The main objective of this research was to quantify the probability of simple linear skull fracture in infants under the age of 6 months when the head contacts a rigid surface at a range of velocities. Probability was quantified by conducting drop tests using the Aprica 2.5 dummy. Other objectives of this study were;​ to develop a methodology that can be used to relate dummy and infant cadaver head impact response;​ to quantify the effects of dummy body orientation on head acceleration biofidelity;​ to identify pediatric head structures that need to be modelled in a child dummy;​ and finally, to identify a child dummy head design which is likely to provide biofidelic head acceleration over a range of impact velocities. Aprica 2.5, a 2.5 kg instrumented infant dummy was dropped from heights of 0.376 m to 3 m onto rigid plates. Isolated head and whole body dummy drop tests were conducted. Dummy head impact response, when appropriately scaled, is very similar to infant cadaver head response for rigid plate contact. Contact velocities in this study ranged from 2.3 m/s to 6.3 m/s. The probability of linear skull fracture ranges from ≤ 5% for contact velocities to ≤ 3 m/s and < 50% for contact velocities ≤ 5.5 m/s. Results confirm the validity of 5% fracture tolerance limit for CRABI – 6M dummy obtained previously through mass and material scaling.

Work presented in this paper indicates that a one-piece moulded dummy head, such as the one in Aprica 2.5 may preserve biofidelity over a range of impact velocities. This work provides insights for FE modelers and dummy designers about the importance of various skull model parameters. Such a dummy design with human like moments of inertia when used in conjunction with a human like head – neck connection may also provide reasonable estimates of infant head angular accelerations.