On the physical relevance of power law-based equations to describe the compaction behaviour of resin infused fibrous materials

Abstract

On the physical relevance of power lawbased equations to describe the compaction behaviour of resin infused fibrous materials.

Compaction behaviour of continuous fibre-reinforced thermoplastic composites under rapid processing conditions

“…The slight reformulation of Belnoue et al [71] model for prepreg compaction used in this paper justifies a slight amendment of the energy potential which controls the corresponding hyperviscoelastic model [51]. Details of the required reformulation are presented here.…”

“…At the meso-scale, this gave rise to the existence of a compaction limit [70] past which the fibres are so tightly packed that the melt cannot compact anymore. Recently, the model was slightly reformulated [71] in the light of a new physics-based reinterpretation of the power-law fluid proposed by Chandler [72]. This led to the removal of the artificial change of flow direction at locking hypothesised in the original model formulation.…”

“…More precisely, under squeezing, the material is assumed to be incompressible whilst it is hypothesized that, under bleeding, a thickness change is not accompanied by a lateral expansion of the block of material considered. More information on the model assumptions and formulation can be found in references [51] [71].…”

“…In order to understand the impact of the viscosity as well as its evolution with processing conditions, the experimentally measured load-displacement curves, obtained from the ramp-dwell compaction tests, were transformed into strain rate and real stress values as described in [51] [71]. The experimental pressure-strain dependency across the entire range of strain rates can converge to a linear function in the vs. log-log diagram if the value of is properly chosen.…”

“…This procedure was automated using an in-house Python code (described in [73]) -allowing for the model parameters ( 𝑎, 𝑏 and ) to be extracted. The displacements were translated into strain and strain rate as described in [51] 𝑘 [71]. These values are presented in Table 1 and Table 2 The viscous parameters were implemented as a UMAT subroutine in the Finite Element (FE) package ABAQUS/Standard, following the hyper-viscoelastic model described in [51] [71].…”