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M. Merola:
"Mechanical and tribological characterization of GFRP and CFRP laminates obtained by VARTM";
Supervisor: V. Archodoulaki, A. Ruggiero; Werkstoffwissenschaft und Werkstofftechnologie + University of Salerno, 2014; final examination: 2014-11-18.

The present thesis work is the outcome of an international synergy between the University of Salerno, the Vienna University of Technology and the University of Leoben. The thesis consists in the analysis of twelve composite laminates made of epoxy resin reinforced with carbon or glass fibers. The aim was to understand the influence of materials and processing parameters on the impregnation quality of
fiber reinforced polymer laminates and to characterize their mechanical and tribological properties. During the formative period spent in Austria for six months were identified the subject matters to investigate on, realized the laminates and carried out the thermal and mechanicals tests.
The laminates were produced using the Vacuum Assisted Resin Transfer Molding (VARTM) process, a production technology to realize Fiber Reinforced Polymer (FRP) which leads to a highly controlled resin ratio of the final product, for the exceeding resin is pulled away from the laminate. During this process it was possible
to modify the pressure applied when creating the vacuum.
The materials chosen for the realization of the laminates were an epoxy resin, acting as the matrix, glass and carbon fibers, acting as the reinforcement. The geometry of the reinforcement textile were unidirectional and plain woven. This various combination of parameters provided different levels of wettability. Furthermore
the pressure parameter applied by the vacuum pump during VARTM leads
another control over the impregnation velocity. Thus, three level of pressure were chosen: 500, 800 and 950mbar.
Thermal investigations were executed, Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The DSC provided the values of the glass transition temperature (Tg) of the laminates, showing how this temperature is influenced
by the presence or not of the reinforcement and by the different fibers material. TGA was used to indirectly obtain an estimation of the fiber and matrix volume ratio and the void content inside the plates.
Tensile and bending tests were executed to observe how the reinforcement material and process parameters influence mechanical properties. Both tests evidence how the fiber material and geometry have a strong impact on the mechanical characteristic,
whereas the applied pressures chosen in this work (during VARTM process)hardly influences these aspects.
Through a series of micrographs (microscopical photos) was made an investigation of the laminates´ sections. Particular attention was dedicated on the voids evaluation inside the laminates. Deducting an unexpected trend of micro and macro pores concentration in relation to the impregnation velocity. Both kind of voids, in fact, appear to decrease till totally disappear while raising the impregnation velocity.
Finally tribological tests were made. This study, made by a reciprocating sliding tribometer and using a sphere-on-plane configuration, evidenced the reduction of the coefficient of friction when the pure resin is reinforced with one of the used fiber
material. Analysis were also made to study the influence of the relative orientation fiber - sliding direction and the laminate final quality. The worn surfaces were analyzed using a profilometer, which provided 3D images of the track.