Optimisation of framed child restraints
This thesis documents a study into the effects of various parameters on the performance of Framed Child Seats (FCS) for automobiles. The work investigated the effect of three different sets of parameters: FCS design parameters, vehicle design parameters and occupant biomechanical parameters. The work was conducted at Middlesex University using a combination of experimental crash testing and computerised crash simulations. The experimental crash tests were conducted using the Road Safety Engineering Laboratory, Middlesex University impact test rig and the computerised simulations were conducted using MADYM03D software. The performance of the FCS configuration was assessed in terms of the potential injury to a child occupant in a 50 km/h frontal impact to ECE R44 test specification. All the FCS design parameters examined were shown to have a potential effect on the performance of the FCS. In particular FCS footprint area was shown in the experimental tests to have a significant affect on the performance. A large flat footprint was observed to reduce chest acceleration by 33%, although this was at the expense of a large increase in forward head excursion. Various vehicle design parameters were shown, by MADYM03D simulation, to have a considerable affect on FCS performance. A standardised semi-rigid or rigid anchorage system is recommended to overcome such problems in real vehicles. The biomechanical work was largely based around the potential for injury to the occupant's neck. An improved MADYM03D representation of the dummy neck was developed for this work and several factors were examined. Chin-chest contact, head mass and neck fulcrum for bending were all shown to have a potential affect on the likelihood of injury. Limitations of both experimental crash testing and computerised simulations were identified during this work and are discussed in this thesis.