Will it ever fly?

[bigvalboy]

Curious....Are members flying the Dreamliner, and do you think about recurring problems when you board.

 

http://247wallst.com/aerospace-defense/2014/08/10/787-dreamliner-engine-fails-over-the-atlantic/

[fedssocr1]

I hadn't heard about that one yet. It certainly does seem to be cursed.

 

It will interesting to see if the A350 roll out is any smoother.

[jimboivyo]

Curious....Are members flying the Dreamliner, and do you think about recurring problems when you board.

 

http://247wallst.com/aerospace-defense/2014/08/10/787-dreamliner-engine-fails-over-the-atlantic/

 

 

Doesn't bother me in the least and I've flown on the 787 over a dozen times already

 

This scare hype is media driven cow plop. There are many more worrisome issues out there today, including the huge recalls that GM is currently going through. I've had nothing but great flights with the 787

[armadillo]

http://nypost.com/2014/08/08/terror-filled-flight-as-planes-engine-fails-over-atlantic/

 

According to the above article, this 787 was losing 500' / minute. How comforting after an hour/

 

Wonder if it will retain in its ETOPS certification / rating.

[armadillo]

http://seattletimes.com/html/businesstechnology/2024473735_sundaybuzz07xml.html

 

I am even less limey to flyone of these birds now.

[bigvalboy]

http://seattletimes.com/html/businesstechnology/2024473735_sundaybuzz07xml.html

 

I am even less limey to flyone of these birds now.

 

Interesting. I saw this the other day. For all the miles I have logged in the many decades that I have been circling the globe, rarely if ever, in all those years did I inquire as to what type of plane I would be traveling on, until now. Yesterday as I finalized plans for travel later this year, it was one of the first things that I asked about.

[+ azdr0710]

cool little video posted yesterday ahead of the Paris Air Show this month.....

 

Edited June 14, 2015 by azdr0710

[+ sync]

It wouldn't matter to me if they rolled out the starship Enterprise, I'm never at ease in an airplane.

[bigvalboy]

It wouldn't matter to me if they rolled out the starship Enterprise, I'm never at ease in an airplane.

 

They can take off, fly it all over Paris, and land it's ass on top of the Eiffel Tower for all I care, it's going to be a long time before I climb aboard one.

 

http://poolo.kermeet.com/Data/kmsiae/event/F_2313fbd7faef911eac8191d26a2d9717533986bdd87b2.jpg

Edited June 14, 2015 by bigvalboy

[AdamSmith]

While the teething problems have been the batteries and now that electrical-system-shutdown programming glitch, some of my engineer friends inside Boeing remain most anxious about that composite airframe. Specifically that (1) they don't know as much as they would like about long-term fatigue life of large-scale composite structures, (2) inspection techniques for composite materials are primitive, consisting mainly of thumping the skin with a rubber mallet and listening for 'funny' sounds, (3) they may have missed some failure modes related to how composite panels interact with their fasteners over time, (4) etc., etc.

[bigvalboy]

While the teething problems have been the batteries and now that electrical-system-shutdown programming glitch, some of my engineer friends inside Boeing remain most anxious about that composite airframe. Specifically that (1) they don't know as much as they would like about long-term fatigue life of large-scale composite structures, (2) inspection techniques for composite materials are primitive, consisting mainly of thumping the skin with a rubber mallet and listening for 'funny' sounds, (3) they may have missed some failure modes related to how composite panels interact with their fasteners over time, (4) etc., etc.

 

Three observations...

#1...What?

#2...What?

#3...What the fuck?

[+ ArVaGuy]

While the teething problems have been the batteries and now that electrical-system-shutdown programming glitch, some of my engineer friends inside Boeing remain most anxious about that composite airframe. Specifically that (1) they don't know as much as they would like about long-term fatigue life of large-scale composite structures, (2) inspection techniques for composite materials are primitive, consisting mainly of thumping the skin with a rubber mallet and listening for 'funny' sounds, (3) they may have missed some failure modes related to how composite panels interact with their fasteners over time, (4) etc., etc.

 

That's pretty much the same observation I heard from an engineer at Intelsat.

[AdamSmith]

I would fly on one if booked, but the thing is going to be effectively an airborne test lab for the first few years.

[+ dutchmuch]

"Aviation experts say Boeing will cut out the damaged areas and glue or, probably, bolt a large patch, made of overlapping panels of composite materials, onto the shiny new plane, which is less than a year old. “That’s a little like ‘Phantom of the Opera,’ where the guy had this mask to cover the fact that half his face was missing,” said Hans W. Weber, an aviation consultant in San Diego."

http://www.nytimes.com/2013/07/30/business/boeings-787-poses-new-challenges-for-repair-teams.html?_r=0

[+ quoththeraven]

I would fly on one if booked, but the thing is going to be effectively an airborne test lab for the first few years.

 

I was going to compare passengers to guinea pigs or, to be more up to date, beta testers.

[AdamSmith]

I was going to compare passengers to guinea pigs or, to be more up to date, beta testers.

 

To be serious, not quite that bad--the FAA certification regimes are pretty rigorous. But the dearth of experience with these novel materials employed at this scale does seem to keep engineers awake wondering what all they just don't know about them yet.

[AdamSmith]

In this project Boeing also (think I repeat myself from some time earlier in this thread) did something a lot of manufacturing enterprises try to avoid if possible: they radically changed both the product and the production processes at the same time.

 

BMW for example has what it calls, characteristically Teutonically, an "iron law" never to make both those changes on the same car program.

[Lookin]

(2) inspection techniques for composite materials are primitive, consisting mainly of thumping the skin with a rubber mallet and listening for 'funny' sounds,

 

As this was my doctor's primary technique in my recent annual physical, I expect the plane is in about as good a shape as I am. So I would take my chances, and eagerly after seeing AZDR's video from the Paris Air Show. That thing really scoots around the skies! http://www.boytoy.com/forums/public/style_emoticons/default/thumbsup.png

 

(Except, of course, when it loses an engine but let us not be pickers of nits. http://www.boytoy.com/forums/public/style_emoticons/default/rolleyes.gif )

 

This article says that the Dreamliner took eight years and $32 billion to develop. Boeing had originally forecast half the time and five times cheaper. I wonder if they would have gone ahead had they known the actual numbers.

 

http://www.vb.is/media/cache/2e/40/2e40e536e9d0a882b1f38b8d075834fa.jpg

Edited June 15, 2015 by Lookin

[+ quoththeraven]

To be serious, not quite that bad--the FAA certification regimes are pretty rigorous. But the dearth of experience with these novel materials employed at this scale does seem to keep engineers awake wondering what all they just don't know about them yet.

 

I get that. As the daughter of an engineer (chemical, not aeronautical) and a firm believer in Murphy's Law, the idea of flying in something made with materials whose long-term performance is unknown concerns me. Flying is so safe relative to other means of transportation that I'm not excited at introducing this level of uncertainty.

[+ azdr0710]

many here know the story of the airframe metal fatigue problems of the world's first commercial jet, the DeHavilland Comet, in the early 1950s....

 

https://en.wikipedia.org/wiki/De_Havilland_Comet

[AdamSmith]

Wikipedia's little bagatelle on the composite failure called delamination:

 

https://en.m.wikipedia.org/wiki/Delamination

[MsGuy]

AS, thank God we can always count on you coming up with a reassuring link.

[AdamSmith]

Some more delightful engineering details about the Screamliner to start your week...

 

Protecting Aircraft Composites from Lightning Strike Damage

At Boeing, innovation comes in the form of modern aircraft such as the 787 Dreamliner, whose body is made up of over 50% carbon fiber composite. While incredibly lightweight and strong, such aircraft composites are not inherently conductive, thus requiring additional protective coatings to mitigate lightning strike damage. Here, we describe how multiphysics simulation is used to evaluate thermal stress and displacement in the protective coatings that undergo temperature fluctuations associated with the typical flight cycle.

 

High-Performance Coatings for Aircraft Composites

Advanced composites are used extensively throughout the Boeing 787 Dreamliner, as shown in the diagram below. Also known as carbon fiber reinforced plastic (CFRP), the composites are formed from a lightweight polymer binder with dispersed carbon fiber filler to produce materials with high strength-to-weight ratios. Many wing components, for example, are made of CFRP, ensuring that they can support the load imposed during flight while minimizing their overall contribution to the weight of an aircraft.

 

Advanced composites are used throughout the body of the Boeing 787. Copyright © Boeing.

 

Despite their remarkable strength and light weight, CFRPs are generally not conductive like their aluminum counterparts, thus making them susceptible to lightning strike damage. Therefore, electrically conductive expanded metal foil (EMF) is added to the composite structure layup, shown in the figure below, to dissipate the high current and heat generated by a lightning strike.

 

The composite structure layup shown at left consists of an expanded metal foil layer shown at right. This figure is a screenshot from the COMSOL Multiphysics® software model featured in this blog post. Copyright © Boeing.

 

The figure also shows the additional coatings on top of the EMF, which are in place to protect it from moisture and environmental species that cause corrosion. Corrosive damage to the EMF could result in lower conductivity, thereby reducing its ability to protect aircraft structures from lightning strike damage. Temperature variations due to the ground-to-air flight cycle can, however, lead to the formation of cracks in the surface protection scheme, reducing its effectiveness.

 

Thermal Stress, Displacement, and Crack Formation

During takeoff and landing, aircraft structures are subjected to cooling and heating, respectively. Thermal stress manifests as the expansion and compression — or ultimately the displacement — of adjacent layers throughout the depth of the composite structure. Although a single round-trip is not likely to pose a significant risk, over time, each layer of the composite structure contributes to fatigue damage buildup. Repetitive thermal stress results in cumulative strain and higher displacements, which are, in turn, associated with an increased risk of crack formation. The stresses in a material depend on its mechanical properties quantified by measurable attributes such as yield strength, Young’s modulus, and Poisson’s ratio.

 

Simulating Thermal Stress and the Ground-to-Air Flight Cycle

By taking the thermal and mechanical properties of materials into account, it is possible to use simulation to design and optimize a surface protection scheme for aircraft composites that minimizes stress, displacement, and the risk of crack formation.

 

Evaluating the thermal performance of each layer in the surface protection scheme is essential in order to reduce the risks and maintenance costs associated with damage to the protective coating and EMF. Therefore, researchers at Boeing Research & Technology (BR&T), pictured below, are using multiphysics simulation and physical measurements to investigate the effect of the EMF design parameters on stress and displacement throughout the composite structure layup.

 

The research team at Boeing Research & Technology from left to right: Patrice Ackerman, Jeffrey Morgan, Robert Greegor, and Quynhgiao Le. Copyright © Boeing.

 

In their work, the researchers at BR&T have developed a coefficient of thermal expansion (CTE) model in COMSOL Multiphysics® simulation software. The figure shown above that presents the composite structure layup and EMF is a screenshot acquired from the model geometry used for their simulations in COMSOL Multiphysics.

 

The CTE model was used to evaluate heating of the aircraft composite structure as experienced upon descent, where the final and initial temperatures used in the simulations represent the ground and altitude temperatures, respectively. The Thermal Stress interface, which couples heat transfer and solid mechanics, was used in the model to simulate thermal expansion and solve for the displacement throughout the structure.

 

The material properties of each layer in the surface protection scheme as well as of the composites are custom-defined in the CTE model. The relative values of the coefficient of thermal expansion, heat capacity, density, thermal conductivity, Young’s modulus, and Poisson’s ratio are presented in the chart below.

 

This graph presents the ratio of each material parameter relative to the paint layer. Copyright © Boeing.

Edited June 15, 2015 by AdamSmith

[AdamSmith]

...continued...

 

From the graph, trends can be identified that provide early insight into the behavior of the materials, which aids in making design decisions. For example, the paint layer is characterized by higher values of CTE, heat capacity, and Poisson’s ratio, thus indicating that it will undergo compressive stress and tensile strain upon heating and cooling.

 

Multiphysics simulation takes this predictive design capability one big step forward by quantifying the resulting displacement due to thermal stress throughout the entire composite structure layup simultaneously, taking into account the properties of all materials. The following figure shows an example of BR&T’s simulation results and presents the stress distribution and displacement throughout the composite structure.

 

Left: Top-down and cross-sectional views of the von Mises stress and displacement in a one-inch square sample of a composite structure layup. Right: Transparency was used to show regions of higher stress, in red. Lower stress is shown in blue. Copyright © Boeing.

 

In the plots at the left above, the displacement pattern caused by the EMF is evident through the paint layer at the top of the composite structure while a magnified cross-sectional view shows the variations in displacement above the mesh and voids of the EMF. The cross section also makes it easy to see the stress distribution through the depth of the composite structure, where there is a trend toward lower stress in the topmost layers. Transparency was used in the plot shown at the right to depict the regions of high stress in the composites and EMF, which is noticeably higher at the intersection of the mesh wires. Stress was plotted through the depth of the composite structure layup along the vertical red line shown in the center of the plot. The figure below shows the relative stress in each layer of the composite structure layup for different metallic compositions of the EMF.

 

Relative stress in arbitrary units was plotted through the depth of the composite structure layups containing either aluminum (left) or copper EMF (right). Copyright © Boeing.

 

The samples vary by the presence of a fiberglass corrosion isolation layer when aluminum is used as the material for the EMF. The fiberglass acts as a buffer resulting in lower stress in the aluminum EMF, when compared with the copper.

 

Designing an EMF Layer for Reliable Lightning Strike Protection

From lightning strike protection to the structural integrity of the composite protection scheme, it all relies on the design of the expanded metal foil layer. The design of the EMF layer can vary by its metallic composition, height, width of the mesh wire, and the mesh aspect ratio. For any EMF design parameter, there is a trade-off between current-carrying capacity, displacement, and weight. By using the CTE model, the researchers at BR&T found that increasing the mesh width and decreasing the aspect ratio are better strategies for increasing the current-carrying capacity of the EMF that minimize its impact on displacement in the composite structure.

 

The metal chosen for the EMF can also have a significant effect on stress and displacement in the composite structure, which was investigated using simulation and physical testing. Two composite structures, one with aluminum and the other with copper EMF, underwent thermal cycling with prolonged exposure to moisture in an environmental test chamber. In the results, shown below, the protective layers remained intact for the composite structure with copper EMF. However, for the layup with aluminum, cracking occurred in the primer, at the edges, on surfaces, and was particularly substantial in the mesh overlap regions.

 

Photo micrographs of the composite structure layup after exposure to moisture and thermal cycling. A crack in the vicinity of the aluminum EMF is contained within the red ellipse. Copyright © Boeing.

 

Simulations confirm the experiment results. Shown below, displacements are noticeably higher throughout the composite structure layup when aluminum is used for the EMF layer, where higher displacements are associated with an increased risk for developing cracks. The higher displacement is easiest to observe in the bottom plots, which show displacement ratios for each EMF height.

 

Effect of varying the EMF height on displacement in each layer of the surface protection scheme. Copyright © Boeing.

 

The larger displacements caused by the aluminum EMF can be attributed in part to its higher CTE when compared with copper, which exemplifies how important the properties of materials are to the thermal stability of the aircraft composite structures.

 

In the early design stages and along with experimental testing, multiphysics simulation offers a reliable means to evaluate the relative impact of the EMF design parameters on stress and displacement throughout the composite structures. An optimized EMF design is essential to minimizing the risk of crack formation in the composite surface protection scheme, which reduces maintenance costs and allows the EMF to perform its important protective function of mitigating lightning strike damage.

 

Further Reading

Refer to page 4 of COMSOL News 2014 to read the original article, “Boeing Simulates Thermal Expansion in Composites with Expanded Metal Foil for Lightning Strike Protection of Aircraft Structures”.

 

This article was based on the following publicly available resources from Boeing:

• The Boeing Company. “787 Advanced Composite Design.” 2008-2013.
  
• J.D. Morgan, R.B. Greegor, P.K. Ackerman, Q.N. Le, “Thermal Simulation and Testing of Expanded Metal Foils Used for Lightning Protection of Composite Aircraft Structures,” SAE Int. J. Aerosp. 6(2):371-377, 2013, doi:10.4271/2013-01-2132.
  
• R.B. Greegor, J.D. Morgan, Q.N. Le, P.K. Ackerman, “Finite Element Modeling and Testing of Expanded Metal Foils Used for Lightning Protection of Composite Aircraft Structures,” Proceedings of 2013 ICOLSE Conference; Seattle, WA, September 18-20, 2013.
  

https://www.comsol.co.in/blogs/protecting-aircraft-composites-from-lightning-strike-damage/

Edited June 15, 2015 by AdamSmith

[AdamSmith]

#3...What the fuck?

 

P.S. Fasteners in manufactured products never get the glory until they are the cause of failure. For example the Titanic's steel hull plates were calculated to have a certain strength and stiffness, but the iron rivets holding them together became brittle and fracture-prone much sooner in the supercooled water of the north Atlantic.

 

In Weak Rivets, a Possible Key to Titanic’s Doom

http://graphics8.nytimes.com/images/2008/04/14/science/14titanic-600.jpg

Smithsonian

Titanic, left, and Olympic sit next to one another in a double gantry while under construction. More Photos >

 

By WILLIAM J. BROAD

Published: April 15, 2008

The New York Times

 

Researchers have discovered that the builder of the Titanic struggled for years to obtain enough good rivets and riveters and ultimately settled on faulty materials that doomed the ship, which sank 96 years ago Tuesday.

 

Multimedia

http://graphics8.nytimes.com/images/2008/04/14/science/041308Titanic-B.JPG

Slide Show

The Weak Link of the Titanic

http://graphics8.nytimes.com/images/2008/04/15/science/15titanic_graph.190.gif

Not So Unsinkable

 

The builder’s own archives, two scientists say, harbor evidence of a deadly mix of low quality rivets and lofty ambition as the builder labored to construct the three biggest ships in the world at once — the Titanic and two sisters, the Olympic and the Britannic.

 

For a decade, the scientists have argued that the storied liner went down fast after hitting an iceberg because the ship’s builder used substandard rivets that popped their heads and let tons of icy seawater rush in. More than 1,500 people died.

 

When the safety of the rivets was first questioned 10 years ago, the builder ignored the accusation and said it did not have an archivist who could address the issue.

 

Now, historians say new evidence uncovered in the archive of the builder, Harland and Wolff, in Belfast, Northern Ireland, settles the argument and finally solves the riddle of one of the most famous sinkings of all time. The company says the findings are deeply flawed.

 

Each of the great ships under construction required three million rivets that acted like glue to hold everything together. In a new book, the scientists say the shortages peaked during the Titanic’s construction.

 

“The board was in crisis mode,” one of the authors, Jennifer Hooper McCarty, who studied the archives, said in an interview. “It was constant stress. Every meeting it was, ‘There’s problems with the rivets and we need to hire more people.’ ”

 

Apart from the archives, the team gleaned clues from 48 rivets recovered from the hulk of the Titanic, modern tests and computer simulations. They also compared metal from the Titanic with other metals from the same era, and looked at documentation about what engineers and shipbuilders of that era considered state of the art.

 

The scientists say the troubles began when its ambitious building plans forced Harland and Wolff to reach beyond its usual suppliers of rivet iron and include smaller forges, as disclosed in company and British government papers. Small forges tended to have less skill and experience.

 

Adding to the problem, in buying iron for the Titanic’s rivets, the company ordered No. 3 bar, known as “best” — not No. 4, known as “best-best,” the scientists found. Shipbuilders of the day typically used No. 4 iron for anchors, chains and rivets, they discovered.

 

So the liner, whose name was meant to be synonymous with opulence, in at least one instance relied on cheaper materials.

 

Many of the rivets studied by the scientists — recovered from the Titanic’s resting place two miles down in the North Atlantic by divers over two decades — were found to be riddled with high concentrations of slag. A glassy residue of smelting, slag can make rivets brittle and prone to fracture.

 

“Some material the company bought was not rivet quality,” said the other author of the book, Timothy Foecke of the National Institute of Standards and Technology, a federal agency in Gaithersburg, Md.

 

The company also faced shortages of skilled riveters, the archives showed. Dr. McCarty said that for a half year, from late 1911 to April 1912, when the Titanic set sail, the company’s board discussed the problem at every meeting. For instance, on Oct. 28, 1911, Lord William Pirrie, the company’s chairman, expressed concern over the lack of riveters and called for new hiring efforts.

 

In their research, the scientists, who are metallurgists, found that good riveting took great skill. The iron had to be heated to a precise cherry red color and beaten by the right combination of hammer blows. Mediocre work could hide problems.

 

“Hand riveting was tricky,” said Dr. McCarty, whose doctoral thesis at Johns Hopkins University analyzed the Titanic’s rivets.

 

Steel beckoned as a solution. Shipbuilders of the day were moving from iron to steel rivets, which were stronger. And machines could install them, improving workmanship.

 

The rival Cunard line, the scientists found, had switched to steel rivets years before, using them, for instance, throughout the Lusitania.

 

The scientists discovered that Harland and Wolff also used steel rivets — but only on the Titanic’s central hull, where stresses were expected to be greatest. Iron rivets were chosen for the stern and bow.

 

And the bow, as fate would have it, is where the iceberg struck. Studies of the wreck show that six seams opened up in the ship’s bow plates. And the damage, Dr. Foecke noted, “ends close to where the rivets transition from iron to steel.”

 

The scientists argue that better rivets would have probably kept the Titanic afloat long enough for rescuers to arrive before the icy plunge, saving hundreds of lives.

 

The researchers make their case, and detail their archive findings, in “What Really Sank the Titanic” (Citadel Press).

 

Reactions run from anger to admiration. James Alexander Carlisle, whose grandfather was a Titanic riveter, has bluntly denounced the rivet theory on his Web site. “No way!” Mr. Carlisle writes.

Cont...