During accident, the interlayer of windshield plays an important role in the crash safety of automotive and protection of pedestrian or passenger. The understanding of its energy absorption capability is of fundamental importance. Conventional interlayer material of automotive windshield is made by Polyvinyl butyral (PVB). Recently, a new candidate of high-performance nanoporous energy absorption system (NEAS) has been suggested as a candidate for crashworthiness. For the model problem of pedestrian head impact with windshield, we compare the energy absorption capabilities of PVB and NEAS interlayers, in terms of the contact force, acceleration, velocity, head injury criteria, and energy absorption ratio, among which results obtained from PVB interlayers are validated by literature references. The impact speed is obtained from virtual test field in PC-CRASH, and the impact simulations are carried out using explicit finite element simulations. Both the accident speed and interlayer thickness are varied to explore their effects. The explicit relationships established among the energy absorption capabilities, impact speed, and interlayer material/thickness, are useful for safety evaluation as well as automotive design. It is shown that the NEAS interlayer may absorb more energy than PVB interlayer and it may be a competitive candidate for windshield interlayer.

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Before the discovery of fullerenes [1], a great deal of attention was given to diamond film growth by the process of hot filament chemical vapour deposition (HF-CVD). There are two types of fullerenes. The first is a cage-like structure called buckyball [2], for example C60. The second is a tube-like structure called buckytube [3]. During the past three years many studies on theoretical calculations [4], advanced developments and applied applications of buckyballs have been carried out. They can be used as a coating in CVD, for diamond film growth [5], and may be transformed directly into diamonds or diamond-like materials under high pressure at room temperature [6]. As for buckytubes, which are easier to fabricate in large quantities [7], less research has been done. In this letter, we present a primitive investigation on buckytubes used as coatings for Si substrates in diamond film growth by the HF-CVD process. It was found that a buckytube coating can significantly increase the deposition rate of diamond film, both in terms of nucleation density and in quality. We compared and studied non-coated specimens and specimens coated with C60 and C70, and suggest that the results of our experiments should produce a great deal of interest in the engineering applications of buckytubes.Our experiments were conducted by coating Si substrates with buckytubes and pure C60 and C70 (both of which have a purity of 99.5%). C60 and C70 coatings were prepared using a solution of toluene, while the buckytube micro-powders were dispersed on the Si substrate by alcohol. After the toluene and the alcohol were evaporated, perfect coatings several micrometres thick were obtained. A non-coated Si wafer was also used in our experiments. The reactant gases were Hz and CH4, the depositing temperature remained at 700 °C, and the experiment duration was 4 h. Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the deposited samples. An image analyses apparatus was also used to identify the nucleation density of diamond.The X-ray diffraction results are in agreement with the ASTM(6-0628) card of cubic diamonds. Fig. la and b shows the SEM results. It should be noted that almost no diamonds were deposited on the non-coated Si substrate, and that there appears to be no obvious distinction between the C60 and C70 coated samples. This result shows differences between our experiment and a previous report [5]. It 0261-8028 © 1995 Chapman & Hall can easily be seen from Fig. l a that the deposit consists of cubic diamonds, which are dense, uniform and well distributed. The C60 coated specimen, Fig. lb, is composed of large mosaic diamond crystals that fail to completely cover the substTate, accompanying amorphous phases.Raman spectra results are shown in Fig. 2. The sharp peak at 1332 cm -1 and the broad peak at 1536cm -I are obvious. Furthermore, the peak in line(a) is stronger than that of line(b) at 1332 cm -1, which refers to the diamond peak, while the peak at 1536 cm -1 is weaker than that...