Emerging global standards for pedestrian health and safety are triggering innovative plastic designs for automotive front ends.
|A springback action in this newly designed plastic undertray (top photo) helps improve pedestrian safety. Below that, crush boxes such as these with honeycomb designs are being broadly introduced to improve pedestrian safety.|
Two energy-absorbing components using engineering materials from engineering plastics supplier SABIC Innovative Plastics (Pittsfield, MA) are Blue Ribbon finalists in the 2011 Innovation Awards Program run by the Society of Plastics Engineers.
Matthew Marks, marketing manager for SABIC Innovative Plastics, explains, "Steel or glass-filled plastics are commonly used as stiffeners in the lower load path to control knee bend. These stiffeners, however, may undergo permanent deformation or brittle fracture, and may cause a higher injury rate in the ankle area." These parts generally are mounted on brackets near the bottom undercover at the front of a vehicle.
As an alternative, the new Ford C-MAX uses a plastic undertray in its front end that provides a springing action to help protect pedestrians from serious leg injury. The component also serves as an undercover for the front bumper components and help prevents chipping damage from loose road stones. In another design feature, incoming air is guided to the radiator through corrugating that boosts stiffness.
Marks says that the springing action is based on an engineered cantilevered structure as well as a specially tuned stiffness profile for the part. The overall result is a maximum force to a pedestrian's leg in the ankle area is less than 5 kN.
The tray is molded from Xenoy iQ 1103R, a polyethylene butylene terephthalate (PBT) which contains up to 60% post-consumer plastic. Marks says the part helped the Ford C-Max achieve a five star rating in the EuroNCAP system that establishes standards for pedestrian safety. The tougher standards are under consideration for use in North America and Asia as Global Technical Requirements (GTR).
A second finalist in the safety category is an upper load path pedestrian energy absorber for the Range Rover Evoque. Here again SABIC Innovative Plastics supplied the material.
"The bumper height in sport utility vehicles presents a different challenge to control knee bending, as compared to a lower riding sedan," Marks says. In the Evoque, Xenoy iQ is used in a fascia reinforcement that is also specially tuned. The lateral stiffness (rigidity) is tuned to carry the bumper load and the axial stiffness is tuned to support the top of a pedestrian's leg during a pedestrian impact.
In an interview with PlasticsToday, Venkatakrishnan Umamaheswaran, director of Automotive Products & Marketing at the company, said that SABIC Innovative Plastics is developing several other systems that address pedestrian safety, occupant safety, and low-speed vehicle damageability. For example, 10 automotive programs in Europe are using plastic "crush boxes" made with various types of honeycomb structures.
Category and grand award winners in the SPE competition will be announced at a banquet in Livonia, MI Nov. 9.
A springback action in this newly designed plastic undertray (top photo) helps improve pedestrian safety.Below that, these new crush boxes with honeycomb designs are being broadly introduced to improve pedestrian safety.