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Materials and Structures for Energy Absorption
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Vehicle crashworthiness in real-world conditions

Ford Motor Company Limited-P. A. Fay
  • Technical Paper
  • 2000-04-0339
Published 2000-05-09 by Institution of Mechanical Engineers in United Kingdom
It can be shown that over the last 40 or so years, motor vehicles have become safer. There are two fundamentally different ways in which this has been achieved. The first approach (known as ""primary safety"") is the development of measures to avoid crashes occurring in the first place. The second approach (known as ""secondary safety"" or ""crashworthiness"") is the development of measures to minimize the injuries resulting from a crash once it has happened.These two approaches are not alternatives. They are complementary but their relative importance has changed over the years and has been much debated. It is however widely believed that improved crashworthiness of vehicles (such as improved occupant protection, improved structural characteristics and advanced restraint systems) can continue to make substantial improvements to vehicle safety.

Controlling structural collapse in off axis impact of rail vehicles by retrospective modification

WS Atkins Consultants Limited-N. Kirk
WS Atkins Rail Limited-P. Waite
  • Technical Paper
  • 2000-04-0341
Published 2000-05-09 by Institution of Mechanical Engineers in United Kingdom
In 1988 British Rail suffered a multi-fatality accident involving the collision and destruction of several vehicles of the Mark 1 type construction. Vehicle underframes climbing over each other and shearing through the body structural members caused the most severe damage. Subsequent to this accident research and development work was commissioned to establish the feasibility of providing additional strength into these Mark 1 coaches above the underframe and of preventing the underframe structures from climbing over each other during a collision. Whilst strengthening the body structure was found not to be feasible, providing a simple and relatively cheap means of anti- climb was developed and tested on full-size vehicles. This paper describes the key steps taken in the design and development of this solution.

Energy absorption in hybrid composite structures

University of Liverpool-G. Reyes Villanueva, W. J. Cantwell
  • Technical Paper
  • 2000-04-0343
Published 2000-05-09 by Institution of Mechanical Engineers in United Kingdom
The quasi-static and impact properties of a novel fiber-metal laminate based on a tough glass fiber-reinforced polypropylene (GFPP) matrix have been evaluated and compared with those of a conventional thermosetting-based carbon fiber-reinforced epoxy (CFRP). Initially, the mode I, mode II and mixed-mode I/II interlaminar fracture properties of the plain composites were investigated. Here, it was shown that the mixed-mode interlaminar fracture toughness of the GFPP system was close to 5000 J/m2 and that of the thermosetting system was approximately 2000 J/m2. Single cantilever beam tests indicated that the adhesion in the GFPP/aluminum and the CFRP/aluminum systems was excellent at all loading rates and that failure frequently occurred within the composite rather than at the bi-material interface.Low velocity impact tests on both types of fiber metal laminate highlighted the superior impact response and energy- absorbing characteristics of the thermoplastic-based system. Here, it was shown that the GFPP system absorbed significant amounts of energy through matrix cracking in the composite plies and membrane stretching in the aluminum layers. It is believed that thermoplastic-based fiber metal laminates offer…

Woven polypropylene structures

University of Leeds-I. M. Ward, P. J. Hine
  • Technical Paper
  • 2000-04-0340
Published 2000-05-09 by Institution of Mechanical Engineers in United Kingdom
Recent research at Leeds University has seen the development of a new class of "self-reinforced" polypropylene sheet. The essence of the process, termed hot compaction, is to take layers of woven-oriented polypropylene tapes, and compact them together under suitable conditions of temperature and pressure to form a consolidated, homogeneous sheet. The mechanism for consolidation is to melt a small proportion of the skin of each tape, which on cooling recrystallizes to form a polypropylene matrix to bind the oriented tapes together. Research has shown that there is a usable processing window where sufficient melted material can be created to bind the woven structure together without losing too much of the original oriented structures. The process can be seen as a way of converting the properties of a highly drawn polypropylene tape into a consolidated sheet.The compacted polypropylene tapes display an interesting portfolio of mechanical properties, reflecting the "frozen in" molecular orientation, and by virtue of being composed of only a single phase, namely polypropylene. These include reasonable mechanical properties (placed between isotropic polymers and glass-reinforced…

Design and performance of energy-absorbing subfloor structures in aerospace applications

German Aerospace Center (DLR)-A. Johnson, D. Kohlgrüber
  • Technical Paper
  • 2000-04-0342
Published 2000-05-09 by Institution of Mechanical Engineers in United Kingdom
Composite elements such as glass or carbon fiber-reinforced tubes in axial crush exhibit high specific energy absorption and a challenge for the engineer is to utilize these properties in structural applications. The paper considers the application of composites in the design of helicopter and aircraft subfloors with a dual function of being structural elements under flight loads, which may be triggered to absorb energy by folding and crushing under crash loads. Examples discussed are an energy- absorbing (EA) floor beam concept for a general aviation aircraft based on sandwich webs with glass and aramid fabric/epoxy face plates and box element core, and a modular helicopter subfloor concept with hybrid carbon/aramid/epoxy beams and cruciform elements. Progress on the development of design tools for these crashworthy structures based on FE simulation is also discussed and simulation results compared with crash test data.

Development of autobody sheet materials for crash performance

Corus Group plc-M. G. Marsh
  • Technical Paper
  • 2000-04-0344
Published 2000-05-09 by Institution of Mechanical Engineers in United Kingdom
Increasingly stringent crash legislation and the drive to produce lightweight car bodies has promoted the extensive use and development of high-strength steels. In this paper, a number of material properties which are thought to contribute significantly to energy absorption in metallic materials will be highlighted. It will be shown that it is important to understand the relationship between strength and thickness in order to downgauge confidently. The increased dynamic stability exhibited by high strength steels will also be demonstrated. Finally, a brief example will be shown of how the collapse resistance can be increased through the simple manipulation of the joining process. The conclusion from the work is that to maximize energy absorption within a component, it is important to take into account the interaction of the material, the section design, the forming process and the final fabrication technique.