Carbon Fibers In Epoxy Matrix Research Articles

Enhancing the mechanical performance of carbon fiber reinforced polymer using carbonized coconut shell particles

Inorganic fillers have been used to improve the out-of-plane mechanical properties of carbon fiber reinforced polymer (CFRP) composite laminates for decades. Nonetheless, its associated high cost and environmental unfriendliness is a concern. Biomaterials are currently being explored as fillers in polymeric materials due to their low cost, wide availability, and biodegradability. However, the use of coconut shell based biofillers together with carbon fibers in epoxy matrix has not been investigated. This research seeks to improve the out-of-plane mechanical properties of CFRP with low fiber volume fraction using carbonized coconut shell particles (CCSP). Five hybrid epoxy biocomposites with varying concentrations of CCSP were used to impregnate four plies of woven carbon fabric, making up a fiber volume fraction of 29%. The tensile, flexural, and impact behavior of the laminated biocomposites were investigated. The mechanical properties of the biocomposite laminates were enhanced compared to a reference CFRP without CCSP. This work provides a cheaper and greener alternative to inorganic CFRP hybrid composite for potential use in automotive and aerospace industries.

Investigation on electromagnetic shielding and mechanical properties of zirconia graded carbon fiber/epoxy nanocomposite

AbstractThe present study is on the fabrication of epoxy nanocomposites for electromagnetic interference (EMI) shielding in the X‐band and Ku‐band frequency range. Single‐layer unidirectional carbon fiber along with nano zirconia is used to achieve the required EMI shielding and mechanical strength. The microstructural study of the fabricated samples has revealed the good lamination of carbon fiber in epoxy matrix and the uniform dispersion nanoparticles provide a reduction of wettability. Dielectric parameter studies indicate an increase in permittivity and dielectric loss with the addition of zirconia nanoparticles. The shielding effectiveness (SE) shows as high as 25 dB when the electric field is parallel with the carbon fiber orientation. The addition of zirconia nanoparticles to the carbon fiber reinforced epoxy composite have enhanced the ability of microwave absorption shielding. Mechanical properties of the epoxy carbon fiber nano zirconia composites show an improvement in storage modules, activation energy, and impact resistance. It is realized that 3 wt% zirconia added epoxy carbon fiber composite shows high shielding effectiveness with good mechanical properties.

X-ray nanoimaging of a transversely embedded carbon fiber in epoxy matrix under static and cyclic loads

The initial stage of fatigue failure has not been thoroughly clarified for carbon fiber reinforced plastics (CFRPs). Although the initiation of fatigue cracks has been regarded to be interfacial debonding between the carbon fiber and polymer matrix, their detection among numerous carbon fibers, whose diameter is only 7 µm, is extremely difficult. In this study, a single carbon fiber was transversely embedded in a dumbbell-shaped epoxy sample to focus on the interfacial debonding and was observed using synchrotron radiation (SR) X-ray computed tomography (CT). A tabletop fatigue testing machine driven by a piezoelectric actuator was developed to apply static and cyclic loads along the beamline. SR X-ray multiscale CT imaging was conducted by switching between an absorption-contrast projection method (micro-CT) and a phase-contrast imaging-type X-ray microscopic CT (nano-CT). The carbon fiber was entirely captured by micro-CT and then magnified at both ends on the free surfaces. Nano-CT clearly visualized the interfacial debonding under 30 MPa static tensile load and the implication of the coalescence of nano-voids along the interface under 50 MPa. Under cyclic loads, the interfacial debonding gradually progressed under a 8–40 MPa sinusoidal stress after 10,000 cycles, whereas it did not propagate under a stress below 30 MPa.

The flexural properties of self healing fiber reinforced polymer composites

Fiber reinforced polymer composites have a complex damage prediction and repair mechanism. Such complexities made the researchers to implement new techniques like self healing. Amendments in the existing material can modify its properties. So, it is necessary to study the change in property due to inclusion of self healing in fiber reinforced composite materials. This work aims to investigate the self recovery response of composites prepared by reinforcing glass fibers and carbon fibers in epoxy matrix. The healing was achieved by inclusion of dual microcapsules made of epoxy and hardener encased in separate capsules. To investigate the recovery activity of the composite laminate, a 5mm diameter indentation was produced at the centre of specimen and the healing was monitored by measuring the diameter of indentation after 12 hrs and 24 hrs. To notice the influence of micro-inclusions on flexural strength, flexural test was conducted on neat, indented and healed specimens. It was observed that inclusion of microcapsules did not majorly alter flexural strength of glass fiber reinforced and carbon fiber reinforced polymer composites. Results also indicated complete healing of both carbon fiber reinforced polymer and glass fiber reinforced polymer composite specimens with healing efficiency of 103.4% and 101.8% respectively.

Weave geometry generation avoiding interferences for mesoscale RVEs

An algorithm which allows the generation of representative volume elements (RVEs) for complex woven and warp-interlaced fiber-reinforced composite topologies while avoiding unphysical tow intersections is presented. This is achieved by extending an existing RVE generation strategy in two significant ways: (1) the local cross section shape of the tow is adjusted depending on the local tow curvature in a way that preserves the cross sectional area of the tow, and (2) the elementary crimp interval is separated into a planar and a transition region. The modifications facilitate the generation of a wide range of elaborate textile topologies without tow intersections, which are present without the proposed modifications unless complex tow to tow contact models are introduced. The mechanical properties of plain weaves were predicted based on the topology generated with the proposed algorithm as well as based on RVEs which were constructed based on actual micrographs, i.e. a “digital twin” of the actual microstructure. A comparison of the predicted mechanical properties based on finite element and Multiscale Generalized Method of Cells techniques shows close agreement. However, some differences exist with respect to experimentally determined material parameters due to the finite dimensions of the specimens. Lastly, mechanical properties of multilayered weaves are predicted with the finite element method. The considered material systems are carbon fiber in epoxy matrix as well as C/C-SiC. However, the procedure is applicable to a wide range of material systems.

Influence of Dispersion in Composites of Chopped PAN-Based Carbon Fiber Modified by Dodecyl Ether Carboxylate

In this article, dodecyl ether carboxylate (AECNa) was prepared by dodecanol polyoxyethylene, sodium chloroacetate, and sodium hydroxide and employed as a treatment agent for PAN-based carbon fiber (CF) surface. The results show that the optimum adsorption amount of AECNa modifying CF was determined to be 4.0 mg/g. In addition, the equivalent variation regularity is obtained the CF surface charge properties and its dispersion behavior. The optimal dispersion effect of the short CFs in epoxy matrix is achieved when the surface charges reach the maximum by quantitative measurement using Faraday cup; the surface morphology and wettability are improved depending on the field emission scanning electron microscopy, Thermogravimetry, x-ray photoelectron spectroscopy, and monofilament contact angle testing. Furthermore, the flexural strength and modulus of the treated CF composite were proven to advance by flexural tests.

Experimental Fatigue Study of Composite Patch Repaired Steel Plates with Cracks

Cracks are among the most commonly encountered defects in metallic structures operating at sea. Composite patch repairing is a repair method which is gaining popularity as it counters most of the problems faced by conventional renewal repairs. Extensive studies can be found in the literature addressing the efficiency of this novel repair method using techniques which meet higher performance and monitoring standards than these commonly found in naval applications. In this work the efficiency of practices widely used in the ship repair industry for the implementation of composite patch repairing is addressed. To this end, steel plates repaired with composite patches were tested under fatigue loading. The composite patches consisted of carbon fibers in epoxy matrix and were directly laminated to the steel surface using the vacuum infusion method. Two different surface preparation methods, namely grit-blasting and mechanical treatment with the use of a needle gun were studied. In addition, in order to account for the harsh environmental conditions during the operating life of the structure and to study its effect on the repair, two different aging scenarios were considered. Non-destructive evaluation of the patches was performed so as to assess the quality of the repair, and the evolution of debonding during testing.

A thermal study on moisture absorption by epoxy composites

The water sorption kinetics of an epoxy matrix-carbon fiber composite with different degrees of polymerization was studied. It was observed that the diffusion coefficients, determined perpendicularly to the fiber direction, are increased by increasing the cure degree. Only a small portion of the bonded water is released when the specimen are heated to 200 °C.