Patent Application
20200290835
Embodiments of the present disclosure generally relate to continuous tow processing systems and in particular to systems for qualification and repair of individual filament defects in a multi-filament tow prior to depositing coatings on a tow material.
Ceramic matrix composites (CMCs) are comprised of ceramic fibers embedded in a ceramic matrix. CMCs were developed to address limitations with conventional technical ceramics that prohibit use at high-temperatures and in oxidizing environments. Conventional unreinforced technical ceramics, including alumina, silicon carbide, aluminum nitride, silicon nitride, and zirconia, have low crack resistance and therefore fracture easily under mechanical and thermo-mechanical loading. These material limitations can be addressed by integrating multi-strand long ceramic fibers to enable greater elongation to rupture, fracture toughness, thermal shock resistance, and dynamic fatigue resistance.
Non-oxide polycrystalline ceramic fiber, typically silicon carbide (SiC) fiber, is used as continuous-length structural reinforcement in ceramic matrix composites (CMC). SiC-based ceramic fiber for CMC manufacture has small diameter, high thermal conductivity, low surface roughness, and a carbon-free surface. Furthermore, SiC-based ceramic fiber has high tensile strength as-produced, at high temperature, under high mechanical stress, and in oxidizing environments.
Chemical vapor infiltration (CVI) is used to produce an environmental barrier in the form of a thin conformal encapsulation layers on ceramic fibers. In general, the coated fiber has mechanical, thermal, and chemical advantages to un-coated fiber. Boron nitride (BN) and carbon-containing crack-deflecting interfacial coatings on SiC-based fiber surfaces improve SiC-based fiber oxidation resistance at high temperatures.
However, the inventors have observed that defects such as broken or loose filaments and non-uniformities in the polyvinyl acetate (PVA) coating on the multi-filament SiC tow (e.g., an untwisted bundle of continuous filaments) can cause perturbations in the coating process. Such perturbations can lead to problems such as non-uniform coating thickness and filaments sticking together. Furthermore, broken or loose filaments will create fuzz in the tow transport system which can cause further filament breakage and tow rupture.
Accordingly, the inventors have provided improved apparatus for qualification and repair of multi-filament tow.
Apparatus for qualification and repair of multi-filament tow are provided herein. In some embodiments, an apparatus for inspecting and repairing a multi-filament tow includes a first spool having a multi-filament tow wound on the first spool; a first tow tensioner following the first spool to impart a predetermined tension on the multi-filament tow; a de-sizing chamber comprising a heater to heat the multi-filament tow to a first temperature suitable for removing a coating on the multi-filament tow; an inspection chamber configured to inspect the multi-filament tow for defects; a repair chamber configured to repair the defects in the multi-filament tow; a second tow tensioner following the repair chamber to impart a predetermined tension on the multi-filament tow; and a second spool following the second tow tensioner to collect the multi-filament tow.
In some embodiments a method of inspecting and repairing a multi-filament tow, includes de-spooling a multi-filament tow from a first spool; heating the multi-filament tow to a first temperature suitable for removing a coating on the multi-filament tow in a de-sizing chamber; inspecting individual filaments of the multi-filament tow for defects in an inspection chamber; if a defective filament is found, repairing the defective filament in a repair chamber or removing the defective filament from the multi-filament tow; and spooling the multi-filament tow exiting the repair chamber onto a second spool.
In some embodiments, an apparatus for inspecting and repairing a multi-filament tow includes a first spool having a multi-filament tow wound on the first spool; a first motor coupled to the first spool to rotate the first spool and unwind the multi-filament tow from the first spool; a first tow tensioner following the first spool to impart a predetermined tension on the multi-filament tow; a first pitch control in-line with the first spool, between the first spool and the first tow tensioner, to allow the multi-filament tow to de-spool in a controlled manner; a first tension sensor in-line with the first spool, between the first pitch control and the first tow tensioner to measure a force induced on the multi-filament tow by the first tow tensioner a de-sizing chamber comprising a heater to heat the multi-filament tow to a first temperature suitable for removing a coating on the multi-filament tow; a first pulley in-line with the first spool between the first tow tensioner and the de-sizing chamber; an inspection chamber configured to inspect the multi-filament tow for defects; a repair chamber configured to repair the defects in the multi-filament tow; a second tow tensioner following the repair chamber to impart a predetermined tension on the multi-filament tow; a second pulley in-line with the first spool between the repair chamber and the second tow tensioner; a second tension sensor in-line with the second pulley and following the second tow tensioner to measure a force induced on the multi-filament tow by the second tow tensioner; a second pitch control in-line with the second pulley and following second tension sensor to allow the multi-filament tow to spool onto a second spool in a controlled manner; a second spool following the second tow tensioner to collect the multi-filament tow; and a second motor coupled to the second spool to rotate the second spool and wind the multi-filament tow onto the second spool.
Other and further embodiments of the present disclosure are described below.
Embodiments of the present disclosure, briefly summarized above and discussed in greater detail below, can be understood by reference to the illustrative embodiments of the disclosure depicted in the appended drawings. However, the appended drawings illustrate only typical embodiments of the disclosure and are therefore not to be considered limiting of scope, for the disclosure may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
Embodiments of the present disclosure advantageously provide improved apparatuses for qualification and repair of multi-filament tow. Embodiments of the present disclosure advantageously identify and remove or repair defects of individual filaments prior to exposing the multi-filament tow to a barrier coating process. Embodiments of the present disclosure advantageously provide improved uptime, throughput, and yield as well as improved quality tow.
For example, embodiments of the present invention provide an automated system for qualifying incoming ceramic tow for subsequent environmental barrier formation via chemical vapor infiltration. Conventional equipment for ceramic tow chemical vapor infiltration (CVI) relies on in situ repair at the time of tow break or tow jump, resulting in low CVI system productivity. Embodiments of the present invention improve CVI system performance by qualifying and repairing tow ex situ (in advance of initiating the CVI process). Tow, specifically SiC-based ceramic fiber, is de-spooled from a conventional spool (or bobbin), desized (stripped of poly-vinyl acetate (PVA), poly-vinyl alcohol, epoxy, PVA blended with polyethylene oxide), optically characterized for breaks, breaks repaired using various polymer splicing technology, and then transferred to a processing reel and/or otherwise conveyed to the CVI process.
The system 100 comprises a multi-filament tow 102, wound on a first spool 104. The first spool 104 is coupled to a first motor 114 to rotate the spool and unwind the multi-filament tow 102 from the first spool 104. The multi-filament tow 102 passes through a first pitch control 106 which controls the de-spooling of the multi-filament tow 102 to minimize or prevent damage to the multi-filament tow 102 and to allow the individual filaments in the multi-filament tow 102 to maintain their position relative to each other during de-spooling. In some embodiments, the first pitch control 106 is positioned with respect to the first spool 104 to maintain the multi-filament tow 102 in a substantially horizontal orientation. In some embodiments, the first pitch control 106 comprises opposing pulleys or rollers that rotate as the multi-filament tow 102 passes through. The distance between the opposing pulleys is dependent on the thickness of the multi-filament tow 102. In some embodiments, the first pitch control 106 further comprises a sensor to measure the length (i.e., amount) of the tow that has passed through the first pitch control 106.
The system 100 further comprises a first tension sensor 108. In some embodiments, the multi-filament tow 102 passes from the first pitch control 106 to the first tension sensor 108. In some embodiments, the first tension sensor 108 is positioned approximately level with the first spool 104 such that the multi-filament tow 102 travels substantially horizontally from the first spool 104 to the first tension sensor 108. In some embodiments, the first tension sensor 108 is a tension strain gauge coupled to an idler pulley to measure the force on the multi-filament tow 102.
In some embodiments, a first tow tensioner 110 is provided to control the tension on the multi-filament tow 102. For example, in some embodiments, the first tow tensioner 110 provides about 0.4 Newton of tension on the multi-filament tow 102 as measured by the first tension sensor 108. In some embodiments, the first tow tensioner 110 is placed below the height of the first tension sensor 108. In some embodiments, the first tow tensioner 110 is a pulley having a movable axial position in order to increase or decrease the tension on the multi-filament tow 102. In some embodiments, the first tow tensioner 110 is coupled to a third motor that moves the first tow tensioner 110 to control the linear distance between the first tow tensioner 110 and the first tension sensor 108. For example, increasing the distance between the first tow tensioner 110 and the first tension sensor 108 idler pulley will increase the tension on the multi-filament tow 102 while decreasing the distance between the first tow tensioner 110 and the first tension sensor 108 idler pulley will decrease the tension on the multi-filament tow 102. Tension control during spooling and unspooling provides uniform conditions for de-sizing, inspection, repair and re-spooling. In some embodiments, the first tow tensioner 110 is configured to move in a substantially vertical direction.
The multi-filament tow 102 passes over a first pulley 112, which may for example be at about the height of the first spool 104, and into a de-sizing chamber 116. Within the de-sizing chamber 116, the multi-filament tow 102 is heated to a temperature of about 500 to about 1000 degrees Celsius to remove the polyvinyl acetate (PVA) coating on the multi-filament tow 102. The PVA coating holds the individual filaments in a bundle. The de-sizing chamber 116 may heat the multi-filament tow 102 using any suitable heating mechanism capable of heating the multi-filament tow 102 to about 500 to about 1000 degrees Celsius, such as a heat exchanger, heat lamps, or the like.
Once the PVA coating is removed, the multi-filament tow 102 passes through an inspection chamber 118 and then through a repair chamber 120. Within the inspection chamber 118, the multi-filament tow 102 is inspected for defects such as breaks in individual filaments in the multi-filament tow 102. The inspection chamber 118 uses an optical detection process for identifying and quantifying defects in the multi-filament tow 102. In some embodiments, the defective filaments may be physically marked or the location of the defective filaments may be measured, for example in meters or other suitable units, and recorded. Within the repair chamber 120 the identified defect is repaired or removed. For example, in some embodiments, a broken filament is removed from the multi-filament tow 102 and guided to a reject path for disposal or, if possible, to be re-spooled and re-used.
Upon exiting the repair chamber 120, multi-filament tow 102 passes over a second pulley 122, which for example may be at the height of the first spool 104, and to a second tow tensioner 124. The second tow tensioner 124 may be placed below the height of the second pulley 122. In some embodiments, the second tow tensioner 124 is a pulley having a movable axis to control the distance between the second tow tensioner 124 and the second pulley 122. In some embodiments, the second tow tensioner 124 provides about 0.4 Newton of tension on the multi-filament tow 102 as measured by the second tension sensor 126. In some embodiments, the second tow tensioner 124 is coupled to a fourth motor that moves the second tow tensioner 124 to control the distance between the second tow tensioner 124 and the second pulley 122. Increasing the distance between the second tow tensioner 124 and the second pulley 122 will increase the tension on the multi-filament tow 102 while decreasing the vertical distance between the second tow tensioner 124 and the second pulley 122 will decrease the tension on the multi-filament tow 102. In some embodiments, the second tow tensioner 124 moves in a substantially vertical direction.
The multi-filament tow 102 passes over a second tension sensor 126. In some embodiments, the second tension sensor 126 is a tension strain gauge coupled to an idler pulley which measures the force induced by the second tow tensioner 124. The multi-filament tow 102 then passes through a second pitch control 128 which allows the multiple filaments to spool onto the second spool 130 in a controlled manner preventing damage to the multi-filament tow 102 and allow the individual filaments to maintain their position relative to each other during re-spooling. In some embodiments, the second pitch control 128 comprises opposing pulleys or rollers. The multi-filament tow 102 passes in-between the pulleys or rollers. In some embodiments, the second pitch control 128 further comprises a sensor to measure the position of the multi-filament tow 102.
The multi-filament tow 102 is wound onto a second spool 130. The second spool 130 is coupled to a second motor 132 to rotate the spool and wind the multi-filament tow 102 onto the second spool 130. In some embodiments, the second spool is a large diameter spool which provides less bending stress on the multi-filament tow. Once the entire spool of multi-filament tow 102 has been inspected and repaired the spool can be further processed. For example, the inspected and repaired spook can be placed in a chemical vapor deposition chamber to deposit barrier materials on the filaments.
At 206, individual filaments of the multi-filament tow are inspected for defects. The inspection of the filaments can be performed in the inspection chamber 118 as discussed above. For example, within the inspection chamber 118, the multi-filament tow 102 is inspected for defects such as breaks in individual filaments in the multi-filament tow 102. The inspection chamber 118 uses an optical detection process for identifying and quantifying defects in the multi-filament tow 102. In some embodiments, the defective filaments may be physically marked or the location of the defective filaments may be measured, for example in meters or other suitable units, and recorded.
At 208, it is determined if a defective filament has been found. If a defective filament has not been found, the multi-filament tow is spooled onto a second spool at 212. If a defective filament is found, the defective filament is repaired or removed at 210. The defective filament can be repaired or removed, for example, in the repair chamber 120 discussed above. In some embodiments, the defective filament, such as a broken filament, is removed from the multi-filament tow and guided to a reject path for disposal or, if possible, to be re-spooled and re-used.
While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2017/035707 | 6/2/2017 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62344966 | Jun 2016 | US |
