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In this paper an approach to increase the energy absorption capacity of laminated composites is investigated. The interlaminar interfaces of two different composite materials, a 2/2 twill weave of glass fibre reinforced polypropylene and a plain weave of carbon reinforced epoxy, are modified. Perforated, non adhesive polytetrafluorethylene (PTFE-) foils were interleaved between the composite layers leading to different interlaminar contact area (ICA) set-ups. The energy absorption capacity, impact resistance as well as the damage and failure behaviour, especially delamination, are evaluated in Charpy drop weight experiments. Based on the resulting force-displacement-response, initiation and propagation energies as well as the ductility index are evaluated. High speed camera imaging is used to correlate failure phenomena to structural response. It can be shown, that the failure behaviour of textile reinforced composites is significantly influenced by the interface modification concept. As a result, the delamination initiation and propagation is enhanced with lower ICA leading to higher energy absorption capacity on the one hand and higher propagation-to-initiation-energy-ratio on the other hand. Consequently, the already high energy absorption capacity of composite materials can be further increased up to 65% while the ductility index rises up to ten times. Keywords: Delamination, Energy dissipation, Textile reinforcement, Composite, Modified interface, Drop weight impact

This research provides an explorative study to determine the influence of a newly developed nano-silica obtained from the dissolution of olivine (OnS) as an additive in cementitious slurries for oil and gas wells. In this context, the heat evolution of normal density slurries of Class G oil-well cement and OnS, cured at different temperatures and atmospheric pressure, is examined by isothermal calorimetry. Under isothermal and isobaric conditions, the dependency of cement hydration kinetics on curing temperature is related to the activation energy and the degree of hydration of the cementing slurries. The apparent activation energy of the different slurries with OnS is estimated using static and dynamic methods. In addition, the effect of adding OnS in conventional density slurries is investigated using standard methods and procedures such as thickening time, rheology, settling and ultrasonic compressive strength determination, all prescribed by corresponding API standards. A beneficial effect of the OnS addition is found on stability, rheology and hydration degree of cementing slurries. Finally, the potential use of olivine nano-silica as an accelerator and enhancer of mechanical properties of oil-well cementitious composites is demonstrated. Keywords: Nano-silica, Olivine, Oil-well cement, Rheology, Ultrasonic compressive strength