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Journal ArticleDOI

Influence of residual stresses on the mechanical behavior of composite laminate materials

01 Dec 2005-Advanced Composite Materials (Taylor & Francis Group)-Vol. 14, Iss: 4, pp 319-342
TL;DR: In this article, the influence of residual stresses on the mechanical behavior of carbon/epoxy cross-ply laminates under tensile and torsion loading was investigated using the incremental blind-hole drilling technique combined with the finite element analysis.
Abstract: Residual stresses occur during most manufacturing processes (from shrinkage of the resin, difference of thermal expansion coefficients, etc.). Residual stresses may cause local yielding and damage initiation and propagation, and can severely affect performances of a composite structure component. The aim of this work is to investigate the influence of residual stresses on the mechanical behavior of carbon/epoxy cross-ply laminates under tensile and torsion loading. The residual stresses field was determined using the incremental blind-hole drilling technique combined with the finite element analysis. The effect of various cure cycles on the residual stress level is analysed. The quantitative effect of the residual stresses on the mechanical behaviour and the damage initiation and growth is studied by using acoustic emission technique.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the influence of residual stresses on interlaminar fracture toughness (GI) of Carbon/Epoxy laminates was studied using double cantilever beam (DCB) test.
Abstract: Residual stresses are induced in composite laminates during the process of manufacturing due to thermal mismatch between composite constituents during curing. Processes induced residual stresses effects the safety of structural components and can play a main role in matrix cracking, crack initiation and propagation. The objective of this research is to study the influence induced residual stresses on interlaminar fracture toughness (GI) of Carbon/Epoxy laminates. Initially laminates were cured under room temperature followed by post curing at various temperatures using a chosen cure cycle. Slitting method was employed to determine the residual stress distribution in post cured laminates and its effects on GI was estimated using Double Cantilever beam (DCB) test. The results show a gradual increase in GI with increase in compressive residual stresses in composite laminate. Further, the fracture surfaces of laminates were carefully studied using scanning electron microscope to know the interfacial adhesion of matrix and fiber.

15 citations

01 Jan 2013
TL;DR: In this paper, a 1D and 3D thermomechanical models are used to model the phase transitions experienced during the manufacturing process of large fiber reinf orced polymer matrix composites using vacuum assisted res in transfer molding (VARTM1).
Abstract: The present thesis is devoted to numerical modelling of ther momechanical phenomena occurring during curing in the manufacture of large fibre reinf orced polymer matrix composites with thick laminate sections using vacuum assisted res in transfer moulding (VARTM1). The main application of interest in this work is modelling ma nufacturing induced shape distortions and residual stresses in commercial wind turbi ne composite blades. Key mechanisms known to contribute to shape distortions and residua l stress build-up are reviewed and the underlying theories used to model these mechanisms a re presented. The main mechanisms of thermal-, chemicaland mechanical origin ar e; (i) the thermal expansion mismatch of the constitutive composite materials, layer an d tooling, (ii) chemical cure shrinkage of the composite matrix material and (iii) the too ling (i.e. the mould, inserts etc.) influence on the composite part. In the modelling approach taken in the current study, 1D and 3 D thermomechanical models are utilized. A 1D thermomechanical model in a finite diff erence (FD) framework, capable of predicting heat transfer, internal heat generat ion, cure degree development, as well as process induced in-plane strains and residual stres ses i initially presented. This 1D model is the framework for the first attempt at a void growth model, capable of predicting the laminate through-thickness discretized void s ize distribution, as a function of processing parameters. Using a 3D thermomechanical finite element (FE) model in ABAQ US, different constitutive modelling approaches are investigated, including a cure hardening instantaneous linear elastic (CHILE) approach, a viscoelastic approach a nd a path-dependent approach. The latter is a limiting case of viscoelasticity. These appr oaches are investigated with regards to their accuracy in predicting process induced str ain and stress development in thick section laminates during curing, and more precisely r ga ding the evolution of the composite thermoset polymer matrix mechanical behaviour d uring the phase transitions experienced during curing. The different constitutive app roaches are utilized in various case studies and compared, where possible, to experimental r sults from measured in situ internal total strains in laminates using embedded fibre Bra gg grating (FBG) sensors. Due to reasonable model accuracy, ease of implementation an d use of relatively simply obtained material characterization data, the CHILE and pat h-dependent approaches are found to be most favorable. It is shown that use of the viscoel astic approach to accurately predict process induced strains and stresses in modelling m a ufacturing cases where mild tooling constraints on the composite part exist, is not viab le. In a final case study, process Also known as Vacuum Infusion or Vacuum Infusion Resin Trans fer Moulding

8 citations

Journal ArticleDOI
Ce Zhang, Guoli Zhang, Jing Xu, Xiaoguo Shi, Xi Wang 
TL;DR: In this paper , the effect of reinforcement structure optimization, resin modification and process optimization, die surface compensation and tool-part contact optimization on the deformation of carbon fiber reinforced resin composites was analyzed and evaluated.
Abstract: Under the influence of extrinsic curing conditions and intrinsic properties of carbon fiber reinforced resin composites, the formation of curing deformation is inevitable, which makes the shape of the manufactured components differ from the designed structure, and even exceeds the assembly tolerance, resulting in the scrap of parts. Therefore, it is very urgent and important to optimize the curing deformation of carbon fiber reinforced resin composites. In this paper, the mechanism of stress and curing deformation is reviewed firstly, and then the factors affecting the curing deformation are summarized. In particular, from the point of view of materials in curing process, three curing deformation control strategies, including (i) reinforcement structure optimization, (ii) resin modification and process optimization, (iii) die surface compensation and tool-part contact optimization, were proposed. And with the development of curing deformation simulation technology, the (iv) inverse design strategy before curing and (v) hot sizing method from the view of after cured were further put forward, respectively. By analyzing the link between processing details and curing deformation, it is found that the dominant factor affecting deformation may change under different conditions, so the interaction between factors needs to be further discussed. Subsequently, the effect of these distortion control methods on curing deformation was analyzed and evaluated, and the shortcomings were pointed out. Finally, the challenges existed in curing deformation research were identified, in order to contribute to the development of curing deformation research.

8 citations

Journal ArticleDOI
TL;DR: In this article, the curing stresses in a newly proposed bi-axial residual stress testing configuration are studied using a chopped strand mat glass/epoxy specimen, and in-situ monitoring of the curing is conducted using dielectric and fibre Bragg grating sensors.
Abstract: The curing stresses in a newly proposed bi-axial residual stress testing configuration are studied using a chopped strand mat glass/epoxy specimen. In-situ monitoring of the curing is conducted using dielectric and fibre Bragg grating sensors. It is confirmed that a bi-axial residual stress state can be introduced in the specimens during curing and a quantification of its magnitude is presented. An alternative decomposition method used for converting the dielectric signal into a material state variable is proposed and good agreement with models found in the literature is obtained. From the cure cycles chosen it is suggested that any stress build up in the un-vitrified state is relaxed immediately and only stress build up in the vitrified state contributes to the residual stress state in the specimen.

6 citations


Cites background from "Influence of residual stresses on t..."

  • ...The presence of residual stresses at the micro level can have beneficial effects on tensile strength in the fibre [22] and transverse directions [23] attribute to the presence of compressive radial stress, whilst the influence on modulus is significantly lower [24]....

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References
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Journal ArticleDOI
Michael W. Hyer1
TL;DR: In this paper, the cured shape of thin unsymmetric laminates does not conform to the predictions of classical lamination theory and the curvature directions of the cylindrical shapes are predictable.
Abstract: This paper discusses the fact that the cured shape of thin unsymmetric laminates do not conform to the predictions of classical lamination theory. Rather than being saddle shaped, as predicted by the classical theory, the paper shows that thin unsymmetric laminates cure into a shape of a right circular cylinder. This anomalous behavior has been observed by many but the paper serves to quantify the effect and to inspire investigators to begin thinking about using the phenomenon to advantage. The paper indicates that the anomalous behavior is repeatable and that thicker laminates con form to the predictions of the classical theory. Laminates of the [0/902 /θ ]T, [02 /θ2 ] T and [04 /θ4 ] T families are investigated for this be havior and it is shown the principal curvature directions of the cylindrical shapes are predictable.

447 citations


"Influence of residual stresses on t..." refers background in this paper

  • ...Within the framework of a viscoelastic approach of the classical laminate theory (CLT), the residual stresses level depends directly on the difference between the cure and the room temperature [8, 12]....

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  • ...The most widely used for non-symmetrical laminates is the observation and measurement of the out-of-plane residual deformation [12, 13]....

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Journal ArticleDOI
TL;DR: In this article, the damage mechanisms of four short-glass-fibre-reinforced polypropylenes are investigated in tensile, tensile fatigue and crack propagation tests.

353 citations

Journal ArticleDOI
TL;DR: In this article, a process model was developed for investigation of residual stress development during autoclave or hot press processing of thermosetting polymer matrix composites, which is used in this paper.
Abstract: In a companion paper [1] a process model was developed for investigation of residual stress development during autoclave or hot press processing of thermosetting polymer matrix composites. Several ...

251 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of dwell temperature, dwell time, cool-down rate, cooldown pres sure, and postcure on residual stresses were investigated using unsymmetric cross-ply laminates.
Abstract: The control and reduction of processing-induced residual stresses has been investigated by modifying processing conditions for a graphite/BMI composite material. The effects of dwell temperature, dwell time, cool-down rate, cool-down pres sure, and postcure on residual stresses were investigated using unsymmetric cross-ply laminates. The effects on transverse mechanical properties were also measured. Experi mental results have shown that residual stresses can be reduced by as much as 25-30% while retaining or enhancing transverse mechanical properties by curing at lower tempera tures for longer times or utilizing an intermediate low-temperature dwell in three-step cure cycles. Overall process cycle times are not lengthened for three-step curing.

214 citations


"Influence of residual stresses on t..." refers background in this paper

  • ...Within the framework of a viscoelastic approach of the classical laminate theory (CLT), the residual stresses level depends directly on the difference between the cure and the room temperature [8, 12]....

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  • ...Many solutions have been considered to reduce the residual stresses level, namely: • Addition of post-cure treatment [8]....

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  • ...• Modification of the isothermal step number [8]....

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Journal ArticleDOI
Süleyman Tekeli1
TL;DR: In this article, shot peening was carried out to create residual compressive stresses caused by deformation hardening at the surface and to remove decarburized layer of the surface resulted in heat treatment.

108 citations


"Influence of residual stresses on t..." refers background in this paper

  • ...Unlike metals, in which the introduction of residual stresses is sometimes facilitated by a specific treatment such as shot-peening or rolling [1, 2], the presence of residual stresses in laminated structures does not...

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