Patent Application
20050136256
This application is based on and claims the priority under 35 U.S.C. §119 of German Patent Application 103 60 808.7, filed on Dec. 19, 2003, the entire disclosure of which is incorporated herein by reference.
The invention relates to fiber-reinforced composite materials, particularly materials with mineral fibers embedded in a metal matrix. Such composite materials are formed by a method as disclosed herein.
It is known to use relatively long mineral fibers in thermal insulating materials in the construction industry. Primarily basaltic fibers are used for thermal insulating purposes or for reinforcing of concrete products. Such basaltic relatively long fibers are also known to be used for making support plates or substrates for electronic components.
European Patent Publication EP 0,181,996 A2, U.S. Pat. No. 4,615,733, and Russian Patent Publication RU 2,182,605 C1 disclose the use of fiber-reinforced composite materials with a metal matrix. The fibers embedded in the matrix are short and distributed at random. Thus, the orientation of the short fibers relative to each other is also random. The conventionally used short fibers are generally made of a mineral material with substantial proportions of silicon oxide (SiO2), aluminum oxide (Al2O3), and iron oxide (Fe2O3). However, conventional fiber-reinforced composite materials with short fibers in a metal matrix do not have the mechanical characteristics required, for example in aircraft construction. Such mechanical characteristics include, for example a substantial tolerance relative to damages, particularly a toughness against crack formations and a resistance against fatigue effects, such as fatigue crack propagation.
In the construction of lightweight structural components emphasis is always on the weight reduction, particularly in the aircraft industry. Moreover, and depending on the respective field of application, such composite materials must meet different requirements with regard to their static and dynamic fatigue characteristics including their tolerance to damages. This requirement applies, particularly in the aircraft construction where lightweight structural components must tolerate damages to avoid failure of the aircraft. An improvement of these damage tolerance characteristics can be achieved in different ways, for example by increasing the skin thickness of an aircraft body or body component. The use of additional locally distributed stiffening components helps increasing the damage tolerance. Adapting the skin thickness in those local positions where stress is largest helps improving the damage tolerance. However, all these measures do not necessarily satisfy weight limitations. Hence, there is a need for a compromise, which particularly in the aircraft industry, is not readily acceptable. Another possibility of increasing the damage tolerance characteristics of such composite materials is the use of materials having inherently better damage tolerance characteristics. Materials having such characteristics are metallic laminates or fiber-reinforced laminates.
Recently, fiber-reinforced composite materials with a metal matrix are achieving an increasing significance because in such materials the fibers permit increasing the strength of metallic materials. More specifically, the damage tolerance characteristics of metallic materials can be significantly increased by reinforcing fibers. However, such an improvement is achieved with noticeably higher costs for such metal based fiber composite materials. One important reason for the higher costs lies in the higher production costs. Particularly, production methods in which the metal matrix is melted onto the fibers, involve a substantial effort and expense with regard to production times and production costs. Such costs have been reduced in a relatively economical production method in which sheet metal layers are bonded to each other by an intermediate adhesive film containing the reinforcing fibers.
In this connection reference is made to European Patent Publication EP 0,312,151 disclosing a laminate comprising at least two sheet metal layers with a synthetic adhesive layer between the sheet metal layers, whereby the adhesive layer bonds the sheet metal layers to each other. The adhesive bonding layer comprises glass filaments. Such laminates are particularly useful for lightweight construction in the aircraft industry because these laminates have advantageous mechanical characteristics while simultaneously having a low structural weight.
European Patent Publication EP 0,056,288 discloses a metal laminate in which polymer fibers are used in the bonding layer. These fibers are selected from the group of aramides, polyaromatic hydrazins, and aromatic polyesters in a synthetic material layer.
European Patent Publication EP 0,573,507 discloses a laminated material in which reinforcing fibers are embedded in a synthetic material matrix. The reinforcing fibers used in EP 0,573,507 are selected from a group of carbon fibers, polyaromatic amide fibers, aluminum oxide fibers, silicone carbide fibers, or mixtures of these components.
The above described sheet metal laminates, if compared with equivalent monolithic sheet metals have the advantages of noticeably higher damage tolerance characteristics. For example, metal laminates reinforced with long fiber bonding layers have crack propagation characteristics that are smaller by a factor of 10 to 20 as compared to respective crack propagation characteristics of monolithic sheet metals. On the other hand, these known laminated materials have frequently static characteristics that are worse than those of monolithic materials. For example, the elastic fatigue limits relative to a tension load or pressure load or a shearing load, are lower by about 5 to 20% compared to respective characteristics of equivalent monolithic materials. The fatigue limits of these known laminated materials depend on the use of the type of the bonding or adhesive system and on the types of fibers used in the system.
Efforts to improve the static characteristics of conventional fiber-composite materials are burdened by higher costs. Conventional manufacturing methods, such as powder metallurgical methods or embedding of fibers in a melted matrix material are very cost sensitive. Moreover, the size of conventional fiber-reinforced composite materials producible by the just-mentioned two methods, are rather limited.
In view of the foregoing it is an aim of the invention to achieve the following objects singly or in combination:
The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification. The attainment of these objects is, however, not a required limitation of the claimed invention.
The above objects have been achieved according to the invention by the combination of the following features in a fiber-composite material comprising a matrix made of a metal selected from a first group comprising aluminum, aluminum alloys, magnesium, magnesium alloys, titanium or titanium alloys, or mixtures thereof. The respective alloys comprise the aluminum or the magnesium or the titanium as a dominant component. Reinforcing anorganic fibers are embedded or enclosed in the metal matrix. The reinforcing anorganic fibers are made of a mineral material that includes at least one additive of any one member of a second group including silicon dioxide (SiO2), aluminum oxide (Al2O3), and iron oxide (Fe2O3). The reinforcing anorganic fibers have a length of at least 10 mm and are oriented in parallel to each other in at least one direction.
The present fiber composite materials are produced by orienting the anorganic mineral fibers having a length of at least 10 mm in at least one direction so that the mineral fibers are arranged in parallel to one another, then heating the mineral fibers to at least 200° C., thereby bonding the fibers to one another to form a fiber film and embedding or enclosing said fiber film in the metal matrix which may be formed by sheet metal layers. A plurality of sheet metal layers may be used and bonded to each other by a plurality of fiber films in a laminated structure.
The heating to at least 200° C. is preferably, but not necessarily combined with a pressurization at a pressure of at least 10 MPa. Moreover, the heating, bonding and embedding or inclusion is preferably performed in a vacuum chamber and still more preferably in an inert gas atmosphere, for example in an autoclave or the like. A plurality of mineral fiber films and sheet metal layers may be bonded to one another in a rolling operation to form the fiber composite laminated sheet material. In all instances the sheet metals are made of aluminum, or aluminum alloys, or magnesium, or magnesium alloys, or titanium or titanium alloys or combinations thereof. The aluminum, or the magnesium or the titanium forms a main or dominant component in the respective alloy. The anorganic reinforcing mineral fibers are preferably made of any one or more of the following mineral materials, namely basalt, granite, diabase, amphibolite, diorite, trachyte, porphyry, and obsidian.
The advantage of these mineral materials is seen in their substantial elasticity module within the range of 90 to 120 GPa. Another advantage of these materials is seen in their substantial temperature working range of −260° C. to +640° C. These materials also have good working characteristics when substantial temperature changes or variations occur. Additionally, these materials have a good corrosion resistance. Moreover, the just outlined good characteristics of these anorganic mineral materials remain constant very well in response to vibrations.
In order that the invention may be clearly understood, it will now be described in connection with example embodiments thereof, with reference to the accompanying drawings, wherein:
In another embodiment the matrix material formed by the cover sheets may be made of aluminum copper alloys such as the AA 2024 type or of aluminum zinc alloys such as the AA 7075 type. An aluminum lithium alloy with a lithium content within the range of 0.5 to 3.0% by weight, titanium alloys as well as copper or copper alloys and magnesium alloys are also suitable to form the metal matrix for the present purposes.
The long fibers 3 made of a basaltic material as set forth in the above listing, preferably have a composition as set forth in the following Table of:
Mineral Fiber Example Materials
As shown in
The fibers 3 according to the invention are provided with the particle coating 4 in a thermal operation to enhance the bonding of the fibers to each other as shown in
As shown in
The sheet metal layers 1, 1′ and 2, 2′ preferably have a thickness in the range of 0.01 mm to 3.0 mm.
As shown in
Once the plies are arranged in a laminate, the fiber composite material is subjected to pressure preferably in a rolling operation. The resulting composite material is particular suitable in aircraft construction, more specifically, for aircraft bodies, whereby at least a portion of the body can be made of the present composite materials forming the aircraft skin and/or reinforcements of the aircraft skin.
Although the invention has been described with reference to specific example embodiments, it will be appreciated that it is intended to cover all modifications and equivalents within the scope of the appended claims. It should also be understood that the present disclosure includes all possible combinations of any individual features recited in any of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 60 808.7 | Dec 2003 | DE | national |
