Windshield wipers and panel adhesives.

[mabbott74]

Hello fellow enthusiasts. I have a couple of questions. First does anyone recognize the windshield wiper in the picture? I need to locate some parts if at all possible. Next question. Has anyone successfully used automotive bonding epoxy to attach the Breeze hood hinge plate or the hidden trunk hinge to the deck lids rather than fiberglassing them?

Windshield Wiper 1.jpg

[PaulProe]

Without looking very close at the numbers, that is a modern day Lucas 14w wiper motor. Wheelbox is also Lucas style. Can't tell manufacturer or the pitch of the drive gear.

You can get parts at https://prdcrrct.com/product-category/wiper/

Paul

[mikeinatlanta]

FFR uses vinylester resin in their laminates. Epoxies and vinylester don't play well together. I won't get into the chemical reasons but suffice it to say that they have bond and curing issues in anyting less than lab perfect conditions. As a result, you cannot judge the bond strength based on any figures shown in the data sheets.

Next issue is the Achillies heel of epoxy bonding. When bonding two surfaces with either no flex or same flex characteristics epoxy does well. When bonding one very rigid surface to one flexible, as in the case of a steel part to fiberglass, epoxy will suffer from poor peel strength and have a reduced bond life.

You might get away with it, but then again you might not. I suggest not going there. If you do want to use a bonding agent to bond steel to vinylester fiberglass I suggest using a urethane adhesive. Urethane adhesives are what both automotive and aerospace use to bond brackets and such to fiber reinforced plastics. 3M makes some good product for this.

[mikeinatlanta]

m, That W/S wiper looks like a Lucas to me. In my experience Lucas lives up to their reputation.
I use a lot of Pliogrip and 3M panel bonder which is an epoxy base. I designed and fabricated aluminum mounts to secure an ECU box and did a test comparison of adhesives because the box was an injection molded cross linked polymer. Pliogrip out performed everything else.
Fiberglass as discussed on this forum is typically polyester or vinyl ester which has weaker structural physical properties and tensile strength than epoxy.
I have filled voids and made support patches with Pliogrip and glass cloth. Surfaces must be roughed-up and clean.
I have not bonded the parts you are working with, surface area is important, bigger is better.
jim

As an FYI: Pliogrip is a sub brand. Like 3M, they also make a range of automotive adhesives in urethane, epoxy, and acrylic base. Pretty sure they also recommend using one of their urethane products when bonding steel brackets to fiberglass. Their epoxies have the same issues with vinylester that all epoxies do.

[mikeinatlanta]

Jim,
Problems arise when free amines from the epoxy inhibit cure of vinylester. Typically the epoxy bonds ok to the vinylester, but any future vinylester repairs may have a fail to cure and will most likely have an inferior bond. Also, as the vinylester body hasn't been through a full post cure cook, it's not fully cured and bond durability may be an issue.

It's not really an epoxy vs vinlyester debate. The vinylester body is a given, so any subsequent products need to be best match for the current configuration.

One small correction to what you posted. Ashland's Pliogrip is not a single product. It is a product family that includes epoxies, urethanes, and acrylics. Would bet that if you contacted their product support and requested best material to bond metal bracketry to any type of frp they would recommend a urethane.

Ultimate bond strength for testing in short term is not indicative of long term bond durability. A lesson aviation learned the hard way. If you follow the engineering you will see that Boeing, Lockheed, Airbus, etc. all bond metal brackets and such to composite with urethanes. GM uses urethane based adhesives to bond brackets and such to the Corvette's composite parts while using epoxies for bonding most everything else. I agree that we should trust what the engineers have learned.

EDIT: A related example of this is the current common aftermarket carbon fiber drive shaft. New they show huge strength on a dyno and will normally self destruct before the epoxy in the aluminum yoke to carbon tube bond fails fails. However: Over time the different flex charictaristics of the yoke and tube cause the bond to fail at seemingly random times. Every racer I know has stopped using the carbon shafts. There were other contributing factors such as lack of electrical isolation, but the flex issues are the primary culprit for durability. Strongest isn't neccessarily most durable.

[mikeinatlanta]

Mike, My body shop supply offers brand name Pliogrip in epoxy only. The instruction sheet details application to aluminum, bare steel, E-coat, SMC/Fiberglass, Metton/DCPD. The only options are (working time) Panel 30, Panel 60, Panel 90 and 5770 Impact Structural (90). 5770 is for Strut Towers and rear body panels, frame rail assemblies and other structural joints. https://crestauto.com/shop/dual-cart...liogrip-5770p/

Another empirical example was a 1989 C4 Corvette I bought as a donor for my Avanti project. It was priced low due to minor RF body damage. When the interior came out I discovered SMC broken under the pedals and around the transmission tunnel. Some DIY repair included sheet metal, screws and polyester/fiberglass mat. All the SMC breaks had re-fractured. I have not found any caveats about aging issues with epoxy application guides.

As you likely know carbon fiber uses epoxy resins, including aircraft parts. I am not aware of polyester or vinyl ester utilized with carbon fiber. Like any technical application it must be developed to meet the requirement.
jim

Carbon fiber uses any resin, same as glass.

EDIT: To be fair and in the interest of full disclosure, I wrote the book on composite repair.

[mabbott74]

Carbon fiber uses any resin, same as glass.

EDIT: To be fair and in the interest of full disclosure, I wrote the book on composite repair.

You may have written a book but did you 'Google it'? LOL. Thanks for the info. Several people including Mark at Breeze suggested attaching it with 3M HSRF.

[mikeinatlanta]

You may have written a book but did you 'Google it'? LOL. Thanks for the info. Several people including Mark at Breeze suggested attaching it with 3M HSRF.

I mix my own equivalent of HSRF and use it as well. Great if wanting to build up a pad. Only issue with 3M HSRF is that it uses talc as a filler which I'm not a fan of. I use milled fibers and fumed silica when wanting high strength. 3M HSRF is the only vinylester based and fully compatible with the FFR body reinforced filler on the market that I have seen. I use it for things like building up rolled edges. I have Breeze hinges on my trunk and built up a pad with the equivalent of 3M HSRF, bonded the steel hinge mount to the pad with Scotchweld Urethane, then encapsulated the mount and pad with a layer of fiberglass.

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