Multiscale simulation and theoretical prediction for the elastic properties of unidirectional fiber‐reinforced polymer containing random void defects

Abstract

Polymer‐matrix composites are widely used in various industries due to their high specific strength and specific stiffness. However, the void formation is inevitable as a by‐product during manufacturing processes, which may have negative effects on its mechanical properties. The purposes of this paper are to quantitatively evaluate the influence of voids on the anisotropic elastic properties of composites and to provide corresponding theoretical prediction models. Firstly, three‐dimensional representative volume elements (RVE) of fiber‐reinforced composite materials with different fiber contents (36.37%, 45.47%, 50.92%) and different void contents (1%, 3%, 5%, 7%) are established. To obtain the elastic properties in different directions, various periodic boundary conditions are applied to the RVE models and corresponding subroutines are developed by ABAQUS‐PYTHON. Secondly, a series of theoretical models are proposed to quickly predict the anisotropic elastic properties of unidirectional fiber/epoxy composites containing random‐sized void defects, which agree well with the finite element simulation results. Especially, the proposed models have concise expressions, which require only a few parameters to be input, and hence they are convenient for engineering application. Both theoretical and numerical results show that void defects have an obvious influence on the transverse modulus, major Poisson's ratio, and the out‐of‐plane shear modulus. When the void volume reaches 7%, all of the properties mentioned above decrease by more than 10% for the FRPs studied.

Thermal cycling of strained nickel‐coated glass‐epoxy composite laminates: Effects on macro mechanical and fiber‐matrix interface properties

“…Moreover, the burn‐off method yielded more consistent V f results for all laminate types, and also in general greater consistency with the measured material densities (i.e., higher V f corresponded to higher material densities). The average void content of unconditioned [0°] 16 laminates was 2.84%; this level is consistent with values obtained by Chu et al [ 62 ] and the trend found by Mujahid et al [ 63 ] for high V f laminates. The average thickness of conditioned in‐plane shear specimens was slightly lower than unconditioned specimens.…”

Stochastic modelling of continuous glass-fibre reinforced plastics–considering material uncertainty in microscale simulations

“…The present model depicts a similar detrimental effect of pores on the transversal stiffness and strength as similarly predicted in literature works with geometrical models of the pores for carbon composites. [7][8][9] In particular, Chu and Jiang numerically predicted a drop of the transverse modulus of about 10% at a void content of 4%, which correlates well with the present numerical results. 8,47 He 7 and Liu 12 predicted a strength drop between 15% and 25% at the same void content, which agrees well with the observed 15% drop in this work.…”

“…7–9 In particular, Chu and Jiang numerically predicted a drop of the transverse modulus of about 10% at a void content of 4%, which correlates well with the present numerical results. 8,47 He 7 and Liu 12 predicted a strength drop between 15% and 25% at the same void content, which agrees well with the observed 15% drop in this work. With about 90,000 tetrahedron elements compared to the 600,000 used by Chu in Ref.…”

“…He 7 developed an approach based on the geometrical representation of sub-ply voids in unidirectional unit cells and predicted the loading-dependent drop of the material strength at increasing void contents. Using similar modelling techniques, Chu, 8 Hyde 9 and Turteltaub 10 simulated the detrimental effect of void content and void shape on the material’s stiffness, strength and energy release rates respectively. The modelling of the voids has been differently handled by Liu in, 11 where elements were randomly deleted at the beginning of simulation.…”

Hybrid multiscale procedure for damage in notched unidirectional composite monitored by thermography

“…Nevertheless, design of composites plates involves several variables since it is a multiscale task [17,18] and experimental results usually have a quite limited application. [19] On the one hand, analytical investigations have the advantage of good approximations and attractive formulae for optimization procedures.…”