[upofadown]

The helmet shattered. In other words it failed. No significant amount of energy was absorbed.

There was blood so it didn't even protect you from abrasions. A construction type hard hat would of provided more protection.

[jschwartzi]

If the helmet shattered, then a significant amount of energy was absorbed. Otherwise it wouldn't have shattered.

[upofadown]

The propagation of cracks results in a very minimal amount of energy absorption.