Micro-mechanical analysis of the effect of ply thickness on curing micro-residual stresses in a carbon/epoxy composite laminate

• Published in: Composite structures 2023-09, Vol.319, p.117158, Article 117158
• Main Authors: Goncalves, Paulo Teixeira, Arteiro, Albertino, Rocha, Nuno
• Format: Article
• Language: English
• Subjects: Finite element analysis (FEA); Micro-mechanics; Polymer matrix composites (PMCs); Residual/internal stress; Thermomechanical
• ISSN: 0263-8223
• DOI: 10.1016/j.compstruct.2023.117158

•Micro-residual stresses reduce effective ply strength in constrained conditions.•Ply residual stresses can achieve more than 50 % of failure load.•Thick ply laminates tend to retrieve more ply residual stresses.•Thin ply laminate exhibits higher strength and lower crack opening after failure. During the manufacturing of thermoset-based carbon fiber reinforced polymers (CFRPs), micro-residual stresses are developed in the material, due a mismatch of the chemical-thermal-mechanical properties of the fibers and the polymer matrix. This ultimately leads to a reduction in the mechanical performance of the composite material. In this work, a representative volume element (RVE) of a composite sub-laminate with a 90° ply discretized at micro-scale level, stacked within homogenized plies, is proposed to study the micro-residual stresses and the ply mechanical response considering the in-situ effect caused by the constraining adjacent layers. A model framework is developed using finite elements in Abaqus®/Standard with user-subroutines. The retrieved micro-residual stresses in the 90° layer are generated by the dissimilar chemical shrinkage and thermal expansions, plus the additional residual meso-scale stresses caused by the constraining effect of adjacent plies. The residual stresses in the constrained condition can achieve almost 80 % of the ply failure load for the 0/90/0 sub-laminate, meaning lower sub-laminate strain to failure. Thick laminates retrieve more residual stresses in the transverse 90° layer and exhibit lower constrained strength and more unstable post-failure response, demonstrating that thin-ply laminates exhibit beneficial constraining effects during the curing process.