Pultrusion of Profiles Having Non-Uniform Cross Sections

Abstract

Composite profiles, such as rotor blades, airfoils, I-beams, and box beams having non-uniform cross sections, and a system, method and process for pultrusion of composite profiles. The pultrusion of a heavier or thicker cross section portion of the composite profile is performed in-line and upstream from pultrusion of a thinner or lighter portion of the pultruded profile using a separate die for the thicker portion of the cross section, or leading edge slug, in order to optimize the processing conditions, productivity, and consistency of the composite profiles.

Claims

1. A method for pultrusion of a composite profile having a non-uniform cross section comprising: providing a leading edge slug die for pultruding a leading edge slug of the composite profile; providing a primary pultrusion die downstream from the leading edge slug die for pultruding a profile body of the composite profile; threading a first set of fibers into the leading edge slug die; threading a second set of fibers into the primary pultrusion die; heating the leading edge slug die; heating the primary pultrusion die; adding a first resin to a leading edge slug wet out bath; pulling the first set of fibers and the first resin through the leading edge slug die to form the leading edge slug; adding a second resin to a main wet out bath; and integrating the leading edge slug with the profile body to form the composite profile by pulling the leading edge slug through the primary pultrusion die while pulling the second set of fibers and the second resin through the primary pultrusion die to form the profile body.

2. The method of claim 1 wherein pulling the first set of fibers and the first resin through the leading edge slug die to form the leading edge slug further comprises inserting a wire rope for forming a leading edge weight insert.

3. The method of claim 1 further comprising partially curing the leading edge slug with the leading edge slug die.

4. The method of claim 3 further comprising completing curing of the leading edge slug with the primary pultrusion die.

5. A composite profile having a non-uniform cross section manufactured by a process comprising the steps of: providing a leading edge slug die for pultruding a leading edge slug of the composite profile; providing a primary pultrusion die downstream from the leading edge slug die for pultruding a profile body of the composite profile; threading a first set of fibers into the leading edge slug die; threading a second set of fibers into the primary pultrusion die; heating the leading edge slug die; heating the primary pultrusion die; adding a first resin to a leading edge slug wet out bath; pulling the first set of fibers and the first resin through the leading edge slug die to form the leading edge slug; adding a second resin to a main wet out bath; and integrating the leading edge slug with the profile body to form the composite profile by pulling the leading edge slug through the primary pultrusion die while pulling the second set of fibers and the second resin through the primary pultrusion die to form the profile body.

6. The composite profile manufactured by the process of claim 5 wherein the first resin comprises a vinyl ester resin and the second resin comprises an epoxy resin.

7. The composite profile manufactured by the process of claim 5 wherein the first set of fibers comprises carbon fibers and the second set of fibers comprises glass fibers.

8. The composite profile manufactured by the process of claim 5 further comprising inserting a wire rope into the leading edge slug for forming a leading edge weight insert.

9. The composite profile manufactured by the process of claim 5 further comprising partially curing the leading edge slug with the leading edge slug die.

10. The composite profile manufactured by the process of claim 9 further comprising completing curing of the leading edge slug with the primary pultrusion die.

11. A pultrusion tooling system for pultruding a composite profile having a non-uniform cross section comprising: a leading edge slug die for pultruding a first portion of the composite profile having a first cross section thickness; a primary pultrusion die for pultruding a second portion of the composite profile having a second cross section thickness, wherein the second cross section thickness is less than the first cross section thickness; a leading edge wet out bath for adding a first resin to the first portion of the composite profile; a mandrel for shaping the second portion of the composite profile; an overwrap infeed tool for wrapping fibers around the mandrel; and a main wet out bath for adding a second resin to the second portion of the composite profile.

12. The pultrusion tooling system of claim 11 further comprising a wire rope spool for inserting a wire rope into the first portion of the composite profile.

13. The pultrusion tooling system of claim 11 wherein a length of the leading edge slug die is greater than a length of the primary pultrusion die.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 illustrates a cross-sectional view of an example composite profile having a leading edge slug and a profile body made by the pultrusion process and method of the present invention.

[0035] FIG. 2 illustrates a top view of a pultrusion tooling and set-up for pultrusion of a composite profile wherein a separate leading edge slug die for pultruding the leading edge slug is upstream from the primary pultrusion die for pultruding the profile body.

[0036] FIG. 3 illustrates an example flow diagram for the pultrusion process of the present invention.

[0037] FIG. 4 illustrates a cross-sectional view of an example I-beam having a thick cap section and a thin web section made by the pultrusion process and method of the present invention.

[0038] FIG. 5 illustrates a cross-sectional view of an example box-beam having a thick cap section and a thin web section made by the pultrusion process and method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0039] The following is a detailed description of embodiments to illustrate the principles of the invention. The embodiments are provided to illustrate aspects of the invention, but the invention is not limited to any embodiment. The scope of the invention encompasses numerous alternatives, modifications, and equivalents. The scope of the invention is limited only by the claims.

[0040] While numerous specific details are set forth in the following description to provide a thorough understanding of the invention, the invention may be practiced according to the claims without some or all of these specific details.

[0041] Various embodiments will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like parts. References made to particular examples and implementations are for illustrative purposes and are not intended to limit the scope of the claims.

[0042] Composite Profiles 100

[0043] FIG. 1 illustrates an embodiment of a composite profile 100 comprising a leading edge slug 120 with a leading edge weight insert 122, and a profile body 105, made by the pultrusion process and method of the present invention. The leading edge slug 120 is made using a pultruded mix of fibers and resin. The profile body 105 is made using a pultruded mix of fibers and resin, and shaped by mandrels 140 as shown in FIG. 2.

[0044] Pultrusion Tooling 115

[0045] FIG. 2 illustrates the pultrusion tooling 115 and set-up for pultrusion of a composite profile, and in particular for pultrusion of airfoil profiles, such as composite profile 100, having non-uniform cross sections. As shown in FIG. 2, a separate leading edge slug die 110 for pultruding the leading edge slug 120 is used upstream of a primary pultrusion die 130 for pultruding the profile body 105 using the pultrusion tooling 115.

[0046] Pultrusion machines suitable for use in conjunction with the pultrusion tooling 115 are well known in the art and therefore are not described in detail here. However, a pultrusion machine that has the pulling capacity and capability to handle the desired size for the composite profile being pultruded should be used. Examples pultrusion machines are built by Pultrex, Martin Pultrusion Group, and Strongwell. Pultrusion tooling 115 shown in FIG. 2 is positioned at the upstream end of the pultrusion machine. The pultrusion machine provides the capability of pulling the materials through the process and cutting composite profile 100 to the desired length.

[0047] Pultrusion tooling 115 for making composite profile 100 in conjunction with a pultrusion machine comprises a leading edge slug die 110, a primary pultrusion die 130, mandrels 140, a main wet out bath 150, an overwrap infeed tool 168, a wire rope spool 165, a leading edge wet out bath 170, a mandrel infeed fold tool 180, and a mandrel anchor 190.

[0048] Mandrels 140 as required to shape the profile body 105 during pultrusion are inserted into the pultrusion tooling 115 with mandrel infeed fold tool 180 and secured by mandrel anchor 190. The overwrap infeed tool 168 wraps the fibers around the mandrels 140 to be fed into the main wet out bath 150 and primary pultrusion die 130 during pultrusion.

[0049] Fiber plies come off rolls and go into overwrap infeed tool 168 that continuously wraps the fibers around the mandrels 140 without wrinkles. The wrapped fibers then travel through the main wet out bath 150 and into the primary pultrusion die 130 along with the leading edge slug 120 that is pultruded upstream from primary die 130.

[0050] The fibers are threaded through both the leading edge slug die 110 and primary pultrusion die 130 at string-up before beginning the pultrusion process, before resin is added, and before the leading edge slug die 110 and primary pultrusion die 130 are heated. Resin is added by the main wet out bath 150 and leading edge wet out bath 170 during the pultrusion process, and excess resin is removed with the squeeze out-plates 155.

[0051] In one embodiment, wire rope is fed into the pultrusion tooling 115 via the wire rope spool 165 for forming the leading edge weight insert 122 of the leading edge slug 120. In this embodiment, the wire rope increases the weight of the leading edge slug 120, but use of wire rope is not required.

[0052] The leading edge slug die 110 is heated to partially cure the fibers and resin from the leading edge wet out bath 170 into the pultruded leading edge slug 120. The leading edge slug 120 exits the leading edge slug die 110 and is inserted into and becomes a part of the profile body 105 during pultrusion to form the composite profile 100. During pultrusion, the profile body 105 passes through the main wet out bath 150, the squeeze-out plates 155, and the primary pultrusion die 130.

[0053] The primary pultrusion die 130 is heated to cure the fibers and resin into the profile body 105, and to complete the cure of the leading edge slug 120 if it is not completely cured by the leading edge slug die 110.

[0054] Gripper pullers, which are not shown but are well known in the art, pull fibers and resin through both the leading edge slug die 110 and the primary pultrusion die 130 at the same time once pultrusion start-up is completed and the pultrusion process is running in steady-state production. However, pultrusion of the leading edge 120 must be started first.

[0055] As the pultruded leading edge slug 120 exits the leading edge slug die 110 and is being pulled along it enters the primary pultrusion die 130. The two pultrusion operations are then ongoing concurrently with the leading edge slug 120 exiting the upstream leading edge slug die 110 and passing into the profile body 105 as both are then pultruded by the primary pultrusion die 130 to ultimately become the composite profile 100.

[0056] In one embodiment, fibers for the leading edge slug 120 and profile body 105 can comprise a higher modulus carbon fiber to increase longitudinal stiffness of the airfoil blade, which may be particularly desirable for the leading edge slug 120. In an alternative embodiment, fibers can also comprise glass fibers. Alternatively, pre-preg materials or partially cured materials can be used as materials for the leading edge slug 120 before it is integrated with the profile body 105 to form a composite profile, such as composite profile 100.

[0057] In another embodiment, different fibers may be used for the leading edge slug 120 than for the profile body 105. For example, carbon fibers may be used for the leading edge slug 120 and glass fibers may be used for the profile body 105 to reduce cost of the composite profile 100 yet still meet strength requirements. Additionally, the coefficient of thermal expansion of the different fibers can be better managed when the leading edge slug 120 is fully cured and enters the primary pultrusion die 130 with the fibers including carbon fibers.

[0058] In one embodiment, resins for the leading edge slug 120 and profile body 105 can comprise polyester or vinyl ester resins typically used in commercial pultruded products. However, these resins are very reactive, and thus when heated by the leading edge slug die 110 and primary pultrusion die 130 they can cure completely. In another embodiment, resins can comprise epoxies typically used for aerospace applications. Epoxy is slower to cure than the resins typically used in commercial pultruded products. However, for epoxies, there are hardener systems known in the art that can be used that have faster polymerization or cure time.

[0059] In one embodiment, when the leading edge slug 120 exits the leading edge slug die 110, the leading edge slug 120 is solid or hard to the touch but is not completely cured. If the leading edge slug 120 is not fully cured, but still semi-hard to the touch, then the resins for the profile body 105 bind well to the leading edge slug 120 as both pass through the primary pultrusion die 130. Therefore, the cure characteristics of the resins can be used to enhance the adhesion of the leading edge slug 120 to the profile body 105 as the profile body 105 passes through the primary pultrusion die.

[0060] Additionally, the resins in the main wet out bath 150 and leading edge wet out bath 170 for the heavy cross section of the leading edge slug 120 can be tailored to optimize overall production. In one embodiment, the formulation of the resins and the catalyst used can be tailored to speed up cure time, and for epoxies there are hardener systems known in the art that have faster polymerization or cure time that can be used.

[0061] In another embodiment, the ability to separately tailor the processes for the leading edge slug 120 and the profile body 105 can be taken to the point where a different resin mix is used for the leading edge slug 120 from that used for the profile body 105. For example, a vinyl ester resin may be suitable for the leading edge slug 120, while an epoxy resin may be more suitable for the profile body 105 depending on application requirements.

[0062] Pultrusion Process 300

[0063] Turning to FIG. 3, the pultrusion process 300 utilizing the pultrusion tooling 115 on an industry available pultrusion machine that has the pulling capacity and capability to handle the desired size of the composite profile 100 is shown. Pultruding the leading edge slug 120 and profile body 105 using separate dies using the pultrusion process 300 eliminates the process problems of prior art methods and allows these two segments of the pultrusion process to be optimized for greater productivity and consistency.

[0064] First, at step 310, the dry (no resin) fibers are threaded into both the leading edge slug die 110 and the primary pultrusion die 130 and attached to the pultrusion tooling 115. The dry fibers are also attached to the pultrusion machine start-up winch (not shown) just downstream of the gripper pullers and of the primary pultrusion die 130.

[0065] Next, at step 320, pultrusion of the larger cross section of the leading edge slug 120 begins by adding resin to the leading edge slug wet out bath 170 and pulling all material. When resin is applied to the process, the start-up winch pulls the composite profile 100 downstream until the gripper pullers can be closed onto the composite profile 100. At this point, the start-up winch is disengaged, and the gripper pullers perform the task of continuously pulling materials.

[0066] At step 330, the leading edge slug 120 exits the leading edge slug die 110, and just before the leading edge slug 120 enters the primary pultrusion die 130, resin is added to the main wet out bath 150. The fibers are also re-clamped to the start-up winch at this point to reduce the amount of dry (no resin) fiber materials pulled. Then, at step 340, the leading edge slug 120 enters the primary pultrusion die 130.

[0067] At step 350, the two pultrusion operations are then ongoing concurrently with the leading edge slug 120 exiting the upstream leading edge slug die 110 and passing into and becoming part of the profile body 105 as it is pultruded by the primary pultrusion die 130. And, after the complete composite profile 100 comprised of both leading edge slug 120 and profile body 105 exits the primary pultrusion die 130 in a fully cured state and progresses downstream far enough to engage the gripper pullers of the pultrusion machine, the transfer from start-up winch to the pultrusion machine's gripper pullers is completed.

[0068] In this the pultrusion process 300, in one embodiment, the upstream leading edge slug 120 is solid but not yet completely cured exiting the leading edge slug die 110 at step 330. Its cure is completed at step 340 as it is co-cured with the profile body 105 as both are pulled through the primary pultrusion die 130. This is because the leading edge slug 120 is encapsulated by the fiber plies of the profile body 105 upstream of the primary pultrusion die 130 such that it is co-cured with the profile body 105 to become the composite profile 100. While fully encapsulated in the profile body 105, the cure of the leading edge slug 120 can also be optimized to be at lower percent of cure completion when it exits the upstream leading edge slug die 110 to enhance adhesion to the profile body 105.

[0069] Furthermore, during start-up, the main wet out bath 150 does not yet contain resin, and the fibers of the profile body 105 are dry. However, the primary pultrusion die 130 is hot. Therefore, just before the leading edge slug 120 begins to enter the primary pultrusion die 130 at step 330, resin is then added to the main wet out bath 150. The fibers of the profile body 105 are then wet out with resin as the leading edge slug 120 and fibers and resin of the profile body 105 enter the primary pultrusion die 130 at step 340. As a result, the profile body 105 is co-cured with the leading edge slug 120, and the composite profile 100 is subsequently pultruded in a continuous manner by the pultrusion tooling 115 as the two pultrusion operations run concurrently at step 350.

[0070] In one embodiment, the pull speed for the leading edge slug 120 and profile body 105 remains the same for both the leading edge slug die 110 and primary pultrusion die 130 at step 350, but the processing conditions can be optimized for each. In one embodiment, the time for pultrusion of the leading edge slug die 110 can be longer than the time for the primary pultrusion die 130 to provide more cure dwell time for the leading edge slug 120 at a given pull speed, different heat profiles, and to optimize the overall process for the larger mass and cross section of the leading edge slug 120 independent of the primary pultrusion die 130.

[0071] As another embodiment, pultrusion start-up of a complex composite profile 100 is made easier by first starting the pultrusion of the leading edge slug 120 and stabilizing this part of the pultrusion process before starting the pultrusion process for the profile body 105 at step 330. A stabilized pultrusion process is one wherein the fibers and resin enter the die in a controlled manner without bunching up and are adequately cured and dimensionally correct. For example, if the die temperature is too low at start-up, the material exiting the die might not be cured. In this case, the process is not working and is not yet stabilized.

[0072] Alternative Composite Profiles 400 and 500

[0073] The composite profile 100 made by the pultrusion process and method disclosed herein is particularly suited for a rotor blade airfoil where the leading edge slug 120 has a thick cross section because the leading edge slug 120 entering the primary pultrusion die 130 is net-to-size and therefore does not push the mandrels 140 sideways towards the trailing edge of the outer mold line portion of the primary pultrusion die 130. This prevents binding the mandrels 140 which increases pull loads and leads to a crooked or curved airfoil or other composite profile. However, this invention is also suitable for any hollow or solid pultruded profile having non-uniform thickness through its cross section.

[0074] For example, as shown in FIG. 4, in one alternative embodiment made by the pultrusion process and method of the present invention, composite profile 400 comprises an I-beam. Composite profile 400 has a thick cap section 410 and a thin web section 420. The thick cap section 410 is pultruded in the leading edge slug die 110, and then integrated with the thin web section 420 to go through the primary pultrusion die 130 to form composite profile 400.

[0075] As another example, as shown in FIG. 5, in another alternative embodiment made by the pultrusion process and method of the present invention, composite profile 500 comprises a box-beam. Composite profile 500 has a thick cap section 510 and a thin web section 520. Again, the thick cap section 510 is pultruded in the leading edge slug die 110, and then integrated with the thin web section 520 to go through the primary pultrusion die 130 to form composite profile 500.

[0076] While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation. Reasonable variation and modification are possible within the scope of the foregoing disclosure and drawings without departing from the spirit of the invention.