Bio-based composites offer potential environmental benefits over fossil-based materials, but limited research exists on manufacturing processes with varying material combinations. This study performs a cradle-to-grave Life Cycle Assessment of five composite types to evaluate the role of fully and partially bio-based composites, focusing on the manufacturing stage. The composite materials include glass or flax fiber-based reinforcements embedded in polymer matrices based on a fossil epoxy, a partially bio-based epoxy, or epoxidized linseed oil, fabricated using vacuum-assisted resin infusion. Flax fibers in a partially bio-based epoxy achieve the lowest environmental impacts in most categories when assessed at equal geometry. Glass fiber composites exhibit a higher fiber volume content and material properties and thus demonstrate competitive environmental performance at equal absolute and normalized tensile strength. Composites using epoxidized linseed oil are the least advantageous, with the manufacturing stage contributing a majority of the environmental impacts due to their comparatively long curing times. These results are based on methodological choices and technical constraints which are discussed together with benchmarking against previous studies. While partially bio-based materials can provide a middle ground for enhancing composite environmental performance, the further optimization of bio-based material functionality regarding material properties and processability is pivotal to exploit the full potential of bio-based composites.

Epoxies are important thermoset materials with a broadrange ofapplications. They are nominally homogeneous, have high strength andstiffness, but are brittle. In this work, we develop heterogeneousepoxies via additive printing with the goal of improvingductility, without compromising the strength and stiffness. To thisend, we develop a reactive inkjet printing technology in which theresin and hardener components are printed successively using multinozzleprintheads and which provides control of the local stoichiometricratio. This allows creating epoxies with both in-plane and out-of-planelocal compositional and mechanical heterogeneity. We print and testheterogeneous materials with several microstructural designs and demonstratesignificant improvement of ductility, with retention of strength andstiffness. Furthermore, the properties of printed nominally homogeneoussamples are close to isotropic and identical to those of the castmaterial of the same composition. The technology developed makes useof commercially available inks (resin and hardener); it is fully automatedand provides sufficient flexibility and productivity to print complexmacroscopic samples with 50 & mu;m resolution of microstructuralcomposition control.

In this work we develop an epoxy nanocomposite reinforced with silica nanoparticles in which the filler-matrix interfaces are functionalized with photosensitive phenylazide moieties, which allows controlling the interface mechanical properties by exposure to UV radiation. We demonstrate that the ability of the material to deform plastically and its toughness depend significantly on the strength of interfaces. Significant toughness improvement is obtained at low filling fractions (1 wt%) when using Stober silica of 520 nm diameter with weak interfaces. We perform testing under different loading modes in order to control the crack tip plastic zone size, and observe substantial toughness improvement when crack tip plastic dissipation is enabled, which we associate with void growth at filler particles. Increasing the filler-matrix interfacial strength by photochemical (UV) activation of phenylazides leads to the reduction of the toughening effect.

Functionalization of silica nanoparticles is needed as to improve the mechanical performance of epoxy nanocomposites. Previous experience showed that direct dispersion of commercially available silica nanofillers does not improve significantly the mechanical properties of resulting nanocomposites. Different methods of fabrication are presented along with comments on the possibilities to improve the quality of obtained specimens. Both functionalized and unfunctionalized silica nanoparticles were added in three epoxy resins. The considered filling fraction was in most cases 0.1, 0.3 and 0.5 wt%. The obtained nanocomposites were subjected to monotonic uniaxial loading at room temperature. The static mechanical properties were not significantly changed regardless the filler type or percentage and type of epoxy resin.

Functionalization of silica nanoparticles is needed in order to improve the mechanical performance of epoxy nanocomposites. Previous experience showed that direct dispersion of commercially available silica nanofillers does not improve significantly the mechanical properties of resulting nanocomposites. Fumed silica nanoparticles from Sigma Aldrich (175-225 nm BET) were functionalized carrying exactly 0.28 mmol of phenylazide per 1g of dry particles. During drying they aggregate and their dispersion in epoxy becomes challenging. We use sonication to break agglomerates and obtain adequate dispersion. Different methods of fabrication are presented along with comments on the resulting tensile composite behavior.

HybridRTM terms a publicly funded project, which aims at the development of a processing technique for manufacturing of light weight structural components from hybrid materials. In particular, components involving metal as well as fibre-reinforced polymer composite materials are manufactured in a single processing step by means of the resin transfer moulding (RTM) technique. Project activities include material development and characterization, modelling of thermally induced residual stresses, process simulation, mould development as well as model-based process control in order to ensure consistently high component quality. This paper outlines the fundamental idea of the project and summarizes the most important results gained during the first two years of project activities.