The present invention relates generally to thermal insu- block being discarded as scrap. As mentioned above, the
lation tiles and more particularly to a method for bonding material that is used to form the raw blocks is relatively
thermal insulation tiles. expensive. Consequently, tiles that are produced in a process
wherein large amounts of the fired blocks are scrapped are 10 extremely costly to produce.
BACKGROUND ART Accordingly, there remains a need in the art for a method
Thermal insulation tiles, such as those used to insulate the for forming relatively large insulation tiles. There also
space shuttle orbiter, are typically formed from low-density remains a need in the art for a method for forming a complex
fibrous materials having extremely high temperature resis- 15 shaPed insulation tile which produces relatively less scrap,
tance and a relatively low coefficient of thermal expansion There also remains a need in the art for a method for bonding
as compared to metals. These materials are well known in insulation tiles together.
the art and include, for example, FRCI (fibrous refractory ... T,,^ ...
. . .' , , • , , , , SUMMARY OF THE INVENTION composite insulation) and AETB (alumina enhanced thermal
barrier) materials. 20 In one preferred form, the present invention provides an
In fabricating the tiles, fibers of an insulating material, insulative body having first and second porous insulation
such as silica, alumina boro-silicate and alumina, are mixed members and a binder. Each of the first and second porous
with water to form a slurry. The slurry is deposited into a insulation members is formed of a fibrous, low-density
casting tower where the water is drained and the silica fibers 25 silica-based material and cooperatively defines a joint. The
are subjected to compressive forces to form a raw block of binder is disposed between a pair of mating surfaces that
insulation material having a cross-sectional area that may tolm the j°int- The binder couples the first and second
range from 144 square inches to almost 576 square inches Porous insulation members together.
depending upon the dimensions of the casting tower. The In another preferred form, the present invention provides
raw block is then dried in an oven and subsequently fired 30 a method for coupling a first porous insulation member to a
(sintered) to bond the fibers of the insulating material second porous insulation member wherein each of the first
together. Thereafter, tiles are formed from the fired block and second porous insulation members are formed of a
through conventional machining processes wherein tiles of fibrous, low-density silica-based material. The method
a desired shape are cut from the solid block. 35 includes the steps of: providing an ceramic/organic thermal
One drawback associated with this process is the maxi- setting binder having a thermal set organic binder and a
mum size of the tiles that can be formed. As the surface of ceramic binder; applying the ceramic/organic thermal set
the space shuttle orbiter, for example, is relatively large, it ting binder between a pair of mating surfaces formed into the
is highly desirable to form the tile as large as possible so as first and second porous insulation members; heating the first
to reduce the labor that is required to affix the tiles to the 40 and second porous insulation members to a first predeter
orbiter, as well as minimize the use of the material which mined temperature to initially cause the thermal set organic
bonds the tiles to the orbiter to thereby minimize the weight binder distribute the ceramic binder through a joint formed
of the orbiter'sthermal protection system. In covering a by the mating surfaces of the first and second porous
leading or trailing edge of a craft, a tile having a length in 45 insulation members and thereafter cure the organic binder to
excess of 6 feet is highly desirable. f°rm a well bonded joint; heating the bonded first and
To some extent, the size of the tiles may be increased by second Porous insulation members to a second predeter
enlarging the size of the casting tower. In practice, however, mlned temperature to bum out the thermal set organic
casting towers that produce raw blocks having dimensions blnder; and finng the bonded first and second Porous lnsu"
greater than 22"x22"x7" inches are not practical due to the 50 latlon members at a thlrd Predetermined temperature to
increased rate at which defects and other problems are cause the ceramlc blnder to fixedly C0UPle the matlng
encountered in the manufacturing process. Problems such as surfaces of the first and second Porous Nation members
weight associated with transporting a large block filled with to one an°ther.
water, the inability to completely dry very large raw blocks, 55 BRIEF DESCRIPTION OF THE DRAWINGS overheating the exterior portion of the raw block during the
firing operation and underheating the interior portion of the Additional advantages and features of the present inven
raw block during the firing operation frequently lead to tlon wlU become aPParent from the subsequent description
defects such as shrinking, cracking and improper bonding of and the aPPended claims, taken in conjunction with the
the fibers. As the material that is used to form the raw blocks 60 accompanying drawings, wherein:
is relatively expensive, the increased rate of defects renders FIG. 1 is a perspective view of an insulative body formed
the formation of relatively large fired blocks commercially in accordance with the teachings of the present invention;
impracticable. FIG. 2 is a schematic illustration of the method of the
Another drawback associated with the previously known 65 present invention;
methods of forming tiles concerns the manner in which tiles FIG. 3 is a side elevation view illustrating an alternate
having a complex shape are formed. Tiles which are rela- joint construction;
