In-jig assembly bond fixture for manufacturing composite components

An in-jig assembly bond fixture for manufacturing a composite component having a plurality of parts includes at least one fixture for holding each of the plurality of parts in proper alignment relative to one another during a bonding operation. A mechanical mechanism is provided integral with the at least one fixture for applying a predetermined uniform compressive force to each bond line between each of the plurality of parts during the bonding operation. A plurality of heating elements is provided for applying heat directly to each bond joint and are each selectively located within the fixture for applying heat uniformly across each bond line during the bonding operation.

BACKGROUND OF THE INVENTION 
The present invention relates to the manufacturing of components made from 
composite materials, and more particularly, to an in-jig assembly bond 
fixture for manufacturing composite components having multiple 
subcomponents, such as a composite gas turbine engine component or the 
like. 
Composite materials are gaining wider application and use as a material for 
aerospace applications and the like, and in particular the manufacturing 
of gas turbine engine components, such as those used in high performance 
engines for aircraft propulsion, because of the light weight and high 
strength of these composite components. Such aircraft engine components 
may include an engine front frame, a fan stator assembly or an airfoil 
type engine assembly. An example of a composite gas turbine engine 
component is the front frame engine assembly 10 shown in FIG. 1. Referring 
also to FIGS. 2 and 3, the front frame assembly 10 includes an annular 
outer forward case 12, an inner hub 14 and a plurality of intermediate 
radially extending strut members 16 which are attached between the annular 
case 12 and the inner hub 14. As best shown in FIG. 3, strut 16 includes 
an outer end 18 having outer strut feet 20, which extend substantially 
perpendicular to the longitudinal extent of strut 16, and radially 
extending flanges 22 extending substantially perpendicular from strut feet 
20. Both strut feet 20 and flanges 22 are attached or bonded to case 12 
during manufacturing. Strut 16 further includes an inner end 24 having 
inner strut feet 26 extending substantially perpendicular to the 
longitudinal extent of strut 16 and radial flange 28 extending 
substantially perpendicular from inner strut feet 26. Inner strut feet 26 
and flange 28 are attached or bonded to inner hub 14 during manufacturing. 
An aft annular casing 30 is bonded to forward casing 12 as shown in FIG. 1 
after assembly of the forward case. 
The frame, therefore, represents a very complex assembly of sub-components 
which must be bonded together using high temperature adhesives. The 
assembly of these different components into the frame 10 represents a 
formidable manufacturing challenge. The bonded joints must be maintained 
at a specific bond line thickness to ensure strength while the adjacent 
constituents are held accurately in place during the curing cycle. Because 
of tight tolerances, positioning of the components is very critical and 
must be accurately controlled to ensure proper airfoil orientation and the 
proper air flow path through the engine during operation of the assembled 
engine. 
A prior art arrangement for retaining the different components in proper 
alignment during a curing cycle in an oven utilized C-clamps, jack screws 
and paste adhesive. The different constituents were prepared with the 
paste adhesive and oriented relative to one another and secured in 
position by tightening the hand jack screws, C-clamps or toggle clamps. 
This arrangement and method provided no control or reliability as to the 
integrity of the finished assembly. This oven fixture provided no internal 
heating or uniform pressure on the different bond joints during the curing 
cycle to ensure a specific bond line thickness and that the different 
constituents remained in their proper orientation relative to one another. 
Additionally, this fixture had no internal monitoring to verify or control 
that the proper amounts of heat and pressure were being applied to each 
respective bond joint. The pressure applied was merely as a result of the 
clamping mechanics of the jack screws, C-clamps or toggle clamps and 
maintenance of a constant uniform pressure was suspect during a curing 
cycle because of the susceptibility of these different clamps to thermal 
growth and distortion caused by the heat of the curing oven. The 
temperature of the oven could be controlled by a thermocouple; however, 
there was no actual monitoring and control of the bond temperatures at the 
individual joints of the assembly or monitoring and control of the bonding 
at critical bonding surfaces. 
Thus, there was a need for a new in-jig assembly bond fixture which was a 
self-contained, stand-alone, integrally heated and pressurized unit 
including a computer controlled/integrated system for monitoring and 
controlling the bonding operation at the different bond joints and at 
critical bonding surfaces. 
SUMMARY OF THE INVENTION 
It is, accordingly, a primary object of the present invention to provide a 
novel assembly bond fixture which is not subject to the foregoing 
disadvantages. 
It is another object of the present invention to provide a novel assembly 
bond fixture which is a self-contained, stand-alone, integrally heated and 
pressurized unit including an integrated computer control system for 
monitoring and controlling the bonding operation. 
It is a further object of the present invention to provide a novel assembly 
bond fixture which is not susceptible to thermal growth and distortion 
during the heat bonding cycle. 
It is yet a further object of the present invention to provide a novel 
assembly bond fixture which provides reliable and consistent assembly of a 
component. 
In accordance with the present invention, an in-jig assembly bond fixture 
for manufacturing a composite component having a plurality of parts 
includes at least one fixture for holding each of the plurality of parts 
in proper alignment relative to one another during a bonding operation. A 
mechanical mechanism is provided integral with the at least one fixture 
for applying a predetermined uniform compressive force to each bond line 
between each of the plurality of parts during the bonding operation. A 
plurality of heating elements is provided for applying heat energy 
directly to each bond joint and are each selectively located within the 
fixture for applying heat uniformly across each bond line during the 
bonding operation. A controller may be provided for monitoring and 
controlling the uniform compressive force applied to each of the bonding 
joints and means may also be provided for monitoring and controlling the 
heat applied to each of the bonding joints. 
These and other objects of the present invention, together with the 
features and advantages thereof, will become apparent from the following 
specification when read with the accompanying drawings in which like 
reference numerals refer to like elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring initially to FIGS. 4, 4A and 5, an in-jig assembly bond fixture, 
indicated generally as 30, includes a base member 32 and a plurality of 
outer fixture means 34 for holding the annular forward case 12 of a gas 
turbine engine front frame assembly 10 (FIG. 1) and each of the struts 16 
in proper position relative to one another to bond each of the struts 16 
to the annular forward case 12. As best shown in FIGS. 4A and 5, each of 
the plurality of outer fixture means 34 includes an arcuate pressure plate 
or block 36 for abutting an outer surface of the annular forward case 12 
of the frame assembly 10 and an arcuate backstop plate 38 for abutting and 
retaining a juxtaposed pair of outer strut feet 20 of two adjacent struts 
16 during a bonding operation. As will be described in more detail 
hereinafter, the pressure plate 36 and the backstop plate 38 operate in 
cooperation with one another to apply a predetermined uniform compressive 
force to the joint 39 between the annular forward case 12 and the outer 
strut feet 20 during a bonding operation. The pressure plate 36 preferably 
has an operating face 40 which is shaped to conform to an outer surface of 
the annular case 12, and backstop plate 38 preferably has an operating 
face 42 which is shaped to conform to the shape of the outer strut feet 
20. Pressure plate 36 is preferably slidably mounted to base member 32 by 
a slide channel 44 which is fixedly attached to base member 32. Slide 
channel 44 permits pressure plate 36 to slide back and forth between a 
non-operating position at a spacing from backstop plate 38 to permit 
insertion of the forward case 12 and struts 16 into the assembly bond 
fixture 30 and to permit removal of the frame assembly 10 after the 
bonding operation, and an operating position with the operating face 40 of 
the pressure plate 36 and the operating face 42 of the backstop plate 38 
applying the predetermined uniform compressive force directly to the joint 
39 between the annular case 12 and the outer strut feet 20 during a 
bonding operation. 
A pressure layer 46 of a high heat resistant conformable material, such as 
RTV rubber or the like, may be disposed between the operating face 40 of 
pressure plate 36 and the annular case 12 to facilitate conformance 
between the pressure plate operating face 40 and the outer surface of the 
casing 12 and to provide uniform pressure across the operating face 40 
when pressure plate 36 is in its operating position. 
The pressure plate 36 and backstop plate 38 each have a plurality of 
electrical resistive heating elements 48 (shown schematically in FIG. 5) 
mounted at selected locations within the plates 36 and 38 to provide a 
desired uniform distribution of heat energy directly to the joint 39 or 
bond line to properly bond the annular case 12 to the strut member 16. The 
pressure plate 36 and backstop plate 38 also include a plurality of 
thermocouples 50(shown schematically in FIG. 5) which are mounted at 
selected locations to provide monitoring and control of the heating of the 
plates 36 and 38 during a bonding operation. 
Each of the plurality of outer fixture means 34 further include an actuator 
arrangement 52 for forcing the pressure plate 36 against the annular case 
12 to provide the predetermined uniform compressive force on the joint 39 
between the case 12 and the outer strut feet 20 during the bonding 
operating. The actuator arrangement 52 includes a pusher bar 54 which is 
pivotably mounted to a first support member 56. The pusher bar 54 may be 
held in position on first support member 56 by a suitable fastener (not 
shown) which permits limited vertical pivotal movement of the pusher bar 
54. First support member 56 is slidably mounted in slide channel 44 for 
movement of the pusher bar 54 between a non-operating position and an 
operating position for applying the predetermined compressive force. The 
pusher bar 54 has an operating end 58 which is shaped for matingly 
engaging a groove or notch 60 formed in the pressure plate 36 to cause the 
pressure plate 36 to move into its operating position to provide the 
compressive force during a bonding operation. An expandable air bladder 62 
is mounted by a second support member 64 to slide channel 44. The air 
bladder 62 has an actuator pin 66 mounted at one end of the air bladder 
opposite to the support member 64 and actuator pin 66 has an opposite end 
for engaging and sliding the first support member 56 into its operating 
position when the air bladder 62 is expanded to provide a controllable 
force during a bonding operation. Second support member 64 is slidably 
positionable on base member 32 within slide channel 44 and may be 
removably affixed at selected locations to accommodate different sizes of 
annular cases 12 or other components for assembly. Air bladder 62 is 
coupled by support member 64 and tubing 68 to a suitable air supply (not 
shown) for actuating the air bladder 62. 
Each of the outer bonding fixture means 34 further includes an adjustment 
mechanism 70 for adjusting and fixing the position of the backstop plate 
38. Adjustment mechanism 70 includes a thumbscrew 72 threadedly received 
in a bore 74 formed in a support pedestal 76 which is attached to base 
member 32 by channel 44. Thumbscrew 72 has an adjustment point 78 
pivotably mounted at one end thereof for engaging backstop plate 38 when 
thumbscrew 72 is advanced. Support pedestal 76 may be fixed in position 
within channel 44 by a suitable set screw arrangement (not shown) or the 
like. 
In operation, expandable air bladder 62 is actuated by the air supply to 
push actuator pin 66 against support member 56 with a predetermined force. 
Support member 56 is urged forward and push bar 54 engages the notch 60 in 
pressure plate 36 to urge pressure plate 36 forward. Backstop plate 38 is 
held in place by adjustment mechanism 70 and the pressure supplied by 
actuated air bladder 62 causes uniform pressure across the operating faces 
40 and 42 of pressure plate 36 and backstop plate 38, respectively, to 
provide a predetermined uniform compressive force at the joint 39 between 
annular case 12 and the outer strut feet 20 of strut 16. The compressive 
force may be monitored and controlled by in-line measurement of the air 
pressure from the air supply or by strain gauges mounted on the pressure 
plate 36 and backstop plate 38. 
Referring to FIGS. 4, 4A and 6, in accordance with the present invention, 
the assembly bond fixture 30 of the present invention further includes a 
plurality of biasing mechanisms 80, one disposed between each pair of 
juxtaposed outer fixture means 34, as best shown in FIG. 4, for applying a 
predetermined compressive force to a joint 82 between each of the outer 
end radial flanges 22 of each strut 16 and a radially extending flange 84 
of the annular case 12. Each of the biasing mechanisms 80 includes an 
actuator bar 86 which is pivotably mounted at one end 87 to a 
pneumatically operated piston 88 and is pivotably mounted at an 
intermediate location 90 to a support stanchion 92. The actuator bar 86 
has an operating end 94 opposite to the one end 87 which is shaped to 
engage an annular ring 96 which is positioned over each of the joints 82 
to provide a uniform pressure across substantially the entire bond line of 
each of the joints 82. The pneumatic piston 88 and the stanchion 92 are 
mounted to a base support member 98 which in turn may be removably mounted 
to base member 32 by sliding into a restraining toe clamp 99 positioned at 
the appropriate location on base member 32, depending upon the size and 
shape of the component being manufactured, for applying the compressive 
force to the different joints 82 during a bonding operation. 
In operation, pneumatic piston 88 is actuated by the air supply to force 
end 87 of actuator bar 86 to pivot about intermediate point 90 and to 
apply a downward force on annular ring 96. Because the case member 12 and 
the strut member 16 are secured between pressure plate 36 and backstop 
plate 38, the force applied by actuator bar 86 creates another 
predetermined uniform compressive force at joint 82. 
Referring back to FIG. 5, the in-jig assembly bond fixture 30 of the 
present invention further includes a center fixture arrangement 100 which 
is mounted to the base member 32 for holding the inner strut feet 26 and 
radial flange 28 of the inner end 24 of strut 16 (FIG. 3) in proper 
position relative to inner hub 14 (FIG. 2) during a bonding operation. 
Center fixture arrangement 100 is mounted on a pedestal 102 to provide 
proper alignment between annular casing 12, strut 16 and hub 14 during the 
bonding operation. The height of pedestal 102 may be adjusted for bonding 
different gas turbine engine components such as a fan stator or other 
airfoil engine assemblies. Center fixture arrangement 100 includes a 
plurality of hub pressure plates 104 which are substantially evenly spaced 
circumferentially about the hub 14, one each between juxtaposed struts 16 
as best shown in FIGS. 4 and 4A (reference numerals for pressure plates 
104 are not shown in FIG. 4 for purposes of clarity). A plurality of 
pneumatically operated cylinders 106 is provided in association with each 
hub pressure plate 104 to provide a predetermined uniform compressive 
force at the joint or bond line 108 between the hub 14 and the inner strut 
feet 26 and flange 28 of strut 16. The pneumatically operated cylinders 
106 each include a piston 110 for engaging the hub pressure plate 104. The 
pneumatically operated cylinders 106 are mounted to the center fixture 
pedestal 102 by an annular bracket 112 having a plurality of channels 114 
formed therein for mounting each of the pneumatic cylinders 106 in proper 
orientation for applying the predetermined force to pressure plates 104. 
A segmented flange adapter cone 116 is inserted within hub 14 to facilitate 
application of the compressive force at the bond line 108 between the hub 
14 and the inner strut feet 26 and flange 28. The flange adapter cone 116 
is segmented into a plurality of parts to facilitate insertion into hub 14 
and removal from the hub 14 after a bonding operation. A cup-shaped 
pressure plate 118 is disposed over the segmented flange adapter cone 116. 
The cup-shaped pressure plate 118 has a flat bottom portion 122 and an 
annular side portion 123 which extends from the bottom portion 122 at a 
selected angle relative to the surface normal of bottom portion 122 to 
mate with the segmented flange adapter cone 116 and to apply the 
compressive force at joint 108 during a bonding operation. The cup-shaped 
pressure plate 118 has a passage 120 formed substantially in the center of 
the bottom portion 122 through which is inserted a pneumatically operated 
actuator rod 124. An alignment disk 126 is attached to actuator rod 124 
which applies a downward force to the bottom portion 122 of cup-shaped 
pressure plate 118 when pneumatically operated actuator rod 124 is pulled 
down into an operating position. Actuator rod 124 may be operated by an 
air cylinder (not shown) or similar pneumatic device known to those 
skilled in the art. Alignment disk 126 may have a plurality of alignment 
pins 128 extending downwardly therefrom for receipt by alignment channels 
formed in the bottom portion 122 of cup-shaped pressure plate 118 to 
provide proper alignment of the cup-shaped pressure plate 118 relative to 
the hub 14 during a bonding operation. The cup-shaped pressure plate 118 
has an annular radially extending flange 130 which extends radially 
outwardly over hub 14 and segmented flange adapter cone 116 to provide a 
downward force on the joints between hub 14 and segmented adapter cone 116 
and the joints between the inner strut feet 26 and flanges 28 and the hub 
14 when actuator rod 124 is pulled into its operating or compression 
position. An annular washer 132 may be disposed between radially extending 
flange 130 and hub 14 to facilitate application of a uniform force for 
bonding joint 108 between hub 14 and inner strut feet 26 and flanges 28. 
Alignment disk 126 is preferably removably attached to actuator rod 124 by 
a clip spring 134 or similar mechanism which is fastenable about an 
annular groove 135 formed in rod 124. Alignment disk 126 is removable to 
permit removal of cup-shaped pressure plate 118 during insertion and 
alignment of strut 16, hub 14 and segmented flange adapter cone 116 before 
a bonding operation and to facilitate removal of the bonded assembly from 
the bond fixture 30 after the bonding operation. 
Cup-shaped pressure plate 118 has a plurality of receptacles 136 formed 
therein at predetermined locations for receipt of electrical resistive 
heating elements (not shown), such as calrod type heaters or the like, to 
supply a uniform distribution of heat across the bond lines or joints 
between the strut 16 and hub 14. Cup-shaped pressure plate 118 further 
includes other receptacles 137 (shown in phantom in FIG. 5) for receiving 
thermocouples for monitoring and controlling the heating of the bond 
joints. 
In operation, actuator rod 124 and alignment disk 126 in cooperation with 
cup-shaped pressure plate 118 provide downward and lateral pressure on the 
joint 108 and hub pressure plate 104 provides opposite upward and lateral 
forces to provide, in conjunction with pressure plate 118, a predetermined 
uniform compressive force on bond joint 108. This compressive force may be 
monitored and controlled by monitoring the air pressure operating 
pneumatic cylinder 106 and pneumatic actuator rod 124 as described in more 
detail hereinafter. 
It should be noted that a high strength adhesive tape is attached to at 
least one surface of each joint or bond line as the different constituents 
of the frame assembly 10 are inserted into the assembly bond fixture, 30 
prior to application of the compressive forces and heat during the bonding 
operation or cycle. 
In accordance with the present invention, a monitoring and control system 
138 for the bonding cycle or operation is shown schematically in FIG. 7. 
The in-jig assembly bond fixture is represented schematically by block 30 
and each of the predetermined uniform compressive forces applied at each 
of the plurality of outer fixture means 34 and at the center fixture 
arrangement 100 are illustrated by arrow 139. The resistive heating 
elements 48 in pressure plates 36 and 38 and in cup-shaped pressure plate 
118 are illustrated schematically by resistor symbol 140. The heating 
elements 140 are connected to a power source 142. In accordance with the 
present invention, a programmable controller 144 is provided to monitor 
and control the application of the uniform compressive forces 139 and the 
application of heat to the different bond lines or joints. A current 
transformer 146 is connected in series between power source 142 and 
resistive heating elements 140 to provide a control input to programmable 
controller 144 for monitoring and controlling the application of heat to 
each of the bond lines or joints. As previously discussed, thermocouples 
50 are collocated with resistive heating elements 140 at predetermined 
locations within the outer fixture means pressure plates 36 and 38 and hub 
pressure plates 104 and cup-shaped pressure plate 118 of center fixture 
arrangement 100. The thermocouples are each coupled to programmable 
controller 144 to provide additional monitoring and control of the 
application of heat to the different bond lines or joints. 
In accordance with the present invention, an air supply 148 is provided for 
actuation of expandable air bladder 62, air cylinder 106 and pneumatic 
actuation rod 124. Air supply 148 is connected to an air manifold 150 for 
distribution of working air to each of the actuation means. A manifold 
pressure sensor 152 is coupled to air manifold 150 for sensing the 
pressure in the manifold and the pressure sensor 152 is in turn coupled to 
programmable controller 144 to provide monitoring and control of the 
application of the compressive forces at each of the fixture means 34 and 
100. A plurality of ball valves 154 are provided to control the 
application of air to each of the force application means or actuator 
means, i.e., air bladder 62, air cylinder 106 and actuation rod 124. An 
air switch 156 is connected to a tap 158 in the output conduit 160 of each 
ball valve 154 to provide a further input to programmable controller 144 
for monitoring the application of the uniform compressive forces at each 
of the fixture means or arrangements 34 and 100. 
Programmable controller 144 may be coupled to a host computer 162 for 
storing process parameters for in-process, real time monitoring and 
control of the bonding operation and for later evaluation as to the 
performance of the bonding operation. A monitor 164 and keyboard 166 may 
be provided and coupled to host computer 162 to facilitate monitoring of 
the bond cycle process parameters and permit operator adjustment of the 
process parameters on a real time basis. Host computer 162 may also store 
historical and statistical data to permit tracking of the bonding cycles 
for different components. 
While the present invention has been described with respect to the assembly 
and bonding of a composite front frame of a gas turbine engine, those 
skilled in the art will recognize that the present invention is also 
applicable to the manufacturing of any type composite component and that 
the present invention is not limited to the specific embodiments described 
and illustrated herein. Different embodiments and adaptations besides 
those shown herein and described as well as many variations, modifications 
and equivalent arrangements will now be apparent or will be reasonably 
suggested by the foregoing specification and drawings, without departing 
from the substance or scope of the invention. While the present invention 
has been described herein in detail in relation to its preferred 
embodiments, it is to be understood that this disclosure is only 
illustrative and exemplary of the present invention and is merely for 
purposes of providing a full and enabling disclosure of the invention. 
Accordingly, it is intended that the invention be limited only by the 
spirit and scope of the claims appended hereto.