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A novel B-stage resin system is developed for the „Resin Transfer Pressing“ (RTP) process. This composite manufacturing technique makes use of nonwoven and recycled carbon fibres (rCF) that are oversaturated with a thermosetting resin. The new resin system is based on two different hardeners, allowing to easily impregnate the rCF, storing the semi-finished parts at room temperature and finally curing them via compression molding. It is shown that a commercially available resin system can be tailored to the required needs by the smart combination of state-of-the art, latent hardener systems.The present study focusses on the route for B-staging of the resin system. The viscosity for impregnation and oversaturation was adjusted to be in the range of 5 to 40 Pa·s at 60°C. The viscosity increases to above 50 Pa·s at room temperature, allowing storage and handling of the semi-finished parts and processing them whenever it is required. Choosing a proper processing temperature is important during the B-staging process to avoid any unintended activation of the second hardener, which is responsible for the final curing stage of the system.

The Solid Sorbent Technology (SST) is a breakthrough technology which separates CO2 from flue gas in a continuous Temperature Swing Adsorption (TSA) fluidized bed process using solid adsorbent. The technology simultaneously delivers > 90% CO2 capture efficiency and > 95% CO2 purity with low to no process related emissions and at lower capture costs compared to state-of-the-art liquid amines technology. This paper will discuss results of a 900 h piloting campaign using Lewatit VP OC 1065 adsorbent and its impact on the cost comparison with liquid amines technology. The successful operation of the pilot plant and finalization of the test campaign marked the progression of the technology readiness level from TRL4 to TRL6.

The toughening performance of hybridized core-shell rubber particles and block copolymers on bulk epoxy and epoxy based carbon fibre reinforced composites was investigated. The results reveal that the interlaminar fracture toughness of the fibre reinforced laminates increased by more than 300% due to an enhanced fibre-matrix adhesion because of a combination of BCP and CSR particles. However, no synergistic improvement of the fracture mechanics properties of the bulk materials was found. Thereby, the critical energy release rate of the bulk and fibre reinforced materials is related to the interparticle distance to particle size ratio of the modifiers in the bulk/matrix systems and the plastic zone size. Furthermore, the fibre volume content of the CFRP influences the final BCP phase morphology, and thus the fracture toughness.

This study focused on the examination of unsaturated polyester resin based continuous glass filament mat reinforced composites (GFRP) and the modification by core-shell rubber particles (CSR). The goal was to evaluate the effect of CSR toughening on processability, mechanical properties and impact strength as well as the interaction with inorganic color particles in the submicron range on the GFRP. The interlaminar fracture toughness GIc of the modified GFRP was improved by about 20% compared to the neat GFRP by using only 2 wt-% of the CSR modifier, while only marginally increasing the viscosity of the reactive mixture. The responsible mechanisms were found to be local shear yielding of the matrix and an improved fiber-matrix adhesion. The hybridization of inorganic color particles and CSR reduced the interlaminar fracture toughness of the laminate, which could be ascribed to the formation of pores due to the introduction of the oxide particles. However, the impact behavior of the GFRP was positively affected.

This study systematically investigates the influence of a Polymethylmethacrylate-block-Polybutylacrylate-block-Polymethylmethacrylate (PMMA-b-PBuA-b-PMMA) triblock copolymer (BCP) on the flexural properties, the static fracture toughness and especially the resistance to fatigue crack propagation (FCP) of a cycloaliphatic amine cured bisphenol A based epoxy resin (EP). The results show that already small concentrations of BCP can significantly improve fracture toughness and the resistance to fatigue crack propagation. Crack growth rate as well as the Paris' law exponent m were considerably reduced from m = 15.5 of the neat epoxy to m = 8.1 for the BCP toughened materials. Simultaneously, the resistance to fatigue crack propagation was found to increase drastically from a critical stress intensity factor range ΔKIc of 0.39 MPam to 0.81 MPam. Fractography and structural analysis reveal that the improved resistance to fatigue crack propagation correlates to crack shielding and zone shielding mechanisms caused by the synergistic interaction of BCP-rich domains and dispersed nanometer sized, presumably BCP-rich particles in epoxy-rich regions. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

The benefit of fiber-reinforced composites originates from the interaction between the fiber reinforcement and the matrix. This interplay controls many of its mechanical properties and is of utmost importance to enable its unique performance as a lightweight material. However, measuring the fiber−matrix interphase strength with micromechanical tests, like the Broutman test, is challenging, due to the many, often unknown boundary conditions. Therefore, this study uses state-of-the-art, high-resolution X-ray computed microtomography (XRM) as a tool to investigate post mortem the failure mechanisms of single carbon fibers within an epoxy matrix. This was conducted at the example of single carbon fiber Broutman test specimens. The capabilities of today’s XRM analysis were shown in comparison to classically obtained light microscopy. A simple finite element model was used to enhance the understanding of the observed fracture patterns. In total, this research reveals the possibilities and limitations of XRM to visualize and assess compression-induced single fiber fracture patterns. Furthermore, comparing two different matrix systems with each other illustrates that the failure mechanisms originate from differences in the fiber−matrix interphases. The carbon fiber seems to fail due to brittleness under compression stress. Observation of the fiber slippage and deformed small fracture pieces between the fragments suggests a nonzero stress state at the fragment ends after fiber failure. Even more, these results demonstrate the usefulness of XRM as an additional tool for the characterization of the fiber−matrix interphase.

The effect of the hybridization of a triblock copolymer and a rigid TiO2 nanofiller on the tensile, fracture mechanics and thermo-mechanical properties of bisphenol F based epoxy resin were studied. The self-assembling block copolymer, constituted of a center block of poly (butyl acrylate) and two side blocks of poly (methyl) methacrylate-co-polar co-monomer was used as a soft filler, and TiO2 nanoparticles were employed as rigid modifiers. Toughening solely by block copolymers (BCP&rsquo, s) led to the highest fracture toughness and fracture energy in the study, KIc = 2.18 MPa&middot, m1/2 and GIc = 1.58 kJ/m2. This corresponds to a 4- and 16-fold improvement, respectively, over the neat reference epoxy system. However, a reduction of 15% of the tensile strength was observed. The hybrid nanocomposites, containing the same absolute amounts of modifiers, showed a maximum value of KIc = 1.72 MPa&middot, m1/2 and GIc = 0.90 kJ/m2. Yet, only a minor reduction of 4% of the tensile strength was observed. The fracture toughness and fracture energy were co-related to the plastic zone size for all the modified systems. Finally, the analysis of the fracture surfaces revealed the toughening mechanisms of the nanocomposites.