In this study, glass fiber (GF)/phenol formaldehyde resin (PF)/epoxy resin (EP) three-phase electrical insulating composites were fabricated by selective laser sintering (SLS) additive manufacturing technology and subsequent infiltration. In the three-phase composites, glass fibers modified by a silane coupling agent (KH-550) were used as reinforcements, phenol formaldehyde resin acted as the binder and matrix, and infiltrated epoxy resin was the filler. Mechanical and electrical properties such as tensile strength, bending strength, dielectric constant, electrical conductivity, and electric breakdown strength of the GF/PF/EP three-phase composite parts were investigated. The results indicated that after being infiltrated with EP, the bending strength and tensile strength of the GF/PF/EP composites increased by 30% and 42.8%, respectively. Moreover, the flexural strength and tensile strength of the GF/PF/EP composite increased with the increase of the glass fiber content. More importantly, the three-phase composites showed high electrical properties. Significant improvement in the dielectric constant, electric breakdown strength, and resistivity with the increase in the content of glass fiber was observed. This enables the prepared GF/PF/EP composites to form complex structural electrical insulation devices by SLS, which expands the materials and applications of additive manufacturing technology.

Due to its superior mechanical properties, graphene (Gr) has the potential to achieve high performance polymer-based nanocomposites. Previous studies have proved that defects in the Gr sheets could greatly reduce the mechanical properties of Gr, while the Stone-Wales (SW) defect was found to enhance the interfacial mechanical strength between Gr and epoxy. However, the combined effects of defects on the overall mechanical properties of Gr/epoxy nanocomposites have not been well understood. In this paper, the effect of the SW defect on the mechanical properties of Gr/epoxy nanocomposites was systematically investigated by using molecular dynamic simulations. The simulation results showed that the SW defect would degrade the mechanical properties of nanocomposites, including the Young’s modulus and in-plane shear modulus. Surprisingly, the transverse shear modulus could be remarkably enhanced with the existence of SW. The reinforcing mechanisms were mainly due to two aspects: (1) the SW defect could increase the surface roughness of the Gr, preventing the slippage between Gr and epoxy during the transverse shea; and (2) the nanocomposite with defective Gr enables a higher interaction energy than that with perfect graphene. Additionally, the effects of temperature, the dispersion and volume fraction of Gr were also investigated.

High-temperature laser bed powder fusion (HT-LPBF) technology is an ideal method for processing poly-ether-ether-ketone (PEEK) implants with personalized bionic structures, but the biological inertia of PEEK limits its medical applications. In this study, we evaluated the mechanical and biological properties of a novel akermanite (AKM)/PEEK composite for HT-LPBF. The results showed that tiny AKM particles are evenly attached to the surface of the PEEK particle. The delayed peak crystallization temperature and stable sintering window ensure the processing feasibility of the AKM/PEEK composites. The tensile strength and Young’s modulus are in the range of 30.83–98.73 MPa and 2.27–3.71 GPa, respectively, which can match the properties of cancellous bones and meet their implanting requirement. The CCK-8 experiments demonstrated the biocompatibility of the composites and the good proliferation of bone marrow stromal cells. The dense hydroxyapatite network layer and petal-like hydroxyapatite demonstrates biological activity, indicating that the composite has a good potential in the orthopedics fields.