Applied Composite Materials最新文献

Material extrusion is an additive manufacturing modality that continues to show great promise in the ability to create low cost, highly intricate, and exceedingly useful structural elements. As more capable and versatile filament materials are devised and the resolution of manufacturing systems continues to increase, the need to understand and predict manufacturing-induced warping will gain ever greater importance. The following study presents a novel in situ remote sensing and data analysis construct that allows for the in situ mapping and quantification of surface displacements induced by residual stresses on specified test structures. This proof-of-concept experimental process shows that it is possible to provide designers and manufacturers with insight into the manufacturing parameters that lead to these deformations, with a greater understanding of the behavior of these warping events over the course of the manufacturing process.

Scarf repair is a common repair method for composite laminate structures. Poor workmanship may cause bonding defects in the repair area. In this paper, the tensile properties of scarf-repaired composite laminates with three types of adhesive pore defects were studied by finite element method, and the effects of defect type, area and location were discussed. The results indicate that adhesive pores lead to local stress concentrations, significantly reducing the damage initiation load of the adhesive and laminate, but have limited influence on the initial stiffness and ultimate load of the structure. Pore defects alter the adhesive damage propagation mode but do not change the ultimate failure mode of the structure. Larger defect areas (porosity) result in lower structural tensile performance, and defects located in high-stress regions cause earlier damage initiation. ‌Different types of adhesive defects exhibit varying effects on structural tensile performance.‌.

Flexible composite materials find extensive utilization in diverse applications. However, during the use of fiber-reinforced flexible composite materials, various types of damage may occur due to aging, improper use, and incorrect manufacturing and assembly, necessitating real-time monitoring of the health status of flexible composite materials to prevent accidents. This article first introduces the main monitoring methods and principles of structural health monitoring, further elaborates and summarizes the research status of structural detection of fiber-reinforced flexible composite materials, and prospects for future development directions.

This paper presents a study on manufacturing a range of hybrid laminated structures made of thermoplastic polyurethan (TPU), glass fibre reinforced plastic (GFRP), styrene-butadiene rubber (SBR) and metal mesh materials, and further on investigating the structural response of the TPU based composite sandwich laminated structures. These laminated structures were tested under quasi-static perforation and low velocity impact loading to determine their structural responses and energy absorption characteristics. It has been shown that three-layer and five-layer laminates with lay-ups of GFRP-TPU-GFRP or TPU-GFRP-TPU and GFRP-TPU-GFRP-TPU-GFRP or TPU-GFRP-TPU-GFRP-TPU subjected to quasi-static perforation demonstrate an increased peak load and stiffness with the core thickness from 1 to 4 mm. Also, the TPU core laminates show a superior ductility in comparison to their GFRP core counterparts. The energy absorption values of the three-layer and five-layer TPU and GFRP based laminated structures under low velocity impact are higher than those under quasi-static loading due to strain-rate effect. However, the hybrid laminates with SBR and wire mesh as a core do not give much improvement on the impact perforation resistance of the laminates with the different size of wire mesh, as metal mesh plays a less important role in the laminated structures to resist perforation. In overall, TPU-GFRP-TPU-GFRP-TPU structure with 4mm thick GFRP core demonstrates the highest peak force, and the GFRP-TPU-GFRP-TPU-GFRP structure with 4mm thick TPU core offers the highest energy absorption.

With the widespread application of sandwich composites, the performance of the core structure in the sandwich composites has received particular attention. As the typical representative of lightweight core structure, honeycombs have excellent designability and are widely used. The emerging fibre reinforced composite honeycombs have incomparable performance advantages over traditional metal or chopped fibre honeycombs. This means that design, manufacturing technologies and performance evaluation of composite honeycombs are important. In this review, grid, hexagonal, Kagome, corrugated and origami structure honeycombs and their associated manufacturing strategies have been summarised. In addition, more attention has been paid to textile structure composite honeycombs fabricated by weaving, braiding, or knitting techniques. Their mechanical performances have been extensively reviewed to clarify the relationship between structure and properties. Based on existing studies, the damage mechanisms of composite honeycomb structures are found to be insufficient; especially for the load-bearing mechanisms and predicting methods for honeycombs, which is a challenge for further development. This review hopes to inspire the innovation in fibre reinforced composite honeycombs from the view of structure design and performance evaluation.

Due to advantages of light-weight, high-strength, and superior energy absorption, honeycomb sandwich composites (HSC) are widely used in the aerospace industry. However, HSC are prone to damage from low-energy impacts, posing a threat to the overall safety of components. This paper presents a comprehensive analysis of the damage resistance of the HSC synergistic approach of experimental validation and finite element (FE) simulation. A drop hammer impact experiment was conducted on specimens with varying upper and lower panels thicknesses, utilizing Digital Image Correlation (DIC) technology to monitor the deformation and strain of the impacted panels. The study identified the upper panel as the initial failure point, characterized by matrix cracking, fiber fracture, and interlayer delamination, with the honeycomb core primarily experiencing crushing damage. A critical impact energy threshold of 40 J was established for upper panel penetration, with lower panel damage becoming evident at energies exceeding 80 J. The quantity of panel layers significantly enhances the damage resistance of the structure. Investigated the damage characteristics of the lower panel under impact load. An FE model was meticulously constructed, incorporating the Hashin failure criterion and damage evolution, and was calibrated to reflect the experimental conditions precisely. The simulation results were found to be in excellent agreement with experimental data, with discrepancies within a 5% margin, thereby validating the predictive capabilities of FE model. The interlayer damage of finite element model, leading to the identification of delamination characteristics. This insight is advantageous for the analysis of the residual strength. Subsequent analysis explored the impact of various design parameters on damage resistance, providing valuable insights for the structural design and material selection in aerospace applications.

Graphene oxide (GO) is a commonly used additive to enhance the mechanical properties of epoxy polymers. The quality of GO and the homogeneity of its dispersion into epoxy can notably improve the mechanical properties of multifunctional polymers. This work aims to clarify contradictory results of the effect of GO on the mechanical properties of bio-based polymers by synthesizing high-quality and low-cost GO. To this end, we investigated the effect of adding solvents (acetone, THF) on the mechanical behavior of polymers subjected to several types of static loading. Five different types of materials were examined: neat epoxy (reference material), enhanced epoxy without solvent, enhanced epoxy with acetone solvent, enhanced epoxy with THF solvent, and epoxy enhanced with pure graphite powder. The concentration of GO or graphite was 0.5 wt%. The findings were analyzed using Scanning Electron Microscope (SEM), Thermogravimetric Analysis (TGA), and Raman Spectroscopy. A significant increase in the tensile strength and fracture toughness of polymers filled with GO without solvent was observed compared to the enhanced materials with solvents. SEM analysis of the fracture surfaces revealed resin penetration into the graphene sheets, indicating strong bonding between amino groups and graphene oxide in the case of the enhanced epoxy without solvent. In contrast, in the enhanced epoxies with solvents, the GO-epoxy bonding appeared to be either deteriorated or destroyed. TGA analysis revealed that both neat and GO-reinforced resins without solvent were thermally stable up to 360 °C. Raman spectra showed epoxy ring vibrations during the curing process, indicating the quantity of free epoxides in the samples.

The performance of composite materials is influenced largely by adding organic or inorganic nanoparticles. The composite properties also depend on the fiber/matrix interface bonding. The present article focuses on the influence of basalt fiber surface modifications using hybrid sizings (silane/and silica nanoparticles (SNPs)) and matrix modifications by adding SNPs in the epoxy resin are studied. Vacuum-assisted resin infusion molding (VARIM) was used to fabricate the basalt fiber/epoxy composites. First, the commercial fibers were washed in acetone to remove the commercial sizing; thereafter, a hybrid sizing (3-Glycidyloxypropyl) trimethoxysilane (GPMS)/SNP was applied using the dip-coating method. The SNPs were dispersed using homogenization and probe sonication before infusion. There is an improvement of about 9.05% and 11.33% in the tensile strength and 2.40% and 4.13% in the tensile modulus of as-received basalt fibers with modified epoxy (ABF/EPSNP) and sized basalt fibers with as-received epoxy resin (SBF/EP) composites, respectively. The flexural strength and modulus have improved by about 30% and 8.5%, respectively. Failure mechanisms were analyzed using scanning electron microscopy. From the current study, it was found that surface modifications could result in better composite performance.

Graphical Abstract

Addressing the rehabilitation needs of individuals with lower limb amputations, prostheses play a crucial role in providing comfort and functionality, facilitating walking and daily activities. Prostheses for transtibial amputon specifically cater to the area below the knee joint, encompassing the tibia, fibula, and foot. Conventionally, prosthetic feet are mass-produced through molding techniques using the autoclave process, resulting in standardized designs lacking personalization. In pursuit of a tailored and cost-effective solution, this study endeavors to conceptualize, fabricate, and assess the feasibility of a novel prosthetic foot design. The methodology involves 3D scanning of a real human foot to obtain an editable design model, subsequently utilized in crafting the structural component of the foot from carbon fiber/epoxy composite. Finite element analysis is employed to evaluate structural integrity, encompassing stress analysis, deformations, and the Tsai-Wu failure criterion. Full-scale models are then 3D printed using thermoplastic polyurethane (TPU) filament, augmented with an internally fabricated reinforcement structure comprising a polymer matrix composite reinforced with carbon fiber. Mechanical testing, in accordance with ISO 10328:2016 standards, is conducted to validate the proposed structures. Correlation between numerical simulations and experimental results demonstrates satisfactory agreement. Notably, mechanical tests reveal a 358% over performance in the heel region, surpassing standard requirements. Conversely, the forefoot segment exhibits failure under a 20% load due to defects inherent in the composite manufacturing process. The findings underscore the potential of the proposed concept as a promising alternative in lower limb prosthetics, offering both customization and affordability.