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Reduced battery discharge rates in electric vehicles (EV) tend to extend single-cycle range as well as battery lifetime. Vehicle features that tend to reduce battery discharge rate thus support viability of EV. Of special interest are features that reduce the load on the heating, ventilation and air conditioning (HVAC) system since that system can in turn impose a significant load on EV batteries. A companion paper quantifies the effect on steady state nominal HVAC load of glazing (i.e. window) thermal conductivity using Computational Fluid Dynamics (CFD) to simulate heat transfer between the ambient and the air in a model car cabin when the cabin air is maintained at a comfortable temperature. For hot and cold climate, and for stationary and moving cars, reductions in HVAC load resulted from replacing a monolithic glass backlite and rooflite with polycarbonate (PC), the latter with a five-fold lower inherent thermal conductivity.

With the increased focus on fuel economy in the automotive industry today vehicle mass reduction is becoming increasingly important to automotive engineers. A common method to reduce mass for bumper reinforcement beams is to use aluminum extrusion technology. However, the use of aluminum extrusions comes at a higher cost than comparable steel systems. Two hybrid design approaches for bumper reinforcement beams are presented in order to reduce mass while maintaining a lower cost than aluminum bumper systems.

This paper describes a methodology to prototype and validate thermoplastic energy absorbers in a broad range of vehicle geometries. The objective of this prototype tool designed with quick prototype methodology is to achieve ready PC/PBT energy absorber designs for pedestrian testing. Generic vehicle models were used to finalize the energy absorber design features. The prototype tool was designed from optimized energy absorber designs that meet pedestrian performance in low packaging space, typically 45–60 mm. A set of prototype tools is being built to match different beam heights and packaging spaces. The tool has also the functionality of achieving different thickness and different design features using the latest manufacturing technologies. A full energy absorber can be built from individual lobes over the width of the car. The finalized design combined with ‘quick prototyping’ methodology was used to finalize the mold design, which can cater to a wide range of vehicle geometries.

This paper presents the effect of finite element analysis (FEA) model improvements to better correlate predictive analyses to pedestrian protection lower leg impact tests. The FEA analysis model prediction is now within 10% of the tested values for tibia deceleration, knee bending angle and knee shear. By using this improved FEA model, new, more efficient energy absorber and vehicle front end design strategies can been developed. A numerical approach to optimizing vehicle front end structures is presented.

This paper discusses a Design for Six Sigma (DFSS) based methodology for designing an injection molded bumper energy absorber to help meet vehicle pedestrian protection requirements. The development process is described, and an example is presented of its use in designing an injection molded energy absorber for a range of various vehicle styling parameters. First, an idealized set-up incorporating the car styling parameters critical for pedestrian protection requirements was developed. Then, the vehicle and Energy Absorber (EA) geometries were parameterized and a DFSS process was employed to investigate the design space using Finite Element Impact Analysis with a commercially available Lower Leg Form Impactor.

This paper describes a bumper system designed to meet the current FMVSS (Federal Motor Vehicle Safety Standard) and ECE42 legislation as well as the European Enhanced Vehicle Safety Committee (EEVC) requirements for lower leg pedestrian impact protection [1] (The EEVC was founded in 1970 in response to the US Department of Transportation's initiative for an international program on Experimental Safety Vehicles. The EEVC steering committee, consisting of representatives from several European Nations, initiates research work in a number of automotive working areas. These research tasks are carried out by a number of specialist Working Groups who operate for over a period of several years giving advice to the Steering Committee who then, in collaboration with other governmental bodies, recommends future courses of action designed to lead to improved safety in vehicles).

Laboratory testing and computer aided engineering (CAE) techniques have long been employed in the development and optimization of automotive bumper systems. However, as more aggressive automotive styling and performance trends and mass and cost reduction objectives continue to push the limits of known bumper system construction, early optimization techniques will need to improve proportionately. The limitations of today's test and analysis techniques for providing accurate predictions can lead to excessive factors of safety (waste) and/or expensive rework during latter stages of vehicle development. Much work has been done to improve the capability of computer simulations for predicting impact behavior (1). However, some of the development limitations can also be attributed to an inability to achieve repeatable results or to accurately simulate the low speed impact behavior of a vehicle with universal test vehicles (UTV).

This paper describes a bumper system design that satisfies both current FMVSS legislation as well as the European Enhanced Vehicle Safety Committee (EEVC) requirements for lower leg pedestrian impact protection. The dual performance solution is achieved through a combination of material properties and design. Using Computer Aided Engineering (CAE) modeling, the performance of an injection molded energy absorber (EA) was analyzed for pedestrian protection requirements of knee bending angle, knee shear displacement, and tibia acceleration, 4Kph pendulum and barrier impacts (ECE42, FMVSS), and 8Kph pendulum and barrier impacts (CMVSS, FMVSS). The results demonstrate how an injection molded EA using polycarbonate/polybutyelene terephthalate (PC/PBT) resin (Figure 1) can meet both FMVSS and pedestrian safety requirements and can do so within a packaging space typical of today's vehicle styling.

Automotive styling and performance trends continue to challenge engineers to develop cost effective bumper systems that can provide efficient energy absorption and also fit within reduced package spaces. Through a combination of material properties and design, injection-molded engineering thermoplastic (ETP) energy absorption systems using polycarbonate/polybutylene terephthalate (PC/PBT) alloys have been shown to promote faster loading and superior energy absorption efficiency than conventional foam systems. This allows the ETP system to provide the required impact protection within a smaller package space. In order to make optimal use of this efficiency, the reinforcing beam and energy absorber (EA) must be considered together as an energy management system. This paper describes the development of a predictive tool created to simplify and shorten the process of engineering efficient and cost effective beam/EA energy management systems.

An efficient energy absorber (EA) will absorb impact energy through a combination of elastic and plastic deformation. However, the EA is typically coupled with a steel reinforcing beam, which can also elastically and plastically deform during an impact event. In order to design and optimize an EA/Beam system that will meet the specified vehicle impact requirements, the response of the entire assembly must be accurately predicted. This paper will describe a finite element procedure and material model that can be used to predict the impact response of a bumper system composed of an injection molded thermoplastic energy absorber attached to a steel beam. The first step in the process was to identify the critical material, geometric, and boundary condition parameters involved in the EA and Beam individually. Next, the two models were combined to create the system model. Actual test results for 8km/hr.

This paper will describe an approach to satisfying proposed European Enhanced Vehicle Safety Committee (EEVC) legislation for lower leg pedestrian impact. The solution for lower leg protection is achieved through a combination of material properties and design. Using Computer Aided Engineering (CAE) modeling, the performance of an energy absorber (EA) concept was analyzed for knee bending angle, knee shear displacement, and tibia acceleration. The modeling approach presented here includes a sensitivity analysis to first identify key material and geometric parameters, followed by an optimization process to create a functional design. Results demonstrate how an EA system designed with a polycarbonate/polybutyelene terephthalate (PC/PBT) resin blend, as illustrated in Figure 1, can meet proposed pedestrian safety requirements.

The primary purpose of an automotive bumper is to protect the vehicle from damage, which may otherwise result from a low speed impact. Major insurance companies typically conduct low speed crash tests of new vehicles in order to establish appropriate insurance classifications based on the estimated costs to repair the resulting damage. One such test, which is carried out by the Allianz insurance organisation, has become the European standard by which automobile insurance rates are set. Although commonly known as the Allianz test, it may be more specifically referred to as the Danner test, after Max Danner, the originator of the test. This test is conducted at 15 km/h with a 0° oriented rigid barrier overlapping 40% of the vehicle for frontal collisions and a 1000 kg moveable barrier with a 40% overlap for impacts to the rear of the vehicle.

Automotive styling trends point to reduced bumper overhang, greater sweeps, and reduced overall package space for the bumper system. At the same time engineers are charged with improving bumper performance to reduce collision repair costs and enhance occupant safety further. Two key performance parameters for the bumper to meet these conflicting objectives are fast but controlled loading and efficient energy absorption (EA). The majority of today's North American passenger-car bumper systems consist of a reinforcing bar either of steel, aluminum, or composite construction, and an energy absorption media. The most widely used energy-absorber construction is made from an expanded-polypropylene foam (EPP). Honeycomb energy absorbers, which are made from an ethylene vinyl acetate (EVA) copolymer, are also still used on some of today's cars. This paper will address an alternative to the bumper energy absorber systems described above.

This paper will address several critical aspects of bumper system performance, including vehicle damage protection and crash-severity sensing considerations, energy-absorption capacity and efficiency, and low-speed impact consistency and sensitivity to temperature changes. The objective is to help engineers and designers establish a realistic perspective of the capability of the various technologies based on actual test performance. The scope of the evaluation will include a comparison of several bumper-beam material constructions when subjected to a 16-km/hr swinging barrier impact over a range of temperatures the bumper could see in service (-30 to 60C).

Today's interior systems design engineer has been challenged with providing significantly lighter, simpler and more cost-effective instrument panel (IP) design solutions, while simultaneously meeting rigorous occupant protection and quality standards. These issues provided the motivation behind the fully-integrated structural instrument panel design developed for Chrysler's Dodge Dakota Truck Platform. This total system design approach greatly depends on the stiffness and ductility of the engineering thermoplastic substrate and cross-sectional design for managing the energy of unrestrained occupants during frontal collisions. The structural IP consists of a fully integrated, three-piece monocoque thermoplastic structure that replaces the traditional retainer, air delivery ducts, steel beams and reinforcements typically used in IP designs.

A fully-integrated thermoplastic structural instrument panel (IP) system will be implemented on Chrysler's Dodge Dakota Truck Platform. The structural IP consists of a three-piece monocoque thermoplastic injection molded structure that replaces the traditional retainer, air delivery ducts, steel beams and reinforcements typically used in IP designs. Ribbed thermoplastic bolster systems have been incorporated as part of the energy management system. The structural IP provides the required stiffness to satisfy noise, vibration, and harshness (NVH) quality targets and the necessary strength and rigidity to effectively meet FMVSS No. 208 requirements for managing occupant and passenger air bag (PAB) deployment loading during 48 km/h (30 mph) frontal crashes.