Effect of neat and reinforced polyacrylonitrile nanofibers incorporation on interlaminar fracture toughness of carbon/epoxy composite

This paper presents an experimental investigation on fracture behavior of epoxy resin-carbon fibers composites interleaved with both neat polyacrylonitrile （PAN） nanofibers and A1203-PAN nanofibers. In particular, the paper focuses on the effect of adding Al2O3 nanopartiles in PAN nanofibers, which were incorporated in unidirectional （UD） laminates. The effectiveness of adding a thin film made of Al2O3-PAN on the fracture behavior of the carbon fiber reinforced polymer （CFRP） has been addressed by comparing the energy release rates, obtained by testing double cantilever beam （DCB） samples under mode I loading condition. A general improvement in interlaminar fracture energy of the CFRP is observed when the both neat PAN nanofibers and Al2O3-PAN nanofibers are interleaved. However, higher interlaminar strength has been observed for the samples with a thin film of Al2O3-PAN nanofibers, suggesting a better stress distribution and stress transformation from resin-rich area to reinforcement phase of hybrid composites.

Development of Morus alba Reinforced Poly-Lactic Acid with Elevated Mechanical and Thermal Properties

This research investigates the mechanical and thermal properties of Morus alba combined with polylactic acid in comparison with other natural fibers. The study uses three different fiber and PLA compositions - 20%, 30%, and 40% respectively - to produce composite materials. In addition, another composite with the same fiber volume is treated with a 4% NaOH solution to improve mechanical properties. The composites are processed by twin-screw extrusion, granulation, and injection molding. Tensile strength measurements of raw fibers and NaOH-treated fibers were carried out using a single-fiber tensile test with a gauge length of 40 mm. It was observed that the NaOH surface treatment increases the resistance against tensile loading and exhibited improved properties for raw fiber strands. The diameter of the fibers was measured using optical microscopy. During this research, flexural tests, impact tests, differential scanning calorimetry (DSC), and heat deflection temperature measurements (HDT) were conducted to evaluate the mechanical and thermal properties of the developed composite samples. The results indicate that the mechanical properties of NaOH-treated Morus alba-reinforced polylactic acid outperform both virgin PLA samples and untreated Morus alba samples.

The flame retardancy of alginate/flame retardant viscose fibers investigated by vertical burning test and cone calorimeter

In this research, the flame retardancy of neat alginate fiber, flame retardant viscose fiber （FRV） and alginate/FRV （50/50） blending fibers were investigated by vertical burning and cone calorimeter tests. The vertical burning test showed that the afterflame time of alginate fiber was 0 s, but alginate presented serious smoldering behavior with the afterglow time of 605 s and damaged length of 85 mm, while the afterglow time of FRV was 0 s. When the FRV was incorporated into alginate with the weight ratio of 50/ 50, the afterglow time and damaged length were significantly reduced to 85 s and 35 mm, indicating the smoldering of alginate can be effectively decreased. The morphology and chemical structure of the alginate residual demonstrated that it was seriously destroyed during smoldering process, which was ascribed to its relative low initial thermal degradation temperature. Based on the thermal properties analysis, alginate and FRV fibers shared the concurrence of rapid degradation in the same temperature region of 250-300 ℃, through which, the compact and stable char formed by FRV can prevent the heat transmission and suppress the smoldering of alginate. Further, the cone calorimeter results demonstrated that the time to ignition （TTI） significantly increased and peak heat release rate （PHRR） decreased for alginate/FRV （50/50） compared with FRV. With this research, a new method to overcome the smoldering of alginate was proposed by blending with FRV

New Test Light Spectrum Design for L/U-Band Extended Optical Fiber Line Testing System

This paper describes a new design for the test light source of an L/U-band extended optical fiber line testing system and the side-band suppresser ratio of the test light should be more than 70 dB.

Failure behavior of interfacial domain in SiC-matrix based composites

In this work,the microstructure,failure behavior and interfacial properties with respective to the interfacial domain in SiCf/BN/SiC and C_(f)/PyC/SiC composites were studied via the fiber push-in test.The differences in the mechanical response of the interfacial domain were observed.During the fiber push-in test for SiCf/BN/SiC,the interface debonding accompanied with interphase fracture occurred,resulting in an obvious sign of the onset of debonding on loading-displacement(P-u)curves.While the good continuity of P-u curves can be observed for Cf/PyC/SiC,which is due to that the failure is in the form of interface debonding along with interphase lateral slipping caused by the extension of buckled carbon fiber,without any interphase fracture.The interfacial properties calculated from the fiber push-in test show that Cf/PyC/SiC possesses a weaker interfacial domain compared with SiC_(f)/BN/SiC.The interfacial shear stress of SiCf/BN/SiC and C_(f)/PyC/SiC composites amounts 94.2 and 48.1 MPa,respectively.

Prediction of cutting forces in ball-end milling of 2.5D C/C composites

Machining of carbon/carbon （C/C） composite materials is difficult to carry out due to its high specific stiffness, brittleness, anisotropic, non-homogeneous and low thermal conductivity, which can result in tear, burr, poor surface quality and rapid wear of cutters. Accurate and fast pre- diction of cutting forces is important for milling C/C composite materials with high quality. This paper presents an alternative cutting force model involving the influences of the directions of fiber. Based on the calculated and experimental results, the cutting forces＂ coefficients of 2.5D CC com- posites are evaluated using multiple linear regression method. Verification experiment has been car- ried out through a group of orthogonal tests. Results indicate that the proposed nmdel is reliable and can be used to predict the cutting forces in ball-end milling of 2.5D C/C composites.