Study on Toughness Improvement of a Rosin-Sourced Epoxy Matrix Composite for Green Aerospace Application

A high temperature epoxy resin was formulated by using a rosin-sourced anhydride-type curing agent, i.e., maleopimaric acid (RAM), and a two-component epoxy consisting of an E51-type epoxy and a solid phenolic epoxy to form a bio-sourced green matrix resin. The glass transition temperature of the final resin was 238 °C Carbon fiber composite prepreg and was manufactured and laminated into composite specimens. Interleaving Toughening Technology (ITT) was applied to the laminates by using Polyamide interleaf veils. The interlaminar fracture toughness and compression after impact (CAI) strength were investigated and showed that the opening Mode I interlaminar fracture toughness GIC and the Mode II interlaminar fracture toughness GIIC of the specimens with interleaves were significantly improved from 227.51 J/m2 to 509.22 J/m2 and 1064.3 J/m2 to 1510.8 J/m2, respectively. Correspondingly, the drop-weight impact test shows that the interleaves reduced the impact damage area from 20.9% to 11.3% of the total area, and the CAI residual strength was increased from 144 MPa to 191 MPa. Meanwhile, mechanical tests showed that the in-plane properties of the interleaved laminates were slightly reduced due to carbon fiber volume fraction reduction. In conclusion, the high glass transition temperature, fracture toughness and CAI behaviour make the green resin matrix composite a potential candidate for aerospace applications.

Download Full-text

Improved interlaminar fracture toughness of carbon fiber/epoxy composites with a multiscale cellulose fiber interlayer

Composites Communications ◽

10.1016/j.coco.2021.100898 ◽

2021 ◽

pp. 100898

Author(s):

Zhongsen Zhang ◽

Kunkun Fu ◽

Yan Li

Keyword(s):

Fracture Toughness ◽

Carbon Fiber ◽

Cellulose Fiber ◽

Epoxy Composites ◽

Interlaminar Fracture Toughness ◽

Interlaminar Fracture ◽

Carbon Fiber Epoxy

Download Full-text

Study of the effect of the reinforcement direction on the identification of relaxation transitions of moisture-saturated carbon fiber VKU-25

Industrial laboratory Diagnostics of materials ◽

10.26896/1028-6861-2021-87-9-38-43 ◽

2021 ◽

Vol 87 (9) ◽

pp. 38-43

Author(s):

O. G. Ospennikova ◽

P. S. Marakhovsky ◽

N. N. Vorobyov ◽

E. V. Nikolaev ◽

A. I. Gulyaev ◽

...

Keyword(s):

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Carbon Fiber ◽

Polymer Matrix ◽

Structural Parameters ◽

Polymer Materials ◽

Thermal Coefficient ◽

Initial State ◽

Relaxation Transitions

Thermodilatometric methods of analysis are used to study the structural parameters of polymer materials, however, when studying moisture-saturated compositions certain difficulties arise in their identification. The results of thermophysical tests of VKU-25 carbon fiber samples in the initial state and after moisture saturation are presented. It is shown that heat treatment of materials affects the recorded values of the glass transition temperature of the epoxy matrix. When the samples are exposed in water or above the water surface, the sorbate penetrates into the polymer at the same rate, which is confirmed by almost identical values of water absorption at the same exposure time. The estimates of the thermal coefficient of linear expansion (TCLE) of the samples in the range of 20 - 250°C are given. Moreover, it is shown that the glass transition temperature of the plasticized polymer matrix depends on the direction of fiber reinforcement. In the case of moisture-saturated carbon fiber (CF)heated to 210°C, the formation of main cracks occurs mainly at the fiber-matrix interface. The glass transition temperature (GTT) of the material in the dry state (176 - 177°C), appeared almost independent on the heating rate, whereas for water-saturated samples, GTT changes significantly and can be described by a polynomial of the 2nd order. After exposure of the carbon fiber under conditions of high temperature and humidity, two relaxation transitions corresponding to the systems occur in the polymer matrix: epoxidian oligomer— amine hardener and polyfunctional resin— amine hardener. The glass transition temperature is 132 and 159°C in the first and in the second, respectively. The results obtained can be used in the development of new polymer composite materials.

Download Full-text

Interlaminar fracture toughness and electromagnetic interference shielding of hybrid-stitched carbon fiber composites

Journal of Reinforced Plastics and Composites ◽

10.1177/0731684418787642 ◽

2018 ◽

Vol 37 (18) ◽

pp. 1131-1141 ◽

Cited By ~ 2

Author(s):

Nisrin R Abdelal ◽

Steven L Donaldson

Keyword(s):

Fracture Toughness ◽

Carbon Fiber ◽

Electromagnetic Interference ◽

Experimental Results ◽

Mode I ◽

Carbon Fiber Composites ◽

Interlaminar Fracture Toughness ◽

Shielding Effectiveness ◽

Electromagnetic Interference Shielding ◽

Interlaminar Fracture

In the current study, the production of multifunctional hybrid-stitched composites with improved interlaminar fracture toughness and electromagnetic interference shielding effectiveness is reported. Unidirectional carbon fiber-epoxy composite laminates stitched with Kevlar, nylon, hybrid stitched with both Kevlar and nylon and unstitched were prepared using resin infusion process. Representative specimens from unstitched and stitched composites were tested using rectangular waveguide and Mode I double cantilever beam tests. The Mode I experimental results showed that composite stitched with Kevlar exhibited the highest crack initiation interlaminar fracture toughness (GIC-initiation), whereas composite stitched with nylon exhibited the highest maximum crack propagation interlaminar fracture toughness (GIC-maximum). The four-hybrid stitching patterns exhibited higher GIC-initiation than the unstitched and stitched with nylon composites and lower than stitched with Kevlar composite, whereas they had higher GIC-maximum than the unstitched and stitched with Kevlar composites, although lower than stitched with nylon composite. The electromagnetic shielding effectiveness experimental results showed that stitched composites exhibited improved shielding effectiveness compared to unstitched composites. For example, composite stitched with nylon had highest shielding effectiveness value of 52.17 dB compared by the composite stitched with Kevlar which had 40.6 dB. The four hybrid-stitched composites exhibited similar shielding effectiveness with an average value of 32.75 dB compared to the unstitched composite shielding effectiveness of 22.84 dB. The experimental results comply with the initial goal of this study to manufacture multifunctional hybrid stitching composites with combined properties between Kevlar and nylon-stitched composites.

Download Full-text

Interlaminar Fracture in Carbon Fiber/Thermoplastic Composites

MRS Proceedings ◽

10.1557/proc-170-351 ◽

1989 ◽

Vol 170 ◽

Cited By ~ 3

Author(s):

J. A. Hinkley ◽

W. D. Bascom ◽

R. E. Allred

Keyword(s):

Fracture Toughness ◽

Carbon Fiber ◽

Carbon Fibers ◽

High Strain ◽

Thermoplastic Composites ◽

Plasma Modification ◽

Interlaminar Fracture Toughness ◽

Interlaminar Fracture ◽

Polyphenylene Oxide ◽

Commercial Carbon

AbstractThe surfaces of commercial carbon fibers are generally chemically cleaned or oxidized and then coated with an oligomeric sizing to optimize their adhesion to epoxy matrix resins. Evidence from fractography, from embedded fiber testing and from fracture energies suggests that these standard treatments are relatively ineffective for thermoplastic matrices. This evidence is reviewed and model thermoplastic composites (polyphenylene oxide/high strain carbon fibers) are used to demonstrate how differences in adhesion can lead to a two-fold change in interlaminar fracture toughness.The potential for improved adhesion via plasma modification of fiber surfaces is discussed. Finally, a surprising case of fiber-catalyzed resin degradation is described.

Download Full-text