×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Why is unidirectional tape(cfrp) difficult to process?
2

Why is unidirectional tape(cfrp) difficult to process?

Why is unidirectional tape(cfrp) difficult to process?

(OP)
Why is unidirectional tape(cfrp) drilling layered?

RE: Why is unidirectional tape(cfrp) difficult to process?

Huh? Please add a lot more details about your issue and materials.

RE: Why is unidirectional tape(cfrp) difficult to process?

2
I guess Eton is asking why it is difficult to cleanly drill holes in composite parts made from unidirectional tape.

Composites are similar to wood in that it has fibers that are oriented in one direction. These fibers are stronger than the glue that holds the fibers together. So, while cutting or drilling, it important that the cutting tool does not snag fibers, which results in their being peeled out for some distance away from the cut. Carbon and glass fibers are far stronger and more and more collimnated than wood fibers so the so peel-out and splintering are a more significant problem.

In woven composites the fiber bundles cross over and under every few mm, which stops any further peeling. This makes the issue less noticeable. In unidirectional composites it is easy to peel-out slivers of fiber from the composite surface that are over a foot long. Thus it critical to make very clean cuts to avoid getting any fiber peeling started.

Delamination on the backside is also a major problem when drilling composite materials, and a backup plate is almost always required. There are special geometries used on tool cutting edges for composites (very sharp) to allow the fibers to be cut with a force that is low enough to avoid debonding the fiber from its matrix.

RE: Why is unidirectional tape(cfrp) difficult to process?

Wow. What a great reply to a sub-optimally posed question.

RE: Why is unidirectional tape(cfrp) difficult to process?

Well, with proper drill bits, speeds, feed rates and backing, drilling uni tape composites is not difficult. Its done everyday by many companies.

RE: Why is unidirectional tape(cfrp) difficult to process?

(OP)
Thank you for Compositepro’s reply; We tried several different PCD drill tip configurations, and the drilling results were not ideal; the original low modulus carbon fiber can achieve perfect drilling, but it is not suitable for high modulus; I doubt it is The bore shrunk during machining, or the tooling didn't fit it well. In addition, the life of its perfect drilling is not ideal, and the life is also poor.

Sorry, my question description is very general; my specific question is that when drilling carbon fiber unidirectional tape, the sheet is extremely prone to delamination

RE: Why is unidirectional tape(cfrp) difficult to process?

Are you getting delams on the drill entry or exit side? If exit, are you using a backing plate?

What is the fiber modulus for “high modulus”?

RE: Why is unidirectional tape(cfrp) difficult to process?

Which [rotary] drilling process are You really concerned about: hand or automated or intermixed?

OBVIOUSLY automated conventional rotary drilling processes can be developed to attain/maintain high levels of quality/consistency among all structural mixes, 100% composite/multi-composites and any level of composites mixed with metals.

Hand-drilling composites can get sketchy without loads of training and proper tools/tooling.

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: Why is unidirectional tape(cfrp) difficult to process?

Is water jet cutting an option?

RE: Why is unidirectional tape(cfrp) difficult to process?

Waterjet may be useful for edge and large holes [lightening/pass-thru]… but not fastener holes. However laminate thicknesses for clean cutting is likely to be limited. Controlling edge-fraying is critical.

Water-jet works well with most thickness of 'flat' aluminum honeycomb panels with aluminum or composite core.

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: Why is unidirectional tape(cfrp) difficult to process?

IFRs, I worked at an composite experimental GA company for a couple of years. The airplane was mostly carbon fiber but had some fiberglass. We tried using the water jet machine to cut fiberglass but quickly eliminated it as a possibility because it created delaminations emanating radially from the jet stream. For example, if we tried to cut a Ø.5 hole in a piece of fiberglass that was 10 plies thick, we would get a circular-shaped area of delamination with a diameter of 1.0-1.5 inches. As the water/garnet stream is moving along it tries to find an escape path and ends up forcing its way between plies creating delams. As I recall, they/we didn't try it out on carbon fiber because we were concerned the same thing would happen. It was easy to visually see the delams in the fiberglass because the delam area was a different shade of tan than the intact fiberglass. We were worried with the carbon fiber we may not be able to detect the damage so didn't even try it and ruled it out as a cutting method.

RE: Why is unidirectional tape(cfrp) difficult to process?

(OP)
I didn't expect a lot of replies, thank you for your active participation.

The drill is used on the cnc, and if you switch to the back of the material immediately, delamination will occur.
As for Stephan Nelle's reply, you can try the pcd drill bit, we have tested it with a large diameter, and the effect is ok (this should not be considered an advertisement, emmm)

RE: Why is unidirectional tape(cfrp) difficult to process?

Perhaps drill on both sides slowly so you don´t get breakout on the farside. If you are getting delmamination in general there is too much heat and speed in drilling.

RE: Why is unidirectional tape(cfrp) difficult to process?

I would expect poor results with a drill - as the cutting edge comes perpendicular to the fibers it will no longer be cutting them but prying them up in a way that they are very strong compared to the matrix/resin ability to hold them. Once loose they are pushed clear leaving shards around the hole.

In wood and thin sheetmetal the same prying action can take place and is far worse on the far side as the pressure of the advancing drill tend to delaminate it even before the cutting edge can get there making a huge mess.

Of course this is what Composite Pro said - just repeated for emphasis.

So, with that in mind, I would look at diamond dust coated grinders to at least start on the the initial layers - like a countersink or a dent. This way the upper layers of the composite, now out of the way with some small clearance and not seeing peeling forces, can act as a local backer for the lower layers.

Same relief is done on hand planing end grain in wood to keep a chunk from splintering - put a chamfer where the cutting edge leaves the material so that there is support right there.

Here's an example of a backer for wood cutting: https://youtu.be/IwaMcUFbvBU?t=103

But it would also work to have a chamfer where the backer is that is deeper than the cut so the edge of the board never sees a cutting load - the required depth of the chamfer will depend on how much support is needed. I tried to find a better video or picture but everyone is concerned about tearout from the chamfer on the endgrain - which, if you start with the diamond dust coated grinder you won't have.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close