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The static strength of carbon/epoxy laminates with three different stacking sequence has been analyzed at different strain rates under three point flexural tests. The materials under study were low cost, low Tg carbon/epoxy laminates with nominal thickness of 1 mm obtained stacking four fabric 0/90 balanced prepregs. The Weibull distribution function was used to compare the data on statistical basis.Quasi–isotropic, cross-ply and angle ply laminates were tested and the strain dependence of static strength was accounted for in the framework of a phenomenological model for fatigue with the objective test the model reliability in predicting the fatigue life and residual strength under variable spectrum with block loadings characterized by different loading frequencies.Preliminary results show that the phenomenological approach can be suitably applied in a rather simple manner solving one of the most intricate tasks within the field of fatigue of composite materials. The research activity represents the last step to build up a software that under variable amplitude loadings comprehensively accounts simultaneously and cycle-by-cycle for the change in the loading ratio, R=σmin/σmax, the maximum applied stress, σmax, and the frequency of loading, f. Details of the approach and the physics behind it are briefly presented with a series of preliminary results.

This paper provides a literature review of one of the most notable models relevant for modelling the fatigue behavior of composite materials. The review first introduced the importance of modelling fatigue in respect of the residual strength degradation of the studied materials, before classifying fatigue models between two categories: the phenomenological models and the mechanistic ones. Among the fatigue modelling approaches, one of them belonging to the category of the “residual strength models” is considered and deepened. In particular, it is analyzed from its genesis to the latest outcomes, passing through the different goals gained during the years.

In this work, based on experimental data available in the literature, we evaluated the reliability of a phenomenological statistical model already developed and commonly utilized for the prediction of fatigue response of composite materials. The data refer to SFRC self-compacting concrete reinforced with steel fibers subjected to compressive fatigue tests. The model was modified to conform to the type of test data. The preliminary approach appears very promising, and deserves to be further developed.

A new approach has been considered for aeronautical composite structures with thermoplastic matrix. The new concept is based on the addition of amorphous PEI films to a semicrystalline thermoplastic PEEK/Carbon Fiber prepreg. The performed chemical-physical analysis demonstrate the good blending between the two resins. The new approach, being presently developed in a project funded by EU, could allow to perform structural parts with affordable costs through the utilization of automated lay-up (ATL and/or AFP) techniques, with a strong cost saving due to the elimination of the autoclave cycle.

In this work a numerical procedure for the design of highly damped multi-layer coating architectures, to be applied in thin-walled mechanic components, is proposed. Optimization restraints with respect to vibration and acoustic emission reduction in operating conditions are considered. The procedure makes use of a multi-layer beam model that takes into account of dissipative actions at the interface between different layers. Dynamic mechanical measurement tests on uncoated and coated symmetric beams are used to identify the unknown material stiffness and interface parameters needed as input by the multi-layer beam model. A virtual prototyping procedure for the simulation of the dissipative effect of different multi-layer coating architectures is proposed and experimentally validated. The damping behaviour of coated slender beam specimens is tested by means of experimental measurements. Coating solutions, based on epoxy organic polymeric materials, and some architectures employing them are presented in this work. Real application examples, concerning the acoustic emission of mechanical gear pumps adopting uncoated and coated casings are presented, by means of the comparison of sound pressure measurements, related to these different configurations, in operating conditions.

The present work presents the evaluation of the performance of single carbon fibers after pyro-gassification treatment in different gasification conditions, i.e. 500°C for 30' and 60', and 600°C for 20', in order to evaluate the intrinsic fiber properties that might contribute to the overall composite behavior when re-impregnated with a polymeric matrix. Such investigation, carried with different analytic techniques such as Raman spectroscopy, XRD diffractometry, SEM Microscopy with EDX atimic mapping and finally mechanical tensile test carried out on single fibers, proves that convenient pyro-gassification conditions might lead to recovery of carbon fibers with properties not far from the pristine ones. While some further tuning of the gasification condition might still be required, 500°C proved to be the optimal temperature for treatment, where the structure and morphology are practically untouched and mechanical properties are well comparable with pristine fibers in terms of Young's Modulus with just a slight drop in ultimate properties.