Date of Award

2008

Publication Type

Doctoral Thesis

Degree Name

Ph.D.

Department

Mechanical, Automotive, and Materials Engineering

Keywords

Applied sciences, Crash injuries, Head and neck injuries, Side impact crashes, Toddlers, Vehicle crashes

Supervisor

William Altenhof

Rights

info:eu-repo/semantics/openAccess

Abstract

This research focuses on methods to reduce injuries, specifically in the head and neck region, sustained by children seated in forward facing child restraint system during a vehicle crash. Three standardized experimental tests were considered in this research for the purpose of model validation and to quantify the injury potential sustained by children in a crash: (i) frontal dynamic sled tests were completed in accordance with FMVSS 213 using a Hybrid III 3-year-old dummy in a five point restraint system, (ii) full frontal vehicle crash test was completed in accordance with the CMVSS 208 with a Hybrid III 3-year-old child dummy, seated behind the passenger seat, restrained in five-point restraint system, and (iii) side impact dynamic sled tests in the presence of a rigid wall and absence of a vehicle body (near side configuration) were conducted by NHTSA using a Hybrid III 3-year-old child dummy seated in a convertible forward/rearward child safety seat. A finite element model of the child restraint seat was developed utilizing CAD data provided by Century/Graco Corporation. Material tests were conducted to obtain the nonlinear material properties of the CRS polypropylene, child seatbelt webbing, and polymeric foams. Numerical simulations were conducted using LS-DYNA, and the simulation results of the frontal and side impact tests were observed to be in a good agreement to the experimental findings. An average percentage error of approximately 20 percent was observed between the numerical and experimental data.

Different countermeasures were investigated to mitigate the head and neck injury potential in frontal and side impact crashes. These methods involved numerical studies utilizing a Hybrid III 3-year-old dummy, Q3/Q3s dummies and a child FE model. Load limiting behaviour into the upper tether and lower LATCH anchors of the CRS in order to reduce the neck injury criteria by increasing forward head excursion in a frontal crash was first examined. It was observed that the implementation of load limiting behaviour in the CRS tethers was effective in reducing the head and neck injury criteria by approximately 60 percent and 35 percent respectively. Secondly, a head and neck restraining device was developed to limit the amount of neck rotation in the dummy's head. A reduction of approximately 50 to 60 percent was observed in the head and neck injury potential in the presence of the head and neck restraining device. Finally, numerical simulations were completed with rectangular and cross-shaped sections of rigid ISOFIX systems for better side impact protection. In addition, studies were conducted to confine lateral movement of the dummy's head by incorporating energy absorbing foam on the side wings in the vicinity of the contact region of the CRS. It was observed that the use of the rigid ISOFIX system reduced the lateral displacement of the CRS and different injury parameters. Addition of energy absorbing foam blocks was effective in further reducing the lateral displacement of the dummy's head by approximately 50 to 60 mm.

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