Processability of Biobased Thermoset Resins and Flax Fibres Reinforcements Using Vacuum Assisted Resin Transfer Moulding

Biocomposite panels consisting of biobased thermoset resins (EP, PU, UP, and tannin) and flax fibre reinforcements were produced using the vacuum assisted resin transfer moulding process. Panels based on a conventional chemical-based resin matrix were also produced, and investigated comparatively. Rheometric analyses were performed to evaluate the suitability of these resins for liquid composite moulding. Tensile, shear, and impactbending tests have been carried out to assess the quality and mechanical performance of manufactured laminates. The impregnation quality was assessed by means of ultrasonic-C-scanning and microscopy. It turned out that the properties of the biobased composite panels made of biobased epoxy resin and a biobased UP-resin from the company Nuplex in New Zealand were onlay slightly inferior to those produced with a conventional epoxy resin. A biobased PU-resin from the company USSC in the USA developed voids during curing. A tannin-based resin containing of formaldehyde was not processable.

Amorphous Polylactide Bead Foam–Effect of Talc and Chain Extension on Foaming Behavior and Compression Properties

Polylactide(PLA)bead foams show a high potential regarding their applicability in packaging or consumer products.Concerning the comparable properties of PLA to Polystyrene(PS)and the good CO_(2) footprint it represents a potential alternative to petroleum-based polymer foams.However,foaming of PLA is challenging,due to its low melt strength,therefore chemical modifiers are often used.Concerning the bead foam technology regarding PLA,the available literature is limited so far.Within this study,the bead foaming behavior of neat and modified amorphous PLA was investigated.The material was modified by talc and an epoxy-based chain extender.These compounds have been investigated regarding their sorption behavior in CO_(2) atmosphere and their foaming behavior.Foaming was conducted by using the batch foaming method based on a rapid temperature increase after saturation with CO_(2).In order to achieve welded bead foams,a one-step processing for foaming and welding has been established.Finally,the compression properties of the PLA bead foams have been investigated.Densities below 50 kg/m^(3) for single bead foams and 80 kg/m^(3) for molded foams were achieved,respectively.

Prediction of the Enhanced Out-of-Plane Thermal Conductivity of Carbon Fiber Composites Produced by VARTM

The thermal conductivity of epoxy resin can be increased by a factor of eight to ten by loading with highly conductive particles. However, higher loadings increase the viscosity of the resin and hamper its use for liquid composite molding processes. Thus, the enhancement of the out-of-plane thermal conductivity of carbon composites manufactured by VARTM and accomplished by matrix filling is limited to about 250%. In order to derive higher increases in out-of-plane thermal conductivity, additional measures have to be taken. These consist of introducing thermally conductive fibers in out-of-plane direction of the preform using a 3D-weaving process. Measured out-of-plane thermal conductivities of 3D-woven fabric composites are significantly increased compared to a typical laminated composite. It has been shown that if introducing highly conductive z-fibers, the use of a particle filled resin is not necessary and furthermore should be avoided due to the manufacturing problems mentioned above. An existing analytical model was altered to predict the effective thermal conductivity as a function of the composite material properties such as the thermal conductivities and volume contents of fibers in in-plane and out-of-plane directions, the thermal conductivity of the loaded resin, the grid-density of the out- of-plane fibers, and material properties of the contacting material. The predicted results are compared with measured data of manufactured samples.