Wibke Exner

Fast Curing of Carbon Fiber Reinforced Plastics Using the Integration of Nanoparticles

Fast curing of carbon fiber reinforced plastics (CFRPs) is limited by the degradation of the resin under high temperatures and by the development of internal strains. The authors counter these problems by adding nanoparticles to the matrix of CFRPs. In the presented work various volume fractions of nanosized aluminum oxide particles are integrated into the epoxy resin RTM6. To demonstrate the increased heat flow within the CFRP component, thermal conductivity tests are presented. Results show increasing values as the filler content is raised.With increasing filler content the reaction speed is also accelerated. This effect is analyzed by differential scanning calorimetry. It is shown that the particle surface has a catalytic effect on the curing of the epoxy resin. The results of the author also show that the added nanoparticles not only change the material composition, but also modify the network of the epoxy resin. In a series of experiments it is demonstrated how nanoparticles decrease the chemical shrinkage. The results show a reduction of the shrinkage higher than the volume fraction of the nanoparticles, which can be explained by the formation of interphases. Thermal mechanical analysis also confirms a decreased thermal shrinkage due to the integration of nanoparticles. Finally, the inspection of L-shaped CFRPs samples with different filler contents show the ability of nanofillers to decrease the spring-in.In summary, the integration of aluminum oxide decreases the thermal as well as the chemical shrinkage, increases the thermal conductivity and accelerates the chemical reaction.Overall, these changes in curing behavior lead to an increased dimensional stability of the CFRPs. Thus, nanoparticles may be one way of overcoming the disadvantages of fast curing cycles.

Nanoscaled Boehmites’ Modes of Action in a Polymer and its Carbon Fiber Reinforced Plastic

Laminates of carbon fiber reinforced plastic (CFRP), which are manufactured by injection technology, are reinforced with boehmite particles. This doping strengthens the laminates, whose original properties are weaker than those of prepregs. Besides the shear strength, compression strength and the damage tolerance, the mode of action of the nanoparticles in resin and in CFRP is also analyzed. It thereby reveals that the hydroxyl groups and even more a taurine modification of the boehmites’ surface alter the elementary polymer morphology. Consequently a new flow and reaction comportment, lower glass transition temperatures and shrinkage, as well as a changed mechanical behavior occur. Due to a structural upgrading of the matrix (higher shear stiffness, reduced residual stress), a better fiber-matrix adhesion, and differing crack paths, the boehmite nanoparticles move the degradation barrier of the material to higher loadings, thus resulting in considerably upgraded new CFRP.