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

GFRP Composite Tear Out and Bearing Strength?

GFRP Composite Tear Out and Bearing Strength?

GFRP Composite Tear Out and Bearing Strength?

I have a bolt going through 3 composite layers loaded in double shear. I need to know the GFRP tear out strength and bearing strength to verify the integrity. Does anyone have any advice/applicable standards to calculate bearing strength and/or tear out strength? How does this usually relate to tensile strength etc.? higher, lower?

RE: GFRP Composite Tear Out and Bearing Strength?

Short answer: you can’t calculate those strengths; need specific joint test data.

Neither is related to tensile strength. Tear out is a shear failure mode. Bearing is sort of a complicated compression failure mode.

Design with large edge margin (e/D = 3+) and you are unlikely to fail in tear out before bearing.

Bearing strength in double shear is usually greater than laminate compression strength.

RE: GFRP Composite Tear Out and Bearing Strength?

Thanks for all your responses SW composites.

Apologies for the double posting - new to the forum and wasnt sur on the rules!

RE: GFRP Composite Tear Out and Bearing Strength?

If it's a single pin joint with composite lugs, strongly recommend test validation. Consider that in metallic pin hoints, sizing methods are usually empirical (eg melcon, cozzone, hoblit) given the complexity of stress state and failure modes. You're adding to this the complexity of composite mayerial failure modes.
Also watch your pin diameter selection, might be a little more susceptible to pin bending failure than a metallic joint, that said being gfrp the laminate is by far likely to be critical.
In metals Ftu can be a conservative preliminary estimate of Fbru, however I wouldnt advise that as a general approach for composites.

RE: GFRP Composite Tear Out and Bearing Strength?

Hi Ng2020. If i understand you correctly - your opinion is that the composite being GFRP, its likely to be quite strong compared to the pin? The pin goes through very thick sections of composite. Two outers being 60mm and the inner bein 80mm.

Apologies for my ignorance - composites are a new area for me in terms of structural engineering.

RE: GFRP Composite Tear Out and Bearing Strength?

Actually I was initially assuming that your laminates would be quite thin and probably less capable than the pin. However those are quite substantial. Make sure you do a pin bending check to ensure you choose the right pin size and material. Keep it simple and choose a conservative moment arm: the laminate will be quite soft so you would be best to conservatively assume a uniform load diatribution through the thickness of the laminate.
I think there's a reasonable example (though nore complex) for a metallic pin joint in the USAF stress manual (google it)

RE: GFRP Composite Tear Out and Bearing Strength?

Please pist a sketch of your joint for clarity. I've seen some of your other posts and now I'm confused about the configuration you're talking about.

RE: GFRP Composite Tear Out and Bearing Strength?


Please note the 3 layers/plates are all different sections of GFRP in which the outer and inner layer are connected to one component and the middle layer is connected to another so the bonding between sections is prone to debonding when the outer and inners are pulled relative to the centre layer.

RE: GFRP Composite Tear Out and Bearing Strength?

That pin looks way too skinny for those thicknesses.

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


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