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Identification of process-induced residual stress/strain distribution in thick thermoplastic composites based on in situ strain monitoring using optical fiber sensors
In thick thermoplastic composite laminates, nonuniform temperature distribution arises in the through-thickness direction during high-rate manufacturing processes. This causes the so-called thermal skin-core effect. The surface region solidified in advance constrains shrinking of the inside region,...
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Published in: | Journal of composite materials 2019-10, Vol.53 (24), p.3445-3458 |
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Main Authors: | , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | In thick thermoplastic composite laminates, nonuniform temperature distribution arises in the through-thickness direction during high-rate manufacturing processes. This causes the so-called thermal skin-core effect. The surface region solidified in advance constrains shrinking of the inside region, so nonuniform residual stress/strain distribution arises in the through-thickness direction. This study quantitatively clarified this mechanism and identified the amount of residual stress/strain by utilizing fiber optic–based internal strain measurement and process simulation. First, in-plane transverse strain of thin carbon fiber/polyphenylenesulfide laminates was measured using fiber Bragg grating sensors to determine two key parameters for stress/strain simulation; thermal/crystalline shrinkage strain and composite stiffness. Abaqus-based simulation using these properties was then performed to calculate stress/strain distribution in thick laminates. The simulated strain agreed well with the measured value and it was confirmed that the residual stress developed in a relatively low temperature range. In addition, transverse three-point bending tests were conducted to validate the amount of residual stress calculated by the simulation. The bending strength increased by the thermal skin-core effect and the amount of strength increase coincided with the simulation, confirming the validity of the simulation. Extension of the proposed approach to the evaluation of the morphological skin-core effect is also discussed. |
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ISSN: | 0021-9983 1530-793X |
DOI: | 10.1177/0021998319837199 |