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The majority of car crash deaths occur in the front seats because the majority of occupants sit in the front seats. Traditionally, the rear seats were safer than the front seats because a front seated occupant would be closer to rigid structures such as the steering wheel, and they would be closer to the location of the impact. Therefore, government crash test regulations as well as academic and industry testing up to this point have principally focused on the front seats. Since the beginning of efforts to make cars safer, innovations were applied to the front seats first. Only some of these safety innovations have transitioned into the rear seats. Over the years, the front seats have gotten much safer due to advanced seatbelts with pretentioners and load limiters, airbags surrounding the driver, and structural changes to the vehicle frame to prevent intrusion into the occupant compartment. At the same time, occupant safety in the rear seats has also improved, however at only a fraction of the improvement of the front seats. With modern vehicles, the front seats have actually become safer than the rear seats for certain occupants and specific crash types (e.g., adult occupants in frontal crash). The lagging performance of the rear seats represents a problem because thousands of rear-seated occupants are injured or killed each year. With the rise in autonomous driving systems, the amount of occupants sitting in the rear seats, and therefore sustaining injury, could increase dramatically. In this dissertation, rear seats of a range of current vehicles were reconstructed to examine injury risk with the finite element models of two anthropomorphic test devices. These models showed a wide range of injury risks in the reconstructed seats. They were also able to show results similar to sled impact tests with the same vehicles. Knowledge gained from these reconstructions was then used to perform parametric studies on key variables that influence injury risk in the rear seats. From the parametric studies, it was found that the seat back angle, the width of the seatbelt anchors, and the presence of a seatbelt pretensioner had the largest influences on the injury risk. One of the injury mechanisms prevalent in the rear seats is submarining. Submarining likelihood and injury probability is difficult to predict with anthropomorphic test devices; however, human body models can help to improve injury prediction in these cases. To improve the injury prediction capability of human body models, several additions to the models are necessary. This dissertation outlines the investigation of spleen and kidney shapes through statistical shape analysis. This type of analysis allows more customizable human body models which could better capture the injury probability to these organs for a wider range of the population. Finally, subject-specific models of ribs were created to investigate factors affecting the predictive capability of finite element models. The findings and methodology from this body of work have the ability to add critical contributions to the understanding of injury risk and injury mechanisms in the rear seats. / Doctor of Philosophy / The majority of car crash deaths occur in the front seats because the majority of occupants sit in the front seats. Traditionally, the rear seats were safer than the front seats because a front seated occupant would be closer to hard objects such as the steering wheel, and they would be closer to the location of the impact. Therefore, government crash test regulations as well as academic and industry testing up to this point have principally focused on the front seats. Since the beginning of efforts to make cars safer, technology such as seatbelts and airbags were applied to the front seats first. Only some of this technology has been added into the rear seats. Over the years, the front seats have gotten much safer due to all the work focused on the front seats. At the same time, the rear seats have also improved, however at only a fraction of the improvement of the front seats. With modern vehicles, the front seats have actually become safer than the rear seats in some cases. The lagging performance of the rear seats represents a problem because thousands of rear-seated occupants are injured or killed each year. With the rise in self driving cars, the amount of occupants sitting in the rear seats, and therefore sustaining injury, could increase dramatically. In this dissertation, rear seats of a range of current vehicles were reconstructed to examine injury risk with the models of two crash test dummies. These models showed a wide range of injury risks in the reconstructed seats. They were also able to show results similar to physical tests with the same vehicles. Knowledge gained from this work was then used to help look at key variables that influence injury risk in the rear seats. It was found that the angle of the seat back, the width of the seatbelt anchors, and the presence of advanced seatbelts had the largest influences on the injury risk. One of the injury mechanisms prevalent in the rear seats is submarining, where the seatbelt slides up off the hips. Submarining likelihood and injury probability is difficult to predict with crash test dummies; however, human body models can help to improve injury prediction in these cases. To improve the injury prediction capability of human body models, several additions to the models are necessary. This dissertation outlines the investigation of spleen and kidney shapes to allow more customizable human body models which could better capture the injury probability to these organs for a wider range of the population. Finally, subject-specific models of ribs were created to investigate factors affecting the predictive capability of rib models. The findings and methodology from this body of work have the ability to add critical contributions to the understanding of injury risk and injury mechanisms in the rear seats.

In the United States, motor vehicle crashes are one of the leading causes of unintentional injury death and disability for children ages 1'15 years. Despite local, state, and federal legislative and educational efforts, children continue to be restrained improperly and thus face harm. Identifying behaviors and barriers that place child occupants at risk is crucial for implementing focused, injury-prevention programs and policies. The purpose of this study was to evaluate the effectiveness of Connecticut's child passenger safety law that was strengthened in 2005. This study involved a multifactorial approach to predicting child seat use, guided by Roger's diffusion of innovations as the theoretical framework. The analysis determined if there was a difference in the prevalence of car seat use before as compared to after law implementation and identified variables that best predicted the use of car seats and premature transition to a seat belt. Using Connecticut's Crash Data Repository, a logistic regression analysis indicated that car seat use was 1.3 times more likely post law (OR 0.75; 95% CI: 0.65-0.86) and that in particular, children ages 4, 5, and 6 (combined) were most positively affected by the law (OR 0.67; 95% CI 0.54-0.82). Driver sex, crash time of day, child age, and child seating position were all determined to be significant predictors of whether or not a child was in a child safety seat. Additionally, these variables were also determined to be predictors of early transition to use of a lap/shoulder belt (versus child seat). The social change implication of this study is that identifying predictors of car seat use and early transition helps to formulate and implement injury prevention measures that could in turn help to decrease medical costs, save lives, and prevent injuries.

O objetivo deste trabalho é mostrar a aplicação de reforços estruturais pré-moldados utilizando o material polimérico PA66 através de simulações em elementos finitos na área de segurança veicular. Os reforços estruturais pré-moldados têm mostrado bom desempenho em testes de impacto, onde a grande vantagem está em seu reduzido peso. Estes reforços são projetados com o intuito de aumentar a rigidez das regiões que estão sujeitas a grandes deformações, estabilizando as seções do veículo que trabalham como caminho de carga durante o impacto. Inicialmente, foram executados testes estáticos e dinâmicos para caracterizar o material PA66, que foi utilizado nas simulações. Os casos de impacto estudados foram aqueles que serão adotados pelo CONTRAN em 2012 e já são adotados por outras normas de grande importância para a segurança do ocupante, como a ECE-R94, ECE-R12, ECE-R95, ECE-R32/34 e a FMVSS216. As simulações executadas no software LS-Dyna ® e MADYMO ® com a aplicação do reforço mostraram, no caso do impacto frontal na configuração ODB a 57km/h, uma redução de 70% na deformação da coluna A, bem como uma redução de 65% na deformação da coluna de direção e uma redução de, aproximadamente, 59% na região das pernas e pés do ocupante. O nível de lesões do ocupante pôde ser avaliado através do software MADYMO ® , e foi possível verificar uma redução de 23,5% na compressão do peito, 80% de compressão na tíbia, o que levaria o ocupante do veículo com este tipo de reforços sair ileso de uma colisão nas condições da norma. A aplicação dos reforços no impacto lateral possibilitou uma redução de 13,8m/s para 10,6m/s na velocidade de deformação da coluna B na região das costelas do dummy e houve um ganho de 140mm de espaço residual. Os reforços adotados para o impacto frontal e lateral proporcionaram um aumento de 47,5% de força de colapso da estrutura superior, segundo a norma FMVSS216. / The objective of this work is to show the application of structural reinforcements using the polymeric material PA66 through finite element simulations in the field of vehicle safety. The preformed structural reinforcements have shown good performance in crash tests, where the great advantage is their reduced weight. These reinforcements are designed with the aim of increasing the rigidity of regions which are prone to large deformations, stabilizing sections of the vehicle that works as load path during the impact. Initially, static and dynamic tests were performed to characterize the material PA66, which was used in the simulations. The impact cases studied were those which will be adopted by CONTRAN in 2012 and already adopted by other standards of great importance for the occupant safety, such as ECE-R94, ECE-R12, ECE-R95, ECE-R32/34 and FMVSS216. The simulations performed in the software LS-Dyna ® and MADYMO ® considering the application of reinforcements in the case of frontal impact regarding ODB at 57km/h configuration, resulted in 70% reduction in the A pillar deformation and 65% in the deformation of the steering column and a reduction of approximately 59% in the occupant\'s legs and feet region. The occupant\'s injury level were assessed by MADYMO ® software, and a reduction of 23.5% in the chest compression and 80% in the tibia compression were verified. Such conditions lead the safety of an occupant of the vehicle with reinforcements in a collision event according to the standard. The application of reinforcements on side impact load case contributed to reduce the B pillar velocity at the dummy\'s ribs region from 13.8 m/s to 10.6 m/s and there was a gain of 140mm of B pillar residual space. Reinforcements adopted for the front and side impact load cases provided an increase of 47.5% in the upper structure crush force, according to FMVSS216 standard.

The Rollover of heavy vehicles operating in the construction, mining and agricultural sectors is a common occurrence that may result in death or severe injury for the vehicle occupants. Safety frames called ROPS (Rollover Protective Structures) that enclose the vehicle cabin, have been used by heavy vehicle manufacturers to provide protection to vehicle occupants during rollover accidents. The design of a ROPS requires that a dual criteria be fulfilled that ensures that the ROPS has sufficient stiffness to offer protection, whilst possessing an appropriate level of flexibility to absorb some or most of the impact energy during a roll. Over the last four decades significant research has been performed on these types of safety devices which has resulted in the generation of performance standards that may be used to assess the adequacy of a ROPS design for a particular vehicle type. At present these performance standards require that destructive full scale testing methods be used to assess the adequacy of a ROPS. This method of ROPS certification can be extremely expensive given the size and weight of many vehicles that operate in these sectors. The use of analytical methods to assess the performance of a ROPS is currently prohibited by these standards. Reasons for this are attributed to a lack of available fundamental research information on the nonlinear inelastic response of safety frame structures such as this. The main aim of this project was to therefore generate fundamental research information on the nonlinear response behaviour of ROPS subjected to both static and dynamic loading conditions that could be used to contribute towards the development of an efficient analytical design procedure that may lessen the need for destructive full scale testing. In addition to this, the project also aspired to develop methods for promoting increased levels of operator safety during vehicle rollover through enhancing the level of energy absorbed by the ROPS. The methods used to fulfil these aims involved the implementation of an extensive analytical modelling program using Finite Element Analysis (FEA) in association with a detailed experimental testing program. From these studies comprehensive research information was developed on both the dynamic impact response and energy absorption capabilities of these types of structures. The established finite element models were then used to extend the investigation further and to carry out parametric studies. Important parameters such as ROPS post stiffness, rollslope inclination and impact duration were identified and their effects quantified. The final stage of the project examined the enhancement of the energy absorption capabilities of a ROPS through the incorporation of a supplementary energy absorbing device within the frame work of the ROPS. The device that was chosen for numerical evaluation was a thin walled tapered tube known as frusta that was designed to crush under a sidewards rollover and hence lessen the energy absorption demand placed upon the ROPS. The inclusion of this device was found to be beneficial in absorbing energy and enhancing the level of safety afforded to the vehicle occupants.

O objetivo deste trabalho é mostrar a aplicação de reforços estruturais pré-moldados utilizando o material polimérico PA66 através de simulações em elementos finitos na área de segurança veicular. Os reforços estruturais pré-moldados têm mostrado bom desempenho em testes de impacto, onde a grande vantagem está em seu reduzido peso. Estes reforços são projetados com o intuito de aumentar a rigidez das regiões que estão sujeitas a grandes deformações, estabilizando as seções do veículo que trabalham como caminho de carga durante o impacto. Inicialmente, foram executados testes estáticos e dinâmicos para caracterizar o material PA66, que foi utilizado nas simulações. Os casos de impacto estudados foram aqueles que serão adotados pelo CONTRAN em 2012 e já são adotados por outras normas de grande importância para a segurança do ocupante, como a ECE-R94, ECE-R12, ECE-R95, ECE-R32/34 e a FMVSS216. As simulações executadas no software LS-Dyna ® e MADYMO ® com a aplicação do reforço mostraram, no caso do impacto frontal na configuração ODB a 57km/h, uma redução de 70% na deformação da coluna A, bem como uma redução de 65% na deformação da coluna de direção e uma redução de, aproximadamente, 59% na região das pernas e pés do ocupante. O nível de lesões do ocupante pôde ser avaliado através do software MADYMO ® , e foi possível verificar uma redução de 23,5% na compressão do peito, 80% de compressão na tíbia, o que levaria o ocupante do veículo com este tipo de reforços sair ileso de uma colisão nas condições da norma. A aplicação dos reforços no impacto lateral possibilitou uma redução de 13,8m/s para 10,6m/s na velocidade de deformação da coluna B na região das costelas do dummy e houve um ganho de 140mm de espaço residual. Os reforços adotados para o impacto frontal e lateral proporcionaram um aumento de 47,5% de força de colapso da estrutura superior, segundo a norma FMVSS216. / The objective of this work is to show the application of structural reinforcements using the polymeric material PA66 through finite element simulations in the field of vehicle safety. The preformed structural reinforcements have shown good performance in crash tests, where the great advantage is their reduced weight. These reinforcements are designed with the aim of increasing the rigidity of regions which are prone to large deformations, stabilizing sections of the vehicle that works as load path during the impact. Initially, static and dynamic tests were performed to characterize the material PA66, which was used in the simulations. The impact cases studied were those which will be adopted by CONTRAN in 2012 and already adopted by other standards of great importance for the occupant safety, such as ECE-R94, ECE-R12, ECE-R95, ECE-R32/34 and FMVSS216. The simulations performed in the software LS-Dyna ® and MADYMO ® considering the application of reinforcements in the case of frontal impact regarding ODB at 57km/h configuration, resulted in 70% reduction in the A pillar deformation and 65% in the deformation of the steering column and a reduction of approximately 59% in the occupant\'s legs and feet region. The occupant\'s injury level were assessed by MADYMO ® software, and a reduction of 23.5% in the chest compression and 80% in the tibia compression were verified. Such conditions lead the safety of an occupant of the vehicle with reinforcements in a collision event according to the standard. The application of reinforcements on side impact load case contributed to reduce the B pillar velocity at the dummy\'s ribs region from 13.8 m/s to 10.6 m/s and there was a gain of 140mm of B pillar residual space. Reinforcements adopted for the front and side impact load cases provided an increase of 47.5% in the upper structure crush force, according to FMVSS216 standard.