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Coated polycarbonate (PC) is a leading engineering thermoplastic used in automotive glazing for replacing laminated glass. Mechanical properties of multi-layer coating systems were investigated using a nano-indenter and the fracture behavior of coating during nano-scratch was studied employing scanning electron and atomic force microscopy. A set of coated samples was prepared, with two layers, namely Layer-1 and Layer-2. Layer-1 was applied directly to the PC substrate and used as adhesion promoter. Layer-2 was prepared with different mechanical properties. Abrasion performance of the coated system was characterized using an ASTM abrasion test methodology. Regression analysis was performed to establish correlation between the mechanical properties of the coating system and its abrasion performance. Fracture behavior of the coating systems and their plausible relationship with abrasion performance was also discussed.

Understanding scratch and mar damage performance of materials is important in the automotive industry. Hence there is need to develop a suitable method to quantify them and relate back to product performance. This paper elucidates a method to quantitatively evaluate mar defects. The method involves marring the surface of a sample with a crockmeter and the damaged surface characterized using a two-camera optical imaging system. These results were then correlated with visual survey results and a transfer function was generated using Design expert DX6net. In the validation stage, a set of newly marred samples were investigated to generate both visual rank and mar index using the transfer functions. Excellent agreement between mar index and visual survey rank reconfirmed the method's effectiveness. Mar performance of different materials (black and high gloss) can be compared using this technique on a 0-100 scale. This method can also be used to characterize polycarbonate glazing surfaces.

Exatec® PC glazing technology team, has developed advanced weathering and abrasion resistant coatings technology that can be applied to protect polycarbonate. It is of particular interest to quantify and understand the factors that determine the surface abrasion performance of coated PC in rear window and backlight applications that have a wiper system. In the present study we describe Exatec's lab scale wiper testing equipment and test protocols. We also describe adaptation of optical imaging system to measure contrast and nano-profiling using nano-indenter, as post wiper surface characterization methods. These methods are more sensitive to fine scratches on glazing surface than standard haze measurement and mechanical profilometry. Three coating systems were investigated; Siloxane wetcoat (A), Siloxane wetcoat (B), and Siloxane wetcoat (B) plus plasma coat (Exatec® E900 coating). The performance comparisons were made using all these surface characterization methods.

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.

We define an effective temperature (Teff) as an irradiance-weighted average temperature of a material during weathering. It is the constant temperature that would give the same amount of damage as the sample sustains during natural cycling and serves as a benchmark for predicting lifetimes. It is weakly dependant on the activation energy (Ea) of the degradation process. The annual effective ambient and black panel temperatures at an Arizona test site were 30° and 42°C, respectively, for Ea = 4–7 kcal/mol. Privacy color polycarbonate minivan sunroof windows had surface Teff = 45–46°C exterior, 54–58°C interior, and 49–52°C exterior blackout surfaces. Maximum recorded temperatures were 73°C, 87°C, and 81°C, respectively.

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).

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.