made from alkylmethacrylate-based polymers (e.g., methyl methacrylate), acetonitrile (e.g., polyacetonitrile), vinylidene chloride, or their combinations. These micro-spheres have an initial expansion temperature lower than the curing temperature of the binder. Examples of such micro-spheres include the Expancel™ products by AKZO-NOBEL.

The core material can be fabricated using traditional techniques for manufacturing fiber-reinforced plastic materials, as detailed in EP-A-1 010 793, with rotary screen printing being a preferred method.

A favored production approach involves placing a metal wire mesh over a fibrous web (or vacuum-depositing a metal network onto the web), then incorporating expandable micro-spheres into the web using a binder material. The micro-spheres are expanded, and the binder is cured, adhering the metal wire mesh to the core material. Ideally, the micro-spheres should start expanding at a temperature below that of the binder’s curing temperature.

Alternatively, the core material can be produced by printing a non-woven fabric, with an electrically conductive wire mesh placed on it, using a binder that includes expanded micro-spheres (polymeric, glass, or ceramic).

When using expandable micro-spheres, the preferred process involves preparing a dispersion of these micro-spheres in a binder material, which may be foamed. This dispersion is applied to a non-woven fabric, which has a thickness less than the final desired thickness, and upon which a conductive wire mesh is placed. The material is then dried and heated to activate the micro-spheres’ expansion.

Optionally, the material can undergo pre-drying at a temperature range of 70 to 100°C before being brought to the expansion temperature of the micro-spheres. As the micro-spheres expand, the temperature is further increased, causing the binder material to cure and set the micro-spheres within the web. Simultaneously, the metal wire mesh is affixed to the core material. This process results in the creation of the core material as envisioned by the invention.

Alternatively, or in conjunction with the aforementioned method, a non-woven base web containing a network of conductive fibers can be utilized. In this scenario, there is no need to overlay the base web with a metal wire mesh; instead, the dispersion of expandable micro-spheres can be directly screen-printed onto the base web. However, this method is less preferred due to the difficulty in ensuring sufficient electrical properties to achieve effective shielding from electromagnetic radiation.

The initial expansion temperature of the micro-spheres is ideally between 120 and 190°C, while the curing temperature of the binder should preferably exceed 170°C.

The fibrous web employed in this invention is typically a non-woven material, which may be reinforced and is based on conventional fibers. The production of suitable non-wovens has been detailed by Dr. H. Jörder in “Textilien auf Vliesbasis” (D. V. R. Fachbuch, P. Kepper Verlag). A combination of a non-woven fibrous web with a reinforcing fabric, positioned either within or on top of the other, is also feasible.

The fibers within the web are preferably chosen from a variety of materials including natural fibers, glass fibers, metal fibers, ceramic fibers, or synthetic fibers such as acrylic, polyethylene, polypropylene, polyester, polyamide (aramid), carbon, or polypropylene fibers, and their combinations. More preferably, the fibers are selected from glass fibers, polyester fibers, and polyester-polyethylene bicomponent fibers, among others. Outstanding results have been observed with polyester fibers, which exhibit excellent adherence to resin and tend to maintain a low moisture content.

According to an exceedingly convenient method, the non-woven fabric is composed of a blend of polyester fibers and polyethylene-polyester bicomponent fibers (or other low-melting fibers or powders). These webs are thermally bonded by the bicomponent fibers. Upon heating the web to the initial expansion temperature of the micro-spheres—above the melting point of the polyethylene bond—the web becomes loose and expands effortlessly. Post-expansion, and upon curing, the final material re-establishes its robust bond, yielding the advantageous combination of properties described in the invention. The thermal bonding also facilitates easy handling of the web during the initial stages of the process.

The micro-spheres incorporated into a fibrous web according to the invention preferably consist of a thermoplastic synthetic resin material solid at room temperature. Suitable resins include polystyrene, styrene copolymers, polyvinyl chloride, vinyl chloride copolymers, vinylidene chloride copolymers, and others.

Expandable micro-spheres typically contain a blowing agent, which causes the micro-spheres to expand when the fibrous web containing them is cured. These micro-spheres are embedded in the fibrous web in an unexpanded form, often via a paste such as foam paste. The blowing agent may be chemical or physical, including substances like azodicarbonamide, isobutane, isopentane, pentane, freon, iso-octane, etc.

The micro-spheres ideally have a diameter of 4-20 μm in their unexpanded state, expanding to a diameter of 10-100 μm. After expansion, the micro-spheres typically constitute 10 to 60 volume percent of the web, depending on the quantity of micro-spheres used and their degree of expansion.

Suitable binders include lower alkyl acrylate polymers, styrene-butadiene rubber, acrylonitrile polymers, polyurethanes, epoxy resins, polyvinyl chloride, polyvinylidene chloride, and copolymers of vinylidene chloride with other monomers, polyvinyl acetate, partially hydrolyzed polyvinyl acetate, polyvinyl alcohol, polyvinyl pyrrolidone, polyester resins, and so on. These binders can be optionally carboxylated, for example using maleic anhydride. Additionally, the binder paste may contain water, surfactants, foam stabilizers, fillers, and thickeners, as described in EP-A-0 190 788.

The present invention further encompasses a laminate composed of at least a core material, as described in the invention, combined with at least one fibrous fleece. This laminate can be formed using various methods, with a preference for stitching or gluing the fleece to one or both sides of the core material. Established techniques for forming such laminates are well known in the art.

One notable advantage of this laminate is its ease of use. By integrating the core material and fleeces into a single step, the laminate simplifies the manufacturing process for composites. This eliminates the need for separately layering the bottom fleece, core material, and top fleece into the mold in individual steps.

Any fibrous fleece suitable for composite preparation can be utilized. Preferred fleeces include glass fiber fleeces, carbon fiber fleeces, polyaramide fiber fleeces, and their hybrids, such as glass-carbon fiber fleeces, glass-polyaramide fiber fleeces, or carbon-polyaramide fiber fleeces.

The core material, as per the invention, is particularly well-suited for creating thin laminates with a smooth, aesthetically pleasing surface. For instance, a laminate according to this invention may ideally have a total thickness ranging from 2 to 10 mm, preferably between 3 to 6 mm. Excellent results have been achieved with a laminate comprising a core material thickness of 1 to 2 mm, covered on both sides with a fleece, preferably a glass fleece, with a thickness of approximately 0.4 to 0.8 mm. For example, a glass fleece of about 225-600 g/m², typically around 450 g/m². This configuration results in a laminate with a thickness of about 2-3 mm, exhibiting superior surface quality after being cured with a resin, particularly an epoxy resin.

The invention also includes a method for manufacturing a shaped article, wherein a fibrous web, as described herein, is impregnated with a liquid resin and an appropriate hardener.

Suitable liquid resins for impregnating a fibrous web, as per the invention, include any synthetic plastic materials that can be applied in liquid form and subsequently cured. Examples encompass polyester resins, phenylester resins, polyurethane resins, phenol resins, melamine formaldehyde resins, and epoxy resins. Depending on the specifications of the shaped article to be manufactured, a skilled artisan can adeptly select the appropriate resin.

Similarly, suitable hardeners for use in this method are those that can effectively cure the chosen liquid resin. These systems are well-known to those skilled in the art, who can combine resin and hardener to achieve optimal results.

The present invention also extends to a shaped article based on the core material described herein, particularly one that can be obtained by impregnating the core material with a resin and curing it.

The shaped article derived from this invention can be advantageously used as a shielding material for static electric charges. Applications include housings for electronics, electric cars, and batteries. These articles can function as Faraday cages. For instance, a composite box with a copper scrim surface can be produced to form a Faraday cage, useful for holding batteries. This is especially beneficial in the automotive industry, as it protects the electronic systems and telecommunication or navigation equipment from the electromagnetic radiation of the batteries. Other electromagnetic compatibility applications include train building, power stations, operating room walls, and nacelles (such as those in aircraft and wind turbines).

A particularly suitable web material for use with this invention is Soric™, a polyester nonwoven material featuring a compression-resistant hexagonal (SF, XF, LRC) or random dot-printed (TF) cell structure. These pressure-resistant cells, separated by channels, contain synthetic micro-spheres. The cells do not absorb resin, and their pressure resistance ensures thickness in the laminate, even under vacuum bag pressure. Thus, Soric can be used as a core material in composite sandwich laminates. The channels facilitate resin flow, creating a pattern of cured resin with excellent mechanical properties and bonding to the outer skins. Due to these favorable flow properties, Soric can also serve as a process-supporting flexible core material.

Soric is designed for closed mold processing, such as Vacuum Infusion or light resin transfer molding (RTM(L)). In these processes, each layer is laid up as a dry stack of materials in a first mold. The second mold can be a vacuum bag (VI) or a solid counter mold (RTM). This second mold covers the first mold and the dry-laid materials. Vacuum is then applied to the bag/second mold. When the stack of materials is under vacuum, resin is applied. The channels in Soric enable resin flow, impregnating the rest of the materials. Once all materials are wetted out, the resin inlet is closed, and the laminate is allowed to cure. Other core materials may also be used in place of Soric in accordance with this invention.

The invention will now be elucidated with the following non-restrictive example.

EXAMPLE

When applied in the main laminate of a wind turbine nacelle, the following core material-scrim combination can establish a Faraday cage to safeguard the electronic devices housed within the nacelle.

A copper scrim was integrated into a chemically bound base web composed of 80 wt. % polyester and 20 wt. % acrylate binder.

The copper scrim was crafted as a woven square wire mesh adhering to ISO-9044 standards. Both the warp and weft of the mesh consisted of 99.9% copper, each with a thickness of 0.050 mm.

A hexagonal pattern, with an average diameter of 6 mm, was imprinted onto this non-woven and scrim combination using a microsphere-binder mixture (comprising 90 wt. % acrylate binder and 10 wt. % expandable microspheres Expancel®, from AKZO-NOBEL; weight percentages based on solids) through rotary screen-printing. This combination was then pre-dried at approximately 90°C, just below the expansion temperature of the microspheres. Subsequently, the microspheres were expanded to a thickness of about 2 mm, and the binder was cured at around 200°C. The pre-drying and subsequent expansion and curing process ensured robust bonding between the base web and the scrim.

CLAIMS

1. A core material ideal for deployment in either closed or open mold systems, comprising:

At least one woven or nonwoven fibrous web

A binder

A layer of electrically conductive material with properties that ensure effective shielding from electromagnetic radiation, securely attached to the fibrous web.

2. According to claim 1, the fibrous web incorporates a foam structure within, composed of multiple members separated by resin-permeable channels.

3. According to claim 1, the electrically conductive material layer consists of a network formed by conductive fibers, ideally with a thickness of 500 μm or less, preferably 10-200 μm. This network typically appears as a wire mesh with an optimal mesh size ranging from 10-1000 μm, preferably 20-500 μm, such as 50-200 μm.

4. According to claim 1, the electrically conductive material is composed of copper, aluminum, and/or stainless steel.

5. According to claim 1, the foam structure contains microspheres, preferably made of glass, ceramic, or thermoplastic materials.

6. Core material as described in claim 2, wherein the foam structure is derived from a mechanically robust foamed binder composition.

7. Core material as described in claim 3, wherein the wire mesh has a thickness of 500 micrometers or less, preferably ranging between 10 and 200 micrometers.

8. Core material as described in claim 3, wherein the wire mesh is applied using a sputtering technique.

9. Core material as described in claim 3, wherein the wire mesh is affixed to the fibrous web via the binder material.

10. Process for manufacturing a core material as outlined in claim 2, which involves incorporating a foamed or foam-generating substance into a fibrous web with at least one binder; positioning the wire mesh on the fibrous web; and solidifying the foam within the web by curing the binder.

11. A laminate comprising a core material according to claim 1, laminated with at least one fibrous fleece, said fibrous fleece-preferably comprising one or more selected from the group consisting of glass fibres, carbon fibres and polyaramide fibres.

12. A process for preparing a shaped article, said process comprising placing a core material according to claim 1, optionally in combination with one or more other non-woven fleeces, or a laminate in a closed mould, introducing a liquid resin into the mould and curing the resin to produce the article.

13. Shaped article obtainable by the process according to claim 12.

14. Shaped article based upon a core material according to claim 1, or a laminate.