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The accelerated testing methodology (ATM) for the statistical life prediction of carbon fiber reinforced plastics (CFRP) under creep and fatigue loads based on the viscoelasticity of matrix resin has been proposed by authors. This method has been successfully applied to the life predictions of unidirectional CFRP with thermosetting epoxy resin as the matrix under tensile and flexural loads. In this paper, this method was applied to the fatigue life prediction of unidirectional CFRP (CF/PP laminates) with thermoplastic polypropylene (PP) as the matrix under tensile and flexural loads, and the effect of matrix viscoelasticity and load cycles on the fatigue behavior of CF/PP laminates were discussed under tensile and flexural loads. First, the viscoelasticity of matrix PP was measured. Second, the static and fatigue strengths of CF/PP laminates were statistically measured at various temperatures and frequencies under tensile and flexural loads. Third, all of material parameters in the fatigue strength formulation in ATM were determined using measured data, and the statistical long-term fatigue strengths of CF/PP laminates were predicted under tensile and flexural loads. As results, comparison with tension and bending test results clarified that the long-term tensile fatigue strength of CF/PP laminates decreases at an accelerated rate as the number of cycles increases, and that the flexural fatigue strength is affected by temperature and frequency rather than by the number of cycles to failure. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced plastics (CFRP) composites are the most widespread advanced composite materials. Still, machining with traditional tools quickly generates defects such as high cutting forces and severe subsurface damage, while micro-textured tools can improve CFRP machining performance. Therefore, to reveal the cutting mechanism of CFRP processing by micro-textured tools and guide the tool design, macroscopic and microscopic orthogonal cutting models were established in this study, which compared and analyzed the material removal process and the indicated topography of unidirectional CFRP with different fiber orientations (0°, 45°, 90°, and 135°) by traditional tools and micro-textured tools, and the accuracy of the models was verified with experiments. Compared with traditional tools, micro-textured tools reduce cutting forces by minimizing the tool-chip contact length to reduce friction and converting the fiber failure form from crush failure to shear failure. Meanwhile, the texture on the rake face enables cutting burrs, effectively improving the surface quality of the workpiece and suppressing the depth of subsurface damage. In addition, the influence of different texture parameters on the machining quality of the workpiece was analyzed. [ABSTRACT FROM AUTHOR]

A composite laminate with high conductivity and high mode I fracture toughness was prepared by using a silver-plated nylon mesh as the interleaf. Through in-depth comparison with the silver-plated non-woven veil interleaved composites, the mechanisms of the conductivity improvement and interlaminar toughening were discussed. The conductivities along the fiber direction, in transverse to fiber direction and through thickness direction reached 739 S/cm, 734 S/cm, and 5.4 S/cm, respectively, which increased by 196%, 344,500%, and 4326%, respectively, and are much higher than these of the other modified systems. At the same time, the mode I interlaminar fracture toughness increased by 112%. Mechanism study shows that the conductivities along the fiber direction and in transverse to fiber direction are greatly affected by the interleaf conductivity, while the conductivity through thickness direction is little affected. The toughening mechanism of the plain or silver-plated nylon mesh is much different from that of the non-woven veils. Both of the composites interleaved with the plain or silver-plated nylon mesh have higher mode I interlaminar fracture toughness, but less improved mode II toughness. The effect of silver-plating on the mode I and mode II fracture toughness was studied. [ABSTRACT FROM AUTHOR]

A new strategy of recycling and reusing abandoned carbon fiber reinforced plastics (CFRP) is proposed: CFRPs are first fully carbonized to CF reinforced carbon (C/C) preforms, and then are manufactured into high value-added C/C composites. The results showed that the carbon residue rate of epoxy-resin (EP) matrix was fully recovered as the decomposition route of EP matrix was changed by charring agent. The recycled CF (rCF) was not markedly oxidized or thermally damaged, and possessed comparable properties with those of the virgin CF (vCF) after pyrolysis. The pyrolytic char had no obvious negative effect on the densification efficiency of the rCF reinforced carbon (rCF/C) composites. Both of the rCF/C and vCF reinforced carbon (vCF/C) composite bodies were quite dense, and exhibited almost no difference in their microstructures. The rCF/C and vCF/C composites therefore had quite close interface bonding strength (12.6 MPa and 13.0 MPa, respectively), and bending strength (106.4 MPa and 111.5 MPa, respectively). Furthermore, the rCF/C composites possessed comparable ablative rate with that of the vCF/C composites. The rCF/C composites derived from abandoned CF/EP composites present a great potential to be used as substitutes for vCF/C composites owing to their indistinguishable properties. [ABSTRACT FROM AUTHOR]