Modeling of manufacturing of thermoplastic composites and residual stress prediction

Fedulov, Boris

doi:10.1007/s42401-018-0018-8

Cited by 12 publications

(8 citation statements)

References 7 publications

(13 reference statements)

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“…the external and internal force factors leading to the appearance of stresses in the structure under repair, using the example of typical temperature-time dependence of the polymeric binder curing mode (Figure 3) [19,22]. Taking into account that technological stresses occur in the structure only after gelation (point O) [25,29,31], the typical curing process can be roughly divided into four stages, as shown in Figure 3.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…The pattern for modelling of residual stresses and technological deformations in the PCM is proposed in [31]. Experimental comparison of the modelling results for all mechanical characteristics at all stages of the phase transformation of the material is given.…”

Section: Introductionmentioning

confidence: 99%

“…The number of areas of division is determined by the required computational accuracy. Taking into account that technological stresses occur in the structure only after gelation (point O) [25,29,31], the typical curing process can be roughly divided into four stages, as shown in Figure 3.…”

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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: Theoretical Backgroundmentioning

confidence: 99%

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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“…The material data are listed in Table 1, which consolidates data from the literature. 8,10,11,20 Effects of consolidation cooling rate on mechanical properties…”

Section: Implementation Of the Thermoplastic Consolidation Model Within Clt Theorymentioning

confidence: 99%

A CLT based constitutive model to predict distortions and residual stresses in semi-crystalline thermoplastic composites

Grandis

Donadon

Faria

et al. 2021

Journal of Composite Materials

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This paper describes a classical laminate theory-based constitutive model for portraying thermoplastic composites’ mechanical properties and the development of residual stresses during consolidation. The extended Hillier model is applied to describe the material’s crystallisation and as such is able to provide final part quality as a function of the process cooling history while taking into account the first and second crystallisation mechanisms occurring concurrently. With the developed model, a parametric study was performed taking into account layups that are commonly used in the aerospace industry, where general design guidelines are suggested. Some of the advantages of using cross-ply and quasi-isotropic laminates became clear as no shear residual stresses were predicted for those laminates. However, highly anysotropic laminates may also offer structural advantages. Numerical simulations indicate that the crystallisation residual strains can be, although smaller than thermal residual strains, relevant to final part quality. The combination of both effects may result in high residual stresses at ply level which in turn can compromise the ultimate strength of the laminates and make it difficult to attain the desired part’s geometrical tolerances.

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“…The process of moulding of PCM products cannot be completely modelled [18,19]. It is due to the complexity of the mathematical description of the processes that occur in the moulded PCM, as well as the necessity to consider their mutual influence (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Determination of the Composite Panel Moulding Pressure Value

et al. 2022

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Currently, prefabricated panel structures are typical products made of polymeric composite materials. The integrity of the composite panels, their structure and accuracy of making a contour are largely associated with the manifestation of residual technological stresses. The above phenomena and associated stress-strain behaviour inevitably occur in the process of moulding of the composite products. However, their value, nature, time of occurrence and dynamics of growth can be fully controlled and regulated. The paper deals with the study of the effect of moulding pressure on the quality of a composite product. A dependence is presented that allows us to determine the time for the degassing of the polymeric composite material package at the given temperature and pressure to obtain a monolithic and nonporous structure. It is shown that the peak of the maximum volatile-matter yield for the considered binder types lies in the temperature range where the degree of curing does not exceed 10%; that is, the viscosity values do not prevent the removal of volatile fractions. The effect of moulding pressure on the values of the volume content of the reinforcing material has been studied, and the dependence of the required thickness of the absorbent layer on the parameters of the package of polymer composite material and pressure has been obtained. The dependence of the required thickness of absorbent layer on the parameters of the package of polymeric composite material and pressure has been obtained. The mathematical model developed by us provides an opportunity to predict the stress-strain behaviour of a composite structure at any time during the moulding process. The model is closely related to chemo-viscous and thermal models. It allowed us to synthetize a method for choosing the rational parameters of the moulding process (temperature, pressure, and time), materials of additional layers and equipment. The experiments proved the presence of several defects, such as de-lamination of edges, waviness, swelling and poor adhesion of upper layers in the specimen of the composite panel cooled stepwise in the absence of the vacuum pressure. The surface quality of the specimen of the panel cooled stepwise under vacuum pressure was significantly better, and no visible defects were observed. The obtained theoretical values of deflections, considering the change in physic-mechanical characteristics that depend on the temperature and rheonomic properties of the material, showed an error that did not exceed 7%, compared to the experimental data. Our results can be applied at the enterprises engaged in designing and manufacturing panel structures of polymeric composite materials.

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Modeling of manufacturing of thermoplastic composites and residual stress prediction

Cited by 12 publications

References 7 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

A CLT based constitutive model to predict distortions and residual stresses in semi-crystalline thermoplastic composites

Determination of the Composite Panel Moulding Pressure Value

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