Shock and / or sound absorbing material, a package comprising a mechanical shock absorbing material, and a sound absorbing element

Abstract

The disclosure relates to a piece of a mechanical shock and / or sound absorbing material formed of an air-laid material comprising natural fibres, and a binder, wherein the air-laid material is provided with a pattern of through-going cuts 5 forming a pattern of elements comprising rotating elements and translating elements, the piece of material being configured to assume a first and a second shape and wherein when the piece of material is transferred from the first shape to the second shape, the rotating elements are configured to rotate relative to the translating elements to which respective rotating element is connected such that an 10 overall in-plane extension of the piece of material is greater in the second shape compared to an overall in-plane extension of the piece of material in the first shape. The disclosure also relates to a package and a sound absorbing element.

Description

[0001] SHOCK AND / OR SOUND ABSORBING MATERIAL, A PACKAGE COMPRISING A

[0002] MECHANICAL SHOCK ABSORBING MATERIAL, AND A SOUND ABSORBING ELEMENT

[0003] Field of invention

[0004] The invention relates to a piece of a mechanical shock and / or sound absorbing material formed of an air-laid material.

[0005] The invention also relates to a package comprising a mechanical shock absorbing material.

[0006] The invention also relates to a sound absorbing element.

[0007] Technical Background

[0008] When designing a mechanical shock and / or sound absorbing material, it is often desirous to take into account a number of different design criteria. The shock and / or sound absorbing material should e.g., often be designed such that it provides a strong structure, makes efficient use of the material, is easy to transport to the point of use, is easy to prepare for use, and is mechanically stable. It is often desirable that the material provides adequate protection and good soundproofing, and which material is suitable to use in packages. It is also often desirable that the shock and / or sound absorbing material is made of an environmentally sustainable material, is space-efficient, and is logistically convenient. Moreover, especially in the case of the protective material, it needs to be easy and cost efficient to produce since it typically adds a cost to the product being protected without offering any advantage to the product.

[0009] Conventionally, mechanical shock and / or sound absorbing materials are bulky, takes up a lot of space, and are logistically inconvenient. So-called bistable auxetic materials have for quite some time been envisioned as a possible remedy of at least some of the above-mentioned shortcomings of said mechanical shock and / or sound absorbing materials. However, there is still no viable solution which adequately addresses the above discussed design criteria.

[0010] US 10767032 B2 discloses a bistable auxetic material exhibiting a negative Poisson's ratio. Such a material typically becomes thicker rather than thinner when stretched. It is said that the material may be made of elastomers, or more rigid materials. Thus, this material has limited usability as sound proofing and its shock absorbing properties renders its usability limited to use for heavy loads.

[0011] US 2011 / 0059291 Al relates to auxetic materials having negative and zero Poisson's ratios. It is disclosed that the constituent material consists of polymer such as an unfilled or filled vulcanized rubber, or the like. Thus, also this material has limited usability as sound proofing and its shock absorbing properties renders its usability limited to use for heavy loads.

[0012] Still, the bistable and / or auxetic materials as disclosed by the above-mentioned prior art suffer from shortcomings pertinent to protection and soundproofing characteristics, sustainability, reliability, versatility etc.

[0013] Summary of invention

[0014] It is an object of the invention to provide a solution addressing at least some of the design criteria that the shock and / or sound absorbing material should provide a strong structure, make efficient use of the material, be easy to transport to the point of use, be easy to prepare for use, and be mechanically stable.

[0015] It is also an object of the invention to provide a shock and / or sound absorbing material being able to provide adequate protection and / or good soundproofing, and which shock and / or sound absorbing material is suitable to use e.g., in packages.

[0016] It is also an object of the invention to provide a shock and / or sound absorbing material being made of an environmentally sustainable material, is space-efficient, and being logistically convenient.

[0017] These objects have been achieved by a piece of a mechanical shock and / or sound absorbing material formed of an air-laid material comprising: natural fibres being provided at a concentration of at least 70 % by weight of the air-laid material, and a binder, wherein the air-laid material has an average density from 10 to 60 kg / m3, characterised in that the air-laid material is provided with a pattern of through-going cuts forming a pattern of elements comprising rotating elements and translating elements, the elements being interconnected, and the piece of material being configured to assume a first and a second shape, and in that when the piece of material is transferred from the first shape to the second shape, the rotating elements are configured to rotate relative to the translating elements to which respective rotating element is connected such that an in-plane centre-to-centre distance between the respective rotating element and the translating elements to which respective rotating element is connected increases such that an overall in-plane extension of the piece of material in at least one direction is greater in the second shape compared to an overall in-plane extension of the piece of material in said at least one direction in the first shape.

[0018] An advantage with the piece of material comprising natural fibres is that natural fibres are recyclable. Natural fibres are also renewable and sustainable. Furthermore, owing to the characteristics of natural fibres, it is also comparably easy to cut a piece of material comprising natural fibres into the desired shape of the piece of material. It is also comparably easy to form the through-going cuts forming the pattern of rotating elements and translating elements. The through-going cuts may be formed by any method as normally used in the art. The piece of material is further easy to handle.

[0019] The air-laid material is preferably designed such that the average density thereof allows the piece of material to be lightweight and convenient to handle while still maintaining the characteristics of being strong and mechanically stable. This is achieved by the average density of the air-laid material being preferably selected within an interval of from 10 to 60 kg / m3. Preferably, the average density of the air-laid material is within an interval of from 15 to 60 kg / m3, and more preferably within an interval of from 15 to 50 kg / m3.

[0020] By an overall in-plane extension of the piece of material being greater in the second shape compared to an overall in-plane extension of the material in the first shape, it is meant that the piece of material may be subjected to an in-plane expansion in at least one direction. Owing to this ability, the piece of material may be intentionally expanded at least in one direction when the piece of material is transferred from the first shape to the second shape. Analogously, the piece of material may be intentionally retracted in said at least one direction when the piece of material is transferred from the second shape to the first shape.

[0021] An advantage with this inventive design is that the dimensions of the piece of material may be intentionally adjusted. For the purpose of using the piece of material as a protecting means for goods, the piece of material may be adjusted to allow for better accommodation of goods. Thus, there is provided a piece of material that is able to be adjusted in a simple and efficient way in order to accommodate goods of varying dimensions. One single unit of such a piece of material may hence be adjusted in a variety of ways in order to accommodate goods with different dimensions. This also renders the piece of material versatile.

[0022] It may in this context be noted that the length of the thermoplastic polymer fibres is calculated as a mean value.

[0023] It may in this context be further noted that the length of the natural fibres as referred to herein is length-weighted average fibre length. Length-weighted average fibre length is calculated as the sum of individual fibre lengths squared divided by the sum of the individual fibre lengths, as described in e.g., ISO 16065-1 or ISO 16065-2.

[0024] It may in this context be further noted that while the rotating elements are configured to rotate, the translating elements are configured to be stationary in their orientation and only translate as the material expands.

[0025] It may in this context be further noted that by the material being in the first shape it is meant that the rotating elements have yet to be rotated relative the translating elements. That is, the rotating elements have rotated relative the translating elements basically zero degrees. It may however, be noted that this first shape with zero rotation refers primarily to the virgin state of the material, i.e., after manufacture but before any deformation has been imparted on the material. When the material returns to the first shape, it may have certain remaining deformation such that there is still a remaining rotation of the rotating elements. By the material being in the second shape, the rotating elements have been rotated relative the translating elements a certain amount of degrees. The second shape is not limited to merely one certain shape. As long as the overall in-plane extension is greater in any shape compared to the first shape, that shape is to be construed as the second shape. Hence, in order to assume the second shape, the rotating elements may rotate an arbitrary amount of degrees as long as this value is greater than zero. It may especially be noted that if the material is used to cushion and follow the contour of a product having an arbitrary and non-uniform shape, the material is capable of expanding differently along its surface.

[0026] It may in this context be further noted that a piece of material may refer to anything from a small piece having a size for a specific use to a long web of such a material e.g., reeled on a bobbin or the like. The piece of material having the size for a specific use may be manufactured directly to that size or may be cut or torn from a larger piece of material. The piece of material may also refer to a portion of a larger piece of material.

[0027] Each rotating element may be hingedly connected to an adjacent translating element via at least one hinge element, wherein when the piece of material is transferred from the first shape to the second shape by application of a first load on the piece of material, the hinge elements are deformed to such an extent that there is a bending deformation set, and wherein when the piece of material is transferred from the second shape towards the first shape by application of a second load on the piece of material the hinge elements are deformed, preferably to such an extent that there is a bending deformation set. Materials having the ability to transfer from a first shape to a second shape are usually subjected to a restorative force, especially should the second shape be an expanded shape. In this context restorative forces refer to such forces that act to bring a material being in its second shape to its first shape, which first shape defines an equilibrium state. Such a restorative force is the result of a kind of a deformation, normally elastic deformation, of the material and not intentionally involving a bending deformation set. In the case of prior art bistable and / or auxetic materials, it is the hinge elements thereof that are subjected to elastic deformation without a bending deformation set when said material is transferred from a first shape to a second shape. In contrast to such prior art materials, there are actually several advantages associated with the hinge elements being intentionally deformed to such an extent that there is preferably a major bending deformation set when the material is transferred from the first shape to the second shape.

[0028] One such advantage is that when the hinge elements are deformed to such an extent that there is a bending deformation set when the piece of material is transferred from the first shape to the second shape, the magnitude of any generated restorative forces in the hinge elements is lower compared to had the hinge elements been elastically deformed without a bending deformation set. Such a reduction in the magnitude of any generated restorative forces in the hinge elements renders the piece of material easy to handle. A user handling a piece of material does not need to exert as much force in order to handle the piece of material in the second shape compared to had the hinge elements been elastically deformed without a bending deformation set in which case the restorative forces had been of higher magnitude. Another such advantage is that by a reduction in the magnitude of any generated restorative forces in the hinge elements, the piece of material is rendered more stable. Once the hinge elements have been deformed involving a bending deformation set, the piece of material becomes more pliable and more predictable. In this context, pliable is to be construed as the hinge elements being subjected to permanent distortion to such extent that the rotating elements become easier to rotate around the translating elements while maintaining sufficient structural integrity. Furthermore, it is noted that force is proportional to acceleration. That is, removal of any loads applied to the piece of material which is subjected to restorative forces of high magnitude might result in the piece of material quickly changing from one shape to another, hence making the piece of material difficult to handle. In this context, predictable is therefore to be construed as the piece of material being comparably slower to being transferred from one shape towards another shape such that it becomes easier to handle.

[0029] By bending deformation set, it is herein meant a deformation of the piece of material after subjecting the piece of material to a load such that rotation of the rotating elements relative the translating element occurs. Such a bending deformation set may be measured by subjecting a specimen, in this case the piece of material, as in the following:

[0030] 1. Application of load onto the specimen hence resulting in angular displacement of the rotating elements relative the translating elements

[0031] 2. Removal of load

[0032] 3. Measurement of the percentage of the angular displacement after the specimen has been left in normal (unloaded) conditions for 30 minutes.

[0033] The bending deformation set, BDS, in percent, is given by BDS = [(0o - 0i) / 0o] * 100, where 0o is the angular displacement of the rotating elements relative the translating elements while subjecting the specimen to a load and 0; is the angular displacement remaining and determined in accordance with the above measurement (i.e. after removal of load and having left the specimen in normal (unloaded) conditions for 30 minutes).

[0034] It may in this context be noted that each hinge element may function as a pivot point around which a rotating element rotates relative a translating element. A rotating element and a translating element may be connected to each other at a pair of vertex points. An in-plane extension between the vertex points of said pair of vertex points may define the hinge element.

[0035] The first shape may be a first stable state and the second shape may be a second stable state, wherein in the first stable state the piece of material maintains the first shape after removal of the second load applied thereon, and in the second stable state the piece of material maintains the second shape after removal of the first load applied thereon.

[0036] It may be expressed that the piece of material is bistable. It may be envisaged should the energy of the piece of material be plotted against the elongation of the piece of material along at least one direction, the first and second stable states may each define an energy minimum. More specifically, the first stable state may define a global energy minimum. The second stable state may define a local energy minimum. When the first load is applied onto the piece of material such that the piece of material is transferred from the first shape towards the second shape, the piece of material is subjected to an increase in energy. Prior to assuming the second shape, the piece of material assumes a main intermediate shape defining a main intermediate state. Said main intermediate state may define a local energy maximum. The mechanism of transferring the piece of material from the first shape to the second shape, and vice versa, will be further substantiated below:

[0037] Firstly, in order to transfer the piece of material from the first shape to the second shape, the piece of material is elongated along at least one direction by applying a first load onto the piece of material. By doing this, the rotating elements rotate relative the translating elements to which the rotating elements are connected a certain amount of degrees. The rotating elements are rotatable allowing the material to change between a first shape and a second shape. The hinge elements are constructed so as to permit relative rotation between the translating elements and the rotating elements. Upon transferring the piece of material from the first shape towards the second shape, the hinge elements undergo deformation and simultaneously an increase in energy. The deformation and energy increase of the hinge elements persist until the piece of material assumes the main intermediate shape. In this context main intermediate shape refers to an intermediate shape with respect to the first and second shapes, which intermediate shape defines an intermediate state which in turns defines a local energy maximum. It may hence be noted that there are several intermediate shapes that the piece of material may assume but which intermediate shapes do not necessarily define an energy maximum.

[0038] Secondly, as discussed above, as the piece of material assumes the main intermediate shape, an energy maximum is attained. Beyond this point, the rotating elements rotate relative the translating elements until the piece of material assumes the second shape, in which the piece of material is energetically stable. Here, release of the first load causes the piece of material to maintain the second shape, instead of returning to the first shape. This mechanism is similar to an over-centre locking mechanism / snap-through buckling. In other words, further elongation of the piece of material while the piece of material is assuming the main intermediate shape entails a decrease of the energy thereof until the piece of material assumes the second shape.

[0039] Thirdly, in order to transfer the piece of material from the second shape towards the first shape a second load is applied onto the piece of material while releasing the first load. Doing this, a main threshold energy which may be defined by the energy difference with respect to the local energy maximum of the main intermediate state and the local energy minimum of the second state, is overcome. Beyond this point, the second load may be released while allowing the piece of material to return from the main intermediate shape towards the first shape due to restorative forces present in the hinge elements.

[0040] An advantage with the material having two stable states is that the material is more reliable when it is used as e.g. a buffer material. When transporting goods in packages, it is essential that goods receive adequate protection. Although the present material may be used in its first shape when used in the form of a buffer material, the material is preferably used in its second shape. In order to provide adequate protection, the material should preferably not be brought back to its first shape once it has been transferred to its second shape. Thanks to the first and second shapes defining first and second stable states, respectively, the material may securely maintain the respective shape. Thus, the material is reliable to use in the form of protection. In this context, by reliable it is generally meant that the piece of material is able to maintain the first and second shapes, respectively.

[0041] Another advantage with the material having two stable states is that the material is convenient to use. The material may maintain the respective shape even when any loads applied thereon is removed. This is logistically convenient. The material may be transferred from the first shape to the second shape without the material being immediately restored to the first shape. Several pieces of the material being in the second shape may hence be stored, e.g., on top of each other, in a secure and reliable way without each piece being restored towards the first shape. Thus, a plurality of pieces of material may be prepared before point of use.

[0042] It may in this context be noted that the most energetically stable state that the piece of material may assume after having been subjected to initial deformation involving a bending deformation set is not a state corresponding to a shape where the rotating elements are at a zero degree rotation relative the translating elements. That is, the initial first state has been rendered less energetically favourable due to deformation involving a bending deformation set of the piece of material. Instead, the most energetically stable state that the piece of material may assume is rather a state corresponding to a shape where the rotating elements have rotated relative the translating elements a certain amount of degrees. This new shape may define a new equilibrium state. In fact, the initial first state is less energetically favourable compared to the new equilibrium state. Thus, once the piece of material has been transferred to the first shape from the second shape, the piece of material will be subjected to restorative forces that act to bring the piece of material from the first shape to the new shape that defines the new equilibrium state.

[0043] The bending deformation set, BDS, in percent, is given by BDS = [(0o - 0i) / 0o] * 100, and wherein the BDS may be 2-20 %.

[0044] Such a bending deformation set may provide sufficient deformation of the piece of material.

[0045] Transferring the piece of material from the first shape to the second shape may involve an elongation of the piece of material along at least one direction, and wherein when the piece of material is transferred back from the second shape towards the first shape, the piece of material maintains at least 5 % of the elongation along said at least one direction.

[0046] When the piece of material is used as e.g., a buffer material in a package, external forces directed towards the piece of material is to be expected, especially should the piece of material be used in conjunction with transportation of goods. Such external forces may cause the piece of material to be transferred from the second shape towards the first shape. However, since the piece of material is preferably used in the second shape, it is advantageous if the piece of material does not deviate from the second shape excessively due to said external forces. Preferably, the piece of material is not completely transferred from the second shape to the first shape. This design ensures that when the piece of material happens to deviate from the second shape, the rotating elements maintain a rotation around the translating elements a certain amount of degrees which corresponds to the material maintaining at least 5 % of the elongation along at least one direction. It may in this context be noted that this material property also results in that the material becomes more relaxed in the second shape and thereby is more easy to handle.

[0047] An advantage with the piece of material being able to maintain at least 5 % of the elongation along said at least one direction is the provision of a reliable use of the piece of material. In this context, by reliable it is generally meant that the piece of material does not deviate from the second shape excessively should the piece of material actually deviate from the second shape. However, due to contingencies it is occasionally difficult to ensure that the piece of material actually maintains the second shape. The piece of material may be used as e.g., a buffer material for protection of goods in a package. In this context, protection of goods may involve covering as much surface area of the goods as possible with buffer material. That is, it is advantageous that portions of the goods are not exposed to such an extent that the goods may be damaged during e.g., transportation or handling of the goods. This design ensures that should the piece of material deviate from the second shape, the deviation will not be of such magnitude that the goods are exposed to such an extent that there is a risk that the goods will be damaged.

[0048] The use of the piece of material is not only pertinent to the fields of protection. For instance, the piece of material is advantageous for use in the field of soundproofing. As mentioned above, the piece of material is preferably used in the second shape. Sound panels may be installed in a variety of ways and in a variety of environments. The sound panels may for instance be installed in a home studio or a home office. The sound panels may even be installed in a school. In such environments it is to be expected a large amount of movements in vicinity of the sound panels. Thus, collisions with the sound panels are to be expected. It is important that the sound panels therefore does not deviate from the second shape excessively should the sound panels actually deviate from the second shape. This design allows for a reliable use of the sound panels in various environments without any deterioration of the ability to soundproof.

[0049] It may in this context be further noted that by the material being able to maintain at least 5% of the elongation along said at least one direction, it is implied that the piece of material has undergone deformation to such an extent that that there is a bending deformation set.

[0050] The piece of material may fully maintain the elongation along said at least one direction.

[0051] When a piece of a prior art material is in the second shape, the piece of material is subjected to a restorative force such that the piece of material has a tendency to be transferred from the second shape towards the first shape. On the contrary, by being able to fully maintain the elongation along at least one direction when the piece of material is transferred from the second shape towards the first shape, it is implied that the piece of material has undergone such a deformation involving a bending deformation set that should the piece of material assume the first shape, the second shape, or any intermediate shapes with respect to the first and second shapes, the piece of material is not subjected to any restorative forces. It may alternatively be expressed that the piece of material has undergone such deformation involving a bending deformation set that the first shape, the second shape, or any intermediate shapes with respect to the first and second shapes, all define equilibrium states. By equilibrium state it is generally meant a energetically stable state.

[0052] Normally, in the case of the first shape defining a first stable state and the second shape defining a second stable state, in order to be transferred from the second shape to the first shape, a second load must be applied onto the piece of material. The second load must be of such a magnitude that the threshold energy, which as discussed above may be defined by the energy difference with respect to the local energy maximum of the main intermediate state and the local energy minimum of the second state, is overcome. With this inventive design, there is no threshold energy to be overcome in order to for the piece of material to be transferred from the second shape towards the first shape, or vice versa. Thus, an advantage with this inventive design is the provision of a piece of material being stable in the first shape, the second shape, or any intermediate shapes with respect to the first and second shapes. Furthermore, since the piece of material is not subjected to any restorative forces in the first shape, the second shape, or any intermediate shapes with respect to the first and second shapes, a user may intentionally configure the piece of material to assume a specific shape while also keeping the piece of material in this shape. For some endeavours, a user might need a certain overall in-plane extension of the piece of material. For instance, in order to cover a bottom panel of a package with the piece of material, the piece of material is transferred to a certain shape from the first shape. The piece of material will maintain this shape since this shape defines an equilibrium state. This facilitates handling of the piece of material.

[0053] The hinge element may have a predetermined thickness as measured inplane and across the hinge element such that at least 10 % of the thickness of the hinge element on a first side of the hinge element where an in-plane centre-to- centre distance between the respective rotating element and the translating elements to which respective rotating element is connected increases is strained to a strain level above a maximum elastic strain level such that deformation to such an extent that there is a bending deformation set of the hinge element is achieved when the piece of material is transferred from the first shape to the second shape.

[0054] During rotation of the rotating elements the material of the hinge elements is deformed. More specifically, the first side of the hinge elements is initially subjected to deformation. However, once the piece of material has reached a certain intermediate shape with respect to the first and second shapes, the first side of the hinge element may be said to have reached a maximum elastic strain level. Beyond this point, at least 10 % of the thickness, as measured as the in-plane extension between the vertex points of a pair of vertex points defining a hinge element, has been deformed to such an extent that there is a bending deformation set. Deformation to such an extent that there is a bending deformation set occurs in the vicinity of the first side of the hinge element.

[0055] In the context where the first and second shapes define first and second stable states, by a certain percentage of the thickness being deformed to such an extent that there is a bending deformation set when the piece of material is transferred from the first shape to the second shape there is provided a piece of material that is subjected to less restorative forces hence making the material less susceptible to deviate excessively from the second shape upon any impacts on the piece of material.

[0056] An in-plane centre-to-centre distance between the respective rotating element and the translating elements to which respective rotating element is connected decreases when the piece of material is transferred from the second shape towards the first shape. In this context, during rotation of the rotating elements relative the translating elements, the material of the hinge elements is again deformed. In order to transfer the piece of material from the second shape towards the first shape, the second side of the hinge element may be subjected to a compressive strain. However, it is conceivable that the material at a second side of the hinge element does not reach a compressive strain level above a maximum compressive strain level such that deformation to such an extent that there is a bending deformation set in the vicinity of the second side of the hinge element is achieved when the piece of material is transferred from the second shape towards the first shape.

[0057] By the term "first side of the hinge element" it is herein meant that side of the hinge element that is located at a free outer edge of the translating element.

[0058] By the term "second side of the hinge element" it is herein meant that side of the hinge element that is located at a free inner edge of the translating element. In other words, the second side of the hinge element is oppositely arranged to the first side of the same hinge element.

[0059] A thickness as measured in-plane and across the hinge element may be 1-5 mm, preferably 2-4 mm. This is suitable for a material being designed to be handled by hand force.

[0060] A material thickness of the piece of material may be 1-10 cm, preferably 2-6 cm. This is suitable for a material being designed to be handled by hand force.

[0061] The binder may be provided at a concentration within an interval of from 2.5 up to 30 % by weight of the air-laid material.

[0062] Each of these designs provides the piece of material with sufficient structural integrity while still allowing for the piece of material to be easily transferred from the first shape to the second shape, and vice versa.

[0063] The natural fibres may be formed of wood pulp fibres. The natural fibres may be cellulose and / or lignocellulose fibres. Hence, the natural fibres may contain cellulose, such as in the form of cellulose and / or lignocellulose, i.e., a mixture of cellulose and lignin. The natural fibres may also contain lignin, such as in the form of lignocellulose. The natural fibres may additionally contain hemicellulose. The cellulose and / or lignocellulose fibres may be cellulose and / or lignocellulose pulp fibres produced by chemical, mechanical and / or chemo-mechanical pulping of softwood and / or hardwood. The cellulose and / or lignocellulose pulp fibres may be in a form selected from the group consisting of sulphate pulp, sulphite pulp, thermomechanical pulp (TMP), high temperature thermomechanical pulp (HTMP), mechanical fibre intended for medium density fibreboard (MDF-fibre), chemo- thermomechanical pulp (CTMP), high temperature chemo-thermomechanical pulp (HTCTMP), and a combination thereof. The natural fibres can also be produced by other pulping methods and / or from other cellulosic or lignocellulosic raw materials, such as flax, jute, hemp, kenaf, bagasse, cotton, bamboo, straw or rice husk.

[0064] The mechanical shock and / or sound absorbing material may preferably have a Poisson's ratio being zero or less than zero.

[0065] The Poisson's ratio ( ) of any material is the ratio between the transverse strain et, and the longitudinal strain EI in the loading direction (wherein p=-Et / Ei). Accordingly, materials having a negative Poisson's ratio (i.e. p is negative) become wider and / or thicker, rather than thinner, when stretched. In other words, such materials which have a negative Poisson's ratio become thicker and / or wider in a direction perpendicular to the direction of the applied force. Such materials are conventionally denoted auxetic materials. Accordingly, materials having a zero Poisson's ratio do not exhibit strain in a direction perpendicular to the direction of the applied force.

[0066] There are several advantages associated with the material having a Poisson's ratio being zero or less than zero. One such advantage is that as the piece of material is transferred from the first shape to the second shape, the piece of material may expand along at least one direction such that the volume of the piece of material increases. Analogously, as the piece of material is transferred from the second shape to the first shape, the piece of material may retract along said at least one direction such that the volume of the piece of material decreases. By the Poisson's ratio being zero or less than zero, the volume of the piece of material assuming the first shape is lower than when the piece of material assumes the second shape. Hence, in order to make efficient use of space when the pieces of material are not to be used in the near future, pieces of material are preferably stored assuming the first shape. This entails efficient logistical management.

[0067] Furthermore, owing to the ability to expand and retract such that the volume of the piece of material is adjustable, a smaller quantity of pieces of material may achieve the same results compared to a large quantity of conventional bulky material which lacks the same ability. This renders the piece of material highly advantageous for a variety of endeavours, especially those pertinent to the protection field and soundproofing. That is, the piece of material may be adjusted to cover more surface area and volume. Accordingly, the piece of material is spaceefficient and sustainable.

[0068] In may in this context be noted that by volume it is generally meant the amount of space that the piece of material occupies in the three-dimensional space. When the rotating elements rotate relative the translating elements, an in-plane centre-to-centre distance between the respective rotating element and the translating elements to which respective rotating element is connected increases. Thus, since the rotating and translating elements are formed by through-going cuts in the piece of material, voids throughout the piece of material may gradually form upon an increase of rotation of the rotating elements relative the translating elements. It may also be expressed that the volume of each void increases simultaneously. It is to be construed that these voids actually form part of the total volume of the piece of material. It is hence implied that these voids actually occupy a certain amount of space in the three-dimensional space. It may in this context be noted that the material generally has a thickness which remains the same and that the volume is changed by the material increasing or decreasing in size as seen along the major surface of the material.

[0069] The above-mentioned objects are also achieved by a package comprising a bottom, a plurality of side walls and a top, and a piece of mechanical shock absorbing material of the kind disclosed above, wherein the piece of mechanical shock absorbing material extends along the bottom, and / or at least one side wall of the plurality of side walls, and / or along the top of the package, and wherein the piece of mechanical shock absorbing material is in the second shape. Preferably, the package comprises at least one piece of mechanical shock absorbing material as disclosed in various levels of details in the summary above and as disclosed in further various levels of details in the following.

[0070] Preferably the package comprises a bottom formed of one or more bottom panels, a plurality of side walls, and a top formed of one or more top panels. Preferably, the at least one piece of mechanical shock absorbing material is positioned along an interior side wall.

[0071] The above-mentioned objects are also achieved by a sound absorbing element having an essentially planar or curved extension comprising at least one piece of sound absorbing material of the kind disclosed above, wherein the piece of sound absorbing material is in the second shape.

[0072] Preferably, the sound absorbing element comprises at least one piece of sound absorbing material as disclosed in various levels of details in the summary above and as disclosed in further various levels of details in the following.

[0073] The sound absorbing element is preferably positioned along walls of a room, such as the side walls and the ceiling. It is even conceivable that the sound absorbing element suspends from a ceiling with suspensions means. Preferably, a plurality of absorbing elements are connected to each other one after another to allow for efficient sound proofing.

[0074] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the [element, device, component, means, step, etc]" are to be interpreted openly as referring to at least one instance of said element, device, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

[0075] The invention may also in short be said to relate to a piece of a mechanical shock and / or sound absorbing material formed of an air-laid material comprising natural fibres, and a binder, wherein the air-laid material is provided with a pattern of through-going cuts forming a pattern of elements comprising rotating elements and translating elements, the piece of material being configured to assume a first and a second shape and wherein when the piece of material is transferred from the first shape to the second shape, the rotating elements are configured to rotate relative to the translating elements to which respective rotating element is connected such that an overall in-plane extension of the piece of material is greater in the second shape compared to an overall in-plane extension of the piece of material in the first shape. The disclosure also relates to a package comprising a piece of mechanical shock absorbing material and a sound absorbing element comprising a piece of sound absorbing material.

[0076] Brief iption of the

[0077] The invention will by way of example be described in more detail with reference to the appended schematic drawings, which shows a presently preferred embodiment of the invention.

[0078] Fig. 1 discloses a piece of a mechanical shock and / or sound absorbing material assuming the first shape according to an embodiment.

[0079] Fig. 2 discloses a piece of a mechanical shock and / or sound absorbing material assuming the second shape according to an embodiment.

[0080] Fig. 3 discloses a unit cell in the first shape and a unit cell in the second shape according to an embodiment.

[0081] Fig. 4 discloses the energy versus elongation of the piece of a mechanical shock and / or sound absorbing material according to an embodiment.

[0082] Detailed description of embodiments

[0083] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as only limited to the embodiments set forth herein. In the following, the piece of a mechanical shock and / or sound absorbing material 100 formed of an air-laid material will be described in detail. More specifically, the material characteristics of the piece of the mechanical shock and / or sound absorbing material 100 will be described in detail without any specific reference to any of Figs. 1-4.

[0084] The piece of a mechanical shock and / or sound absorbing material 100, hereinafter referred to as the piece of material 100, is formed of an air-laid material. The air-laid material comprises natural fibres and a binder. The air-laid material may also comprise one or more additives. The air-laid material is formed by a process known as air-laying, in which natural fibres such as cellulose and / or lignocellulose fibres and binders are mixed with air to form a porous fibre mixture deposited onto a support and consolidated or bonded by heating. This air-laid material, sometimes also referred to as dry-laid material, is characterized by being porous, having the character of an open cell foam and being produced in a so-called dry forming method, i.e., generally without addition of water. An air-laying process is e.g., described in U.S. patent no. 3,575,749.

[0085] The natural fibres may have a length-weighted average fibre length from about 0.8 mm up to about 5 mm. The length-weighted average fibre length of the natural fibres is dependent on the source of the natural fibres, such as tree species they are derived from, and the pulping process. Length weighted average fibre length is calculated as the sum of individual fiber lengths squared divided by the sum of the individual fiber lengths as described in e.g., ISO 16065-1 or ISO 16065-2.

[0086] The natural fibres are being provided at a concentration of at least 70 % by weight of the air-laid material. Preferably, the air-laid material comprises the natural fibres in a concentration of at least 72.5 %, more preferably at least 75 %, such as at least 77.5 %, at least 80 %, at least 82.5 %, at least 85 % by weight of the air-laid material. In some applications, even higher concentrations of the natural fibres may be used, such as at least 87.5 %, or at least 90 %, at least 92.5 %, at least 95 % or at least 96 % by weight of the air-laid material. The natural fibres may be formed of wood pulp fibres. The natural fibres may be cellulose and / or lignocellulose fibres. Hence, the natural fibres may contain cellulose, such as in the form of cellulose and / or lignocellulose, i.e., a mixture of cellulose and lignin. The natural fibres may also contain lignin, such as in the form of lignocellulose. The natural fibres may additionally contain hemicellulose. The cellulose and / or lignocellulose fibres may be cellulose and / or lignocellulose pulp fibres produced by chemical, mechanical and / or chemo-mechanical pulping of softwood and / or hardwood. The cellulose and / or lignocellulose pulp fibres may be in a form selected from the group consisting of sulphate pulp, sulphite pulp, thermomechanical pulp (TMP), high temperature thermomechanical pulp (HTMP), mechanical fibre intended for medium density fibreboard (MDF-fibre), chemo- thermomechanical pulp (CTMP), high temperature chemo-thermomechanical pulp (HTCTMP), and a combination thereof. The natural fibres can also be produced by other pulping methods and / or from other cellulosic or lignocellulosic raw materials, such as flax, jute, hemp, kenaf, bagasse, cotton, bamboo, straw or rice husk.

[0087] The binder may be a polymer binder. The polymer binder being e.g., a thermoplastic polymer binder, may be provided at a concentration selected within an interval of from 2.5 up to 30 % by weight of the air-laid material.

[0088] In a particular embodiment, the polymer binder is a natural polymer selected from the group consisting of starch, agar, guar gum, locust bean gum, carrageenan, and cellulose, such as fibrillar, microfibrillar or nanofibrillar cellulose.

[0089] In one embodiment, the air-laid material comprises the polymer binder, such as the thermoplastic polymer binder, at a concentration selected within an interval of from 10 up to 30 %, such as from 15 up to 30 % by weight of the air-laid material 100. In a particular embodiment, the air-laid material comprises more than 15 % but no more than 30 % by weight of the polymer binder, such as the thermoplastic polymer binder. For instance, the air-laid material may comprise the polymer binder, such as the thermoplastic polymer binder, at a concentration selected within an interval of from 15 or 17.5 up to 30 % by weight of the air-laid material. In a particular embodiment, the air-laid material comprises the polymer binder, such as the thermoplastic polymer binder, at a concentration selected within an interval of from 15 or 17.5 up to 25 %, such as from 20 up to 25 % by weight of the air-laid material.

[0090] In one embodiment, the air-laid material comprises the polymer binder, such as the thermoplastic polymer binder, at a concentration selected within an interval of from 2.5 up to 15 % by weight of the air-laid material, preferably within an interval of from 4 up to 15 % by weight of the air-laid material, or within an interval of from 7.5 up to 15 % by weight of the air-laid material, and more preferably within an interval of from 10 up to 15 % by weight of the air-laid material. These embodiments are, in particular, suitable for usage with thermoplastic polymer binders that are water soluble, e.g., for usage with thermoplastic polymer fibres made from a material or materials selected from the group consisting of PVA, PEG, PEOX, PVE, PVP, PAA, PMAA and copolymers and / or mixtures thereof.

[0091] The binder is included in the air-laid material as binder that binds the air-laid material together and preserves its form and structure during use, handling and storage. The binder may also assist in building up a foam-like structure of the air-laid material. The binder is intermingled with the natural fibres during the air-laying process forming a fibre mixture. The thermoplastic polymer binder may be added in the form of a powder, but are more often in the form of fibres that are intermingled with the natural fibres in the air-laying process. Alternatively, or in addition, the thermoplastic polymer binder may be added as solution, emulsion or dispersion into and onto the air-laid material during the air-laying process. This latter technique is most suitable for thin air-laid materials.

[0092] The thermoplastic polymer binder may be selected from the group consisting of a thermoplastic polymer powder, thermoplastic polymer fibers and a combination thereof.

[0093] The thermoplastic polymer binder has a softening point not exceeding a degradation temperature of the natural fibres.

[0094] In one embodiment, the thermoplastic polymer binder is or comprises thermoplastic polymer fibres cut at a fixed length, which are typically referred to as staple fibres. It is generally preferred for the mixing in the air-laying process and, thereby, for the properties of the formed air-laid material if the length of the thermoplastic polymer fibres is of the same order of magnitude as the length of the natural fibres.

[0095] In one embodiment, the thermoplastic polymer binder is or comprises thermoplastic polymer fibres having an average fibre length being at least 300 %, preferably at least 400 %, of the length-weighted average fibre length of the natural fibres. In a particular embodiment, the thermoplastic polymer fibres have an average fibre length within an interval of from 3 up to 15 mm.

[0096] In one embodiment, the thermoplastic polymer binder is or comprises monocomponent and / or bi-component thermoplastic polymer fibres. Bi-component thermoplastic polymer fibres, also known as bico fibres, comprise a core and sheath structure, where the core is made from a first polymer, copolymer and / or polymer mixture and the sheath is made from a second, different polymer, copolymer and / or polymer mixture.

[0097] In one embodiment, the thermoplastic polymer binder is or comprises, such as consists of, mono-component thermoplastic polymer fibers made of a material selected from the group consisting of polyethylene (PE), ethylene acrylic acid copolymer (EAA), ethylene-vinyl acetate (EVA), polypropylene (PP), polystyrene (PS), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polylactic acid (PLA), polyethylene terephthalate (PET), polycaprolactone (PCL) and copolymers and / or mixtures thereof. In another embodiment, the thermoplastic polymer binder is or comprises, such as consists of, bi-component thermoplastic polymer fibers having a core and / or sheath made of a material or materials selected from the group consisting of PE, EAA, EVA, PP, PS, PBAT, PBS, PLA, PET, PCL and copolymers and / or mixtures thereof. In a further embodiment, the thermoplastic polymer binder is or comprises, such as consists of, a combination or mixture of mono-component thermoplastic polymer fibers made of a material selected from the group consisting of PE, EAA, EVA, PP, PS, PBAT, PBS, PLA, PET, PCL and copolymers and / or mixtures thereof and bi-component thermoplastic polymer fibers having a core and / or sheath made of a material or materials selected from the group consisting of PE, EAA, EVA, PP, PS, PBAT, PBS, PLA, PET, PCL and copolymers and / or mixtures thereof.

[0098] The thermoplastic polymer binder could be made of a single type of thermoplastic polymer fibres, i.e., made of a same material in the case of monocomponent thermoplastic polymer fibres or made of the same material or materials in the case of bi-component thermoplastic polymer fibres. However, it is also possible to use a thermoplastic polymer binder made of multiple different monocomponent thermoplastic polymer fibres made of different materials and / or multiple different bi-component thermoplastic polymer fibres made of different materials.

[0099] In one embodiment, the thermoplastic polymer binder is or comprises a thermoplastic polymer powder made of a material selected from the group consisting of PE, EAA, EVA, PP, PS, PBAT, PBS, PLA, PET, PCL and copolymers and / or mixtures thereof.

[0100] Particular examples of material for the thermoplastic polymer binder that could be used according to the present embodiments include PBAT, PBS, PLA, PCL, and copolymers and / or mixtures thereof. In such a case, the thermoplastic polymer binder made of these materials is compostable under industrial conditions.

[0101] Other examples of material for the thermoplastic polymer binder, which are water soluble, are mono-component and / or bi-component thermoplastic polymer fibres made of a material selected from the group consisting of polyvinyl alcohol (PVA), polyethylene glycol (PEG), poly(2-ethyl-2-oxazoline) (PEOX), polyvinyl ether (PVE), polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), polymethacrylic acid (PMAA) and copolymers and / or mixtures thereof.

[0102] In one embodiment, the thermoplastic polymer binder is or comprises, such as consists of, mono-component thermoplastic polymer fibres made of a material selected from the group consisting of PVA, PEG, PEOX, PVE, PVP, PAA, PMAA and copolymers and / or mixtures thereof. In another embodiment, the thermoplastic polymer binder is or comprises, such as consists of, bi-component thermoplastic polymer fibres having a sheath or a sheath and core made of a material or materials selected from the group consisting of PVA, PEG, PEOX, PVE, PVP, PAA, PM MA and copolymers and / or mixtures thereof. In a particular embodiment, at least the sheath of the bi-component thermoplastic polymer fibres is made of a material selected from the group consisting of PVA, PEG, PEOX, PVE, PVP, PAA, PMAA and copolymers and / or mixtures thereof. In such a particular embodiment, also the material of the core of the bi-component thermoplastic polymer fibres could be selected from this group. Hence, in one particular embodiment, the bi-component thermoplastic polymer fibres comprise a core component made of a material selected from the group consisting of polyethylene PE, EAA, EVA, PP, PS, PBAT, PBS, PLA, PET, PCL and copolymers and / or mixtures thereof and a sheath component made of a material selected from the group consisting of PVA, PEG, PEOX, PVE, PVP, PAA, PMAA and copolymers and / or mixtures thereof. In a further embodiment, the thermoplastic polymer binder is or comprises, such as consists of, a combination of monocomponent thermoplastic polymer fibres made of a material selected from the group consisting of PVA, PEG, PEOX, PVE, PVP, PAA, PMAA and copolymers and / or mixtures thereof and bi-component thermoplastic polymer fibres having a core and / or sheath made of a material or materials selected from the group consisting of PVA, PEG, PEOX, PVE, PVP, PAA, PMAA and copolymers and / or mixtures thereof.

[0103] The piece of material 100 will now be discussed with reference to Fig. 1. The air-laid material is provided with a pattern of through-going cuts 105 forming a pattern of elements comprising rotating elements 110 and translating elements 120. The through-going cuts 105 are formed by perforating a variety of cut motifs into a monolithic piece of the air-laid material. This forms a network of interconnected rotating elements 110 and translating elements 120.

[0104] As seen in Fig. 2, the piece of material 100 is configured to assume a first and a second shape. When the piece of material 100 is transferred from the first shape to the second shape, the rotating elements 110 are configured to rotate relative to the translating elements 120 to which respective rotating elements 110 is connected. Thus, an in-plane centre-to-centre distance between the respective rotating element 110 and the translating elements 120 to which respective rotating element 110 is connected increases such that an overall in-plane extension of the piece of material 100 is greater in the second shape compared to an overall in-plane extension of the piece of material 100 in the first shape.

[0105] Fig 3 illustrates a unit cell in the first shape and a unit cell in the second shape. By the term "unit cel I", it is herein meant a single translating element 120 being interconnected to a plurality of rotating elements 110. Each rotating element 110 is hingedly connected to an adjacent translating element 120 via at least one hinge element 130. Each hinge element 130 functions as a pivot point around which a rotating element 110 rotates relative a translating element 120. The rotating elements 110 and translating elements 120 are connected to each other at a pair of vertex points 131, 132. An in-plane extension between the vertex points of said pair of vertex points 131, 132 defines the hinge element 130. As can be further seen in Fig. 3, an angle a is defined between a rotating element 110 and an adjacent translating element 120. The angle a is defined between that side of a rotating element 110 and an oppositely arranged side of an adjacently arranged translating element 120, said sides extending from a vertex point 132.

[0106] The rotating element 110 is triangularly formed. Each corner of the rotating element 110 is connected to an adjacently arranged translating element 120. That is, each rotating element 110 is connected to three translating elements 120. Alternatively, the rotating element 110 may be rectangularly formed. In such case, each rotating element 110 is connected to four adjacently arranged translating elements 120. In general, the rotating element 110 may be any polygon. The rotating element 110 may be a pentagon or a hexagon. The sides of the polygonal rotating elements 110 may have any length. Thus, the rotating elements 110 may be scaled to be suitable for small-scale as well as large-scale applications.

[0107] The translating element 120 has a different shape and size than that of the rotating element 110. The translating element 120 is a non-rotating structure and has a shape complementary to that of an adjacently arranged rotating element 110. The translating element 120 as shown in Fig. 3 may generally be described as a multi-lobed flat structure. The translating element 120 has a center portion and three lobes extending away from the enter portion. Each translating element 120 is connected to three adjacently arranged rotating elements 110. The translating element 120 may have an alternate shape than that illustrated in Fig. 3. For instance, the translating element 120 may have more than three lobes in order to accommodate more than three rotating elements 110.

[0108] It may in this context be noted that not every rotating element 110 is connected to three translating elements 120. Similarly, not every translating element 120 is connected to three rotating elements 110. For instance, in order to form the rotating elements 110 and the translating elements 120, through-going cuts 105 are formed by perforating a variety of cut motifs into a larger monolithic piece of material. The larger monolithic piece of material may then be cut into smaller pieces of material 100. In doing so, rotating elements 110 and translating elements 120 at the sides of the piece of material 100 are arbitrarily intersected.

[0109] As illustrated in Figs. 2 and 3, when the piece of material 100 is transferred from the first shape to the second shape by application of a first load on the material 100, the hinge elements 130 are deformed. Preferably the hinge elements 130 are deformed to such an extent that there is a bending deformation set. The first load may, for instance, be characterized by a stretching load along a longitudinal axis or a transversal axis. When the piece of material 100 is transferred from the second shape towards the first shape by application of a second load on the piece of material the hinge elements 130 are deformed once again. Preferably, the hinge elements 130 are deformed to such an extent that there is a bending deformation set.

[0110] In its intended form, the first and second shapes of the piece of material 100 define first and second stable states, respectively. In this context, shape is merely associated with the appearance of the piece of material 100. Hence, by "first shape" it is herein meant a shape in which the rotating elements 110 have barely, preferably not, rotated relative the translating elements 120. Alternatively expressed, the piece of material 100 assumes the first shape as soon as the through-going cuts 105 have been formed in the piece of material 100. By "second shape", it is herein meant a shape in which the rotating elements 110 have rotated relative the translating elements 120 a certain amount of degrees being greater than the amount of degrees the rotating elements 120 have rotated relative the translating elements 120 when the piece of material has assumed the first shape. In contrast, state is rather associated with an energetic state of the piece of material 100. Alternatively expressed, state is associated with the stress of the internal structure of the piece of material 100.

[0111] In the first stable state the piece of material 100 maintains the first shape after removal of the second load applied thereon. The second load may, for instance, be characterized by a compressive load having a gradient being directionally opposite to the stretching load as discussed above. In the second stable state the piece of material 100 maintains the second shape after removal of the first load applied thereon.

[0112] In order to facilitate any further elaboration of the intricacies of the piece of material 100, the energy of the piece of material 100 is plotted against the elongation of the piece of material 100 along at least one direction in a graph as illustrated in Fig. 4. The x-axis of the graph represents elongation in percentage, %. In this context, elongation in percentage refers to how much the piece of material 100 is elongated in relation to its initial dimensions. For instance, the piece of material 100 may be a quadrilateral rectangular piece as illustrated in Fig. 1. The piece of material 100 may be 100 cm long along the longitudinal direction L and 50 cm wide along the transversal direction T. Thus, when the piece of material 100 is elongated along the longitudinal direction 25 %, the piece of material 100 is stretched to 125 cm along the longitudinal direction L. The y-axis of the graph represents energy in a dimensionless unit, (1). It is to be noted that the graph does not necessarily depict the relationship between the elongation and the energy of the piece of material 100 in a factual manner. In fact, the graph has merely been adapted for facilitation of understanding the following description. Hence, the relationship between the elongation and the energy of the piece of material 100 as illustrated in the graph is to be interpreted in a qualitative manner. For instance, the piece of material 100 has two energetically stable states, Egmin, Eimin but not necessarily at an elongation of exactly 0 % and of approximately 25 %. The piece of material 100 may e.g., have two energetically stable states Egmin, Eimin at 0 % and 15 % elongation, respectively, or alternatively, the piece of material 100 may have two energetically stable states Egmin, Eimin at 0 % and 50 % elongation, respectively. In any case, the piece of material 100 has a first energetically stable state Egmin as the piece of material has barely been elongated, and a second energetically stable state Eimin as the piece of material has been elongated. Furthermore, the unit energy is dimensionless and has been adapted to merely depict the energy of the piece of material 100 as the piece of material 100 is elongated. That is, it is not the role of the graph to determine an exact amount of energy stored in the piece of material 100 for a certain percentage of elongation of the piece of material 100. It may also be noted that the relation between the Eimax and the Eimin may be different from what is shown in Fig. 4. It is to be understood that any reference to a certain percentage of elongation of the piece of material 100 in the following description does not necessarily imply an exact amount of energy stored in the piece of material 100. Any reference to a certain percentage of elongation of the piece of material 100 is done for the purpose of facilitating understanding of the relationship between elongation and energy of the piece of material 100. Alternatively, the x-axis and the y-axis may represent strain and stress, respectively. In such case, the graph depicts a stress-strain curve for the piece of material 100. Henceforth, when the piece of material 100 is said to be subjected to an increase in energy, the piece of material 100 may alternatively be said to be subjected to an increase in stress. Likewise, when the piece of material 100 is elongated, the piece of material 100 may be said to be strained. However, for the sake of consistency, the terms energy and elongation will be used from now on.

[0113] Since the piece of material 100 preferably defines two stable states, the piece of material 100 may be said to be bistable. That is, the first and second stable states each defines an energy minimum. More specifically, the first stable state defines a global energy minimum Egmin. In this particular case, a global energy minimum Egmin is attained at an elongation of 0 % of the piece of material 100. That is, the piece of material 100 is completely energetically stable when the piece of material 100 has yet to be, or barely been, elongated. The second stable state defines a local energy minimum Eimin. In this particular case, a local energy minimum Eimin is attained at an elongation of 25 % of the piece of material 100. As can be seen in Fig. 4, the energy of the local energy minimum Eimin is higher than that of the global energy minimum Egmin- Upon applying a first load, e.g. a stretching load along a transversal direction, onto the piece of material 100, the piece of material 100 is transferred from the first shape towards the second shape. In doing so, the piece of material 100 is subjected to an increase in energy. Prior to assuming the second shape, the piece of material 100 assumes a main intermediate shape defining a main intermediate state. Said main intermediate state defines a local energy maximum Eimax- The mechanism of transferring the piece of material 100 from the first shape to the second shape, and vice versa, will be further substantiated below with reference to Fig. 4:

[0114] Firstly, in order to transfer the piece of material 100 from the first shape to the second shape, the piece of material 100 is elongated along at least one direction by applying a first load onto the piece of material 100. As discussed above, the first load may be a stretching load. By doing this, the rotating elements 110 rotate relative the translating elements 120 a certain amount of degrees. That is, the angle a as defined above increases. The rotating elements 110 are rotatable between a first shape and a second shape. The hinge elements 130 are constructed so as to permit relative rotation between the translating elements 120 and the rotating elements 110. Upon transferring the piece of material 110 from the first shape towards the second shape, the hinge elements 130 undergo deformation and simultaneously an increase in energy. It may alternatively be expressed that the piece of material 100 increases in energy as the piece of material 100 is transferred from the first shape towards the second shape. The deformation and energy increase of the hinge elements 130 persist until the piece of material 100 assumes the main intermediate shape. In this context, main intermediate shape refers to an intermediate shape with respect to the first and second shapes. The main intermediate shape defines an intermediate state which in turns defines the local energy maximum Eimax- As discussed above, the second shape is not limited to merely one certain shape. As long as the overall in-plane extension is greater in any shape compared to the first shape, that shape is to be construed as the second shape. Hence, in order to assume the second shape, the rotating elements 110 may rotate an arbitrary amount of degrees as long as this value is greater than zero. However, preferably, the second shape defines a state in which the piece of material 100 is energetically stable, and wherein this energy is higher than that of the first stable state.

[0115] It may hence be noted that there are several intermediate shapes that the piece of material 100 may assume but which intermediate shapes do not necessarily define an energy maximum.

[0116] Secondly, as discussed above, as the piece of material 100 assumes the main intermediate shape, a local energy maximum Eimax is attained. Beyond this point, the rotating elements 110 rotate relative the translating elements 120 until the piece of material 100 assumes the second shape, in which the piece of material 100 is energetically stable. Here, release of the first load causes the piece of material 100 to maintain the second shape, instead of returning to the first shape. This mechanism is similar to an over-centre locking mechanism / snap-through buckling. In other words, further elongation of the piece of material 100 while the piece of material 100 is assuming the main intermediate shape entails a decrease of the energy thereof until the piece of material 100 assumes the second shape.

[0117] Thirdly, in order to transfer the piece of material 100 from the second shape towards the first shape a second load is applied onto the piece of material 100 while releasing the first load. The second load may for instance be a compressive load having a gradient being directionally opposite to that of the first load. In other words, if the first load entails stretching the piece of material 100 along the longitudinal direction, the second load entails compressing the piece of material 100 in the opposite direction. Doing this, a main threshold energy Ethreshoid which may be defined by the energy difference with respect to the local energy maximum E imax of the main intermediate state and the local energy minimum of the second state Eimin, is overcome. Beyond this point, the second load may be released while allowing the piece of material 100 to return from the main intermediate shape towards the first shape due to restorative forces present in the hinge elements 130.

[0118] The energy of the piece of material 100 increases should the piece of material 100 further be elongated beyond the point of having attained the second stable state. Beyond this point the piece of material 100 is subjected to restorative forces which act to bring the piece of material 100 to a stable state.

[0119] The piece of material 100 has preferably a Poisson's ratio being zero or less than zero. The Poisson's ratio (p) of any material is the ratio between the transverse strain Et, and the longitudinal strain EI in the loading direction (wherein =-Et / Ei). Accordingly, materials having a negative Poisson's ratio (i.e. p is negative) become wider and / or thicker, rather than thinner, when stretched. In other words, such materials which have a negative Poisson's ratio become thicker and / or wider in a direction perpendicular to the direction of the applied force. Such materials are conventionally denoted auxetic materials. Accordingly, materials having a zero Poisson's ratio do not exhibit strain in a direction perpendicular to the direction of the applied force.

[0120] The piece of material 100 has preferably a Poisson's ratio being zero or less than zero along at least a first plane of the piece of material. However, it is conceivable that the piece of material 100 has a Poisson's ratio being zero or less than zero along a further second plane being perpendicularly defined in relation to the first plane. With such a design, the piece of material 100 is able to expand and retract along two planes, rather than just one single plane.

[0121] In some circumstances, it is preferred that the piece of material 100 maintains a certain amount of elongation once the piece of material 100 has been transferred from the second shape to the first shape.

[0122] Transferring the piece of material from the first shape to the second shape may involve an elongation of the piece of material 100 along at least one direction. When the piece of material is transferred back from the second shape towards the first shape, the piece of material may maintain at least 5 % of the elongation along said at least one direction. In some circumstances, it is even preferable that the piece of material fully maintains the elongation along said at least one direction. By designing the piece of material 100 to be able to maintain a certain percentage of the elongation, it is conceivable that the graph of Fig. 4 will be altered. It is expected that the main threshold energy Ethreshoid will decrease should the piece of material 100 be designed to be able to maintain a higher percentage of elongation. Furthermore, it is to be expected that the energy of any state, with the exception of the first stable state, of the piece of material 100 is reduced. The ability to maintain a percentage of an elongation implies a deformation of the piece of material 100 to such an extent that there is a bending deformation set. More specifically, it is the hinge elements 130 that undergoes deformation to such an extent that there is a bending deformation set. This further implies that the magnitude of any generated restorative forces in the hinge elements 130 is lower compared to had the hinge elements 130 not been designed to maintain a percentage of the elongation. The restorative forces of the hinge elements 130 act to bring the piece of material 100 towards its first shape. In other words, the structural integrity of the hinge elements 130 is deliberately weakened hence reducing the energy of any state, with the exception of the first stable state, of the piece of material 100.

[0123] The hinge element 130 may have a predetermined thickness as measured inplane and across the hinge element 130. When the piece of material 100 is transferred from the first shape to the second shape, at least 10 % of the thickness of the hinge element 130 on a first side 130a of the hinge element 130 where an inplane centre-to-centre distance between the respective rotating element 110 and the translating elements 120 to which respective rotating element 110 is connected increases is strained to a strain level above a maximum elastic strain level such that deformation to such an extent that there is a bending deformation set of the hinge element 130 is achieved. As best seen in Fig. 3, the hinge element 130 may be said to have a first side 130a and a second side 130b. The first side 130a of the hinge element 130 is located at a free outer edge of the translating element 120. The second side 130b of the hinge element 130 is located at a free inner edge of the translating element 120.

[0124] A thickness as measured in-plane and across the hinge element 130 may be 1-5 mm. Such a dimension is suitable for small-scale applications. The thickness of the hinge element 130 is preferably greater for larger-scale applications. In such a case the hinge elements may e.g., have a thickness of about 5-15 mm.

[0125] A material thickness of the piece of material may be 1-10 cm. This is suitable for a material being designed to be handled by hand force.

[0126] An in-plane centre-to-centre distance between the respective rotating element 110 and the translating elements 120 to which respective rotating element 110 is connected decreases when the piece of material 100 is transferred from the second shape towards the first shape. During rotation of the rotating elements 110 relative the translating elements 120 the material of the hinge elements 130 is also deformed. In this context, the second side 130b of the hinge element 130 is subjected to a compressive strain. However, it is conceivable that the material at a second side 130b of the hinge element 130 does not reach a compressive strain level above a maximum compressive strain level such that deformation to such an extent that there is a bending deformation set in the vicinity of the second side 130b of the hinge element 130 is achieved when the piece of material 100 is transferred from the second shape towards the first shape.

[0127] The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

[0128] Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

Claims

CLAIMS1. A piece of a mechanical shock and / or sound absorbing material (100) formed of an air-laid material comprising: natural fibres being provided at a concentration of at least 70 % by weight of the air-laid material, and a binder, wherein the air-laid material has an average density from 10 to 60 kg / m3, characterised in that the air-laid material is provided with a pattern of through-going cuts forming a pattern of elements comprising rotating elements (110) and translating elements (120), the elements (110, 120) being interconnected, and the piece of material (100) being configured to assume a first and a second shape, and in that when the piece of material (100) is transferred from the first shape to the second shape, the rotating elements (110) are configured to rotate relative to the translating elements (120) to which respective rotating element (110) is connected such that an in-plane centre-to-centre distance between the respective rotating element (110) and the translating elements (120) to which respective rotating element (110) is connected increases such that an overall in-plane extension of the piece of material (100) in at least one direction is greater in the second shape compared to an overall in-plane extension of the piece of material (100) in said at least one direction in the first shape.

2. The piece of material (100) according to claim 1, wherein each rotating element (110) is hingedly connected to an adjacent translating element (120) via at least one hinge element (130), wherein when the piece of material (100) is transferred from the first shape to the second shape by application of a first load on the piece of material (100), the hinge elements (130) are deformed to such an extent that there is a bending deformation set,wherein when the piece of material (100) is transferred from the second shape towards the first shape by application of a second load on the piece of material (100) the hinge elements (130) are deformed, preferably to such an extent that there is a bending deformation set, and wherein the bending deformation set, BDS, in percent, is given by BDS = [(0o - 9i) / 0o] * 100, where 0o is the angular displacement of the rotating elements (110) relative the translating elements (120) while subjecting the piece of material (100) to a load and 0; is the angular displacement remaining and determined in accordance with the above measurement.

3. The piece of material (100) according to claim 2, wherein the first shape is a first stable state and the second shape is a second stable state, wherein in the first stable state the piece of material (100) maintains the first shape after removal of the second load applied thereon, and in the second stable state the piece of material (100) maintains the second shape after removal of the first load applied thereon.

4. The piece of material (100) according to any one of claims 2 or 3, wherein the BDS is 2-20 %.

5. The piece of material (100) according to any one of the claims 1, 2 or 4, wherein transferring the piece of material (100) from the first shape to the second shape involves an elongation of the piece of material (100) along at least one direction, and wherein when the piece of material (100) is transferred back from the second shape towards the first shape, the piece of material (100) maintains at least 5 % of the elongation along said at least one direction.

6. The piece of material (100) according to claim 5, wherein the piece of material (100) fully maintains the elongation along said at least one direction.

7. The piece of material (100) according to any one of the claims 2-6, wherein the hinge element (130) has a predetermined thickness as measured in-plane and across the hinge element (130) such that at least 10 % of the thickness of the hinge element (130) on a first side (130a) of the hinge element (130) where an in-plane centre-to-centre distance between the respective rotating element (110) and the translating elements (120) to which respective rotating element (110) is connected increases is strained to a strain level above a maximum elastic strain level such that deformation to such an extent that there is a bending deformation set of the hinge element (130) is achieved when the piece of material (100) is transferred from the first shape to the second shape.

8. The piece of material (100) according to any one of the preceding claims, wherein a thickness as measured in-plane and across the hinge is 1-5 mm, preferably 2-4 mm.

9. The piece of material (100) according to any one of the preceding claims, wherein a material thickness of the material is 1-10 cm, preferably 2-6 cm.

10. The piece of material (100) according to any one of the preceding claims, wherein the binder is provided at a concentration within an interval of from 2.5 up to 30 % by weight of the air-laid material.

11. The piece of material (100) according to any one of the preceding claims, wherein the natural fibres are formed of wood pulp fibres.

12. The piece of material (100) according to any one of the preceding claims, wherein the piece of material (100) has a Poisson's ratio being zero or less than zero.

13. A package comprising a bottom, a plurality of side walls and a top, and a piece of mechanical shock absorbing material (100) according to any one of claims 1- 12, wherein the piece of mechanical shock absorbing material (100) extends along the bottom, and / or at least one side wall of the plurality of the side walls, and / or along the top of the package, and wherein the piece of mechanical shock absorbing material (100) is in the second shape.

14. A sound absorbing element having an essentially planar or curved extension comprising a piece of sound absorbing material (100) according to any one of claims 1-12, wherein the piece of sound absorbing material (100) is in the second shape.

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