Residual stresses associated with post-cure shrinkage in GRP tubes

Life cycle strain monitoring in glass fibre reinforced polymer laminates using embedded fibre Bragg grating sensors from manufacturing to failure

“…High cure temperatures and fast heating/cooling rates can result in highly non-uniform temperature and cure gradients within the part resulting in differential curing and subsequent development of internal stresses. 3,[4][5][6]11 Similar effects in the form of a non-uniform distribution of in-plane shear stresses can arise due to constraints posed by tooling during processing. 10,12 A combination of the above-named residual stress mechanisms and manufacturing defects can cause local premature failure at lower load magnitudes than would otherwise be predicted in a defect-free composite structure.…”

“…For instance, large process-induced residual stresses are known to induce matrix cracking, interfacial debonding and delamination in fibre-reinforced composites. 1 In other works, [4][5][6] demonstrated that for thick-walled composite tubes, residual stresses can be so great that matrix cracking was promoted. At a micromechanic level, Nedele and Wisnom 7 showed that process-induced stresses at the fibre-matrix interface can be as large as 30 MPa, due to the combination of hoop and radial stress components.…”

The effect of residual stresses and wind configuration on the allowable pressure of thick-walled GFRP pipes with closed ends

“…Unfortunately these are promoted by increased laminate thickness (Stone et al 1997), to the extent that they are often comparable to the stresses arising from applied loads. The strain through the pipe thickness is the combination of both mechanical strain and residual strain.…”

“…The strain through the pipe thickness is the combination of both mechanical strain and residual strain. In the case of filament-wound pipes, the residual stresses that develop are generally tensile at the inner surface (Stone et al 1997), and thus adversely affect the allowable operating pressures of pipes used to transport aggressive media. The residual stresses in composite pipes are a consequence of a number of factors including the manufacturing parameters, the resin cure shrinkage, thermal shrinkage due to elevated processing temperatures and wind angle.…”

Characterisation of residual stresses in a single fibre composite with FBG sensor

“…In another study [2] the residual stresses associated with post-cure shrinkage of adjacent layers in composite tubes of polyester and vinyl-ester resins reinforced with glass fibres are modelled by considering the material's shrinkage after gelation as an equivalent thermo-elastic problem. Other investigators have addressed the problem of local residual stresses by use of concentric circular cylinders configurations.…”