Steady-state modelling and analysis of process-induced stress and deformation in thermoset pultrusion processes

Sandberg, Michael; Yuksel, Onur; Baran, İsmet; Spangenberg, Jon; Hattel, Jesper Henri

doi:10.1016/j.compositesb.2021.108812

Cited by 10 publications

(6 citation statements)

References 58 publications

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“…In future research, the authors intend to perform 3D analysis for the case of pultruded flat laminate to evaluate the influence of pulling speed and of profile thickness on the formation of cracks and distortions. Thus, a novel steady-state 3D-Eulerian numerical framework is intended to be applied in future works with the aim of accelerating the computational process [ 31 ].…”

Section: Discussionmentioning

confidence: 99%

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Modeling Spring-In of L-Shaped Structural Profiles Pultruded at Different Pulling Speeds

et al. 2021

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Cure-induced deformations are inevitable in pultruded composite profiles due to the peculiarities of the pultrusion process and usually require the use of costly shimming operations at the assembly stage for their compensation. Residual stresses formed at the production and assembly stages impair the mechanical performance of pultruded elements. A numerical technique that would allow the prediction and reduction of cure-induced deformations is essential for the optimization of the pultrusion process. This study is aimed at the development of a numerical model that is able to predict spring-in in pultruded L-shaped profiles. The model was developed in the ABAQUS software suite with user subroutines UMAT, FILM, USDFLD, HETVAL, and UEXPAN. The authors used the 2D approach to describe the thermochemical and mechanical behavior via the modified Cure Hardening Instantaneous Linear Elastic (CHILE) model. The developed model was validated in two experiments conducted with a 6-month interval using glass fiber/vinyl ester resin L-shaped profiles manufactured at pulling speeds of 200, 400, and 600 mm/min. Spring-in predictions obtained with the proposed numerical model fall within the experimental data range. The validated model has allowed authors to establish that the increase in spring-in values observed at higher pulling speeds can be attributed to a higher fraction of uncured material in the composite exiting the die block and the subsequent increase in chemical shrinkage that occurs under unconstrained conditions. This study is the first one to isolate and evaluate the contributions of thermal and chemical shrinkage into spring-in evolution in pultruded profiles. Based on this model, the authors demonstrate the possibility of achieving the same level of spring-in at increased pulling speeds from 200 to 900 mm/min, either by using a post-die cooling tool or by reducing the chemical shrinkage of the resin. The study provides insight into the factors significantly affecting the spring-in, and it analyzes the methods of spring-in reduction that can be used by scholars to minimize the spring-in in the pultrusion process.

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Section: Discussionmentioning

confidence: 99%

“…Residual stresses developing during the production and assembly stages are detrimental to the final mechanical performance of a structure [ 29 , 30 ]. Thus, the ability to predict, control, and compensate for process-induced deformations is crucial for the effective design and assembly of composite structures [ 31 , 32 ].…”

Section: Introductionmentioning

confidence: 99%

Modeling Spring-In of L-Shaped Structural Profiles Pultruded at Different Pulling Speeds

et al. 2021

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“…They are mainly focused on the determination of the value of the pulling force for smoothly production and the force distribution in the dies. [ 4–10 ] However, the study of the effect of pretension force of fiber yarns on the tensile strength is also important to get optimal pulling parameters.…”

Section: Introductionmentioning

confidence: 99%

Failure mechanism of unidirectional basalt fiber‐reinforced polymer composites with pretension of fiber yarns

Zhao

Wang

et al. 2022

Polymer Composites

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The pultrusion process has received increasing attention because of its high productivity, low cost, and good product quality. During the pultrusion process, the pulling and pretension force is a key factor to control the quality of the products. In this paper, the effect of the pretension force on the tensile strength of basalt fiber‐reinforced polymer (BFRP) composites was studied. The pretension force was controlled using different weights. Tensile tests were performed on the BFRP specimens and the microscopic analysis was examined by scanning electron microscopy. The results showed that the static tensile strength of specimens climbed up initially, followed by a decrease with the increase of pretension weights. Three microscopic changes under different pretension forces were found and discussed to explain the damage and failure mechanism. It is essential to optimize the pretension force to improve the strength quality for the pultrusion products of BFRP.

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“…In [15,16], 2D and 3D mechanical models in the Lagrangian frame were coupled with a 3D thermo-chemical model in the Eulerian frame to predict the residual stress formation in pultrusion. Accordingly, in a recent paper, a fully coupled 3D Eulerian model was developed [17]. Using these approaches, numerous studies have been carried out in the literature to predict the residual stress in pultruded components with different cross-sectional shapes, reinforcement configurations, and for different process parameters [6,7,9,15,18,19].…”

Section: Introductionmentioning

confidence: 99%

Mesoscale Process Modeling of a Thick Pultruded Composite with Variability in Fiber Volume Fraction

et al. 2021

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Pultruded fiber-reinforced polymer composites are susceptible to microstructural nonuniformity such as variability in fiber volume fraction (Vf), which can have a profound effect on process-induced residual stress. Until now, this effect of non-uniform Vf distribution has been hardly addressed in the process models. In the present study, we characterized the Vf distribution and accompanying nonuniformity in a unidirectional fiber-reinforced pultruded profile using optical light microscopy. The identified nonuniformity in Vf was subsequently implemented in a mesoscale thermal–chemical–mechanical process model, developed explicitly for the pultrusion process. In our process model, the constitutive material behavior was defined locally with respect to the corresponding fiber volume fraction value in different-sized representative volume elements. The effect of nonuniformity on the temperature and cure degree evolution, and residual stress was analyzed in depth. The results show that the nonuniformity in fiber volume fraction across the cross-section increased the absolute magnitude of the predicted residual stress, leading to a more scattered residual stress distribution. The observed Vf gradient promotes tensile residual stress at the core and compressive residual stress at the outer regions. Consequently, it is concluded that it is essential to take the effects of nonuniformity in fiber distribution into account for residual stress estimations, and the proposed numerical framework was found to be an efficient tool to study this aspect.

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Steady-state modelling and analysis of process-induced stress and deformation in thermoset pultrusion processes

Cited by 10 publications

References 58 publications

Modeling Spring-In of L-Shaped Structural Profiles Pultruded at Different Pulling Speeds

Modeling Spring-In of L-Shaped Structural Profiles Pultruded at Different Pulling Speeds

Failure mechanism of unidirectional basalt fiber‐reinforced polymer composites with pretension of fiber yarns

Mesoscale Process Modeling of a Thick Pultruded Composite with Variability in Fiber Volume Fraction

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