scholarly journals The Thickness Effect of PSF Nanofibrous Mat on Fracture Toughness of Carbon/Epoxy Laminates

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3469
Author(s):  
Hamed Saghafi ◽  
Ali Nikbakht ◽  
Reza Mohammadi ◽  
Dimitrios Zarouchas
Keyword(s):  
Fracture Toughness ◽  
Composite Laminates ◽  
Double Cantilever Beam ◽  
Thickness Effect ◽  
Toughening Mechanism ◽  
Geometrical Features ◽  
Electrospinning Method ◽  
Fracture Tests ◽  
Mat Thickness ◽  
First Time

The geometrical features of nanofibers, such as nanomat thickness and the diameter of nanofibers, have a significant influence on the toughening behavior of composite laminates. In this study, carbon/epoxy laminates were interleaved with polysulfone (PSF) nanofibrous mats and the effect of the PSF nanomat thickness on the fracture toughness was considered for the first time. For this goal, the nanofibers were first produced by the electrospinning method. Then, double cantilever beam (DCB) specimens were manufactured, and mode-I fracture tests were conducted. The results showed that enhancing the mat thickness could increase the fracture toughness considerably (to about 87% with the maximum thickness). The toughening mechanism was also considered by presenting a schematic picture. Micrographs were taken using a scanning electron microscope (SEM).

Effects of hybridization and ply thickness on the strength and toughness of composite laminates

2021 ◽  
pp. 002199832110417
Author(s):  
F Danzi ◽  
RP Tavares ◽  
J Xavier ◽  
D Fanteria ◽  
PP Camanho
Keyword(s):  
Fracture Toughness ◽  
Composite Laminates ◽  
Mechanical Response ◽  
Hybrid Composites ◽  
Ductile Failure ◽  
Image Correlation ◽  
Thickness Effect ◽  
Hybridization Technique ◽  
X Ray Imaging ◽  
Fracture Tests

This work presents the results of an experimental study performed in carbon/epoxy composite materials manufactured using a ply-level hybridization technique. The aim of the study is to investigate the potential of such hybridization technique to promote pseudo-ductile failure, and to enhance fracture toughness. Two thin-ply carbon-epoxy systems and three different carbon-carbon hybrid lay-ups are considered. Both strength and fracture tests are performed on the manufactured laminates and the properties of the hybrid materials are compared to those of the baseline non-hybrid composites. Digital Image Correlation and post-mortem X-ray imaging are used to analyze the fracture process of the different materials. The comparison of the mechanical response of the different materials demonstrates that, by means of thin ply hybridization, a pseudo-ductile failure in tension can be obtained, associated with fibre fragmentation. However, the hybridization seems not to be responsible for the increased fracture toughness that is ascribable to the ply-thickness effect.

scholarly journals Influence of interface ply orientation on delamination growth in composite laminates

2021 ◽  
pp. 002199832110316
Author(s):  
A Raimondo ◽  
I Urcelay Oca ◽  
C Bisagni
Keyword(s):  
Fracture Toughness ◽  
Composite Laminates ◽  
Double Cantilever Beam ◽  
Numerical Approach ◽  
Field Variable ◽  
Numerical Analyses ◽  
Structural Components ◽  
Closure Technique ◽  
Ply Orientation ◽  
Delamination Propagation

The standard experimental procedures for determining the interlaminar fracture toughness are designed for delamination propagation in unidirectional specimens. However, in aerospace structural components, delamination usually occurs between plies at different orientations resulting in different damage mechanisms which can increase the value of the fracture toughness as the delamination propagates. Generally, numerical analyses employ the value measured at the delamination onset, leading to conservative results since the increase resistance of the delamination is neglected. In this paper, the fracture toughness and the R-curves of carbon/epoxy IM7/8552 are experimentally evaluated in coupons with delamination positioned at 0°/0° and 45°/−45° interfaces using Double Cantilever Beam (DCB) and Mixed-Mode Bending (MMB) tests. A simplified numerical approach based on the Virtual Crack Closure Technique (VCCT) is developed to simulate variable fracture toughness with the delamination length within a Finite Element code using a predefined field variable. The results of the numerical analyses compared with the experimental data in terms of load-displacement curves demonstrate the effectiveness of the proposed technique in simulating the increase resistance in delamination positioned between plies at 45°/−45° interface.

Improvement of Vibration Damping Capacity and Fracture Toughness in Composite Laminates by the Use of Polymeric Interleaves

1999 ◽  
Author(s):  
Ronald F. Gibson ◽  
Hui Zhao
Keyword(s):  
Fracture Toughness ◽  
Composite Laminates ◽  
Critical Thickness ◽  
Vibration Damping ◽  
Thickness Effect ◽  
Damping Capacity ◽  
Mode Ii ◽  
Interlaminar Fracture Toughness ◽  
Interlaminar Fracture ◽  
Mode Ii Fracture Toughness

Abstract It is shown that simultaneous improvement of vibration damping capacity and interlaminar fracture toughness in composite laminates can be achieved by using polymeric interleaves between the composite laminae. The specific case of Mode II interlaminar fracture toughness and flexural damping capacity of interleaved composite laminates is studied. Graphite/epoxy, E-glass/epoxy and E-glass/polyetherimide composite laminates with polymeric interleaves of several different thicknesses and materials were tested using both the end notch flexure (ENF) test for Mode II fracture toughness and the impulse-frequency response test for flexural damping capacity. The Mode II energy release rate GIIc for all three composites increased linearly with increasing interleaf thickness up to a critical thickness, then dropped off with further increases in thickness. The damping loss factor η for all three composites increased linearly with increasing interleaf thickness up to the maximum thickness. Analytical models for predicting the influence of interleaves on GIIc and η are developed, along with a hypothesis for the critical thickness effect with regard to fracture toughness.

Effect of Film Thickness on Fracture Toughness of Amorphous Diamond-Like Carbon

2005 ◽  
Author(s):  
Krishna Jonnalagadda ◽  
Ioannis Chasiotis
Keyword(s):  
Fracture Toughness ◽  
Film Thickness ◽  
Sacrificial Layer ◽  
Thickness Dependence ◽  
Diamond Like Carbon ◽  
Specimen Thickness ◽  
Atomic Force ◽  
Fracture Tests ◽  
Cracked Specimens ◽  
First Time

Fracture toughness, KIC, measurements were conducted for the first time on hydrogen-free tetrahedral amorphous Diamond-like Carbon (ta-C) MEMS-scale specimens of different thicknesses. Uniform gage microscale specimens with mathematically sharp edge pre-cracks were prepared by microindentation on the SiO2 sacrificial layer. The radial-median crack from the indent propagated into the specimen generating a sharp pre-crack. The crack length was measured by an Atomic Force Microscope (AFM). Freestanding fracture specimens were then obtained by wet etching the SiO2 sacrificial layer. Microtensile tests were performed on the pre-cracked specimens under mode-I loading in fixed grip configuration. In order to investigate the specimen thickness dependence of KIC, fracture tests were conducted on specimens with thicknesses in the range of 0.5-3 μm. KIC was 4.25 ± 0.7 MPa m for 0.5 μm specimens, 4.4 ± 0.4 MPa m for 1 μm specimens, and 3.06 ± 0.17 MPa m for 3 μm thick specimens. The 25% lower fracture toughness of the 3 μm films points to a film thickness dependence of fracture toughness that was attributed to different through-the-thickness stresses in considerably thick ta-C films and compositional changes occurring during post-deposition processing.

Improvement of Vibration Damping Capacity and Fracture Toughness in Composite Laminates by the Use of Polymeric Interleaves

2001 ◽  
Vol 123 (3) ◽  
pp. 309-314 ◽  
Author(s):  
Ronald F. Gibson ◽  
Yu Chen ◽  
Hui Zhao
Keyword(s):  
Fracture Toughness ◽  
Composite Laminates ◽  
Critical Thickness ◽  
Vibration Damping ◽  
Thickness Effect ◽  
Damping Capacity ◽  
Mode Ii ◽  
Interlaminar Fracture Toughness ◽  
Interlaminar Fracture ◽  
Mode Ii Fracture Toughness

It is shown that, under certain conditions, simultaneous improvement of vibration damping capacity and interlaminar fracture toughness in composite laminates can be achieved by using polymeric interleaves between the composite laminae. The specific case of Mode II interlaminar fracture toughness and flexural damping capacity of interleaved composite laminates is studied. Graphite/epoxy, E-glass/epoxy and E-glass/polyetherimide composite laminates with polymeric interleaves of several different thicknesses and materials were tested using both the end notch flexure (ENF) test for Mode II fracture toughness and the impulse-frequency response test for flexural damping capacity. The Mode II energy release rate GIIc for all three composites increased linearly with increasing interleaf thickness up to a critical thickness, then dropped off with further increases in thickness. The damping loss factor η for all three composites increased linearly with increasing interleaf thickness up to the maximum thickness. Analytical models for predicting the influence of interleaves on GIIc and η are developed, along with a hypothesis for the critical thickness effect with regard to fracture toughness.

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