Composites Part C Open Access最新文献

Omni first-ply-failure (FPF) envelopes are an elegant yet conservative approach to assess composite laminate failure on a global level. Omni envelopes can be found increasingly in recent publications. However, the development process of those envelopes shows a lack of clarity. At some point the illustration switches from a laminate-strain basis $({\varepsilon }_x,{\varepsilon }_y,{\gamma }_{xy})$ to the particular case of laminate principal-strain $({\varepsilon }_I,{\varepsilon }_{II})$ basis. The latter is elegant, as the principal-strain space can be easily plotted in 2D. This article presents two procedures to directly determine omni FPF envelopes and it clarifies the transfer to principal strains.

While the Tsai–Wu criterion is used in almost all available publications, the present article uses Cuntze’s failure mode concept (FMC). The article provides a simple example case, which demonstrates the application of omni envelopes in context of FEA based CFRP design.

Unidirectional long fiber reinforced polymers generally exhibit unfavorable abrupt and brittle failure under mechanical stresses without pre-warning which currently limits their use in safety critical applications. The lack of ductility of such composites can be overcome by interlayer hybridization where Low Strain (LS) material is sandwiched between High Strain (HS) material. This results in complex failure mechanisms, including multiple interacting damage modes, such as ply fragmentation and delamination. All-carbon unidirectional hybrid laminates with different layup sequences were designed and manufactured to study the pseudo-ductile behavior. An available analytical model was exploited to predict the damage scenarios of the laminates, both with stress-strain diagrams and damage mode maps. Tensile tests were carried out using different measurement and observation techniques including digital image correlation (DIC), embedded distributed fiber optic sensors (dFOS) and helicoidal X-ray computed tomography (CT). A finite element model was also developed to predict the damage mechanisms. Validated by experimental results, the numerical model was found to accurately predict the tensile damage modes and their evolution in the considered unidirectional thick ply all-carbon hybrid laminates.

Fluororubber (FKM) is an irreplaceable sealing material that plays a critical role in new energy vehicles, petrochemical and aerospace industries. Their broad applications arise from the excellent thermal stability and solvent resistance of fluororubber. Despite there are increasing number of reports on preparation methods, properties and characterization of FKM in literature, there is still a lack of a thorough and comprehensive review that summarizes these results. This paper provides an overview of FKM types, preparation methods, property testing and microscopic characterization, and attempts to give a comprehensive introduction to the vulcanization mechanism of FKM using ternary fluororubber. The mechanical mixing method was identified as the most versatile preparation method in the review, but it is susceptible to causing agglomeration of nanomaterials. Furthermore, different vulcanization systems and reinforcing fillers can be chosen based on the application direction of FKM. Carbon nanomaterials with high inherent strength have the best reinforcing effect on FKM, although they also exhibit the most significant self-agglomeration effect. This can be mitigated through synergistic use of fillers of multiple dimensions and interfacial modification in future research. Additionally, current challenges and future prospects for FKM nanocomposites are also discussed.

4D printing of composites (4DPC) is a technique that can make composite structures with curved geometry without the need to use a curved mold (only a flat mold is used). This technique has been used to make composite springs and cones, where not only the shape is obtained but the mechanical properties are equivalent to those made using conventional technique (where a curved mold is used). The principle of operation of 4DPC utilized anisotropy in unsymmetric laminates as the mechanism for the shape transformation. However it is not always straightforward that a certain unsymmetric lay-up of composite layers will provide a certain shape. Hyer [1,2] observed that laminate theory is accurate to predict the shape of the [0/90] laminate only in some cases, but not in all cases. He attributed this to the assumption of linear relation between the strains and displacements. He then used the non-linear relation between strains and displacements and assumed some functional forms for them. This approach was able to predict the shape of square thin laminates such as those made of [0/90] and [0₂/90₂] lay sequences, but not for rectangular laminates or laminates of other shapes. Finite element method was also used for this prediction. This method worked only with some twikking of the modeling procedure. As such work of previous researchers in the past more than 40 years only show success in ad-hoc situations. The reason for this is due to the lack of an explanation for why there are so many different shapes in different situations. The work in this paper provides an explanation as to why there are different shapes for different situations. This understanding provides a direction for the development of a new finite element procedure that can determine the shape of the laminates in different situations. The new understanding is used to explain the behavior of many cases. This new finite element procedure is then used to generate guidelines on the effect of different parameters such as the effect of geometric dimensions, and material properties on the final shape. These guidelines are useful for the selection of lay-up sequences to make structures in the technique of 4D printing of composites.

Market demands for sustainability has propelled the need for cost-effective manufacturing techniques and eco-friendly materials in several industries, such as the automotive. Bio-materials are a current trend due to qualities like renewability and biodegradability, combined with exceptional mechanical properties. The rise of biocomposites, especially those derived from bioprepregs materials, become a reality in this industry. With the uniqueness of a fully bio-based prepreg, where the matrix and reinforcements themselves are obtained from bio-sources such as plants, the industry can unlock the full potential of biocomposites, paving the way for a future where sustainable materials play a central role in automotive manufacturing. As sustainability remains a core priority, continued research, development, and collaboration will be crucial in realizing the vision of a more environmentally responsible automotive sector. Extensive research is necessary to comprehend the distinct properties of natural or natural based fibers and the biopolymeric materials and their intrinsic interactions associated a different type of process, such as hot-melt impregnation and coating, powder sputtering, film stacking, and hybrid structures.

This article's primary objective is to review the current trends and developments in bioprepreg innovation, exploring formulation techniques and materials to achieve fully bio-based prepregs covering various textile bioprepregs, delving into their properties, reinforcement structures, matrix systems, processing technologies, performance achievements, and their applications, particularly in the automotive sector. Additionally, it briefly examines fully bio-based composites, representing a significant step towards mitigating the environmental impact of composite materials.

In recent decades, there has been a significant rise in the utilization of composite materials for various engineering applications. These advanced materials offer the potential to improve the mechanical properties and vibration characteristics of structural components. This particular study is dedicated to enhancing the vibration performance of coupled curved-curved beams that feature a linear elastic mid-layer, achieved through the incorporation of carbon nanotubes (CNTs), graphene nanoplates (GNPs), and graphene oxide powder (GOPs). The governing equations of the system are solved using the generalized differential quadrature (GDQ) method. While previous research primarily focused on the use of CNTs to enhance the vibration behavior of coupled-curved beams, this study delves into the utilization of multiple nanofillers for this purpose. An essential aspect of modeling composite materials lies in determining their equivalent mechanical properties. This research undertakes a comparison between the rule of mixture (RoM) and Halpin-Tsai methods for calculating these properties, revealing that frequencies derived from the RoM method are higher than those obtained through the Halpin-Tsai approach. Additionally, the study highlights that systems incorporating GNPs demonstrate higher frequencies at lower nanofiller volumes, with CNTs and GOPs following in ranking. However, this hierarchy shifts at higher nanofiller volumes. The arrangement of nanofillers within the system is influenced by its boundary conditions, with the curvature of the bottom beam playing a significant role in affecting vibration behavior. Increasing the radius of the bottom beam (R₂) leads to higher system frequencies, which subsequently decrease with higher R₂ values.

We experimentally determined the decrease of residual compressive strength of the pultruded glass-fiber laminate after tension-compression cyclic loading. The adapted Arcan rig was used for tension-compression fatigue tests. The cyclic load was applied with the critical stress ratio R=−0.87. The residual compressive strength was determined after applying the predefined number of loading cycles with the stress amplitudes of 242 MPa and 173 MPa. The results indicated that the residual compressive strength was reduced about 20% at 77% of fatigue life under the stress amplitude of 242 MPa and at 83% of fatigue life under the stress amplitude of 173 MPa. The microstructural analysis showed that the crack growth path and failure mode depend on the stress amplitude.

Short carbon fibre reinforced plastic composites (SCFRP) that can be used in 3D printing exhibit excellent properties such as high specific strength and modulus, fatigue resistance, and efficient production at a lower cost. However, in the process of 3D printing, short carbon fibres tend to be distributed along the axial direction of the printed filament when they flow in the nozzle, leading to anisotropy and dispersity at the macro level. This brings difficulties to the design and application of materials. This paper developed a novel fix point iteration method based on classical laminate theory and Euler's integral method to accurate predict the nonlinear mechanical behaviour of SCFRP and verified via experiments. Results showed that the predicted curve and experimental data were in excellent agreement with only a 5 % error for 0°/90° laminate under uniaxial tensile loading. The accuracy of strength prediction for the -45°/45° laminate was improved and stabilised with the introduction of the fix point iteration method. These findings provide a useful framework for predicting the mechanical properties of the short fibre reinforced composited prepared by 3D printing.

Wood is a very aesthetically pleasing and environmentally friendly material that can be used both indoors and outdoors. Many research teams are now paying closer attention to polymer modification using furfuryl alcohol or biochar because of its potential for commercial applications. It is anticipated that this kind of material will be long-lasting and maintain its mechanical properties over time. In this paper, spruce wood was modified by a furfuryl alcohol solution enriched by biochar using vacuum infiltration. Therefore, the purpose of this work was to investigate whether spruce wood was suitable for this treatment and to evaluate the effects of thermal degradation properties on prepared composite. Thermogravimetric analysis of raw wood (W), furfurylated wood (FW), and biochar-furfurylated wood bio-composite (BFW) reveals significant differences in its thermal stability. Wood exhibits the lowest thermal stability due to its composition. BFW showed higher thermal stability than wood. FW decomposes similarly to BFW but shows higher mass loss at low temperatures. The obtained results proved increasing two key fire characteristics (decrease of effective heat of combustion and carbon monoxide yield) of BFW in comparison with pristine spruce wood.

Epoxy resins, prized for their versatile properties, are derived from bio-based materials, contributing to sustainability and eco-friendliness in both production and application. This study focuses on the application of gradient boosting machine learning techniques in the field of machining to predict the surface roughness and also the contour based experimental validation of the numerical results. The turning experiments, conducted via Taguchi's L₂₇ array, aimed to explore the effects of depth of cut, feed rate, and spindle speed. Higher spindle speeds, lower feed rates, and shallower cuts led to smoother surfaces in turned jute/basalt epoxy composites. Machine learning models (Gradient Boosting Machine, AdaBoost, and XGBoost) were then used to predict surface roughness. Amongst these, XGBoost outperformed GBM and AdaBoost, exhibiting maximum and average prediction errors of 3.78 % and 2.24 %, respectively. XGBoost accurately predicted 2D surface roughness contours that closely matched experimental contours for training and test cases. Taguchi's Orthogonal Matrix identified minimum surface roughness values as 0.773 μm (experimental), 0.800 μm (GBM), 0.880 μm (AdaBoost), and 0.774 μm (XGBoost). All were achieved at 1500 rpm spindle speed, 0.05 mm/rev feed rate, and 0.3 mm depth of cut.