I mentioned in chat the other day the significant cracks I found in my door panels when removing the interior felt strip. I have debated using two-part epoxy, figerglass and resin, and even a thin metal backing strip to repair. Here are a few photos (lighting isn't too good in some) so you may offer some suggestions.







(I put some epoxy on this already)

First, what is the black material? ABS?

On the cracks:

Anytime you try to repair a crack, you need to V-grind the crack. This exposes virgin material for the repair goo to grip and, it gives you double the surface area for the goo to bond to.

It's almost a guaranteed failure to just put epoxy/resin in a crack.
The repair also needs back up maretial epoxied on but I'll need to know what the black plastic is.

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You could replace. Just don't get caught.

http://www.fullthrottlecorvette.com/8 ... -Panels--Pair-_p_414.html

Bill, I don't know what kind of plastic it is. Any way to determine that?

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Maybe if I had T-Bone money!

I used a Bondo repair kit on mine and it lasted since 1997 when I bought the car, i used the fiberglass mat with the putty and hardener after I had the panel clamped into potion the way i wanted it, the hardener will make it like steel when it is done.

warning, the bondo will smell like a body shop for a week ro so, but it was worth the effort.

I would do something like you are doing with a mesh bandage or screen with epoxy or glass. My wife just calls me a rigger when I try to make repairs like that. I'm with you. Whatever works, and it's in an unseen area. What about patching with another plastic like cut milk jug as a bridge. You can spray it black when finished. These are just my rigging thoughts I'm passing along. I'm well known around home for trying cheap fixes. T-Bone money is better kept in savings.

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When you first posted this in chat, I thought you were talking about the mounting holes in the door itself (fiberglass).

The door pannel is definately not glass, it's plastic.

The least expensive way to determine if it's ABS would be to get some ABS cement at Home D. It's the stuff ised with the black plumbing pipe. Cut a sliver off one of the cracks or somewhere and dab some of the cement on it. It should melt the plastic somewhat before it hardens.
If it does melt, this cement will give you the best repair.

There's a lot of plastic, 2 part automotive adhesives out there but they usually run $35+ per tube,
JB even has a plastic epoxy but I've never seen it in stores - gotta internet it.

What I would do is first take the $6 gamble trying the HD ABS cement. Also mix a tiny bit of your JB and dab it on a clean part of the plastic to see if it holds when cured (probably will).

The repair:
Grind off all the epoxy in the cracks.
V-grind (or sand) the crack edges to about 1/8 in. or so.
Clean all the areas with alcohol of brakeclean on a rag then,
Scuff up anywhere you will be using adhesive.
The cracks should have a backup strip (about 1 in. wide), you can use ABS or aluminum.
I think HD has ABS, the alum - I keep a roll of alum roof flashing in the shop, it's handy.
If you can't get ABS, let me know, I'll mail you some strips.

The crack and the bonding strips must be done at the same time. You may need to put some weight on the bonding strips if the door panel is slightly curved, won't take much weight, just enough to hold the strips. masking tape on the weight will prevent any sticking.

The r/a metal tab - JB - Put a bunch of JB between the metal and the panel. It would be best to lightly clamp it. And you need to use more JB on the 3 edges of the metal piece and into the JB that's squeezing from clamping. This will will give the repair a lot more strength.
Clamping that small part and still getting to the edges will be tricky. You may be able to use a small socket as a standoff to get the clamp head up out of the way. Put masking tape on the socket so that it won't get any adhesive on it.

When I replaced the door window strips, the one panel was almost cracked in half. I went to H.F. and bought a plastic welder, really a glorified soldering iron, that came with the plastic strips, and it turned out great ang strong

I am all for using fibreglass...

When I raced RC Cars, we had these clear bodies made of lexan for the cars. When the lexan broke, we would fix them with epoxy and/or superglue and a small piece of filiment tape. It worked. Very well.

Same type of fix for the leading edges of the chassis, which is also a fibreglass composite.

I like the idea of the plastic welder... just not sure if the materials are all compatible.

The plastic welding strips looked a little different, but when melted looked the same, hell I even used it under the spoiler where the bolt pushed thru on the rubber bumper,sanded smooth, and pushed real hard on it and couldn't get it to break. BTW this is under the spoiler and isn't seeable. Also if I remember right the add did say it was compatible with a lot of different plastics. Just my .02

oh, cool! I will have to check this out then!

You have to spread out past the stress area in order for it to last, bondo is like steel when its done.

X2, that is exactly what I did

Mark, I've been thinking about buying a welder....forever, just never got around to it.

Andy, fiberglass won't bond to ABS, it will stick for a while but it will come off. The door panel is either ABS or very close to ABS.

Larry, regular car Bondo or the Bondo plastic (bumper) repair kit?

Putting bondo on fiberglass mat will make it stronger but so will any kind of mat.
The regular Bondo hardner won't activate fiberglass mat. The mat has a mixture on it that is activated by the combination of the resin and the MEKP activator.

Though, your repair worked and that's all that matters.

BTW, with fiberglass you need to check weither your buying finishing resin or laminating resin. I have both in the shop.

And though Bondo body puddy is well known and sold everywhere, I won't use it on my bodywork.

I used Professional Sno Wite Body Filler Repair kit, I still have the can,, with mat and hardener, its been on since 1997, never had an issue with it not sticking or coming loose, a bondo kit is cheap too.

I sell plastic bonding equipment, i.e. Ultrasonic welders in 20, 30, 40, kHz ( www.dukane.com ) and they sort of weld, really they melt material together, so I guess you could weld a strip over the top, but you would need a tip that has a protrusion on the end of the horn that would penetrate through both materials.

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I've seen ultrasonic, we had them in various research labs. (AMP Inc. - electric/electronic connectors). It's certainly the best way to fuse plastic together.

The home welders are just a soldering iron with a flat tip.
In fact some of the Wen kits come with a tip like that. I've never tried it bacause I didn't have the filler sticks.

I do do my own ski repair with P-Tex sticks that you melt into the gouges in the ski bottoms. I should tru some of that on ABS just for the hell of it.

Thanks a lot guys, some excellent suggestions. I like the idea of pvc cement and a plastic (ie milk jug) backing strip. I guess I have some experimenting to do.

Matthew

It's certainly a cheap experiment - $3.27

Lookin forward to the results.

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I already have pvc cleaner and glue in the garage from various plumbing projects, so my cost for this will be zero if it works.

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Cool, nada to loose.

Remember that PVC glue is different from ABS glue tough,

I know that with some amorphous resins, i.e. ABS PET PAT etc, you can flash the gloss off the surface with a flame and that helps with adhesion, we do this before pad printing parts such as the window up down info, mirror info on your car door panels

melting it back together could work, its worth a try, maybe i got lucky

Depending on how you could camouflage the heads, and the importance of appearance, how about countersunk aluminum pop rivets through the face into a thin sheet metal gusset and glue on the backside?

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If the correct adhesive is used, Joe, the pop rivets would not contribute much to the structural integrity of the repair.
Matt will find out if the PVC stuff works. I know the ABS cement and the JB will work. And I have 2 kinds of 3M structural adhesive in the shop. Incredible stuff, I use it to bond a one piece aluminum belly pan to the bottom of an open wheel racecar. It will hold 20+ years without separating even under race conditions.

Any good resolution on this? I need to repair a crack almost exactly like picture #3.

I'm thinking I saw that JB Plastic Weld at one of the parts stores here, just can't remember!


Thanks
Joel

Unfortunately no updates. I haven't worked on the door panels...been so busy otherwise I haven't had a chance. But looking forward to what you have to say if you try a fix.

I might bring it by my buddy's body shop. I was talking to him last week about a new way they have to fix bumpers that involves adhesive or something like that.

Guess I'm a little late to the party but I'd repair that door pannel with regular old JB WELD...

V the crack out like Bill said and fill it with JB Weld, overlapping some on to the flat surface of both sides.

I use to track a Kawi ZX7R and your going to go down and smash up the plastic on a bike.... I've repaired a ton of plastic with fiberglass, plastic weld and epoxy's and nothing holds up as well as JB weld on cracked injection molded plastics.

It's very easy to work with as well.
Will

Thanks, Will, I will check that out as a viable option.

OK. I went with the regular JB Weld as a test try to check how it would adhere to the plastic. Should cure late on Friday afternoon for a check.
I cleaned the damaged area with brake cleaner, then used 40 grit paper to rough up the smooth surface. Now, JB Weld by itself will not be strong enough to prevent more cracking. I cut some 4 inch long pcs of that thin pipe hanging strap. The cheap kind that's not galvanized.
Applied a thin coat of the JB, then placed the re-enforcement across the crack running the opposite direction. Applied more JB to cover the area good, set aside to cure.
Will report back for results.

Joel

OK, here are my results. The areas I used JB on did adhere very well. I actually flexed the panel slightly and it looked good, no signs of any cracking around the edges.

With the re-enforcement strips and the JB I'm satisfied this will work on this type of plastic damage repair.

Gotta be clean and the surface needs to be rough!

Joel

I have some pictures of my door panel repair on my home pc. I carefully fabricated a C channel out of aluminum and riveted it to reconstruct the top edge of the plastic.

VERY solid. But it was tedious as hell to do. The door though is slowly disintegrating around it, I've had it off many times. Next time in there it may be time to get out the checkbook.

I got lucky on mine, the top channel was still solid. Mine was split down the middle, like Mat's #3 picture.
I would like to see your repair, just in case!


Joel