Does the chassis get weak over time?

[MotorMo]

Having a hard time finding information about how a cars chassis gets weaker over the span of its life time.
My reasoning for this question is this- some chassis flex is normal, but when tracking the car the chassis will flex alot more than casual driving. Over time, can this flexing cause a weaker chassis? Or as long as the welds hold up, the integrity of the chassis will remain as sturdy as the day it was made.
I currently have an EJ6 hatch that I'm going to be Auto crossing this season.
I am running an EK9 rear sway bar and a DC2 front sway bar in my EJ6 hatch with coil overs. My thought was to not add "strut towers bars" until after feeling how the car handles with out them to further tune my suspension.
But my fear is that this can damage my chassis. After all, if a piece of sheet metal is bent back and forth it gets weaker....
I'm open to any info on this subject. Thanks in advance.

 

[MotorMo]

Bump-
Two seasons ago I ran a 24mm front sway bar (GSR) and a 22mm rear sway bar (ITR) on a 94 civic with F+F type 2 suspension. The cars chassis was already beat badly from previous owners lowering the crap out of it. So I wasn't too worried about doing any chassis damage when I raced that season. The car already had alot of creaks. But it handled super good, as well as I loved the "rotation" with that combo.

 

[HeX]

I'm no expert on the subject so I'll state what I'm aware of. Civics are relatively lightweight which shouldn't put significant strain on the frame unless the engine was really powerful, which is hardly the case with Civics unless its a very high end custom power build. Crappy suspension or aggressive driving tends to put more of a strain on the bolted on arms, bushings and bolts than the frame itself which is designed to have some level of flex but not enough to create excessive bend to stretch and weaken metal. Sway bars are technically more to tighten suspension feel and steering control. We have plenty of member far better versed at this than I, so wait for their input as well. For AutoCross I'd be more concerned with control arms, bushings and great quality struts & springs than frame bend. Just make sure the car hasn't experienced any frame altering accidents. With that said, a straightened frame is definitely weakened because structure was compromised.

 

[MotorMo]

I'm no expert on the subject so I'll state what I'm aware of. Civics are relatively lightweight which shouldn't put significant strain on the frame unless the engine was really powerful, which is hardly the case with Civics unless its a very high end custom power build. Crappy suspension or aggressive driving tends to put more of a strain on the bolted on arms, bushings and bolts than the frame itself which is designed to have some level of flex but not enough to create excessive bend to stretch and weaken metal. Sway bars are technically more to tighten suspension feel and steering control. We have plenty of member far better versed at this than I, so wait for their input as well. For AutoCross I'd be more concerned with control arms, bushings and great quality struts & springs than frame bend. Just make sure the car hasn't experienced any frame altering accidents. With that said, a straightened frame is definitely weakened because structure was compromised.

Thanks for your time and input. The current car is straight and has no damage. I just replace all front LCA bushings, ans replaced the UCA's with some quality after market units. Currently running on Koni yellows and GC's. I appreciate your input. And I hear what your saying- The chassis is designed to flex a bit to allow the bushings and other suspension to receive the main stress load.