JEC COMPOSITES MAGAZINE - Issue #36 - October 2007 - 44

g…/… Mass transit application pultrusion. The company has also developed a method to produce three-directional fabrics with a foam core. This automated production method is best suited for compression moulding or 3-D laminates. Some parts for the trucking industry require filament winding or tape wrapping. The thermoplastic process provides maximum flexibility in design, product fabrication and assembly options. The use of fabrics, tapes or laminates with a foam core also provides opportunities for welding, rapid stamping, co-consolidating and in in-situ tape placement. The main advantage is a significant weight and price reduction, with the opportunity to increase production volumes. expanding and rapidly curing closed-cell foam core that bonds to the interior surfaces of the profile makes the product incredibly strong and light. The use of thermoplastic foam reduces or eliminates the fatigue problems observed with other foams. The foam not only increases the sandwich strength but also provides the high thermal stability required in temperature-controlled environments. Thermoset process Once the desired profile has been designed using optimizing software, relatively inexpensive dies are designed and built for the different stages of the process. Injection die The injection die is used to wet out the fibres. This eliminates the air trapped in the fibres that could produce voids and reduce impregnation of the fibres by the resin. The injection die is designed according to the specific part shape and wall thickness. The goal is to provide maximum resin penetration to ensure a very good wet out without trapping air or off-gas inside the laminate. Injection box Gel coat die To complete the process and obtain parts with a superior surface finish, a gel coat is applied in a gel die. This streamlined process enables the MP composite profile to emerge from the die in a finished state. It can simply be cut to any length with a flying diamond-tipped saw-blade, ready for immediate packaging and shipping. Pultrusion die The dies used are shorter than traditional pultrusion dies. The length of a specific pultrusion die depends on many factors such as wall thickness, expected speed, expected surface finish, number of internal ribs, etc. The die length also depends on the time required to bring the composite skins to the expected process temperature. Shorter dies make it possible to heat the die to the expected temperature faster. A shorter pultrusion die reduces the pull force dramatically and proper temperature distribution allows for higher pultrusion speeds. Properties of the final material The resulting MP profile/panel offers the following characteristics: - Thermal performance: the most energy efficient product available - Dimensional stability: virtually no contraction or expansion - Structural strength: improved shear strength - Design flexibility: high strength provides endless design options - Low maintenance: minimal maintenance requirements - Environmental impact: the lowest energy consumption in lineal production combined with the longest life expectancy - Resistance to rotting, splitting, warping and corrosion: the highest resistance to warping and twisting, and it will not separate or crack – durability is the basic characteristic of MP composites - Easy installation: the profiles remain square, level and plumb during the installation process - Energy efficiency: better thermal performance over other materials - Condensation: reduced moisture and condensation - Sound transmission: high resistance to sound transmission, reducing exterior noise to a minimum The main advantage of composites is that high strength and stiffness can be achieved with relatively low densities, and therefore, lower weight. Pultrusion die Foam injection die A foam die is then used to continue the external skin forming process and to obtain the best surface finish. While the shell is hardening, closed-cell foam (of any desired density) is injected into the hollow portions of the profile. This combination of an outer glass-fibre, carbon-fibre, or blended glass/carbon skin with an JEC Composites Magazine / No36 October - November 2007

JEC COMPOSITES MAGAZINE - Issue #36 - October 2007

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #36 - October 2007