Strength and cohesive behavior of thermoset polymers at the microscale: A size-effect study

Qiao, Yao; Salviato, Marco

doi:10.1016/j.engfracmech.2019.03.033

Cited by 47 publications

(10 citation statements)

References 51 publications

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“…A similar phenomenon, associated to the greater splitting development in load-bearing plies for the specimens with an intra-laminar central crack compared to the ones with an open hole, has been reported by several authors on notched Carbon Fiber Reinforced Polymer (CFRP) laminates [60,73]. However, since the failure behavior of notched composites depends on the size of the non-linear Fracture Process Zone (FPZ) occurring in the presence of a large stress-free crack compared to the specimen width [74][75][76][77][78][79][80][81][82][83],…”

Section: Multi-axial Quasi-static Tests On Notched Specimensmentioning

confidence: 99%

A study on the multi-axial fatigue failure behavior of notched composite laminates

Qiao

Deleo

Salviato

2019

Composites Part A: Applied Science and Manufacturing

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Section: Multi-axial Quasi-static Tests On Notched Specimensmentioning

confidence: 99%

A study on the multi-axial fatigue failure behavior of notched composite laminates

Qiao

Deleo

Salviato

2019

Composites Part A: Applied Science and Manufacturing

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“…The use of macroscopically observed values of GIC in the microscale simulations encountered in this study would lead to physically unrealistic response. Recently, Qiao and Salviato [6] proposed a two-scale cohesive traction-separation law. Based on measurements, they showed that the fracture strength of thermoset polymers at the microscale is noticeably higher than the macroscopically observed fracture strengths, whereas the fracture toughness, GIC, associated with Mode I cracking is up to two orders of magnitude lower than what is observed in macroscopic specimens.…”

Section: Introductionmentioning

confidence: 99%

Influence of Unit Cell Size and Fiber Packing on the Transverse Tensile Response of Fiber Reinforced Composites

D’Mello

Waas

2019

Materials

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Representative volume elements (RVEs) are commonly used to compute the effective elastic properties of solid media having repeating microstructure, such as fiber reinforced composites. However, for softening materials, an RVE could be problematic due to localization of deformation. Here, we address the effects of unit cell size and fiber packing on the transverse tensile response of fiber reinforced composites in the context of integrated computational materials engineering (ICME). Finite element computations for unit cells at the microscale are performed for different sizes of unit cells with random fiber packing that preserve a fixed fiber volume fraction—these unit cells are loaded in the transverse direction under tension. Salient features of the response are analyzed to understand the effects of fiber packing and unit cell size on the details of crack path, overall strength and also the shape of the stress-strain response before failure. Provision for damage accumulation/cracking in the matrix is made possible via the Bazant-Oh crack band model. The results suggest that the choice of unit cell size is more sensitive to strength and less sensitive to stiffness, when these properties are used as homogenized inputs to macro-scale models. Unit cells of smaller size exhibit higher strength and this strength converges to a plateau as the size of the unit cell increases. In this sense, since stiffness has also converged to a plateau with an increase in unit cell size, the converged unit cell size may be thought of as an RVE. Results in support of these insights are presented in this paper.

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“…To capture the effects of a finite, non-negligible FPZ, the introduction of a characteristic (finite) length scale, related to the fracture energy and the strength of the material, is necessary [18,19,[29][30][31][32][33][34][35][36]38]. This is done in the following sections.…”

Section: Analysis and Discussionmentioning

confidence: 99%

Mode I and II Interlaminar Fracture in Laminated Composites: A Size Effect Study

Salviato

Kirane

Bažant

et al. 2019

Journal of Applied Mechanics

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This work investigates the mode I and II interlaminar fracturing behavior of laminated composites and the related size effects. Fracture tests on geometrically scaled Double Cantilever Beam (DCB) and End Notch Flexure (ENF) specimens were conducted to understand the nonlinear effects of the cohesive stresses in the Fracture Process Zone (FPZ). The results show a significant difference between the mode I and mode II fracturing behaviors. It is shown that, while the strength of the DCB specimens scales according to the Linear Elastic Fracture Mechanics (LEFM), this is not the case for the ENF specimens. Small specimens exhibit a pronounced pseudo-ductility with limited size effect and a significant deviation from LEFM, whereas larger specimens behave in a more brittle way, with the size effect on nominal strength closer to that predicted by LEFM. This behavior, due to the significant size of the Fracture Process Zone (FPZ) compared to the specimen size, needs to be taken into serious consideration. It is shown that, for the specimen sizes investigated in this work, neglecting the non-linear effects of the FPZ can lead to an underestimation of the fracture energy by as much as 55%, with an error decreasing for increasing specimen sizes. Both the mode I and II test data can be captured very accurately by Bažant's type II Size Effect Law (SEL).

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Strength and cohesive behavior of thermoset polymers at the microscale: A size-effect study

Cited by 47 publications

References 51 publications

A study on the multi-axial fatigue failure behavior of notched composite laminates

A study on the multi-axial fatigue failure behavior of notched composite laminates

Influence of Unit Cell Size and Fiber Packing on the Transverse Tensile Response of Fiber Reinforced Composites

Mode I and II Interlaminar Fracture in Laminated Composites: A Size Effect Study

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