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Research Papers

Dynamic Response of Orthogonal Three-Dimensional Woven Carbon Composite Beams Under Soft Impact

[+] Author and Article Information
P. Turner

Centre for Structural Engineering
and Informatics,
Composites Research Group,
Department of Civil Engineering,
Faculty of Engineering,
The University of Nottingham,
University Park,
Nottingham NG7 2RD, UK

T. Liu

Centre for Structural Engineering
and Informatics,
Composites Research Group,
Department of Civil Engineering,
Faculty of Engineering,
The University of Nottingham,
University Park,
Nottingham NG7 2RD, UK
e-mail: Tao.Liu@nottingham.ac.uk

X. Zeng

Composites Research Group,
Faculty of Engineering,
The University of Nottingham,
University Park,
Nottingham NG7 2RD, UK

Contributed by the Applied Mechanics Division of ASME for publication in the JOURNAL OF APPLIED MECHANICS. Manuscript received June 16, 2015; final manuscript received August 24, 2015; published online September 22, 2015. Assoc. Editor: Weinong Chen.

J. Appl. Mech 82(12), 121008 (Sep 22, 2015) (18 pages) Paper No: JAM-15-1316; doi: 10.1115/1.4031455 History: Received June 16, 2015; Revised August 24, 2015

This paper presents an experimental and numerical investigation into the dynamic response of three-dimensional (3D) orthogonal woven carbon composites undergoing soft impact. Composite beams of two different fiber architectures, varying only by the density of through-thickness reinforcement, were centrally impacted by metallic foam projectiles. Using high-speed photography, the center-point back-face deflection was measured as a function of projectile impulse. Qualitative comparisons are made with a similar unidirectional (UD) laminate material. No visible delamination occurred in orthogonal 3D woven samples, and beam failure was caused by tensile fiber fracture at the gripped ends. This contrasts with UD carbon-fiber laminates, which exhibit a combination of widespread delamination and tensile fracture. Post impact clamped–clamped beam bending tests were undertaken across the range of impact velocities tested to investigate any internal damage within the material. Increasing impact velocity caused a reduction of beam stiffness: this phenomenon was more pronounced in composites with a higher density of through-thickness reinforcement. A three-dimensional finite-element modeling strategy is presented and validated, showing excellent agreement with the experiment in terms of back-face deflection and damage mechanisms. The numerical analyses confirm negligible influence from through-thickness reinforcement in regard to back-face deflection, but show significant reductions in delamination damage propagation. Finite-element modeling was used to demonstrate the significant structural enhancements provided by the through-the-thickness (TTT) weave. The contributions to the field made by this research include the characterization of 3D woven composite materials under high-speed soft impact, and the demonstration of how established finite-element modeling methodologies can be applied to the simulation of orthogonal woven textile composite materials undergoing soft-impact loading.

Copyright © 2015 by ASME
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References

Figures

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Fig. 1

(a) Microscopic image of the composite cross section along the weft direction, with crimping of the weft tows caused by the presence of the TTT reinforcement. (b) Sketch of 3D orthogonal woven carbon composites showing full TTT reinforcement with the binder-to-warp-stack ratio of 1:1 on the left and half TTT reinforcement with the binder-to-warp-stack ratio of 1:2 on the right, with the dimensions as the average measurements of the cured composites. (For interpretation of the color legend in this figure, the reader is referred to the web version of this article.)

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Fig. 2

Quasi-static stress–strain relationships for 3D woven carbon composite material for (a) tension, and (b) compression. (c) Quasi-static uniaxial compression stress–strain curve for the Alporas aluminum foam projectile.

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Fig. 3

Sketch of experimental setup of dynamic soft-impact tests on orthogonal 3D woven composite panels

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Fig. 4

Finite-element model for the simulation of orthogonal 3D woven carbon composite beam samples undergoing soft impact, with beam orientated along the x-direction (warp). Arrows indicate direction of fiber orientation. Sketches of top layers for (a) full TTT, (b) no TTT, and (c) equivalent UD-laminate models are also shown. (For interpretation of the color legend in this figure, the reader is referred to the web version of this article.)

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Fig. 5

Comparison of experimental results for full TTT material and FE prediction for normalized back-face deflection δ̂≡δ/l0 as a function of normalized time t̂≡t v0/lp. Full TTT beams orientated along the y-direction (weft). Three different case studies for numerical modeling results are presented: full TTT reinforcement, no TTT, and an equivalent UD-laminate material. Projectile impulses I0 were (a) 2.5 kPa s, (b) 2.6 kPa s, (c) 3.3 kPa s, and (d) 4.0 kPa s. Points A–E corresponds to the montage images presented in Fig. 6.

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Fig. 6

Deformation montage of full TTT 3D orthogonal woven carbon-fiber composites under soft impact of impulse I0=2.64 kPa s beams orientated along the y-direction (weft) (a) experiment, and (b) finite-element prediction. Points A–E refer to the corresponding positions on Fig. 5(b).

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Fig. 7

Comparison of the normalized maximum back-face deflection δ¯max during soft impact as a function of normalized impact impulse Ī0 upon 3D woven carbon composites of two different TTT reinforcement densities

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Fig. 8

Maximum normalized back-face deflection δ̂≡δ/l0 against normalized time after impact t̂≡tv0/lp. FE simulation and experimental results for beams orientated along the x-direction (warp). Points V–Z correspond to the montage images presented in Fig. 9.

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Fig. 9

Deformation montage of carbon-fiber composites under soft-impact testing showing (a) half TTT 3D orthogonal woven composite beam orientated along the x-direction (warp) I0=4.19 kPa s, (b) finite-element prediction of half TTT 3D orthogonal woven composite beam orientated along the x-direction (warp) I0=4.19 kPa s, and (c) UD-laminate material presented in Ref. [10]1I0=2.90 kPa s. Points V–Z correspond to the locations noted in Fig. 8.

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Fig. 10

Photographic images and FE predictions of damage modes exhibited by half TTT 3D woven carbon composite undergoing soft impact, tested at I0=4.19 kPa s. Beam orientated along the x-direction (warp).

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Fig. 11

Finite-element simulations of the predicted compressive damage initiation on the front surface of orthogonal 3D woven composite beams undergoing a soft-impact event I0=3.33 kPa s for (a) full TTT, and (b) half TTT material. Time t is the time after moment of projectile impact upon beam. A value of 1 corresponds to the onset of compressive fiber damage. (c) Optical microscopic images of fiber breakage on the front surface of impact tests of a half TTT orthogonal 3D woven material after experimental impact of impulse I0=3.33 KPa s. Beams orientated along the y-direction (weft). (For interpretation of the color legend in this figure, the reader is referred to the web version of this article.).

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Fig. 12

Sketch showing the experimental setup of the clamped beam quasi-static bending test

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Fig. 13

Load imposed by the roller P against roller vertical displacement δp for post-impact clamped–clamped beam tests for full TTT material. Beams orientated along y-direction (weft).

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Fig. 14

(a) Summary of the peak load during post-impact clamped beam testing versus the velocity of impact v0. (b) Stiffness of post-impact clamped beam testing versus the velocity of impact, v0.

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Fig. 15

Finite-element-predicted deformation of an orthogonal 3D woven carbon composite undergoing a soft-impact event I0=4.03 kPa s showing (a) full TTT, and (b) no TTT model. Contour plot shows damage variable of cohesive interaction, ℏ, demonstrating locations of delamination within the beam. A value of ℏ=1 indicates fully delaminated regions. t = 0 corresponds to the moment of projectile impact on the sample. Beams orientated along the y-direction (weft). (For interpretation of the color legend in this figure, the reader is referred to the web version of this article.)

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Fig. 16

Montage of finite-element simulations of a soft-impact event of impulse I0=2.96 kPa s with cohesive contact removed on (a) full TTT orthogonal 3D woven composite, (b) half TTT orthogonal 3D woven composite, (c) 3D woven composite with TTT reinforcement removed, and (d) equivalent UD-laminate material. t = 0 corresponds to the moment of projectile impact upon the beam. Beams orientated along the x-direction (warp).

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