Rapid processing of net-shape thermoplastic planar random composite preforms

A novel thermoplastic composite preforming and moulding process is investigated to target cost issues in textile composite processing associated with trim waste, and the limited mechanical properties of current bulk flow- moulding composites. The thermoplastic programmable powdered preforming process (TP-P4) uses commingled glass and polypropylene yarns, which are cut to length before air assisted deposition onto a vacuum screen, enabling local preform areal weight tailoring. The as-placed fibres are heat- set for improved handling before an optional preconsolidation stage. The preforms are then preheated and press formed to obtain the final part. The process stages are examined to optimize part quality and throughput versus processing parameters. A viable processing route is proposed with typical cycle times below 40 s (for a plate 0.5 × 0.5 m2, weighing 2 kg), enabling high production capacity from one line. The mechanical performance is shown to surpass that of 40 wt.% GMT and has properties equivalent to those of 40 wt.% GMTex at both 20°C and 80°C

L'HYDROPTERE: HOW MULTIDISCIPLINARY SCIENTIFIC RESEARCH MAY HELP BREAK THE SAILING SPEED RECORD

In 2009, l’Hydroptère broke the symbolic barrier of 50 knots and became the world fastest sailing boat over both 500 meters and 1 nautical mile. This major achievement relied on the high skills of the sailing team but also on technical advances of the boat, resulting from the scientific collaboration between the Hydroptère Design Team and the Ecole Polytechnique Fédérale de Lausanne (EPFL). In the present article, we highlight the multidisciplinary research activity performed within EPFL in the course of this collaboration involving aero- and hydrodynamics, materials and structure as well as computer vision. Various foils were tested at reduced scale in a high speed water tunnel, and the results used to validate the numerical simulations. Composite materials, their processing parameters and assembly components were tested. The structural behaviour was also investigated to determine strains and stresses in normal and extreme sailing conditions, taking waves into account, and a combined model was derived for dynamic simulation. Finally, advanced computer vision methods were developed and implemented on the boat to monitor foil immersion and cross beams deformations

Reproducible generation of explosive traces for detection system testing

Explosive trace detection (ETD) systems need to be tested against the target substances on a nanogram scale applied to various different surfaces. To reach this goal a solvent-free method using inert particles coated with explosives was researched. A powder pipette was developed that is able to perform a dry transfer which can place a required number of particles on a target area to guarantee a reproducible generation of traces on different surfaces. A negative pressure is used to grasp a singular particle from a powder bed into the round pore of the pipette. The particle can be released by an electric stimulus of the pipette which is integrated into a platform solution enabling a fully automatic control. Combining the knowledge of the explosive amount on each particle and the possibility to perform the deposition of an exact number of particles it is possible to create reproducible and quantitative test specimen for explosive trace detection systems. Explosive vapour detection (EVD) systems need to be tested with controlled concentrations of explosive vapour down to ppt level. A suited gas generator was developed taking into account measures to prevent unwished adsorption and to ensure a controlled gas concentration output. The developed gas generator is able to evaporate small amounts of dissolved explosives from a liquid circle into a gas stream. By controlling the gas stream, the concentration of explosive in the liquid circle and the numbers of pulses, it is possible to create defined explosive vapours down to ppt level