System and Apparatus for Fiber Reinforced Thermoplastics Joiner

Abstract

A system for, and method making and repairing a fiber-reinforced component including bonding a first thermoplastic matrix possessing reinforcing fibers distributed therein to a second composite member possessing a thermoplastic matrix with reinforcing fibers distributed therein; and metals and more particularly a method and apparatuses for joining fiber reinforced thermoplastics utilizing a combination of heat, force and rotational force.

Claims

1. A method for joining fiber reinforced thermoplastic to fiber reinforced thermoplastics and metals comprising: employing at least one stationary member; employing at least one rotational element; checking the thickness of the at least one stationary member; employing a certain rotational velocity of the at least one rotational element; approaching the at least one rotational element to the at least one stationary member in contact to generate heat to a joining temperature to melt thermoplastic resin in a fiber reinforced thermoplastic; employing a displacement of the at least one rotational element on a joining area; and employing a designated downward force of the at least one rotational element and the at least one stationary member to offer an intimate contact between fiber reinforced thermoplastics and between fiber reinforced thermoplastic and metal; wherein the area and shape of the at least one stationary member should at least fully cover the joining area; wherein the length of the at least one rotational element should not exceed five times the diameter of the rotational element and the diameter of the rotational element is determined based on the shape and size of the joining area; wherein the thickness of the at least one stationary element is between 2 mm and 4 mm for aluminum alloy; wherein the rotational velocity is determined based on the material and diameter of the rotational element, the material and thickness of the stationary member, and the material for joining; wherein the joining temperature equals to the melting point of thermoplastic plus 50 degree Celsius; wherein a maximum velocity of displacement is calculated as the diameter of the rotating element per second and the minimum time for displacing the rotational element from its original location to the adjacent location without overlap or gap should be one second; and wherein the designated downward force is calculated based on the diameter of the rotational element, which equals to the area of rotating element (mm.sup.2) multiply 0.2 to 2 MPa.

2. The method for joining fiber reinforced thermoplastic to fiber reinforced thermoplastics and metals of claim 1 further comprising the steps of: employing a vacuum system to improve the performance of joining and avoid oxidation; and choosing a vacuum system according to the materials for joining.

3. The vacuum system in claim 2 for joining fiber reinforced thermoplastics and metals further comprising the step of: choosing polyimide as the material of vacuum bag when joining titanium and fiber reinforced thermoplastics.

4. The method for joining fiber reinforced thermoplastic to fiber reinforced thermoplastics and metals of claim 1 further comprising the step of: selecting the rotational element from a group consisting of a solid component and a component with thermometer embedded.

5. An apparatus for joining fiber reinforced thermoplastic to fiber reinforced thermoplastic and metal comprising: at least one joining tool, wherein the at least one joining tool comprises an at least one rotational element; at least one stationary member in contact with the at least one rotational element; wherein the at least one stationary member is inserted between the at least one rotational element and the fiber reinforced thermoplastic to cover an entire joining area and the at least one stationary member makes contact with a bottom of the at least one rotational element and a top of an overlap region of the joining fiber reinforced thermoplastic; and wherein the at least one joining tool contacts the at least one rotational element to rotate, displace, and subject downward force to contact the at least one stationary member to generate heat to melt a thermoplastic resin in the fiber reinforced thermoplastic.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Advantages of the present system will be apparent from the following detailed description of exemplary embodiments thereof, which description should be considered in conjunction with the accompanying drawings, in which having thus described the system in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0020] FIG. 1 illustrates a perspective view of a mechanical schematic of the operation of the joining method.

[0021] FIG. 2 illustrates a side view of a mechanical schematic of the operation of the joining method.

[0022] FIG. 3 illustrates a perspective view of a mechanical schematic of an alternative operation of the method shown in FIG. 1, in which case the joining process is achieved in a vacuum environment.

[0023] FIG. 4A illustrates an exploded view of the joining tool which is the direct implement for joining fiber reinforced thermoplastic to fiber reinforced thermoplastic and, for joining fiber reinforced thermoplastic to metals.

[0024] FIG. 4B illustrates an exploded view of an additional joining tool which is the direct implement for joining fiber reinforced thermoplastic to fiber reinforced thermoplastic and, for joining fiber reinforced thermoplastic to metals, illustrating a three actuator alignment including a rotational actuator, a vertical displacement actuator, and a horizontal displacement actuator 164.

[0025] FIG. 5 illustrates a perspective view of the alternative rotating elements. which should be installed at the position of the dash box B in FIG. 4A.

[0026] FIG. 6 illustrates a side view of a mechanical schematic of the first embodiment of the apparatus which is used for repairing defects and damage on fiber reinforced thermoplastic aero structures.

[0027] FIG. 7 illustrates a side view of a mechanical schematic of the second embodiment of the apparatus which is used for joining a metal feature to fiber reinforced thermoplastic aero structures.

[0028] FIG. 8 illustrates a side view of a mechanical schematic of the third embodiment of the apparatus which is used for joining fiber reinforced thermoplastic to reinforced metal automotive structures.

[0029] FIG. 9 illustrates a side view of a mechanical schematic of the fourth embodiment of the apparatus which is used for joining fiber reinforced thermoplastic to repair damaged metal civil structures.

[0030] FIG. 10 illustrates a flow chart of the method for joining fiber reinforced thermoplastics to fiber reinforced thermoplastics or metal through use of the present apparatus.

DETAILED DESCRIPTION OF THE SEVERAL EMBODIMENTS

[0031] The detailed description set forth below in connection with the appended drawings is intended as a description of presently preferred embodiments of the system and does not represent the only forms in which the present system may be constructed and/or utilized. The description sets forth the functions and the sequence of steps for constructing and operating the system in connection with the illustrated embodiments.

[0032] FIG. 1 illustrates a perspective view of a mechanical schematic of the operation of the joining method. Prior to joining, the first article prepared for joining 28 and the second article prepared for joining 20 are overlapped to form the joining area 21 which is covered by the stationary element 16. The stationary element 16 is temporarily fixed to ensure the joining area 21 is consistently covered by the stationary element 16 which furthermore will be removed from the joining area 21 after the joining process. The stationary element 16 comprises low cost materials with large thermal conductivity, e.g. aluminum alloy, since the stationary element 16 is working as consumable in this process.

[0033] The joining process comprises the rotating element 14 rotating under a designated quantity of rotation velocity which approaches the stationary element 16. Heat is created as a result of the contact between the rotating element 14 and stationary element 16 through the friction between the rotating element 14 and the stationary element 16. The rotating element 14 is suggested to be constructed in a cylinder shape with high hardness materials to reduce the friction wear. The aforementioned heat will melt the thermoplastic resin 38 in fiber reinforced thermoplastic articles adjacent to the rotating element 14. In one embodiment, fiber reinforced thermoplastic and fiber reinforced thermoplastics are joined due to the inter-diffusion between the polymer chains, and the fiber reinforced thermoplastic and metal are joined by forming metal-thermoplastic bonding.

[0034] A designated downward force 12 is subjected through the rotating element 14 to this molten region 40, which will induce an intimate contact between the first article of thermoplastic material 28 and the second article of thermoplastic material 20 within this molten region 40. Such intimate contact will reduce the amount of entrapped air between the first and the second article to offer a high quality joining.

[0035] Since the initiation of the contact between rotating element and stationary element, after a designated period of waiting time, a designated temperature of the joining area underneath rotating element is reached, afterwards the rotating element 14 will leave this molten region 40 to move across the joining area 21 under a designated quantity of movement velocity, meanwhile the rotating velocity is maintained. The molten thermoplastic resin 40 cools down when rotating element 14 leaves, the molten thermoplastic resin 40 will solidify again resulting in an accomplished joining.

[0036] It should additionally be noted that utilization of a support mechanism underneath the joined area may be required in order to withstand the vertical displacement of the articles.

[0037] The following paragraphs detail the operating parameters in applying this invention:

[0038] The length of the rotating element should not exceed a certain value to avoid buckling, which is suggested to be shorter than five times of the diameter of rotating element. The determination of suitable diameter of rotating element is according to the shape and size of joining area, which should be designed to minimize the movement distance of rotating element to minimize the tool wear. For example, FIG. 1 shows a rectangular joining area with a certain width and length, therefore the diameter of rotating element can be designated to equal to the width of joining area.

[0039] The area and shape of stationary element should at least fully cover the joining area as the example shown in FIG. 1. The thickness of stationary element is suggested to be between 2 mm to 4 mm for aluminum alloy. Too thick stationary element can result an excessed time of reaching the designated temperature of the joining area, which reduces the efficiency of joining. Too thin stationary element can be quickly worn, which may result the rotating element penetrate through the stationary element and damage the material of the joining area. Therefore, it is suggested to measure the thickness of stationary element before joining. If the thickness of the used stationary element is lower than 50% of the original stationary element, then a new stationary element is required.

[0040] The velocity of rotating element influences the time of reaching the designated temperature and the maximum reachable temperature of the joining area. The designated temperature suitable for joining, is dependent to the melting point of matrix material of thermoplastic composite. The joining temperature should not be lower than the melting point. In addition, by elevating the joining temperature, a faster joining process can be achieved due to a faster polymer diffusion. However, a too high temperature will degrade the thermoplastic matrix resulting a low joining strength. The joining temperature is suggested to be calculated as the melting point of thermoplastic plus 50 degree of Celsius. For example, 393 degree of Celsius is suitable for joining fiber reinforced poly ether ether ketone (PEEK) with a melting point of 343 degree of Celsius. The following chart shows an example of the maximum reachable temperature and time of reaching the maximum temperature of the joining area underneath the rotating element as a function of different velocity of rotating element, which is measured by using a 30 mm diameter hardened steel rotating element and aluminum alloy stationary element with 4 mm thickness. According to chart, 400 or 500 RPM can be used as suitable rotating velocity. The aforementioned designated waiting time can be equal to the time of reaching maximum temperature which can be read from the embedded thermometer in rotating element.

TABLE-US-00001 TABLE 1 Rotating velocity (RPM) 200 300 400 500 600 700 Max reachable 304 335 428 422 478 467 temperature ( C.) Time of reaching 255 204 184 156 145 134 max temperature (s)

[0041] The velocity of movement of rotating element across the joining area determines the total time required for joining. After the temperature of the joining area underneath the rotating element reaches the maximum temperature, it is suggested to maintain the position of rotating element for at least 1 second to realize complete joining, then the rotating element can start to move to the adjacent location of joining area, i.e. the minimum time for translating the rotating element from its original location to the adjacent location without overlap or gap should be 1 second. Therefore, the maximum velocity of movement is calculated as diameter of rotating element per second.

[0042] The subjected downward force is suggested to be capable to generate a pressure of 0.2 to 2 MPa to the joining area underneath the rotating element, i.e. Subjected force (N)=Area of rotating element (mm.sup.2) multiply 0.2 to 2 MPa.

[0043] The performance of joining can be evaluated by measuring the shear strength of the joint. For example, the shear strength of a carbon fiber reinforced poly ether ether ketone-aluminum alloy joint can reach a value of 12 MPa, which is far stronger than the shear strength of epoxy adhesive bonded joint as 7 MPa. The joining parameter of realizing such performance is introduced as: [0044] Rotating element: Hardened steel, 10 mm diameter, 60 mm length [0045] Stationary element: Aluminum alloy, 4 mm thickness [0046] Joining area: 30 mm by 30 mm [0047] Rotating velocity: 400 RPM [0048] Velocity of moving: 1 mm/s [0049] Waiting time: 200 s

[0050] For pragmatic application of the overall process, the steps illustrated in FIG. 10 should be utilized in order to ensure a high quality joining.

[0051] FIG. 2 illustrates a side view of a mechanical schematic of the joining process illustrating the joining of two continuously fiber reinforced thermoplastic articles 30. FIG. 2 further illustrates that the molten region 40 may not be identical to the overlapped region 41 between two articles. Furthermore, it is not necessary for the entire overlapped region 41 to be melted.

[0052] FIG. 3 illustrates a perspective view of a mechanical schematic of an alternative embodiment of the system and accompanying method shown in FIG. 1. In said embodiment, the joining process is best achieved by utilizing a vacuum environment 50. For some material combinations, e.g. joining titanium to fiber reinforced poly ether ether ketone, the existence of oxygen will deteriorate the strength of joining by introducing weak titanium oxides. In this case, the joining process is preferred to be operated in the presence of vacuum. A vacuum bag 54, attached with a pipe connected to a vacuum pump 52, is used to seal the articles to ensure the joining process is operated in vacuum environment. The vacuum bag 54 can be made by a plurality of materials.

[0053] FIG. 4A illustrates an exploded view of the joining tool 61 for joining fiber reinforced thermoplastic to fiber reinforced thermoplastic and metal. The first actuator 72, accompanying with the support structure for the joining tool 82, enables an elaborate control of the displacement velocity of the rotating element 14 to move across the joining area. The second actuator 74, accompanying with the second structural element 84, enables an elaborate control of the downward force of the rotating element 14 subjected to the joining area. The third actuator 76, accompanying with the third structural element 86, enables an elaborate control of the rotation velocity of the rotating element 14.

[0054] FIG. 4B illustrates an exploded view of an additional embodiment of the joining tool 161 which is the direct implement for joining fiber reinforced thermoplastic to fiber reinforced thermoplastic and, for joining fiber reinforced thermoplastic to metals, illustrating a three actuator alignment including a rotational actuator 162 for driving the rotation of any embodiment of rotating element 170, a vertical actuator 163 for subjecting downward force with vertical element 171 upon the rotating element, and a horizontal actuator 164 for subjecting relative displacement of the rotating element.

[0055] FIG. 5 illustrates a perspective view of two alternative embodiments of rotating elements 14 which may be utilized in conjunction with either embodiment of the joining tools 61, 161 illustrated herein, for driving the rotation of rotating element either the joining tool 61, 161, in order to introduce the respective rotating element 14, 170 to the stationary element. Additionally, the base embodiment rotating elements 14, 170 comprise a solid component.

[0056] In an alternative embodiment the of rotating elements 145, 175 respectively, a thermometer may be embedded directly into the rotating element and thus, very accurate temperature readings at the joining area may be yielded in conjunction with a constant monitoring process or system, in order to facilitate the optimization of joining process.

[0057] FIG. 6 illustrates a side view of a mechanical schematic of the first embodiment of the apparatus which is used for repairing defects and damage on fiber reinforced thermoplastic aero structures 100. This illustrates the first embodiment as the apparatus is used for repairing fiber reinforced thermoplastic aero structure 108 with cracks and damages 104. In this embodiment, the damaged aero structure 108 plays as the role of second article, while the first article is the fiber reinforced thermoplastic 102 used for repairing. Thermoplastic resin in the entire first article 102 and part of the damaged aero structure 108 adjacent to the crack 104 are melted, which are further fused together to achieve the target of repairing. In this case supporter may not be necessary if the rest of aero structure 108 can withstand downward force with negligible displacement. The stationary element 16 should be temporarily fixated, and release agent 106 is suggested to be inserted between the stationary element 16 and the first article 102 to facilitate the removal of the stationary element 16.

[0058] FIG. 7 illustrates a side view of a mechanical schematic of the second embodiment of the apparatus which is used for joining a metal stiffener feature to fiber reinforced thermoplastic aero structures 110. At least one Metal stiffener 114 are joined with fiber reinforced thermoplastic aero structures 112. In this embodiment, the stationary element 16 is optional, depending on the property of metal stiffeners 114 and joining parameters.

[0059] FIG. 8 illustrates a side view of a mechanical schematic of the third embodiment of the apparatus which is used for joining fiber reinforced thermoplastic to reinforced metal automotive structures 120, increasing the stiffness and strength of that structure. Fiber reinforced thermoplastic 122 is joined with the metal automotive structure 124 as the second article. The metal surface can be treated to facilitate the joining performance between metal and thermoplastic composite. The stationary element 16 should be temporarily fixated or restrained, and the release agent 106 is suggested to be inserted between the stationary element 16 and the fiber reinforced thermoplastic 124 to facilitate the removal of the stationary element 16. The rotation velocity of the rotating element 14 should be elaborated to melt the thermoplastic resin in the fiber reinforced thermoplastic 122. An optional supporter of metal structure 126 may be required to withstand the downward force which may deform the metal structure.

[0060] FIG. 9 illustrates a side view of a mechanical schematic of the fourth embodiment of the apparatus which is used for joining fiber reinforced thermoplastic to repair damaged metal civil structures 130. In this embodiment the damaged metal structure 134 is the second article, while the first article is the fiber reinforced thermoplastic 122 employed for repairing. Thermoplastic resin in molten region 40 is melted, and the molten thermoplastic resin 136 in the first article will flow into the crack 132 and the undamaged metal surface will also bond with the fiber reinforced thermoplastic 122. The damaged metal structure 134 is thus reinforced by the joined fiber reinforced thermoplastic 122. In this case supporter may not be necessary if the metal structure 134 can withstand downward force with negligible displacement. The stationary element 16 should be temporarily fixated, and release agent 106 is suggested to be inserted between the stationary element 16 and the fiber reinforced thermoplastic 122 to facilitate the removal of the stationary element 16.

[0061] FIG. 10 illustrates a flow chart of the method for joining fiber reinforced thermoplastics to fiber reinforced thermoplastics or metal through use of the present apparatus. At step 510 the thickness of current stationary element is checked to decide whether new stationary element is required. At step 520 the Material, length and diameter of rotation element, and material, size and shape of stationary element are chosen based on the material, dimension and size of the joining area. At step 530 the rotating velocity and waiting time before moving are chosen based on the material and diameter of rotating element, material and thickness of stationary element and material for joining. At step 540 the maximum velocity of movement and subjected downward force of rotating element are calculated based on the diameter of rotating element. At step 550 the employment of the vacuum system is decided according to the material type.