Review on the performance improvements and non-destructive testing of patches repaired composites

Zhou, Wei; Ji, Xiao-long; Yang, Sa; Liu, Jia; Ma, Lianhua

doi:10.1016/j.compstruct.2021.113659

Cited by 65 publications

(32 citation statements)

References 126 publications

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“…The developed method allows for increasing the repair efficiency [7,12,47] by taking into account the temperature-time regime of curing and methods of its implementation. The advanced comprehensive algorithm for choosing the effective parameters of the damaged panel repair process can be represented as follows.…”

Section: Discussionmentioning

confidence: 99%

“…According to research [7,8], installation of repair patches is considered an effective method for the repair of defects such as dents, failures of bearing skins and delaminations in the metal and composite panel structures. High physico-mechanical characteristics of the modern polymeric composite materials (PCM) [9][10][11] determine successful use of the composite patches for the repair of both polymeric and metal structures [12,13]. The composite patch can also have potential applications in constructing electromagnetic nanocomposites or intelligent materials, as there is carbon materials in the composite [14,15].…”

Section: Introductionmentioning

confidence: 99%

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Effects of the Temperature–Time Regime of Curing of Composite Patch on Repair Process Efficiency

et al. 2021

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Repair procedures with the use of composite patches are considered to be the most effective among the current technologies of repair of the structures of various applications. In the process of moulding-on of a patch made of polymeric composite material by means of curing, technological stresses arise in the patch. Determination of residual technological stresses is a priority task for the modelling of the repair process. Reduction of residual stresses can be achieved by optimization of the mode of repair patch curing. For meeting this objective, the method for determination of technological stresses, which arise in the structure under repair in the process of curing of a composite patch, has been developed. The method takes into account the shrinkage, change in physico-mechanical characteristics, rheological processes occurring in the binder during moulding process, and determination of stresses in the structure under repair at any time. Therefore, premature failure of the repair joint at the stage of repair can be avoided. It is shown that the method adequately describes the level of deformations and stresses in the structure being repaired at the stage of heating and holding of the composite patch. Increase in the moulding temperature leads to a reduction in residual stresses in the structure under repair. However, current stresses at the stages of heating and temperature holding are increased significantly. Reliability of assumptions and developed method is confirmed by the comparison with the experimental data. The obtained experimental graph of total deformation of the composite patch allowed us to clearly determine the moment of residual stress occurrence in the structure under repair. This moment matches quite exactly (with the discrepancy not exceeding 5 min) the gel point determined analytically based on dependence of the degree of curing on the moulding mode. Consequently, the research together with the results previously obtained allows making an integrated choice of geometric parameters of the repair composite patch and temperature–time regime of its curing in order to ensure the specified level of strength and stiffness of the structure under repair.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of the Temperature–Time Regime of Curing of Composite Patch on Repair Process Efficiency

et al. 2021

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“…Total stresses σ i αT , σ i βT and τ i αβT are determined by substitution of the total temperature and shrinkage deformations ε i αT , ε i βT and γ i αβT (13) instead of the general deformations ε i α , ε i β and γ i αβ , accordingly, into the formulas (7). For the determination of stress-strain behaviour of the shell of step-variable thickness, we use the Ritz-Timoshenko method [25,27].…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…From the point of view of increasing the economic efficiency of the operation of structures used in aircraft construction, rocket and space technology, power engineering, construction industry, mechanical engineering and other industries, the most promising is the development and improvement of repair technologies aimed at restoration of the structure's bearing capacity [4][5][6]. According to the results of studies [7], the rational method for repair of the most technological and operational defects in load-bearing structures is the use of repair patches. This repair method consists in layer-by-layer removal of the damaged area and further restoration of structural integrity by using a patch [8].…”

Section: Introductionmentioning

confidence: 99%

Stress–Strain Behaviour of Reparable Composite Panel with Step-Variable Thickness

et al. 2021

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There is an urgent problem of finding an economically viable method of maintenance and restoration of the bearing capacity of structures of various applications. Repair of structures with patches made of polymeric composite materials is one of the most promising repair technologies. However, an improper choice of parameters of the composite patch leads to unjustified increase in the structure mass and the cost of its further operation. These situations result from the lack of reliable methods for developing the repair process, which take into account the influence of the patch geometry and conditions for performance of repair works on the bearing capacity of the repaired structure. The mathematical model of the reparable composite shell–type panel taking into account inhomogeneity of transverse shear deformations at stepped variation of its thickness has been developed. In contrast to the classical theory of layered shells, the model allows simplifying a three-dimensional problem by setting of the displacement field on the layers’ interfaces and their linear interpolation over thickness of the panel, as well as considering the transverse shear deformations resulting from the strength, temperature, or shrinkage loading. According to results, the maximum rise in stresses in the case of a notched panel occurs in the weakened layer, and it is from this layer the failure of the structure will start. In the event of the patch, the panel surface opposite the reinforcement is the most loaded (i.e., susceptible to failure) surface. To confirm the reliability of the developed model, we compared the analytical calculations with the results of experimental and numerical studies of the deformed state of a panel of step–variable thickness by the method of holographic interferometry and modelling by the finite element method. Displacement fields available from experiments correspond to the predicted theoretical results. The resulting maximum error does not exceed 7%. The data obtained during numerical modelling allowed us to conclude that the accuracy of theoretical calculations is sufficient for engineering practice. Results of the work can be used to solve the practical problems such as determination of stress–strain behaviour of a damaged structure or structure after repair, specification of the permissible delamination dimensions, and defining of parameters of the bonded repair process.

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“…One of the most rational methods of repair of typical operational defects (cracks, penetration defects of skin, delaminations) in metal and composite panel constructions is the installation of patches made of polymeric composite materials [15,16]. The high physical and mechanical properties of the composites and the significant advantages of the adhesive joints over mechanical ones, determine the successful use of patches made of polymeric composite materials for the repair of both polymeric and metal structures of various applications [17][18][19]. Because the need for repair of structures in the future will continue to grow, increase in the efficiency of repair processes is no less important than improvement of the methods of designing of new structures [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Self-Heating Mould for Composite Manufacturing

et al. 2021

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The shipbuilding industry, engine manufacturing, aviation, rocket and space technology are promising fields of application for polymeric composite materials. Shape-generating moulding tools with internal heating are used for the creation of a more economically viable method of moulding of internally heated composite structures. The use of a fine-fibered resistive structure in the heated tools allows implementation of effective heating of the composite and elimination of the need for expensive and energy-intensive heating equipment. The aim of this paper was the reduction of energy consumption for internally heated moulding tools by choosing the optimal parameters for their resistive layer. A method for determination of the parameters of the moulding tool resistive layer was developed. This method allows calculation of the heating layer parameters and implementation of the specified time–temperature regime for moulding of the composite structure. It was shown that energy saving for the heated fiberglass shape-generating moulding tools was from 40 to 60%. It was found that the increase in the thickness of the moulded package of the polymeric composite material resulted not only in a higher supplied power for the heating system, but also in a complication of the method for system control, because of the growing exothermic effect of the binder curing reaction. For composite products based on Hysol EA 9396 binder, thicknesses more than 4 mm are critical, because it is not possible to cope with the self-heating effect only by cooling with ambient air already utilized at the twentieth minute of the moulding process. The influence of the physical and mechanical characteristics of the moulding tool material and stiffening ribs was analysed in terms of energy consumption and controllability of the heating system. Fiberglass shows the lowest energy consumption. Heating of the aluminium and steel moulding tools for the same purpose will require 20% and 45% more power, respectively. An increase in the number of stiffening ribs has a strong effect on the heat removal of the heating system. With a small number of aluminium ribs it is not possible to maintain the specified temperature–time regime for a fiberglass moulded package of 5 mm thick with the use of the equipment. However, when the number of stiffeners is increased to 10, the exothermic effect of the reaction becomes smoother and then the heating equipment can cope with the task. An experimental prototype of heating equipment of moulding tools for the manufacturing of structures of polymeric composite materials, as well as a flexible thermal blanket for repair of non-separable structures, were developed. The results can be the basis for a new method of optimal design of parameters of moulding tool structure at minimal heat removal to the environment.

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Review on the performance improvements and non-destructive testing of patches repaired composites

Cited by 65 publications

References 126 publications

Effects of the Temperature–Time Regime of Curing of Composite Patch on Repair Process Efficiency

Effects of the Temperature–Time Regime of Curing of Composite Patch on Repair Process Efficiency

Stress–Strain Behaviour of Reparable Composite Panel with Step-Variable Thickness

Self-Heating Mould for Composite Manufacturing

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