Papers by Author: Michelle Salvia

Abstract: It is a serious problem that short carbon fiber reinforced polyamide 66 (SCFRPA66) cannot be easily shaped by 3D-printing for practical usages. In order to improve on the brittleness, homogeneous low potential electron beam irradiation (HLEBI) to both sides of 3D-SCFRPA66 samples was found to increase strain at tensile strength (εts), corresponding to homogeneous deformation and fracture strain (εf), as well as resistant energy of homogeneous deformation (Ehd), whereas the HLEBI decreased the tensile strength (σts). This improvement in ductility can be explained by lone pair electrons, dangling bond generation, shortening and relaxation of the polymeric chains by the HLEBI.

Abstract: Carbon fiber reinforced polymers (CFRP), which are typical composite materials, and have been applied as light structural materials with high strength [1, 2]. The further strengthening has been always expected to develop high speed transports with small energy consumption. Although influences of electron beam (EB) irradiation with high energy on the fracture toughness of carbon cross of carbon fibers in thermo-hardened epoxy resin matrix (thermo-hardened CFRP) have been often reported [3], no one has succeeded the strengthening of CFRP irradiated by electron beam. On the other hand, the homogeneous low voltage electron beam irradiation (HLEBI) often induces not only the hardening, high wear resistance and sterilization for practical use of polymer, but also the mist resistance [4–6]. In addition, the irradiation has improved not only the bending fracture strain of carbon fiber [7, 8], but also the deformation resistivity, strength and fracture strain on static tensile test [9]. In our recent research, it has succeeded that the EB-irradiation also enhances the fracture stress and fracture strain of static bending test of thermo-hardened CFRP [10]. Furthermore, the improvement of impact value of thermo-hardened CFRP by EB-irradiation has been also reported to apply to high-speed transports [11]. However, the production rate of thermo-hardened CFRP has been serious problem in mass production.

Abstract: In dry clutch systems, the clutch facing is an annular shaped continuous fibre composite with organic matrix (thermo set resins) which transmits the torque from the engine to the wheels. In use it is submitted to thermo-mechanical cycling. Due to the composite fibre organisation, the strain field under thermo-mechanical loading is not homogenous. Full field data is needed to describe the material behaviour. Digital Image Stereo-Correlation (DISC) was used to determine the coefficient of thermal expansion (CTE) of the material. To determine the effect of temperature and cyclic loading on the mechanical properties, the composite was subjected to different thermal cycles. The material properties are modified with increasing temperature and number of cycles. These results were confirmed by dynamic mechanical analysis which showed thermal ageing of the resin. The local information given by the strain fields revealed a non uniform evolution of the material properties with thermal cycling.

Abstract: The use of natural fibers as reinforcement in composites is emerging. Several studies are underway to improve the mechanical characteristics of these fibers and its matrix interface properties for better load transfer. However, the treatments generally used are relatively expensive and complicated to apply. This work deals with the effect of new Fibroline process on tensile and interfacial properties of hemp fiber reinforced in polypropylene. Fibroline is a dry powder impregnation method which consists of submitting fibers and polymer powder under strong alternating electric field. Morphology and tensile properties of hemp fibers after different surface treatments (raw, dried, raw and Fibroline-treated, dried and Fibroline-treated) are evaluated. Interface properties of treated hemp fibers on polypropylene matrix are then characterized by fragmentation test of monofilament composites. Results showed the Fibroline treatment reduces the fiber mechanical properties but improves the load transfer efficiency due to random generation of surface cracks and better fiber/matrix adherence, respectively. For the case of dried and Fibroline-treated hemp fibers, large decrease in mechanical and interfacial properties was observed.