JEC COMPOSITES MAGAZINE - Issue #53 - November/December 2009 - 34

FEATURE “Automotive” - possibility to design and manufacture complex shapes, - dimensional stability and absence of distortion, even in case of fast temperature increases, - no burn-through, even in case of fire, - possibility to combine the high-temperature composite with another composite to improve durability and mechanical performance (hybrid composites), - possibility to apply coatings to improve thermal management, e.g. reflective coatings for improved shielding against radiant heat. A typical structural heat shield made of PyroSic is shown in Figure 2. g…/… User-friendly composites that take the heat Fig. 1: Selected thermo-mechanical properties Example of application – Exhaust ducts for motorsports Race car exhausts are complex systems where the use of composite was hardly thinkable less than 10 years ago. The elevated exhaust gas temperatures (600ºC to 1000ºC), part complexity and high levels of stress and vibration were major challenges that made Inconel or steel the only viable options for headers, collectors, mufflers and tailpipes. In 2006, Pyromeral Systems considered using PyroSic glass-ceramic matrix composites to manufacture composite components for exhaust systems, with the objective to reduce exhaust weight, improve thermal management, and give more flexibility to engineers when designing the components. The techniques used and the features of these composite exhaust systems are presented below. The material’s density – which is lower than that of titanium (4.5 g/cm3) and much lower than that of Inconel (8.2 g/cm3) – is an essential parameter to achieve significant weight reductions. It is also worth noting that the material can withstand short exposures to very high temperatures, e.g. retaining 95% of its mechanical properties after a 30-minute exposure to 1100ºC. Example of application – Heat shields Heat shields and fire barriers are important components of motorsports and aerospace systems. They are also one of the most difficult applications for traditional materials, especially when structural properties are also needed. Heat shields made of PyroSic are frequently used in motorsports applications, where the material has proven to be a reliable solution for lightweight structural heat shields located in tight spaces and exposed to both extreme heat (close to 800ºC in some areas) and high vibrations. The technical attributes of heat shields made of PyroSic glass-ceramic matrix composites include: - thin walls, typically ranging from 0.6 mm to 1.2 mm, Fig. 3: PyroSic exhaust component Design and manufacturing Due to the complexity of the parts (e.g. 5-in-1 or 4-in-1 collectors), advanced manufacturing techniques were used. For example, destructible mandrel materials were found to be compatible with the material, and they were used successfully to manufacture seamless hollow shapes. Additionally, it was demonstrated that, if properly designed, the components could be adhesive-bonded without loss of mechanical properties. Further productivity improvements were achieved by using braids instead of prepreg material, although braid availability was an issue. A typical PyroSicbased collector is shown in Figure 3. Fig. 2: PyroSic heat shield jec composites magazine / No53 November - December 2009

JEC COMPOSITES MAGAZINE - Issue #53 - November/December 2009

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #53 - November/December 2009