The kinematic behaviour and responses of Hybrid III 3YO dummy and child human FE model in ISOFIX CRS in frontal impact

摘要

An ISOFIX-attached child restraint system (CRS) implements a simple, rigid and standardised attachment to a vehicle seat compared to the conventional-type CRS attached by a vehicle seat belt. The goal of this research is to investigate the kinematic behaviour and responses of a child restrained by an ISOFIX CRS in frontal impact and to investigate the effect of utilising a force limiter in the top tether of the ISOFIX CRS on reducing injury assessment measures. A finite-element (FE) model of a Hybrid III 3-year-old dummy and a child human model restrained by a five-point harness conventional-type CRS (using a vehicle seat belt for installation) and a five-point harness ISOFIX CRS were developed and validated using frontal sled tests. Since the thoracic region of the spine of the human model is flexible as compared to the Hybrid III dummy model, the contact behaviour of the chin and chest differs between the Hybrid III dummy model and the child human model. This behaviour led to different upper neck forces and moments. The energy absorption efficiency of the CRS harness for the chest was calculated to understand the relation with the chest acceleration levels in various usage conditions. A top-tether force limiter proved to be useful. Particularly, the torso of both the Hybrid III dummy model and the child human FE model showed an upright posture in the ISOFIX CRS with a top-tether force limiter, and the head and chest accelerations and upper neck forces and moments were reduced, although the head excursion increased slightly.