Composites Science and Technology最新文献

Epoxy-impregnated aramid composites, notable for their excellent mechanical and insulation qualities, are pivotal in electrical engineering and electronics. However, their performance is severely restrained by interface issues. This research proposes an effective modification strategy for improving interface property by employing non-thermal atmospheric plasma to introduce active functional groups onto aramid paper. The modified composites demonstrated a 26 % increase in tensile strength and a 20 % enhancement in breakdown strength at best, alongside inhibited charge transport properties and reduced partial discharge under operational electric fields. Molecular simulation suggests that plasma treatment bolsters interface hydrogen bonding, restricting the chain mobility of the resin molecular, and thus augmenting inter-phase compatibility. This study offers a factual perspective on improving resin-impregnated composites, laying a theoretical foundation for advancing high-performance materials in power industries.

This paper proposes an innovative class of two-and-a-half dimensional (2.5D) hybrid continuous fiber reinforced lattice structures (CFRLSs) that rationally combine distinct lattice designs to leverage the tensile strength of fibers for achieving superior compression performance. These hybrid structures are fabricated through a self-supporting suspension printing (SSSP) method, which enables the fabrication of suspension structures across substantial gaps through continuous fiber 3D printing (CF-3DP). The compression behavior of the proposed 2.5 D hybrid CFRLSs was optimized by focusing on two key variables in hybridizing the basic lattice along the build direction: composition ratio and distribution strategy. Finite element and analytical models were developed to elucidate their three failure mechanisms and related control strategies. Compared to the conventional single-type structure, i.e., honeycomb design, the proposed hybrid structures show a substantially higher compression performance, with improvements of up to 141.3 % and 330.1 % in specific strength and modulus, respectively, even at a lower density. This hybrid lattice design method based on SSSP opens up new horizons for engineering high-performance CFRLSs with superior compression performance by fully exploiting the design freedom offered by CF-3DP.

Hydroxyapatite/polyether-ether-ketone (HA/PEEK) composites are promising prosthesis materials due to their biological activity, but they often have mechanical properties that fall short of clinical requirements, typically with HA content below 40 wt%. This study utilized a customized screw extrusion-based 3D printhead, incorporating carbon fiber (CF) to produce HA/CF/PEEK composites with enhanced mechanical properties and HA content up to 60 wt%. The investigation focused on the effects of HA and CF content on the crystallization process and mechanical properties. Results showed that HA and CF affect crystallization differently due to varying densities; a phase volume ratio above 20 % inhibits crystallization. The elongation at break for composites with 10 wt% HA was 27.9 %, a record for 3D-printed HA/PEEK composites. The tensile strength for composites with 10 wt% HA and 40 wt% CF reached 115.7 MPa, the highest among the tested three-phase composites. Data fitting indicated that the effects of HA and CF on strength are independent. The toughness decreases exponentially with increased reinforcing phase content. This study explored a new method for preparing HA/PEEK and HA/CF/PEEK composites, expanding the performance boundaries of PEEK composites, enhancing their potential applications in bone implants.

The three-dimensional failure process experimentally observed by synchrotron radiation X-ray computed tomography (SR X-CT) regarding the influence of the interfiber distance is discussed on the basis of the results of numerical experiments. Triaxial stress states in the fracture process zone of carbon fiber reinforced polymers were analyzed on the mesoscale under mode I and mixed-mode (mode I + II) loading. Yield and damage models depending on stress triaxiality were used to accurately simulate three-dimensional stress states in the damage zone around the crack tip. Owing to the heterogeneity of composites, deviatoric stress is prominent in the thin resin region where the interfiber distance is small under mode I loading. On the other hand, matrix resin is triaxially stressed in the middle point between carbon fibers in the thick resin region where the interfiber distance is large. Under mode II loading, the shapes of fiber/matrix debonding depended on the interfiber distance. Areas with stress concentration were found owing to a large debonding area in the thick resin region resulting in a matrix cracking-prone stress state. These findings explain the damage and failure processes well observed by SR X-CT and provide a fundamental understanding of the damage mechanism at a mesoscale.

Multiscale models for fibre-reinforced polymer composites currently lack experimentally validated microscale damage descriptors as input parameters. This work demonstrates the occurrence of strain localisation phenomena at the fibre/matrix level using nanoscale digital image correlation. Unidirectional carbon-fibre reinforced epoxy and glass-fibre reinforced PMMA composites were loaded in transverse compression in a scanning electron microscope. Radial and shear strain maps were extracted and compared with finite element simulations based on a conventional elastoplastic model. Near the interface, an interphase layer is present in the matrix, presumably due to locally different polymerisation conditions. A skin-core structure was found in carbon fibres, corresponding to an increased transverse modulus towards the interface.

Recently, metamaterial absorbers (MAs) with a multi-layered anisotropic substrate have received significant attention due to their huge potential for application in major engineering fields like aircraft stealthing, electromagnetic sensing, and materials processing, etc. However, the working mechanism of this type of structural materials has not been well-understood yet, as the classical equivalent circuit model was only proposed to describe the conventional overall isotropic metal-substrate MAs. In this paper, for the first time, a generalized equivalent circuit model that considering the anisotropy of the multi-layered substrate is constructed, based on new findings about the unique distribution of the induced current inside the MA with a carbon fiber reinforced polymer (CFRP) composite substrate – a typical multi-layered anisotropic laminate. The effectiveness of the generalized analytical model is validated by predicting the structure-performance relationship of the CFRP-substrate MA, which is in excellent agreement with numerical simulation results based on Maxwell's equations. Experimental cases have also been conducted to demonstrate the strong power of this model in inverse design of several tunable MAs. Through the above research, the scope of the equivalent circuit modelling has been greatly broadened, which can help to design a series of MAs with more extreme performance in future.

The external load angle is known to have a significant influence on the mechanical behavior of two-dimensional triaxially braided composites (2DTBCs). However, the experimental data for 2DTBCs under off-axial loading provide limited information for understanding the failure mechanisms. In this study, a comprehensive mesoscale finite element (FE) model for simulating 2DTBC specimens was established to evaluate the mechanical responses and damage characteristics when off-axial tensile loads are applied. The FE model effectively captured the mechanical response at five distinct angles (0°, 30°, 45°, 60°, and 90°) and revealed the evolving patterns of failure behavior, damage morphology, and out-of-plane deformation mechanisms corresponding to the different loading angles. The findings indicate that, when the external load aligns with the axial fiber bundle direction, the primary failure mechanism involves the fracture of load-bearing fiber bundles. In contrast, deviations from the axial loading direction resulted in failure that was primarily due to the undulation of the bias fiber bundles, resulting in a loading angle–dependent warping at the edge of the specimen due to local shear stress concentration. The findings of this study provide valuable insights that can inform the design of structures with improved application.

Thermal interface material (TIM) has a great potential for efficient heat management and safety of electronic devices. However, achieving high performance polymer-based TIM is still challenging because of its intrinsic thermal conductivity and weak mechanical properties. In particular, electromagnetic interference shielding effect (EMI SE) of polymer-based composites has a great attraction according to electronic devices have become ubiquitous, playing integral roles in everyday life in our increasingly interconnected world. Herein, a porous carbon cloth (CC) for use as a continuous thermally and electrically conductive template is prepared via a freeze-casting method, after which mxene (MX) is chemically grafted onto the CC surface. Then, the as-prepared MX-CC is used along with alumina (AO) to fill a poly vinyl alcohol (PVA) matrix in order to fabricate a thermally conductive film with electromagnetic interference (EMI) shielding properties. The resultant composite demonstrates remarkable characteristics, including an excellent EMI shielding effect of 28 dB, substantial tensile strength of 19 MPa, and impressive out of plane thermal conductivity (3.98 W/mK). When applied to a light-emitting diode (LED), the PVA/MX-CC/AO composite effectively manages heat, thereby resulting in a 49 °C reduction in the operating temperature. Therefore, the composites developed herein hold great promise for improving thermal management in electronic devices.

The design of carbon fiber (CF)-reinforced polyetheretherketone (PEEK) composite materials with suitable interfaces has consistently been challenging. In this study, we sulfonated poly (phthalazinone ether sulfone ketone) (PPESK) and PEEK to prepare water-soluble SPPESK and SPEEK. Subsequently, we prepared a water-soluble sizing agent (SPPESK/SPEEK) via a straightforward blending process. This sizing agent tended to accumulate randomly on the surfaces of CFs, forming a thin film with a heterogeneous structure in the nanoscale. At the molding temperature of the composite material, the two components on the fiber surface exhibited different rheological behaviors, with PEEK preferentially infiltrating the SPEEK region, forming strong molecular entanglements. Meanwhile, the SPPESK region provided a rigid supportive structure, offering the potential for the mechanical interlocking of PEEK in the interface layer. The performance of the prepared composite materials was significantly enhanced, with their interlaminar shear strength and flexural strength reaching 87.1 MPa and 975.8 MPa, respectively. With respect to those of commercial fiber-reinforced PEEK composites, an 89.8 % increase in interlaminar shear strength and a 79.39 % increase in flexural strength were observed. This interface reinforcement mechanism presents a universally applicable strategy for the future development of fiber-reinforced composite materials.