Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1999-08-19
2002-03-19
Le, Hoa T. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C052S638000, C052S648100, C052S649100, C052S649800
Reexamination Certificate
active
06358603
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a shaped article which is capable of resisting impact, including high velocity impact and other high energy impact.
A number of impact challenges, such as attacks with projectiles, shells, grenades, missiles and bombs, have as their main purpose to penetrate and/or damage the objects which they are aimed at. Another class of potentially damaging impact is accidental events such as gas explosions, vehicle (ships, aeroplanes, cars, etc.) collision, impact occurring during earthquakes, and the accidental dropping of articles, e.g. in the offshore industry.
Another type of impact is impact processing, such as impact hammering, explosion shaping, etc. Another type of impact occurs in connection with quarrying of stone. For example, large pieces of stone may fall onto trucks or other machinery, and high energy impacts of this type can cause extensive damage.
Impact challenges also occur in the form of high energy impact from e.g. explosives. For example, bank vaults must be able to withstand an explosive impact of this type.
In high velocity or high energy impact, the behaviour of materials is in many ways fundamentally different from the behaviour under slow static influences—often resulting, inter alia, in fatal failure or destruction of the articles in question, even where the articles have very high load bearing capacity under static conditions.
For protection against damaging impact and for tools used for impacting processing, articles having better resistance against impact than hitherto obtainable are desired.
The present invention provides such articles. The articles of the invention can be designed to provide protection or resistance under influences where known art materials would fail or would be vastly inferior, in particular high energy impact such as high velocity impact.
DISCUSSION OF THE PRIOR ART
It is known to produce various high-strength composite materials, for example construction materials based e.g. on a matrix of Portland cement and very small particles such as ultrafine silica, and with reinforcement incorporated therein in the form of e.g. fibres, steel bars or wires, etc.
EP 010777 discloses very strong and dense composite cement-based composite materials prepared from Portland cement, inorganic solid silica dust particles, fibres, a concrete superplasticizer and water, the composite materials having a large content of silica dust particles and superplasticizer and a small water content, e.g. typically 10-30% by volume of silica dust particles based on the volume of the cement and silica dust, 1-4% by weight of superplasticizer dry matter based on the weight of the cement and silica dust, and a water/powder weight ratio of 0.12-0.30 based on the weight of the cement, silica dust and possible other fine powder present.
EP 042935 discloses improved composite materials based on the matrix of EP 010777 and additionally containing a strong aggregate with a strength exceeding that of ordinary sand or stone used as aggregate for ordinary concrete.
WO 87/07597 discloses a compact reinforced composite (CRC) material based on a combination of a rigid, dense and strong matrix comprising a base matrix corresponding to the composite materials described in EP 010777 and EP 042935 which is reinforced with a high content of relatively fine fibres and which is further reinforced with a high content of main reinforcement, e.g. in the form of steel bars, wires or cables, to result in a novel composite material which is both strong and rigid as well as ductile.
A technical paper (“Role of shear reinforcement in large-deflection behavior”, Kiger et al.,
ACI Structural Journal
, November-December 1989) describes the use of “lacing” or “single-leg stirrups” in order to tie the two principal reinforcement mats together in reinforced concrete structures designed for blast-resistance. The paper concludes that requirements for shear reinforcement such as lacing may be more restrictive and expensive than necessary, and it is stated that although transverse shear reinforcement (in the form of lacing or stirrups) can provide additional confinement for reinforced concrete beams, it provides very little, if any, additional confinement for slabs. It is furthermore suggested that the use of smaller but more numerous principal reinforcing bars may be a more effective way of preventing breakup of a concrete slab than the use of such transverse shear reinforcement. The emphasis of the paper is on the reinforcement itself, and there is no suggestion to use e.g. lacing with any particular type of concrete matrix.
Although the principle of “lacing” of reinforcing bars in a concrete structure designed for blast-resistance, e.g. as described in the technical paper referred to above, was known, the prior art contains no suggestion to combine this or a similar principle of reinforcement together with any particular type of concrete matrix. On the contrary, the cited technical paper suggests that an increased amount of main reinforcing bars might be a more effective solution to the problem of blast-resistance than the use of transverse reinforcement such as lacing. Thus, the problem of providing structures, in particular cement-based structures, with improved blast- or impact-resistance remains unsolved.
The CRC concept described in the above-cited WO 87/07597, on the other hand, emphasises both the nature of the matrix (a rigid, dense and strong cement-based matrix) and the reinforcement (a high content of reinforcing fibres together with a high content of main reinforcement in the form of e.g. steel bars, wires or cables). However, the concept of a 3-dimensional arrangement of main reinforcement, wherein individual reinforcing elements are interlocked with each other in at least one dimension, is in no way suggested by WO 87/07597, for the simple reason that such an intricate arrangement of reinforcement would have been regarded by a person skilled in the art as involving an unnecessary expense and difficulty without any expectation of technical benefit.
BRIEF DISCUSSION OF THE INVENTION
It is an object of the present invention to provide novel shaped articles with improved performance characteristics, in particular under dynamic conditions. One aspect of the present invention represents a further development of the CRC concept mentioned above, enabling the production of materials that are extremely strong and durable under both static and dynamic conditions, and which also show extremely high impact resistance.
The present invention relates in general to impact-resistant articles which are based on a combination of a hard, but fracture-ductile matrix and a three-dimensional reinforcement which is internally tension interlocked in at least one dimension. Articles according to the invention are unique in showing high strength, rigidity and ductility in all three directions and showing, upon being subjected to a large load, high strength, toughness and rigidity, as well as the capability of absorbing high energy with retention of a substantial degree of internal coherence, also under exposure to high-velocity or high-energy impact.
In its broadest aspect, the invention can be characterized as a shaped article, at least one domain of which has a three-dimensionally reinforced composite structure, the composite structure comprising a matrix and a reinforcing system, the reinforcing system comprising a plurality of bodies embedded in the matrix and extending three-dimensionally in first, second and third dimensions therein, the reinforcing system being tension interlocked in at least one dimension in that reinforcement components extending in the first and/or second dimension are tension interlocked to reinforcement components extending in the same dimension(s), but at a transverse distance therefrom, by transverse reinforcement components extending in a dimension transverse to a plane or surface defined by the reinforcement in the first and/or second dimension,
the matrix having a compressive strength of at least 80 MPa, a modulus of elasticity
Aalborg Portland A/S
Le Hoa T.
Merchant & Gould P.C.
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