Making carbon composites robust and fast5 October 2016
Carbon Composites are very promising materials for designing lightweight structural car components. However, the high cost and lack of processing robustness prevent a broader introduction in large volume passenger car manufacturing. Luuk Groenewoud explains how AOC is helping its customers to make Carbon Composite processing robust and fast, introducing a new series of Daron® resins.
STEEL IS GOOD, BUT NOT GOOD ENOUGH
Many of the passenger cars of today are being manufactured in steel, as this material provides great mechanical integrity and strength. So far, steel has also been very cost effective in larger volume production. “However, in many cases steel may not be the preferred material solution for future car models”, explains Luuk Groenewoud, Strategic Project and Portfolio Manager at AOC. “The number of models per car platform is increasing, reducing the series size per model and increasing the cost per car. Also, steel is simply not light enough to sufficiently reduce the weight of future car designs.”
FIT FOR THE FUTURE
EU regulations are driving down car emissions, requiring a reduction from 130 g of CO2/km today to 95 g of CO2/km in 2020 (source: Lucintel, CW Magazine). It is anticipated by the Automotive industry that in the next decade additional major emission reductions will be imposed by legislators around the world for passenger cars. Changing to lightweight materials is regarded as a vital contributor for minimizing CO2 emissions.
Several light weight material solutions are available on the market as steel alternatives, including, Thermoplastics, Aluminium, and Carbon Composites (see overview below, source: McKinsey).
“Among all these solutions, Carbon Composites bring the desired combination of strength and light weight capability”, adds Luuk Groenewoud. “However, the cost of Carbon Composites is still prohibitive for broad introduction in high volume passenger car manufacturing.“
This is caused by the high market price of carbon fiber and insufficient productivity of current RTM-based part manufacturing processes. As incumbent Epoxy resin solutions have long cycle times, it is a challenge for Tier Ones and OEMs to obtain parts in large production series. Also, current Carbon Composites processes create high waste levels of costly carbon fibers and parts, limiting long term competitiveness.
BEST OF TWO WORLDS
AOC is introducing a new series of Daron® RTM, SMC and Pultrusion resins that provide processing robustness, manufacturing ability in large production series, and at a much lower cost. In terms of functional performance and processing, these resins bring the “best of two worlds” when compared with equivalent UPR, VE and Epoxy resins.
Fit for use both with carbon and glass fibers, the novel Daron® resins enable to design lightweight composite components for many structural applications. Also, because they bring the right balance of Tensile Modulus and Tensile Strength as desired by Automotive OEMs.
FIT FOR LARGE VOLUME PRODUCTION
With the novel Daron® resin systems, parts can be produced at high processing speed. Molding cycle times are very low (unlike systems based on equivalent Epoxy resins): 1 min is typical for 2 mm of wall thickness. With SMC conversion processes this means production output is high and waste generated is minimal.
SMC COMPONENT WITH
60 WT% 12K CARBON FIBER
|Flexural Strength (MPa)||500||450|
|Flexural Modulus (GPa)||32||30|
|Tensile Strength (MPa)||300||230|
|Tensile Modulus (GPa)||38||36|
|Molding time at 145 °C (min)||1||5|
|Shelf life at 20°C (days)||60||15|
The processing of the novel Daron® resins is robust and “idiot proof”, as it is relatively insensitive to variations in resin viscosity, curing system, temperature, and fiber sizing. Impregnation viscosity, resin flow and curing profiles are tunable over a broad range, without the risk of changing end-properties of the part. Yet processing is consistent when parameters are fixed. Post-cure is typically not required for reaching final part properties. Parts made with new Daron® resins feature ultra-low emission and smell from the part.
For OEMs and Tier Ones, manufacturing composite parts with Daron® resins means low risk on process errors and part property variation. But even more important, the robust processing contributes to achieving low system cost.
“AOC is well positioned to support its customers developing new components in Carbon Composites”, explains Luuk Groenewoud. “Working throughout the entire Automotive value chain we are able to provide maximum part performance and lowest possible cost.”