A thermo-viscoelastic model of process-induced residual stresses in composite structures with considering thermal dependence

Investigation of non-uniform gelation effects on residual stresses of thick laminates based on tailed FBG sensor

“…Due to the prepreg applied here is a no-bleeding prepreg, constant fibre volume fraction of 57% was used.  is usually assumed to be zero before gelation [7][8][9].…”

“…Esory et al [7,8] studied the development of residual stresses and cure deformation of L and C section composites with both experimental and numerical methods. Ding et al [9] also developed numerical model to predict residual stresses in L shaped thin laminates.…”

Cure-induced residual stresses for warpage reduction in thermoset laminates

“…This is typically done by characterizing the viscous-elastic material properties of epoxy resins and implementing them in coupled thermo-mechanical finite element (FE) models analysis. 1,[17][18][19] Furthermore it has been shown that application of different cure cycles generates different levels of residual stresses 1,[20][21][22] and that manufacturer recommended cure cycles (MRCC) do not lead to optimal solutions in terms of residual stresses generation therefore studies on optimal cure cycles to minimize residual stresses have been undertaken. 21,23,24 The optimization studies showed that cure cycle tuning is an effective tool to minimize the level of residual stresses.…”

Multi-scale modeling of the viscoelastic behavior of 3D woven composites

“…The homogenized viscoelastic behavior is used to calculate the evolution of the apparent moduli of the composite with temperature between −50 • C and 200 • C. The results are in good agreement with experimental data over the temperature range where the matrix behavior was properly identified.While the mechanical behavior of carbon or glass fibers is linear elastic in a good approximation and almost independent of temperature, at least below the glass transition temperature (T g ) of typical thermosetting polymers (usually not exceeding about 200 • C), the mechanical behavior of the polymer matrix depends strongly on temperature and on the degree of cure [14,15,16,17,18,12]. Moreover, it is time dependent, i.e., creep and relaxation phenomena are observed, which may have a significant impact on the residual stresses and the final shape of composite parts [13,19,20,21]. As a consequence, residual stresses can be reduced by adapting the cure cycle such that relaxation phenomena are intensified [13,22].Since in the aeronautical industry highly precise part shapes are required, it is currently common practice to adapt the mold shape several times until the composite part fits the shape tolerances.…”

“…Significant cost reduction is possible if only the constituent materials are fully characterized and the composite properties are predicted using multi-scale models.At small strains, creep, relaxation, and strain rate dependence of polymer resins are well described by viscoelastic models of the generalized Maxwell type [23,14,15,16]. This kind of model was used by several authors to simulate the generation of residual stresses in composites with both thermosetting and thermoplastic polymer matrices [24,25,26,20,27]. In all these works, the time-temperature superposition principle used, as it was shown to describe well the temperature dependence of the viscoelastic behavior of polymers [14,15,16,28].…”