A Study on the Best Conventional Shapes for Composite Repair Patches

Echer, Leonel; Souza, Carlos Eduardo de; Marczak, Rogério José

doi:10.1590/1980-5373-MR-2021-0304

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Article • Mat. Res. 24 (Suppl 2) • 2021 • https://doi.org/10.1590/1980-5373-MR-2021-0304 copy

A Study on the Best Conventional Shapes for Composite Repair Patches

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Adhesively bonded repair patches are an excellent approach for repairing locally damaged composite components. If correctly applied, fiber-reinforced patches may restore/increment the mechanical response of damaged laminates without significantly increasing the structure’s mass or altering its geometry. However, in order to take full advantage of this repairing technique, one must employ patches with a minimal surface area and maximum efficiency in incrementing the strength of the component. The present work aims to study optimum-based patch shapes for conventional repair geometries, namely rectangular and elliptical. Shell Finite Elements models were used to simulate a parent plate, which is a rectangular flat laminate with a central trespassing damage region. Unbalanced single-ply patches were modeled on the upper surface of the damaged laminate. The patches' efficiency was computed as its capability in restoring the modal response of the repaired component to its undamaged configuration. Sequential linear programming was employed alongside shell finite element models to obtain optimal geometrical parameters for the patches' shape. The study cases comported two different boundary conditions and two stacking sequences. The optimum-base repair patches were defined regarding size and fiber orientation angle.

Keywords:
Repair patch; damaged laminate; structural optimization; modal response; shell FE

	Repair type	Patch shape
	Skewed repair patch⁹9 Kumar AM, Hakeem S. Optimum design of symmetric composite patch repair to centre cracked metallic sheet. Compos Struct. 2000;49(3):285-92. http://dx.doi.org/10.1016/S0263-8223(00)00005-2. http://dx.doi.org/10.1016/S0263-8223(00)...
	Modified skewed repair¹⁰10 Brighenti R, Carpinteri A, Vantadori S. A genetic algorithm applied to optimisation of patch repairs for cracked plates. Comput Methods Appl Mech Eng. 2006;196(1-3):466-75.
	Arrowhead repair patch¹¹11 Rachid M, Serier B, Bouiadjra B, Belhouari M. Numerical analysis of the patch shape effects on the performances of bonded composite repair in aircraft structures. Compos, Part B Eng. 2012;43(2):391-7.
	H-shaped repair patch¹¹11 Rachid M, Serier B, Bouiadjra B, Belhouari M. Numerical analysis of the patch shape effects on the performances of bonded composite repair in aircraft structures. Compos, Part B Eng. 2012;43(2):391-7.
	Bow tie repair patch⁸8 Bouchiba MSE, Serier B. A step towards the optimization of composite bonded repair shape using an estimation distribution approach. J Braz Soc Mech Sci Eng. 2016;39:1755-1771.

Transversely isotropic CFRP14.
Elastic Modulus	$E_{11}$	147	GPa
Elastic Modulus	$E_{22}$	9.8	GPa
Shear modulus	$G_{12}$	2.35	GPa
Shear modulus	$G_{23}$	3.3	GPa
Poisson’s ratio	$ν_{12}$	0.405
Poisson’s ratio	$ν_{23}$	0.4848
Density	$ρ$	1588	$Kg / m^{3}$

Adhesive epoxy-nitrile FM73M15
Young’s modulus	$E_{a d s}$	2.16	GPa
Poisson ratio	$ν_{a d s}$	0.35
Density	p	1220	$Kg / m^{3}$

Repair Shapes
	Elliptical Patch design variables, $x_{i}$ :		Rectangular Patch design variables, $x_{i}$ :
	• Radius $R_{h}$		• Length $l_{h}$
	• Radius $R_{v}$		• Length $l_{v}$
	• Fibers orientation $ϕ$		• Fibers orientation $ϕ$

	Laminate [0/45/-45/90]s		Laminate [45/-45/0/90/60/-30/90/-45]
	Fully Clamped	Simple Supported	Fully Clamped	Simple Supported
Iterations	$25$	$25$	$18$	$27$
Initial Guess, $ϕ_{1}$	$- 33.23 °$	$32.80 °$	$36.43 °$	$80.30 °$
$ϕ_{o t i m}$	$- 3.15 °$	$- 6.02 °$	$32.16 °$	$13.69 °$

	Laminate [0/45/-45/90]s		Laminate [45/-45/0/90/60/-30/90/-45]
	Fully Clamped	Simple Supported	Fully Clamped	Simple Supported
$f_{1}$	$65.46 Hz$	$54.19 Hz$	$83.59 Hz$	$62.41 Hz$
$f_{2}$	$104.75 Hz$	$85.62 Hz$	$108.67 Hz$	$87.15 Hz$
$f_{3}$	$157.59 Hz$	$115.29 Hz$	$148.64 Hz$	$125.73 Hz$

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E-mail: pessan@ufscar.br

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[1] *e-mail: leonel.echer@ufrgs.br