The materials carbon and Kevlar fiber composites have the highest strength to weight ratio. Molded panels and structures are relatively cheap and lightweight to construct and launch.

However, meteoroids are a very real danger in space do to a high potential of catastrophic decompression upon impact. Although composite materials have the highest strength to weight ratios of available materials, they disintegrate upon impact as was discovered during ballistics testing of the YF-22′s wing. Subsequently, one third of the spars were replaced with titanium. This kept the plane structurally able to continue flight.

In space, this would not be enough to prevent decompression. The best materials to prevent penetration would be quite heavy. Think tank armor: depleted uranium, high nickel super-alloys or the titanium alloy Tiadyne 3515 (Titanium 50%, Vanadium 35%, Chromium 15%) which has the highest strength to weight ratio of the metal alloys.

Thermal differential is also a problem and should be considered. The sunny side in space is 200 F and the shady side is 200 F below zero. A temperature differential of 400 F can cause thermal cracking in some otherwise desirable materials. Nickel alloys do quite well with thermal differential.

The conventional terrestrial bearing materials do not work in space. Oils evaporate in the vacuum of space. Graphite bearings depend upon air molecules for lubrication. Metal to metal contact always results in rapid bearing failure with metallic fusion a near certainty. Ceramic bearings with thin films of solid lubricants can be utilized.

It all boils down to levels of protection and probabilities of survival. At $10,000 per kilogram to get things into orbit, one might consider using available resources on your space settlement. If on the moon, for example, tunneling under the surface would be best. The moon itself would then be the most durable, and lightest material.