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Novel solutions using renewable materials are needed to tackle sustainability issues in industry. Totally cellulose-based composites, suitable for thermoplastic processing are introduced in this paper. The polymer matrix was a thermoplastic cellulose ester, Thermocell. Composites reinforcing fibres consisted of microcellulose, bleached softwood kraft pulp fibres, or long regenerated viscose fibres. The latest allowed to improve composites mechanical performance, especially at 20 wt-% loading. In the extrusion process, fibres oriented along processing direction, giving hopes for a future use in extrusion type additive manufacturing (AM). However, further developments of the AM system are required to print this material. With 20 wt- % microcellulose, the composite could be 3D printed using a fused granular fabrication process. Improved microcellulose dispersion was achieved with 2 wt-% tall-oil fatty acid lignin ester or cellulose ester ether additives. Wood-based additives also helped to decrease the internal porosity, leading to better mechanical performance of 3D printed materials.

The ferritic-martensitic steel P91 (X10CrMoVNb9-1) is widely used in high temperature steam systems of power plants, and it is a candidate material for Gen-IV reactors. In comparison to austenitic steels, thick-wall P91 has relatively attractive mechanical and physical properties combined with resistance to stress corrosion cracking in water-steam environments. This study aimed to explore the combined cyclic, creep and relaxation behaviour of P91 material up to a component wall thickness of 60 mm. Uniaxial specimens were subjected to cyclic loadings with periodic forward creep or relaxation at peak stress. The results indicate that prior creep or intermediate relaxation periods up to 72 h will influence the subsequent cyclic softening of P91, but do not significantly reduce the cyclic life. In contrast, prior cycling has a detrimental effect on the subsequent creep life. A simplified creep-fatigue model is shown to predict life better than usual code-based approaches for cyclic service of P91 steel. Improved verification of all models would benefit from the availability of more extensive long-term data on P91 steel.

Oxygen-free phosphorus-doped (OFP) copper is a prime candidate outer shell (overpack) material to protect the spent fuel canisters against corrosion in the underground repository. As the canister and its copper shell are subject to internal heating by residual activity of the contents, it is possible that with sufficient loads or strains from e.g. thermal, handling or other sources shell will creep to some extent. In this work the isothermal uniaxial relaxation behaviour of OFP copper is considered from the point of view of basic relaxation modelling and experimental model validation. Validation is considered necessary before extending the modelled relaxation behaviour to multi-axial cases and finite element analysis (FEA) of the canister (overpack) details. The initial candidate relaxation models were selected for the expected performance at relatively low temperatures and likely tolerance of transients when implemented to FEA. The initial experiment however shows little difference between the selected models, and further testing appears necessary. Nevertheless, classical relaxation models appear to provide fair agreement with to the observed low temperature relaxation in OFP copper

Ni-based superalloys, such as alloy 263, have excellent creep strength at high temperatures due to precipitation of gamma prime. Therefore they are candidate materials for thick section components as well as tubing in advanced ultra-supercritical (A-USC) power plants where temperatures exceed 700 °C. Because of the lower thermal expansion coefficient the Ni-based superalloys are less prone to thermal fatigue damage than the austenitic stainless steels. A series of creep-fatigue (CF) and low cycle fatigue (LCF) tests have been performed in order to study the effect of the test temperature, hold time, total strain range and a pre-creep exposure of 178MPa / 3000h / 750ºC on the creep-fatigue life of alloy 263. All LCF and CF tests were per-formed using the high precision pneumatic loading system (HIPS) at temperatures in the range of 700-750ºC, the total strain range between 0.5-1.0% and with hold periods up to 10h in both tension and compression. In this paper stress relaxation time plots, ?-N plots and ??-N plots are presented for alloy 263. The creep-fatigue test results are analysed using time fraction ap-proach utilized in the nuclear material assessment and design codes, such as RCC-MRx and ASME III NH. The results are compared against public domain data and fitted to the recently developed ? -model. The ? -model utilizes the creep rupture strength and tensile strength for predicting CF life with a minimum amount of fitting parameters. It is shown that the number of cycles to failure for CF data for alloy 263 can be accurately predicted by the ? -model. Furthermore, the practicality in using the time fraction approach for presenting the combined CF damage is discussed and recommendations for alternative approaches are made

In this paper the creep-fatigue (CF) and low cycle fatigue (LCF) properties of alloy 263 are considered. Both virgin and pre-crept (750ºC / 178 MPa / 3000 h) test materials were tested to investigate the impact of creep damage prior to cycling. The tests performed on the high precision pneumatic loading system (HIPS) are in the temperature range of 700-750ºC, total strain range of 0.6-1.0% and with hold times in both tension and compression. Curves of peak stress as a function of cycles and curves of stress relaxation are presented for the alloy 263. The creep-fatigue test results are also analysed using methods described in the assessment and design codes of RCC-MR, R5 and ASME NH as well as by the recently developed -model. It is shown that the number of cycles to failure for CF data can be accurately predicted by the simple -model. The practicality in using the life fraction rule for presenting the combined damage is discussed and recommendations are given on alternative approaches.