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The goal of this research project was to evaluate and compare the effect of fabric architecture on the processing and properties of composites made by Vacuum Assisted Resin Transfer Molding (VARTM). The fabric architectures investigated included plain weave, satin weave, and warpknit unidirectional. The fiber types included E-glass and standard modulus carbon fiber. Flat panels were fabricated with a lab scale VARTM process using an epoxy resin system. Fabric plies were cut to 45 cm x 30 cm (18 in. x 12 in.), and the number of plies used depended on the fiber areal weight of each fabric to produce panels of similar final thickness. The speed of resin infusion was recorded by visually monitoring the flow front which was visible through the bag. Fiber volume fraction was evaluated using thickness measurements, and porosity was investigated via optical microscopy. Mechanical testing was performed via tensile and 3-point flexure. The results showed the fabric type had minimal effect on the infusion speed with the exception of the plain weave and satin weave fiberglass. From the mechanical testing results, there are many comparisons made of the modulus, strength, and strain-to-failure results, for example carbon vs. glass, unidirectional vs. woven, tensile vs. flexure. The rule of mixtures was able to predict some but not all of these properties. The results, which are discussed in detail herein, illustrate the main advantage of selecting carbon vs. glass in stiffness driven applications. [ABSTRACT FROM AUTHOR]

Polymer composites have garnered significant attention due to their lightweight nature and high strength-to-weight ratio, making them promising materials for various engineering applications. However, their inherent brittleness often limits their practical utility, especially in high-impact scenarios. To address this challenge, advanced techniques for toughening polymer composites have been developed, aiming to enhance their fracture toughness and energy absorption capabilities. This comprehensive review highlights recent advancements in toughening mechanisms and strategies employed in polymer composites. Various approaches such as interface engineering, incorporation of toughening agents, and hierarchical structures are discussed in detail, elucidating their underlying mechanisms and effects on the mechanical properties of composites. Furthermore, advanced characterization techniques for evaluating toughening mechanisms and assessing the performance of toughened composites are reviewed. The potential applications of toughened polymer composites across diverse fields including aerospace, automotive, and sports equipment are also explored. Through a thorough examination of recent research, this review provides valuable insights into the state-of-the-art in toughening polymer composites, offering guidance for future developments and applications in engineering materials science. [ABSTRACT FROM AUTHOR]

The influence of measurement temperature on the high velocity (>100 m/s) impact performance was investigated for a model thermosetting resin composite system. Plain weave S-2 glass composite panels were fabricated using VARTM and an epoxy resin cured with a polyetheramine curing agent. Overall, the energy absorption for the composite remained approximately constant over a broad testing temperature (T) range. The damage area caused by high-strain rate delamination, however, showed remarkable dependence on the T-Tg. The damage area was high in the glassy state (low T-Tg values) and decreased as the resin traversed its Tg into the rubbery region. Impacted samples showed that an increase in back face deflection correlated to lower damage areas and enabled more energy absorption. These results illustrate the critical importance of the temperature dependent viscoelastic behavior on the impact properties of composites. [ABSTRACT FROM AUTHOR]

The northern regions characterized by harsh climatic conditions should be developed using modern technology employing polymeric materials suitable for use at temperatures down to -60 °C. The creation of polymer composite materials based on polytetrafluoroethylene (PTFE) with highly perfected service characteristics is one of the priority tasks of modern materials science. The paper discusses the physical-mechanical, tribological, and thermodynamic properties of composites based on PTFE and various types of fillers. The results of the study show that complex filling in a certain combination provides a high degree of interaction between the polymer and the filler, thereby significantly improving the properties of PTFE-based composites. [ABSTRACT FROM AUTHOR]

In several research fields, the properties at the interphase between two materials in contact can be quantified by the degree of adhesion. Previous research indicated that a rigorous prediction of the quality of cooperation between biomaterial substrate and human component (cells/tissue) can be achieved though analytical models. In the present investigation, an established theory related to the interphase adhesion in composite materials has been used to redefine the adhesion process of human tissue to a substrate and furthermore, to analyze the type of cooperation between them. Through the present investigation it is shown that modeling-based design of biomaterials can enable the optimum feedback of the human component. Thus, the aim of the present study is to interconnect elements of material science, mechanics and biology in a common theory on the analytical modeling at the interphase between inert materials and human cells/tissues and further on, to develop a strategy of programmed biomaterial design based on modeling output and property prediction. It has been concluded that phenomena at the interphase decide for the implant integration in the host body. [ABSTRACT FROM AUTHOR]

The paper presents research results on the properties of polymer composite materials based on ultrahigh molecular weight polyethylene and polytetrafluoroethylene modified with carbon fibers. It has been established that an increase in CF concentration is accompanied by a decrease in the stress-strain properties of a PCM based on PTFE, as well as by a change in the behavior of tensile strain curves of the PCM. It has been found that the decrease in stress-strain properties and the change in the failure mode of PTFE-based composites containing CF of the LO-1-12N/40 grade occur at a concentration of 5 wt%, and with the introduction of fibers of the Belum brand, 10 wt% concentration is required. This is probably due to the different values of the critical volume content (φm) of CF in PTFE. It has been detected that the strength is increased by 80% at 5% compression of PCM, and it is doubled at 10% compression in comparison with unfilled PTFE. The rate of mass wear of the PCM based on PTFE containing discrete carbon fibers decreases with an increase in filler concentration. The prospects of using carbon fibers as a reinforcing element of UHMWPE with the aim of obtaining new composites with high tribotechnical characteristics intended for operation under conditions of limited lubrication or dry friction are shown. It has been established that, to improve the stress-strain properties and wear resistance of the PCM based on UHMWPE, it is efficient to use carbon fiber of the Belum brand as a filler, since the interphase interaction of UHMWPE with the fiber is strong due to a hydrophobic fluoroorganic coating on the surface of these carbon fibers. [ABSTRACT FROM AUTHOR]

In this paper, an approach to solving the problem of the determination of effective stress-strain, thermophysical and electrophysical properties of filled composite materials on the basis of the variational principles is developed. In the numerical implementation, it might be reduced to the use of the finite element method (FEM). An approach, possessing a certain generality, to finding effective physical-mechanical, thermophysical and electrophysical properties of filled polymer composites is proposed and described. Firstly, a general concept based on obtaining detailed parameters of the composite state under external impact taking into account the actual structure of the material is developed. Then, the averaging procedure aimed at obtaining effective properties of the composites is employed. Secondly, the realization of boundary problems is reduced, for all cases (physical-mechanical, thermophysical and electrophysical), to the formulation of the corresponding variable principles and their realization by the methods of computational mechanics, in particular, by the finite element method. [ABSTRACT FROM AUTHOR]

Ongoing work aims to relate microstructural properties of Al2O3-SiCw composites such as whisker orientation and size distributions to the macroscopically measured electrical properties of the composite. The tools of the study include newly developed stereological techniques, impedance spectroscopy and Monte Carlo simulations. The key results will relate the microstructure to electrical properties through theoretically or experimentally determined percolation properties of the composite. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Spatial and temporal limitations of atomistic simulations necessitate the development of multiscale methodologies that link atomic and continuum scales. In this paper, a hierarchical multiscale model is presented to study the thermomechanical behavior of carbon nanotube (CNT) based composites. The method explicitly accounts for the behavior of nanoscale interfaces existing between the matrix and CNT. Molecular dynamics simulations based on Tersoff-Brenner potential are employed to study the interfaces in CNT based composites, while finite element method simulates macro behavior with the link provided by cohesive zone model parameters. The multiscale model is used to study the effect of interface strength on stiffness of the composite. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]