Questão 67453
(IME - 2021/2022 - 2ª fase)
Text 3
Weight reduction of a carbon fibre composite wheel
Stefan Czypionka and Frank Kienhofer
Abstract — The wheel of a passenger vehicle must be designed to be safe and light. (...) Manufacturing and testing carbon fibre reinforced plastics (CFRP) prototypes is expensive. Thus, it is advantageous to develop simulation models for composite weight reduction. The simulation models can provide insight into how lighter CFRP wheels can be designed. This study presents the design development of a CFRP wheel for a high-performance roadster; the CFRP wheel is offered by an automotive manufacturer as a high-performance option instead of aluminium wheels. Finite element (FE) simulations were initially conducted assuming an isotropic material. This initial model was used to eliminate stress concentrations and to design and manufacture an initial CFRP wheel. The CFRP wheel weight is 6.8 kg as compared to the original aluminium wheel which weighs 8.1 kg. This initial design passed the dynamic cornering fatigue test (the most stringent strength test for wheels). Thereafter the wheel was instrumented with strain gauges, and a bending moment was applied to the hub using a custom-built test rig. The test rig produced a static load equivalent to the dynamic cornering fatigue test (in which the applied bending moment varies sinusoidally). (...)
1. Introduction
1.1 Background
The wheel is arguably one of the most important components of a road going vehicle. It is responsible for the transmission of power from the drive components of the vehicle to the road, while also enabling the vehicle to make directional changes. Overdesigning a wheel by adding material increases the wheel mass and rotational inertia which negatively affects the vehicle’s performance and efficiency. This has led to substantial development efforts to reduce the wheel weight and rotational inertia while simultaneously maintaining or increasing the material strength. A wheel must be designed to be safe and light.
Numerous research studies have been published on the development of steel and aluminium wheels. Steel and aluminium alloy wheels have arguably reached the peak of possible weight reduction and composite materials offer the next advance. Despite the tremendous potential of carbon fibre as an automotive material due to high strength, low density and superior fatigue properties, (38) . Giger and Ermanni demonstrated the development process of a CFRP motorcycle rim. However, this wheel was not tested to certified standards. Rondina et al. investigated a high volume production method for carbon fibre wheels. The paper simulated the production process; however, no certified wheel appears to have been produced. As early as 1979, studies have been conducted into the viability of composites for use as automotive wheels.
Unlike isotropic materials, CFRP components are expensive to test and certify. Even small changes in geometry to prevent failure or reduce stresses could cause a production line to be retooled during the development process and existing equipment to be scrapped. This research paper illustrates the development of a validated finite element (FE) model to investigate laminate configurations to improve the stiffness of the CFRP wheel and be 18% lighter than the original aluminium wheel. The case study is of an original equipment (OE) wheel designed and manufactured by Blackstone Tek (BST). (...)
https://doi.org/10.1515/secm-2019-0018 Received Jan 28, 2019; accepted Feb 25, 2019. Adapted from: Weight reduction of a carbon fibre composite wheel. Available at: [Accessed on May, 3rd, 2021].
Choose the correct option.
A
For a car wheel to be strong, it shouldn’t be light, and carbon fibre can provide the necessary strength.
B
To make and test a CFRP prototype used to be prohibitively expensive. This is why it was avoided up to sometime ago, but it has become less costly recently.
C
Simulation models are a solution to help reach some conclusions without spending what would be spent if CFRP prototypes were always built.
D
A wheel weight is not reduced by the use of CFRP materials.
E
If a vehicle that carries passengers is light, it is not safe since the wheel might not be strong enough.
Gabarito:
Simulation models are a solution to help reach some conclusions without spending what would be spent if CFRP prototypes were always built.
Resolução:
A. Incorreta. Segundo o texto, a roda do carro precisa ser leve (light) e segura (safe).
B. Incorreta. Fazer e testar uma roda com CFRP é caro, o texto indica que essa é uma desvantagem dessa combinação de materiais e, segundo ele, esse problema permanece.
C. Correta. Enquanto o alto preço das rodas CFRP é apontado como uma desvantagem, a possibilidade de simulação é uma vantagem dessa roda. Isso porque os protótipos permitem que sejam pesquisadas e simuladas condições das rodas CFRP, mas sem precisar utilizá-las, o que seria mais caro.
D. Incorreta. Os materiais CFRP são mais leves, o texto aponta que a roda CFRP é 1,3 kg mais leve que uma de alumínio.
E. Incorreta. O texto diz que a roda do carro precisa ser leve para ser segura. Isso porque a massa e a inércia rotacional são afetadas negativamente quando há peso excessivo na roda, o que prejudica a performance e a eficiência do carro.