Experimental evaluation of hard hat performance during impacts to a forward-flexed head.

Traumatic brain injuries frequently occur in the construction industry when workers are struck with their heads in a forward-flexed position. Hard hats, the primary form of protection against such events, may not be optimized for these forward-flexed impacts since certification testing is performed with a head form in an upright configuration. In response, this study assesses the impact mitigation of six commercially available hard hats when subjected to impacts in different head orientations - upright and with 30° of forward flexion. Impactors with a mass of 3.6 kg were dropped vertically onto a Hybrid III 50th percentile head/neck form. Kinematic outcomes related to TBI (e.g. accelerations) were compared across impact conditions. Results indicated that impacts to the forward-flexed head resulted in the largest angular accelerations, and hard hats were the least effective at mitigating angular accelerations in this head position. Furthermore, correlation analysis indicated that hard hats that performed well in upright testing often performed poorly in forward-flexed conditions (or vice versa). Taken together, these results suggest consumers/employers are not equipped with the necessary information to select the safest products for all impact conditions based on safety certification results using upright testing alone.