WO1990000970A1

WO1990000970A1 - Bonding of plastic and plastic matrix composite materials

Info

Publication number: WO1990000970A1
Application number: PCT/US1989/003256
Authority: WO
Inventors: Henry D. Swartz
Original assignee: Swartz Henry D
Priority date: 1988-07-28
Filing date: 1989-07-27
Publication date: 1990-02-08
Also published as: JPH04502737A; CA1339405C; EP0427793A1; EP0427793A4

Abstract

Joining of thermoplastic parts (2, 4) of indeterminate thickness to each other is effected by application of heat to selected surface areas thereof (42, 44) by intense focussed infrared heat lines produced by parabolic-elliptical-reflection heat sources (22, 24) displaced by a reciprocating linear actuator (26), removable by a robotic controller (36) after completion of heating to enable intermediate pushing together of the parts by further actuators (32, 34) for bonding.

Description

BONDING OF PLASTIC AND ELASTIC MATRIX COMPOSITE MATERIALS

FIELD OF INVENTION/BACKGROUND OF THE INVENTION

The present invention relates to methods and apparatus for the fuse melting or binding of plastic materials and plastic matrix composite materials.

A composite is a resin or resin-like crystalline, amorphous or semi-crystalline matrix in which is embedded wires, fibers, whiskers or flakes typically of carbon, graphite, fiberglass or boron. Reinforcing materials can be long, short, layered, chopped, orderly or random. Typically, layers composed of parallel fibers are oriented and laminated in different directions to produce a stress-free, lightweight, uniform sheet of unusual strength.

Reinforced polymer composites can maintain material strength and integrity at continuous source temperatures typically at 400 deg. F. and higher and have substantial usage in the fields of aircraft, automotive structures, construction materials, machine parts and a variety of consumer product constructions as a replacement for metal and wood.

A major problem which has plagued the plastic and plastic matrix composite industry is the lack of appropriate technology for joining of these composites. Present state-of-the-art bonding methods are unsatisfactory; these include adhesives, resistance welding, ultrasonic bonding, vibration welding, induction bonding, high frequency welding, mechanical fasteners and infrared radiant heat. Each method has inherent problems which this invention overcomes. It is an object of the invention to provide a quick and effective method of bonding plastic matrix composites and melt fusing monolithic thermoplastics and elastomers which overcomes virtually all of the problems inherent in present state-of-the-art bonding processes and results in bonds and fusions which consistently test in excess of 2,000 psi in lap shear, 1,000 or more in flat pull strength, and over 5 lbs. in peel.

It is a further object of this invention to provide a uniform bond which avoids the discontinuity introduced by adhesives; avoids the vibration and tearing inherent in ultrasonic bonding; avoids the ferrous residue inherent in induction bonding; avoids the thinning and weakening produced by high frequency welding; solves the problem of material puncture which is a problem with mechanical fastening; and eliminates the installation of high resistance wire that remains in the seam during resistance welding.

It is an object of this invention to provide a strong, stress-free bond of any geometric configuraticn.

It is an object of this invention to provide a leak-proof homogenous Bond line without any reduction of the composite sheet's or part's thickness by means of molecular bonding within the resin of the joined thermoplastic composites such that the bond is as strong as the resin itself.

It is a further object of this invention to provide a method of bringing together the surfaces to be bonded immediately on the cessation of heating which result in bond strengths up to and in excess of 2,000 psi in lap shear on a 1"x1" bond line, and over

/test 1,000 psi in a flat tensile pull, and more than 5 lbs. in a peel on the same 1"x1" bond specimen.

It is a further object of this invention to provide non-contact heating of bond line material without reducing the thickness of the pre-joined sheets or parts in substantially reduced times of approximately 30 seconds to 10 minutes.

It is a further object of this invention to provide intermittent focused radiant heat means to both surfaoes to be bonded prior to bonding and to provide heat means to the enriching matrix prior to bonding whereby only the outermost layers of the designated bonding areas on surfaces to be bonded are heated, leaving the internal temperature and fiber structure of the material essentially unaffected, and leaving the adjacent surface material unheated.

SUMMARY OF THE INVENTION

According to the invention, intermittent focussed infrared radiant energy is focussed simultaneously on the designated bonding areas on surfaces of multiple parts to be joined. A bonding agent consisting of a "neat" layer (i.e., essentially free of reinforcement or other foreign infusion) of the matrix material may be applied to one or both designated areas of the surfaces to be bonded. The surfaces are than brought into immediate bonding contact with sufficient pressure to accomplish the bonding without distorting the material. The steps to accomplish the bonding are as follows :

/or clean /e.g. with solvent)

Step One: Abrade the bonding areas to be jointed (optional) and/or enrich the bonding areas with a "neat" layer of thermoplastic resin, compatible with the natrix of each part.

Step Two: Apply with heat a pellet of neat resin or an extruded monolithic tape of neat resin to the bond line of one or both bonding surface areas of each interface of the material to be bonded. (Alternatively, the resin tape may contain dispersed fibers or other reinforcement in some embodiments. )

Step Three: Heat the tape (if any) and bonding area quickly without heating the inner layers of the plastic matrix material.

/and Step Four: As soon as the upper and lower interfaces bonding tapes or pellets have been softened sufficiently to be reformed as a single fusion, the press is brought together quickly. A mechanical stop prevents the upper and lower press parts from crushing the material; however, sufficient pressure between 10 psi and 300 psi is applied to provide the pressure necessary to fuse the bonding material together.

Other objects , features and advantages of the invention will appear frαn the following detailed description of preferred embodiments thereof, reference being made to the accompanying drawing, in which:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1a is a schematic vertical cross section showing a preferred method and apparatus according to the invention or heating the bonding matrix in the bending zones by means of a robotically activated, reciprocating, non-contact, focussed, intense, infrared heat source disposed between the two press parts.

FIG. 1b is a schematic prospective view of FIG. 1a.

FIG. 2 is a schematic view of the press parts being brought together immediately after the heating cycle with sufficient pressure, typically between 20 psi and 300 psi, to accomplish the bonding.

FIG. 3 is schematic vertical cross section taken transverse to the materials to be bonded showing the advantage of using a non-fibrous, neat, monolithic themoplastic resin to enhance the bonding area.

FIG. 4 shows a schematic view of a preferred manner of applying, an extruded monolithic tape of the same matrix resin on the bond line of each interface of the joining sheets or parts.

FIG. 5 is an alternative embodiment of FIG. 3 showing the application of a preferred tape directly from an extruder onto the sheet or formed part to be bonded.

FIG. 6 is a schematic vertical cross section taken transverse to the materials to be bonded showing an optional method of abrading the fusion side of the bonding areas prior to heating.

FIG. 7 is a schematic vertical cross section showing a preferred method and apparatus according to the invention

/Stepped

illustrating the increase in surface temperature of the bonding zone with each stroke of the focussed infrared heat source. FIG. 8a through 8e are schematic cross sections showing a sample of the wide variety of joint configurations possible with this invention.

FIG. 9a, 9b and 9c are schematic vertical cross sections showing joint configurations of various multi-dimensional structures.

FIG. 10 is a schematic vertical cross-sectional view of the robotic arm with affixed parabolic elliptical infrared reflectors illustrating adjustment of the focal lengths of said heat sources.

FIG. 11 is a schematic perspective view illustrating the use of this invention for fusing parts of pre-molded elatromeric or composite thermplastics.

FIGS. 12 and 12a are schematic vertical cross-sectional views of point focus parabolic elliptical infrared heat sources mounted back to back on a robotic arm which can be preprogramed to trace on a circular or elliptical path.

FIG. 13a, 13b and 13c are alternate embodiments of this invention showing the use of focussed parabolic elliptical infrared spot beams at various angles mounted on a robotic armature which can be programmed to move in any geometric configuration.

FIGS . 14-15 and 17 are schematic representations of another preferred embodiment at various position of operation, as described.

FIG. 16 is a temperature-time trace applicable to operation of the FIGS. 14-15 and 17 apparatus.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

There is shown in FIG. 1 an apparatus, 10, aocording to a

preferred embodiment of the present invention for bonding two

thermoplastic objects, comprising press platens, 12 and 14 , heating means, 22 and 24, mounted on a robotic armature, 26, the respective support and activating means, 32, 34 and 36.

The timing and closure pressure of the press is controlled by the press. Plastic materials to be bonded, 2 and 4, are affixed to the respective press platens by vacuum suction devices (not shown) integral to the platens.

During the heating phase the press remains in its open position. When the heating cycle is complete, the upper and lower press parts are brought quickly and forcefully together into the closed position, as shown in FIG. 2.

The heating sources 22 and 24, fixedly mounted on the robotic arm 26, are movable into or out of a work zone between parts 12 and

14, and are capable of reciprocal and pivotable movement within such zone. Each of the heat sources 22 and 24 are elongated perpendicularly to the cross-sectional plane shown in FIG. 1.

The focal vector of the upper heat source 22 is pointed upward essentially normal to the surface of the first plastic material 2 to be heated. The focal vector of the lower heat source 24 is pointed downward essentially normal to said second plastic material 4 to be heated. The heat sources 22 and 24 consist of commercially available parabolic/elliptical infrared lamps. The displacement, velocity, periodicity, temperature and focal lengths and path of said heat sources are independently controlled.

Prior to the heating of the plastic materials to be bonded, 2 and 4, bonding zones 42 and 44 of said materials to be fused are enriched with resin identical to the resin which forms the matrix of the thermoplastic composite FIG. 3). To accomplish the placing of the resin enrichment pellet 50 or tape 52 which must be preheated prior to the heating of the plastic matrix composite materaials, a robotic feeding arm is utilized (not shown). In alternative embodiments, extruded monolithic tape 52 is applied, as shown in FIG. 4, or preformed tape 54 is applied directly by an extruder (FIG. 5). An optional step, as shown in FIG. 6, is the abrading of the surfaces to be joined.

The incremental temperature of the surfaces of the bonding zones increases 80 with each stroke 82 of the reciprocating robotic armature with affixed, focussed heat sources, as shown in FIG. 7. Because plastic has a low coefficient of heat conductivity, during each brief cooling phase 84 of the oscillating focussed heat application the heat is radiated away from the surface to the air rather than to the interior material. Thus the internal temperature 86 remains virtually unaffected while the suraoe temperature increases to the melt fusion point as shown at 88 in

FIG, 7. It is this alternate "endothermic/exothermic" process which is essential to the present invention. Alternatively, the

/can be heat souroes can remain stationery and the materiaIs reciprocated.

A multitude of joint configures is possible, as shown in

FIGS. 8a through 8e. Three-dimensional preformed plastic objects can be bonded together as shown in FIGS. 9a, 9b and 9c. For example, any size corrugated board may be constructed by bonding flat sheets on either side of a stamp pressed board, as shown in

FIG. 9c. The focal lengths of the lamps can be adjusted to coincide with the surface of the material to be heated as shown in FIG, 10. This means that the heat is at maximum intensity at the bonding zone. Indeed, if such intense heat were applied continuously, the plastic would melt or burn.

In an alternative embodiment this invention can be used to melt-fuse two halves of a preformed bulb as shewn in FIG. 11. The two lamps 22 and 24 are mounted back to back on the reciprocating robotic armature 26 while the halves of the preformed elastomeric bulb 60 and 62 are placed on the upper and lower press parts 12 and 14. The focussed heaters 22 and 24 are then reciprocated and when the melt fusion temperature is reached, the robotic arm is removed and the two press parts 12 and 14 brought together. The result is a completely fused bulb 64.

In an alternative embodiment the heat souroes are point-focus, parabolic elliptical, infrared reflectors 70, 72 mounted back to back on a robotic armature 26 which rotates in a circle or ellipse thus tracing out a circular or elliptical path en the materials to be bonded, as shown in FIG. 12. This embodiment allows the intermittency of heat application to be accomplished not by a reciprocating back and forth motion, but by a continuous cycle which touches any given point on its path only once in every revolution.

In an additional preferred embodiment the robotic arm 26 with affixed, focussed heat sources 70, 74 can be computer controlled and preprogrammed to trace out any path, thus enabling a variety of geometrically shaped bonds to be accomplished, as shown in FIGS. 13a and 13b. This embodiment gives a flexibility of application to this invention which far exceeds not only the reciprocating armature, but also surpasses any bording machine in the prior art.

In each embodiment the geometric paths, displacements, velocities, periodicities, temperatures, focal lengths and duration of heating of the heat sources are controlled by electronic circuitry which can be preprogrammed by the operation by means of the control panel, not shown.

FIGS. 14-15 shows a system more or less as in the previous species, with certain enhancements. It includes press platens 12 and 14, mounting parts 2 and 4 to be joined, IR heaters 22 and 24 mounted on a reciprocating arm 26 of a robot machine 36. IR sensing units 122 and 124 are mounted on the IR heaters and have respective temperature control and power control systems, TC and PC (both per se conventional) to control platen positions, reciprocation rate and IR heating temperatures and times. Through this loop control, based on monitoring the temperature of matrix resin on each of the adherends parts 2 and 4, process parameters are tuned to variable conditions of the materials to be joined. The sensint units 122 and 124 continuously read the rising temperatures of the respective interface bond line zones and send signals back to the lamp (22, 24) power controls to increase or decrease lamp power, thereby varying lamp intensity and projected radiation until both interface temperature footprints match. When the targeted fusion temperature of each material's surface is reached, the sensors signal the lamps to shut off, the robot arm 26 to withdraw, and the press (32, 34) to cycle.

The convergence of the lines in the temperature-time trace of FIG. 16 indicates that the upper and lower part interface temperatures have reached reconsolidation temperature, which signals the removal of the robotic arm. Thus, the temperature of the matrix resin is taken on a continuous, noncontact basis and is used to precisely control the overall welding cycle.

The heating wavelength of the lamps is approximately 1.1 microns; the optical sensors have a spectral response of 8.0 to 14.0 microns, which blinds them to visible light. Because the ambient air may be very hot, the sensors may be provided witn an air cooling jacket. Alternatively, each sensor can be located outside the heat area and mounted so that its optical lens faces properly positioned right angle mirrors.

High-temperature thermoplastics and thermoplastic composites tend to cool rapidly. It is essential, therefore, that the press holding the parts have a rapid downstroke of at least one foot per second. To prevent deleterious effects on the joint created by high-pressure impact of the adherends, the press utilizes a double-downstroke function, as shown in FIGS. 17A, 17B, 17C. The press first closes at high speed to a deceleration zone, which is about one half inch from material surface. Then final pressure is applied on a decelerated basis to a die stop.

FIG. 15 shows that parts 2A and 4A comprising layered quasi-isotropic composite panels (the cross-sections of which are exaggerated) may have face layers 22 and 42 which are locally reconsolidated. FIG. 15 also indicates the reciprocating movement (arrow A, dark line and phantom end positions. FIGS. 14-15 also show the parabolic/elliptical focus of the heaters reflective portion at points on layers 22, 42.

Adaptable to demanding applications in the aerospace/aircraft, automotive, medical, and other market sectors, the process accomodates simple and complex joint configurations, including spot welds, three-dimensional welds, and continuous welds.

This invention has been practices to achieve outstanding weld strengths with leading advanced engineering thermoplastic materials of significant military and commercial utility uses. These materials include glass-, carbon-, and aramid-fiber reinforced polyetheretherketone (PEEK), polyphenylene sulfide (PES), polyamideimide (PAI), polyetherimide (PEI), polyarylate, polysulfones, thermoplastic polymides, and liquid crystal polymer (LCP's).

Thermoplastic composites (TPC's) for high-performance applications generally consist of a high-performance theremoplastic matrix resin reinforced with fibers of carbons, graphite, fiberglass, or aramid. Some matrix resins used in TPC's are capable of continuous service at 350' F to 700'F. They include PEEK, PPS, PEI, PES, PAI, and others. The reinforcements are usually continuous and parallel or laminated in different directions to provide a stress-free, lightweight sheet of unusual strength.

The potential performance and economic benefits of thermoplastics vis-a-vis thermosets in advanced composite applications has been well documented and include lower-cost manufacturing, indefinite prepreg stability, thermoformability of flat sheet stock reprocessing to correct flaws and effect repairs, faster processing cycles, high toughness, and easier quality control. Most of these advantages are due to the fact that unlike thermosets, which are infusible and cannot be softened by heating once cured into shape, thermoplastics became more viscous and flow when subjected to heat. This characteristic makes thermoplastics weldable and facilitates the elimination of adhesives and mechanical fasteners, both of which are less than desirable for high-performance structural applications. See, Benatar, et al. , "Methods For fusion Bonding Thermoplastics Composites", SAMPE Quarterly Vol. 18, No. 1 (Oct. 1986).

There are many problems applying these traditional thermoplastic welding methods to high-performance TPC's such as APC-2 carbon fiber reinforced PEEK or Ryton PPS composites, which are targeted for applications that may require joints that are as strong as the composite itself. TPC laminates comprise up to seventy wt.% of reinforcement. While the introduction of reinforcing fibers into a matrix dramatically upgrades the physical properties of the composite, it often makes welding more difficult since there is less resin available to melt and reconsolidate into a fused joint. Reducing the amount of reinforcement may increase weldability, but only at the expense of composite strength. Also, the advanced thermoplastics used as matrix resins in TPC's must be processed at higher temperatures and have narrower "processing windows" than commodity and general purpose engineering resins. This demands extremely precise control of welding variables — particularly the amount and time of heat to achieve optimum joints. Welding methods such as induction, resistance, ultrasonics, and others that involve preclamping of parts before the introduction of heat do not readily facilitate the direct sensing and measurement of joint melt temperatures without the embedment of thermocouples or sensors in the joint area, a possible negative in many applications. The present invention avoids these difficulties.

The basic process steps used to join high-performance TPC's using focused infrared melt fusion are as follows:

Surface preparation: good wetting of a clean, release agent-free, bond line is essential. Cleaning solutions or plasma treatment is preferable to sanding or abrading the surface, which may remove resin in the two facing adherend plies and loosen the fibers. The high temperatures of the focused IR reciprocating beams (up to 1,200'F) tend to burn off surface contaminants that may be trapped in asperites of the interface layers.

Positioning of parts into press: two parts are placed into upper and lower holding fixtures in a suitable press. The facing parts are held in open position during the heating stage.

Application of matrix tape (optional): A fiber-free tape of film or resin may be applied to one part surface (the tape is chemically and thermally compatible with the matrix resin of the composite; a resin-rich, surface on the composite surfaces may eliminate the need for this step). Another variable that may enhance weld strength is to have the graphite fibers in unidirectional orientation in the first interface layers of each adherend.

Setting of welding parameters: Surface melt temperature goals for each adherend are set on two temperature controllers; the press cycle time, robotic stroke distance, and speed are set.

When the start button is pressed, the robot will move the focused infrared heating lamps into the open press area and commence horizontal reciprocation over the bond lines. during the reciprocation stage, the lamps illuminate immediately on the first stroke and remain on while the optical sensors read the rising surface temperature of each interface. The sensors signal the lamps power controls to increase or throttle down each lamp's intensity until both interface temperature footprints match. At this point, the sensors signal the robot to remove the lamp fixtures from the press and start the downstroke of the press for completing the operation. the press remains closed until the part cools sufficiently for removal and handling.

The focal vector of the upper heat source is pointed upward; the focal vector of the lower heat source is pointed downward. To limit percolation in the laminates (which can cause interlaminar slippage, separation of fibers, and matrix distuption), the parts to be joined are held as close to the focal vector of the lamp fixtures as possible.

During the reciprocation stage the surface temperature of both adherend interfaces increases with each stroke of the robotic arm. Because the plastic has a relatively low coefficient of heat conductivity, during each brief cooling phase heat radiates away from the surface to the air rather than to interior layers of the composite. Thus, the internal temperature remains virtually unaffected while the surface temperature increases to the melt fusion point.

If the focused infrared heat lamps were stationary over the adherends at these high temperatures the matrix resin would burn immediately. However, the bean is moving and not in any one place long enough to cause burning. Daring the reciprocation of the lamps the material of each adherend undergoes an accelerated exothermic reaction, that is, a chemical change in which there is a liberation of heat, and an endothermic reaction, that is, a chamical change in which there is an absorption of heat. It is the periodicy of the intensely focused moving beams that creates a faster growth of temperature at just the interfaces of each adherend. This alternate "endothermic/exothermic" process is a unique aspect of focused infrared melt fusion.

Bond lines up to sixteen inches long and four inches wide have been produced and it is possible to produce much larger bond line areas. Bond line length is controlled by the length of the focused infrared lamps, which are commercially available up to one hundred inches long. The reciprocation zone controls bond line width. Very wide bond lines are possible by using multiple lamp fixtures that are placed side-by-side on the robotic arms. For example, four sets of back-to-back forty eight inch focused infrared lamps spaced four inches apart can be used to heat a bond line area twenty inches wide by forty eight inches long.

Claims

1 1. A method of hording monolithic plastic and/or

2 plastic-matrix-composite materials reinforced with strength and/or

3 stiffening enhancing agents comprising the steps of:

4. (a) providing selected bonding zones on the surfaces of

5 the materials to be jointed essentially free of the reinforcing

6 agent;

7 (b) briefly and repeatedly applying adjacent points or

8 series of points of intense heat to surfaces of the materials in

9 said designated bonding zones thereof to thereby effectively fill

10 selected and limited areas of bonding zones with heat;

11 (c) continuously displacing the points or series of

12 points of intense heat through the bonding areas in an

13 intermittent, repeated notion;

14 (d) terminating the heat application and immediately

15 bringing the heated areas into bonding contact before substantial

16 cooling thereof,

17 the said steps being controlled to produαe at said heated

18 surfaces temperatures in excess of respective melt fusion

19 temperatures while areas away from and internal to said designated

20 bonding zones remain substantially below such temperatures and

21 effecting the bonding before the surface temperatures at said zones

22 decline to below melt fusion temperatures.

1 2. A method in accordance with claim 1 wherein said bonding

2 zones are enriched with additional plastic material essentially

3 free of reinforcement.

3. A method in accordance with claim 1 wherein said bonding zones are overlaid by resin tape.

4. A method in accordance with claim 3 wherein the resin tape is preheated prior to placement at a bonding zone.

5. A method in accordance with claim 1 wherein said adjacent lines or points of intense heat are produced by focussed radiant heat.

6. A method in accordance with claim 5 wherein said focused radiant heat is produced by parabolic elliptical reflection which concentrates heat at one or more focal points wherein said focal points may be adjusted to coincide with the surface of the material to be heated.

7. A method in accordance with claim 1 wherein said adjacent lines or points of intense focussed radiant heat means are intermittently and repeatedly applied to said bonding zones.

8. A method in accordance with claim 7 wherein said adjacent intermittent lines or points of intense focused heat comprise reciprocably oscillating focussed radiant heat sources which are oscillated back and forth across the said respective designated bonding zones at preselected velocities with a preselected periodicity.

9. A method in accordance with claim 8 wherein the lateral displacement (i.e., stroke lengths) of the reciprocably operable radiant heat sources can be individually controlled.

10. A method in accordance with claim 1 wherein the temperature of said radiant heat sources at the respective focal points can be independently controlled.

11. A method in accordance with claim 1 wherein said moving lines or points focussed heat can be reciprocated in directions essentially oblique to each other.

12. A method in accordance with claim 1 in which said moving focussed points or lines of heat can be rotated in any configuration.

13. A method in accordance with claim 1 in which the said path of moving focussed points or lines of heat can be controlled to trace out any preselected geometric path.

14. A method in accordance with claim 13 in which the path of said moving focussed points or lines of heat can be controlled to trace out any geometric planar surface, whether curved or flat.

15. A method in accordance with claim 1 wherein the said bonding zones define any chosen two-dimensional geometric configuration in three-dimensional space.

16. Apparatus for bonding plastic resin and plastic or resin-like materials reinforced with strength and/or stiffening enhancing agents comprising:

(a) a press comprising a first press part and a second press part with pressure applying surfaces movable between a first open position with space between the two press surfaces and a second closed position wherein the two press surfaces bearing the two are resin or resin-like thermoplastic objects to be bonded are brought together;

(b) means for attaching the first resin or resin-like object to be bonded to the first press part and attaching the second resin or resin-like object to be bonded to the second press part;

(c) means for establishing bending zones on the surfaces to be bonded;

(d) means for applying enriching matrix to said bonding zones;

(e) means for simultaneously repeatedly applying brief and adjacent lines of intense heat to the facing surfaces of the materials to be bonded;

(f) means for controlling the frequency of intermittency, the duration, and the area of the applied intense intermittent heat in said bonding zones;

(g) means for pivotably removing said robotic armature and said heat source means from the space between said first and second press parts;

(h) means for immediately bringing the heated surfaces of the materials to be bonded together before substantial cooling thereof.

17. Apparatus in accordance with claim 16 wherein said heat means are mounted on an armature pivotably movable between the first and second press parts.

18. Apparatus in accordance with claim 16 wherein said heat means are mounted on said armature oriented so that their respective focal vectors point in opposite directions.

19. Apparatus in accordance with claim 16 wherein said intermittent intense heat means comprise infrared parabolic elliptical reflector lamps mounted on moving shuttles which oscillate the lamps back and forth in a direction essentially lateral to the surface to be bonded.

20. Apparatus in accordance with claim 16 wherein the focal length, displacement, oscillation period and temperature, velocity and length of total heating cycle of each heat lamp is independently controlled.

21. Apparatus in accordance with claim 16 wherein said heat means which produces said points or series of point (lines) of intense heat can be reciprocated in directions essentially lateral to each other.

22. Apparatus in accordance with claim 16 in which said focussed heat means can be repeatedly moved in preselected paths to produce any configuration of points or series of points of intense heat on the surfaces of the designated bonding areas having any two-dimensional geometric shape.

23. Apparatus in accordance with claim 21 and wherein the focal length, path, frequency of intermittency, velocity, period, temperature and total length of heating cycle of each heat source is independently controlled.

24. Apparatus in accordance with claim 16 wherein said first and second material to be bonded are attached to said respective first and second press parts by vacuum means.

25. Apparatus in accordance with claim 16 wherein said first and second material to be bonded are attached to said respective first and second press parts by mechanical means.

26. Apparatus in accordance with claim 1 wherein electrical switching circuitry is provided to effectively activate and control:

(1) the electric motors which control motion of the shuttles and/or moving armatures carrying the heat sources;

(2) the timing and initial opening and closing of the electric motors which effectivate the press parts;

(3) the voltage and current through the heat lamp;

(4) the electric motors which control position and focal point of the heat lamp relative to the bonding zones;

(5) the electric motor which effectivate timing, position and motion of the robotic armature.

27. Apparatus in accordance with claim 16 wherein

computer means is provided to effectively preprogram and control the path, periodicity, velocity, focal length, temperature and length of time of the heating cycle.

28. Apparatus in accordance with claims 16. wherein

computer means is provided to effectively preprogram the motion of the robotic armature and the opening and closing of the press partss

₁

29. In the method of bending parts of indeterminate thickness of

₂ monolithic plastic and/or plastic-→matrix-composite materials reinforced

₃ with strength and/or stiffening enhancing agents, the improvements compri¬4 sing the steps of:

5 (a) effecting a temperature rise at each of selected surface 6 areas of the parts to be joined by cyclic application of intense, ₇ focussed, infrared radiant heat to surfaces of the materials in said 8 selected areas to establish a stepped rise of temperature essentially 9 limited to said selected surface areas, with each of several steps

10 comprising a rise portion and a decline portion until melt fusion

11 temperature is achieved; and

12 (b) then terminating the heat application and immediately

13 bringing the parts together to place said surface areas thereof into 14 bonding contact before substantial cooling thereof.

₁

30. A method in accordance with claim 29 wherein said focussed

2 radiant heat is produced by parabolic elliptical reflection which

3 concentrates heat at one or more lines of cross-section focussed at the

₄ part surfaces.

1 31. Apparatus for practice of the method of claim 30 comprising

2 parabolic-elliptical-heat-reflecting-infrarred-heat-source means con¬

3 structed and arranged to produce movable lines of intense focussed heat

₄ at said bonding surface areas.

32. A method in accordance with claim 1 and further comprising monitoring the bonding zone continuously to establish substantial identity of temperatures at the surfaces to be joined, as well as rise thereof above a threshhold.

33. Method in accordance with claim 32 and further comprising modification of at least one of the heating and processing steps in response to the temperature monitoring.

34. Apparatus for practice of the method of claim 33 comprising rapidly translatable focussed IR heaters with directly associated IR monitoring means and constructed and arranged to be inserted and removed between confronting surfaces of opposed parts to be joined and while so inserted to be rapidly reciprocated, control means for heater temperature, insertion/removal and pressing conditions and thermal loop feedback means connected between said monitoring means and control means to enable an effective press joinder of the parts at their heated surfaces under pressure, time and temperature conditions suited to the particular parts.