Best known for adhesives and personal care products, German chemical giant Henkel has developed a new matrix plastic for composites that could speed development of carbon fiber reinforced plastics. The new polyurethane matrix resin for the resin transfer molding process (RTM) is expected to speed up the production of composite components in the automotive industry. Curing times of just one minute are now possible, according to Hemkel.
Properties of the cured pure resin
|Pure resin properties||Polyurethane matrix resin|
|Tensile modulus [MPa]||
|Tensile strength [MPa]||
|Glass transition temperature [°C]||
|Glass transition temperature [°C]K1c [MPa*m0.5]||
* after tempering
Henkel says that specific interactions between the polyurethane molecules that take place in addition to chemical cross-linking help to enhance a property called stress intensity factor, which is a measure of toughness. The excellent toughness of the resin is also said to have a positive effect on the fatigue behavior under load.
The high tolerance to stress peaks delays the formation of critical cracks, thus prolonging the part life. In automobiles, which are constantly subjected to dynamic loading under driving conditions, materials with a high fatigue tolerance are essential in order to be able to exploit lightweighting potential to its fullest extent.
Henkel and KraussMaffei worked together to improve the speed and reliability of composite manufacturing. Machine technology has been modified for the new resin system. KraussMaffei’s engineers optimized the mixing and dispensing stations and the mixing heads in order to improve the controllability in high temperature processes.
The Molding Skinny
|Injection parameters||Polyurethane matrix resin|
4 layers of CF fabric 300 g/m2
|Resin injection rate||
|Time to demolding||
The resin is injected into the preheated mold under vacuum and removed after one minute. The fiber volume was approximately 50 percent, with no fiber distortion being detected regardless of the laminate structure. Milling to the final shape was performed directly after cooling of the components.