Composites Part A: Applied Science and Manufacturing最新文献

This work quantifies the impact of chemical functionalization of carbon nanotubes and carbon fibres on the interfacial shear strength, tensile and interlaminar shear strength properties of additively manufactured nylon composites. The surface chemistry of functionalized carbon materials was evaluated through infrared spectroscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Single carbon fibre was dip-coated in a suspension of nanotubes and embedded into a nylon matrix. The fibres were pulled out to measure the interfacial shear strength, and the fibres with attached neat, carboxylated, and silanized nanotubes increased it by up to 67 %, 112 %, and 216 %, respectively. Composite samples were manufactured using a novel hybrid additive manufacturing method, which was able to deposit nylon layers and a suspension containing carbon reinforcement. The use of chemically functionalized nanotubes in the suspension led to carbon layers that improved tensile strength by 49 % and tensile modulus by 126 % over neat nylon. Functionalization of carbon reinforcement increased the interlaminar shear strength by up to 63 %. Overall, this paper demonstrates the importance of chemical modification in composite materials containing a large interface area of carbon materials.

This study investigates deformation, interfacial, and particle damage in a magnesium-partially stabilized zirconia (Mg-PSZ) particle-reinforced transformation-induced plasticity (TRIP) steel composite using scanning electron microscope (SEM) in situ tensile tests and finite element simulations. The simulation models employ an elastic model for ceramic particles and a Johnson-Cook plastic model for the matrix, and compares the performace of perfect, cohesive zone model (CZM) and combined CZM/extended finite element method (XFEM) models at the ceramic/matrix interface. The simulation and experimental results are qualitatively and quantitatively consistent for the initiation and evolution of interfacial damage and particle failure with a relative error in crack length of only 4.6 %. Furthermore, debonding angle analysis of ceramic/matrix interface reveals that damage starts earlier in a sharp edged particle geometry. Prioritizing non-linear interfacial morphologies in particles and controlling reinforcement edges perpendicular to the loading can achieve lower and constrained debonding angles, thereby continuing to provide a strengthening effect and finally enhancing material behavior.

Composite materials with 3-dimensional (3D) reinforcement were manufactured and corresponding simulation models were created in parallel. The used simulation approach has earlier been shown to produce close to authentic geometrical representation of the yarn architecture in 3D reinforcement. It is shown that although the as-woven reinforcement pattern can be modelled quite reliably, significant distortion from the nominal fibre arrangement might take place later in manufacturing, primarily related to compression during moulding. Such effects have earlier received significant attention for composites with 2-dimensional reinforcement but not as much for their 3D counterparts. The yarns in the real and the simulated materials are studied and compared, and some of the discrepancies and the mechanisms behind are discussed. The distortions are partly attributed to the relatively sparse weave that allows yarns oriented in the through-thickness direction, in particular, to deviate from their original positions.

The AA2024 aluminum alloy is difficult to manufacture by laser powder bed fusion (L-PBF) due to its crack sensitivity. This work introduces a novel crack-free graphene nano-platelets (GNPs) and ZrO₂ nanoparticles hybrid-modified AA2024 alloy suitable for laser powder bed fusion (L-PBF). The columnar-to-equiaxed transformation caused by nanoparticles-inducing nucleation sites eliminates the cracks. A bimodal microstructure consists of coarse columnar grains and ultrafine equiaxed grains, which are formed in the as-built composites. Compared with the L-PBF prepared AA2024 alloy and 1 wt% ZrO₂/AA2024 composite, the (0.2 wt% GNPs + 1 wt% ZrO₂)/AA2024 composite exhibit the highest tensile strength of 382 MPa and elongation of 16 %. The introduction of GNPs and ZrO₂ nanoparticles provide dual increment in both tensile strength and ductility compared with single ZrO₂ nanoparticles modified AA2024. Following further T6 heat treatment, the tensile strength increased significantly to 624 MPa, but the elongation decreased dramatically to 5.6 %. In-depth analysis was provided of the strength and ductility improvements induced by GNPs/ZrO2 nanofiller in this investigation.

Improving thermal conductivity in textile/composites is crucial for heat dissipation in apparel and engineering. Apparel textiles’ thermal conductivities rarely exceed 1.0 W/(m·K), limiting efficient personal thermal management. Advances in silver conductive yarn and heat-stretched polyethylene show promise for ultra-high thermal conductivity materials. In electronic packaging, materials’ thermal conductivities rarely exceed 40 W/(m·K), causing overheating and reduced reliability. Techniques like freeze-drying and templating can enhance boron nitride composites’ thermal conductivity. Aerospace and automotive composites with mechanical and flame-retardant properties rarely exceed 120 W/(m·K), leading to potential safety hazards. Recent advancements indicate that mechanical structure enhancement and chemical surface modification can improve carbon composites’ thermal conductivity. Understanding existing enhancement techniques and mechanisms is essential. This paper reviews these techniques, discussing their potentials and limitations for future high thermal conductive textiles and composites development.

This investigation presents an experimental and numerical approach to developing 4D printed multi-shape actuators with an integrated electrical self-triggering system. It employs a multifunctional shape memory carbon black Polylactic Acid (PLA) layer embedded within rubbery thermoplastic polyurethane (TPU). Notably, these thermo-responsive actuators are programmed and triggered using Joule’s effect, eliminating the need for an external heat source and enabling precise control of temperature gradients. Two distinct motion mechanisms are employed: the differences in thermal expansion coefficient between the PLA/TPU polymers below the glass transition temperature, and the shape memory effect of the PLA layer above the glass transition temperature. As a result, a diverse range of motion responses can be achieved by adjusting the potential differences. A coupled electro-thermo-mechanical finite element model is used to gain further insight into the motion mechanisms, offering predictive capabilities beyond the ones reported by previous models. The developed technology provides enhanced actuation capabilities to conventional bi-shape SMP actuators, offering a versatile range of bending cycles. Furthermore, Joule’s effect enables the implementation of closed-loop control systems, which is essential for developing autonomous robotic systems.

This work presents a modification of the lap shear test for application to the intralaminar shear failure of fiber reinforced composites. The proposed method involves an S-shaped double-cracked specimen loaded under uniaxial in-plane compression. The resulting loading is akin to a lap shear test but inducing intralaminar shear failure (not interlaminar). Elastic stress analysis confirms a shear dominated stress state in specimen ligament, and numerical contour-integral confirms a mode II dominance in the near tip region. Experimental results for an epoxy/carbon twill woven composite are presented, demonstrating the ease of the test method. Nonlinear quasi-ductile behavior is observed, as expected, and necessitates the use of elastoplastic fracture mechanics to interpret the fracture toughness. The estimated initiation toughness values are successfully verified via cohesive crack simulations. The presented test represents a simple and repeatable method to characterize the intralaminar shear failure of fiber-reinforced composites.

Polycarbonate/acrylonitrile–butadiene–styrene (PC/ABS) features superior mechanical properties but suffers from high flammability, presenting a grand challenge in enhancing its flame retardancy with halogen-free additives. Herein, we developed an efficient flame-retardant system (BH/CuATP) by incorporating phosphazene additive (HP), copper oxide modified attapulgite (CuATP) and bisphenol A bis (diphenyl phosphate) (BDP). This system achieves a UL-94V-0 rating without melt-dripping and leads to reductions in the peak heat release rate (43.1 %), total heat release (29.8 %) and total smoke production (5.7 %). The strength effect of CuATP in both gas-phase and condensed-phase significantly contributes to its enhanced fire safety. Additionally, the mechanical properties of PC/ABS/B₁H₁/CuATP₁ are improved due to the rod-like CuATP, showing enhanced comprehensive properties superior to other reported systems. This work presents valuable insights into the effectiveness of mineral-strength intumescent flame retardancy for PC/ABS, offering practical guidance for the development of high-performance PC/ABS composites.

This study proposes a data-driven model for thermal history prediction during in-situ Automated Fiber Placement of thermoplastic composites. Temperature data was experimentally collected with fast-response thermocouples placed within carbon fiber AS4/PEEK composite substrates. The temperature for various combinations of hot gas torch temperatures, heat source velocity, and locations through the thickness and width were collected. A feedforward neural network (FNN) was developed to predict the entire 3-dimensional thermal history. The FNN had five input features and one output: the temperature at a given position and a combination of the process parameters. The FNN predictions for data unseen during training are validated for cases of interpolation and extrapolation. As expected, suitable performance was obtained for cases of interpolation, but predictions suffered in extrapolation. The computational efficiency of FNNs makes them an appropriate candidate for on-line thermal history prediction or process optimization, given that they are used within their training range.

In this work, Mg-9Al-1Zn (AZ91) alloy reinforced with zinc-decorated titanium (Zn@Ti) particles was fabricated using the powder metallurgy method. Zn nanoparticles effectively dissolved into magnesium (Mg) matrix, which led to a reduction in the solid solubility of aluminum (Al) and precipitations of submicron sized Mg₁₇Al₁₂. As a result, the Zn@Ti/AZ91 composite displays a bimodal grain structure, achieving a remarkable balance between strength and ductility, with a yield strength of 248 ± 3.5 MPa, an ultimate tensile strength of 378 ± 5.3 MPa, and an elongation of 15.0 ± 2.8 %. The improved strength of Zn@Ti/AZ91 composite primarily stems from the synergistic effect of a significant volume fraction of submicron sized Mg₁₇Al₁₂ and Al₈Mn₅ precipitations strengthening, Zn solid solution strengthening, and grain boundary strengthening. Regarding ductility mechanisms, the presence of Mg₁₇Al₁₂ and Al₈Mn₅ precipitations effectively impede crack propagation and enhance ductility. This innovative approach represents a promising strategy for developing high strength and ductility of Mg composites.