zeke wrote:

The reason for using the terminology in this case is not in the sense of fixing the issue, it is to do with who has the authority to perform the task, does the person need to hold a licence or can it just be a mechanic.

Repairs need to be performed under the supervision of a licence holder.

License holders perform temporary repairs all the time, as they await a final repair procedure from the OEM, or so another license holder can perform a more involved repair.

I'm a nobody here and I like reading but the discussion better not drift far and for long from the subject otherwise the admin locks the thread (again)

Avatar2go wrote:

As I said, the mesh has a layer of composite resin above it. This is beyond dispute.

Could you please provide the direct quote and reference to where you have said Airbus claimed there was a layer of composite above the mesh ?

As far as I am aware from the documents I have seen there is no layer of composite above the mesh pre-preg, composite consisted of one or materials (hence the term), normally a matrix which often is some form of epoxy when used on aircraft and some form of fibre, that can be metal, carbon, Kevlar etc. The mesh pre-preg is in itself a composite, it is placed on the outside of the carbon fibre composite that makes up the the structural parts because carbon fibre is a poor conductor. The mesh is there to conduct the electrical charge into the electrical structure network (ESN) in the pressurised areas and the metallic bonding network in the non-pressurised areas.

“ Because the fuselage sections’ carbon fiber composites do not conduct electricity as well as aluminum alloy structures, the current from a lightning strike will seek any metal paths available, such as fasteners. For this reason, both the 787 and the A350 make strategic use of metal parts. Selections were made based on the parts’ ability to provide necessary structural reinforcement in some highly loaded regions while facilitating an electrical return path for the internal electrical systems and equipment. All of the A350’s metal parts — including aluminum seat rails and a mix of aluminum, aluminum/lithium alloy and titanium for lower frames and passenger cabin structural floor grid beams — do double duty. Each part has a structural function, and it also forms part of the overall electrical structure network (ESN) within the aircraft. The A350’s composite panels incorporate an outer copper mesh to manage the direct effects of lightning, and they work with the ESN to maintain the Faraday cage principle, channeling the electrical current around the fuselage harmlessly rather than letting it pass through to damage fasteners and operational structures. This multifunctionality avoids added structure associated with dedicated ESN components and the resulting weight penalty that would offset the lightweighting advantage of a CFRP fuselage. As a result, the six assembled sections of the center fuselage, at 64.6 ft/19.7m long and 22 ft/6.7m in diameter, will weigh a mere 9,000 lb/4,082 kg.”

From https://www.compositesworld.com/article ... ufacturing

From the Airbus response document:

4.3 During the aircraft manufacturing process, the ECF is embedded into a surfacing film which is then co-cured on to the CFRP. This means that the ECF layer forms an integral part of the airframe

21.4.1 (3) The memorandum found that the initial “crazing cracks” provide an entrance for moisture, condensation and other fluids that could lead to an oxidation of the ECF and a reduction of the adhesion between the ECF layer and the surrounding resin.

This means, as evidenced by the "Condition" described by Airbus, as well as the photos/videos provided by Qatar, that the overlying resin which forms the embedding layer, loses adhesion to the ECF and is dislodged, thus visibly exposing the ECF to ambient conditions. The ECF in most cases remains attached to the aircraft, but in some cases may itself be dislodged, either through damage or oxidation.

Avatar2go wrote:

From the Airbus response document:

4.3 During the aircraft manufacturing process, the ECF is embedded into a surfacing film which is then co-cured on to the CFRP. This means that the ECF layer forms an integral part of the airframe

21.4.1 (3) The memorandum found that the initial “crazing cracks” provide an entrance for moisture, condensation and other fluids that could lead to an oxidation of the ECF and a reduction of the adhesion between the ECF layer and the surrounding resin.

This means, as evidenced by the "Condition" described by Airbus, as well as the photos/videos provided by Qatar, that the overlying resin which forms the embedding layer, loses adhesion to the ECF and is dislodged, thus visibly exposing the ECF to ambient conditions. The ECF in most cases remains attached to the aircraft, but in some cases may itself be dislodged, either through damage or oxidation.

That does not say there is a layer of composite above the mesh, and that does not say there is a layer of resin placed above the mesh, the mesh is embedded in epoxy as a pre-preg.

The mesh layer is composite, the mesh is embedded in an epoxy that forms a pre-preg composite sheet. The composite is two part, the metallic mesh, and the epoxy (resin) it is embedded within.

zeke wrote:

Avatar2go wrote:

From the Airbus response document:

4.3 During the aircraft manufacturing process, the ECF is embedded into a surfacing film which is then co-cured on to the CFRP. This means that the ECF layer forms an integral part of the airframe

21.4.1 (3) The memorandum found that the initial “crazing cracks” provide an entrance for moisture, condensation and other fluids that could lead to an oxidation of the ECF and a reduction of the adhesion between the ECF layer and the surrounding resin.

This means, as evidenced by the "Condition" described by Airbus, as well as the photos/videos provided by Qatar, that the overlying resin which forms the embedding layer, loses adhesion to the ECF and is dislodged, thus visibly exposing the ECF to ambient conditions. The ECF in most cases remains attached to the aircraft, but in some cases may itself be dislodged, either through damage or oxidation.

That does not say there is a layer of composite above the mesh, and that does not say there is a layer of resin placed above the mesh, the mesh is embedded in epoxy as a pre-preg.

The mesh layer is composite, the mesh is embedded in an epoxy that forms a pre-preg composite sheet. The composite is two part, the metallic mesh, and the epoxy (resin) it is embedded within.

I think the non-technical view is that the mesh is not on the outside of the aircraft. There is composite (and paint) between the mesh and the air.

How then surface layers are constructed is interesting, but seems to be a distraction from the fact that the paint peeled and the composite surface degraded, exposing mesh.

zeke wrote:

Avatar2go wrote:

From the Airbus response document:

4.3 During the aircraft manufacturing process, the ECF is embedded into a surfacing film which is then co-cured on to the CFRP. This means that the ECF layer forms an integral part of the airframe

21.4.1 (3) The memorandum found that the initial “crazing cracks” provide an entrance for moisture, condensation and other fluids that could lead to an oxidation of the ECF and a reduction of the adhesion between the ECF layer and the surrounding resin.

This means, as evidenced by the "Condition" described by Airbus, as well as the photos/videos provided by Qatar, that the overlying resin which forms the embedding layer, loses adhesion to the ECF and is dislodged, thus visibly exposing the ECF to ambient conditions. The ECF in most cases remains attached to the aircraft, but in some cases may itself be dislodged, either through damage or oxidation.

That does not say there is a layer of composite above the mesh, and that does not say there is a layer of resin placed above the mesh, the mesh is embedded in epoxy as a pre-preg.

The mesh layer is composite, the mesh is embedded in an epoxy that forms a pre-preg composite sheet. The composite is two part, the metallic mesh, and the epoxy (resin) it is embedded within.

Zeke, it says exactly what it says. The ECF loses adhesion with the embedding resin, which flakes away and leaves the ECF exposed. This is clearly evident in the Qatar photos as well. You are arguing even against Airbus here, and I don't understand why, but won't argue any further because it's become a stupidity at this point.

If I understand Zeke's comment, and I may be completely wrong about it, he means that because the mesh is embedded into the epoxy, then when that epoxy component of the composite epoxy/mesh outer layer breaks away, it would break both "over" and "under" the mesh. Is that it ? The mesh would, in fact, be potentially exposed from both sides, again if I understand well.

It may look byzantine from the outset but I guess it means the repair is not quite the same in that case… Not quite like if indeed it was only an outer layer of something giving way to an inner layer of mesh.

… please, no flak, just trying to understand.

Aircellist wrote:

If I understand Zeke's comment, and I may be completely wrong about it, he means that because the mesh is embedded into the epoxy, then when that epoxy component of the composite epoxy/mesh outer layer breaks away, it would break both "over" and "under" the mesh. Is that it ? The mesh would, in fact, be potentially exposed from both sides, again if I understand well.

It may look byzantine from the outset but I guess it means the repair is not quite the same in that case… Not quite like if indeed it was only an outer layer of something giving way to an inner layer of mesh.

… please, no flak, just trying to understand.

The ECF mesh is embedded into composite material resin, which is then bonded and cured onto the surface of the structural CFRP. Then covered with a multi-layer paint protective system.

For surface degradation that exposes the mesh, all the layers above it have to come off. That necessarily includes the upper layer of the ECF embedding resin. Airbus acknowledges that the loss of material occurs, and claims it results from moisture penetration of the upper layers due to expected gradual decline of the paint protection system. Whereas Qatar questions that assertion and is concerned there is some internal bonding flaw involved.

As to whether the ECF loss of adhesion occurs on both sides, I would suspect you are right that it does, as in some cases the ECF is missing as well. In the Airbus recommended repair, sections of ECF that are missing or have suffered oxidation, must be replaced with new ECF sections, which is part of the patching procedure. In the finished repair, the integrity of the ECF and the surface are fully restored.

Thank you very much, Avatar2go

Avatar2go wrote:

Aircellist wrote:

Avatar2go wrote:

Zeke, it says exactly what it says. The ECF loses adhesion with the embedding resin, which flakes away and leaves the ECF exposed. This is clearly evident in the Qatar photos as well. You are arguing even against Airbus here, and I don't understand why, but won't argue any further because it's become a stupidity at this point.

No it does not say the words you claim.

It says cracking can lead to moisture to enter, when the aircraft cycles that water freezes (water expands as it freezes which is the mechanism which separates the mesh from the matrix). That leads to air getting to the mesh to further oxidase it. It does not say “ which flakes away and leaves the ECF exposed”, that is your unfounded editorial opinion.

The fix to this is to address the crack early to prevent further water ingress, that stops the cycle.

I am not going against Airbus at all, you have made several false claims :
1) there is a layer of composite above the mesh
2) there is a layer of resin above the mesh
3) ECF loses adhesion with the embedding resin, which flakes away

None of those comments are supported by any of the court documents, that is all your false opinion.

zeke wrote:

Avatar2go wrote:

Zeke, it says exactly what it says. The ECF loses adhesion with the embedding resin, which flakes away and leaves the ECF exposed. This is clearly evident in the Qatar photos as well. You are arguing even against Airbus here, and I don't understand why, but won't argue any further because it's become a stupidity at this point.

No it does not say the words you claim.

It says cracking can lead to moisture to enter, when the aircraft cycles that water freezes (water expands as it freezes which is the mechanism which separates the mesh from the matrix). That leads to air getting to the mesh to further oxidase it. It does not say “ which flakes away and leaves the ECF exposed”, that is your unfounded editorial opinion.

The fix to this is to address the crack early to prevent further water ingress, that stops the cycle.

I am not going against Airbus at all, you have made several false claims :
1) there is a layer of composite above the mesh
2) there is a layer of resin above the mesh
3) ECF loses adhesion with the embedding resin, which flakes away

None of those comments are supported by any of the court documents, that is all your false opinion.

Zeke, as I said, I am done arguing. You are welcome to your own opinions, as always.

The evidence stands on its own. Oxidation can occur from moisture, which everyone knows. The ECF mesh being exposed requires the loss of all overlying layers, as everyone knows, and is visible in the photos. Everyone is free to read the 67 page Airbus response, which lays things out pretty clearly. There is really nothing else to say.

Avatar2go wrote:

The ECF mesh is embedded into composite material resin, which is then bonded and cured onto the surface of the structural CFRP. Then covered with a multi-layer paint protective system.

Using any buzz word you know into a sentence does not add weight to what you are claiming. This sentence again is factually wrong, the pre-preg that contains the mesh is not bonded “onto the surface of the structural CFRP”. Bonding (gluing) is a different process used in composite manufacturing that is used for example to attach a skin to a honeycomb core.

The fuselage panels are made as one piece, the matrix in the different pre-preg layers are seamlessly combined in the autoclave under temperature and pressure, if you were to cut through a section of the fuselage after it left the autoclave you would not be able to tell where the pre-preg layers are, it does not look like rings in a tree. The matrix forms a uniform continuous material from the upper to lower surface.

zeke wrote:

Avatar2go wrote:

The ECF mesh is embedded into composite material resin, which is then bonded and cured onto the surface of the structural CFRP. Then covered with a multi-layer paint protective system.

Using any buzz word you know into a sentence does not add weight to what you are claiming. This sentence again is factually wrong, the pre-preg that contains the mesh is not bonded “onto the surface of the structural CFRP”. Bonding (gluing) is a different process used in composite manufacturing that is used for example to attach a skin to a honeycomb core.

The fuselage panels are made as one piece, the matrix in the different pre-preg layers are seamlessly combined in the autoclave under temperature and pressure, if you were to cut through a section of the fuselage after it left the autoclave you would not be able to tell where the pre-preg layers are, it does not look like rings in a tree. The matrix forms a uniform continuous material from the upper to lower surface.

Interesting, I work with composite wings in aviation, and when cut or drilled, you can definitely see the different layers within and it does look like rings in a tree. And yes that same cfrp is also formed in an autoclave under pressure and temperature.

Spetsnaz55 wrote:

zeke wrote:

Avatar2go wrote:

The ECF mesh is embedded into composite material resin, which is then bonded and cured onto the surface of the structural CFRP. Then covered with a multi-layer paint protective system.

Using any buzz word you know into a sentence does not add weight to what you are claiming. This sentence again is factually wrong, the pre-preg that contains the mesh is not bonded “onto the surface of the structural CFRP”. Bonding (gluing) is a different process used in composite manufacturing that is used for example to attach a skin to a honeycomb core.

The fuselage panels are made as one piece, the matrix in the different pre-preg layers are seamlessly combined in the autoclave under temperature and pressure, if you were to cut through a section of the fuselage after it left the autoclave you would not be able to tell where the pre-preg layers are, it does not look like rings in a tree. The matrix forms a uniform continuous material from the upper to lower surface.

Interesting, I work with composite wings in aviation, and when cut or drilled, you can definitely see the different layers within and it does look like rings in a tree. And yes that same cfrp is also formed in an autoclave under pressure and temperature.

Having worked with 3D microscope on composite material, you can indeed see the layer when it is cut and rightly polished, but the composite should have a global breaking/tearing behaviour. If the different zones in the composite can dissociate by layer, this is not composite anymore, or it implies quality issues.

Bordeauxline wrote:

Having worked with 3D microscope on composite material, you can indeed see the layer when it is cut and rightly polished, but the composite should have a global breaking/tearing behaviour. If the different zones in the composite can dissociate by layer, this is not composite anymore, or it implies quality issues.

Correct if you can see where the layers are after it’s cured they are considered to be voids. A common reason for this on hand layups is not wearing gloves and fats from human hands being transferred onto the pre-preg. Can be seen on an x-ray of the part also. A part with voids should fail QA.

This thread has run its course and will be locked, feel free to start a new thread in case there are any news about this subject.