scholarly journals Analytical corrections for double-cantilever beam tests

2021 ◽  
Author(s):  
T. Chen ◽  
C. M. Harvey ◽  
S. Wang ◽  
V. V. Silberschmidt
Keyword(s):  
Elastic Foundation ◽  
Analytical Solutions ◽  
Data Reduction ◽  
Crack Tip ◽  
Beam Theory ◽  
Dynamic Loads ◽  
Structural Vibration ◽  
Mode I ◽  
Mode I Fracture ◽  
Reduction Methods

AbstractDouble-cantilever beams (DCBs) are widely used to study mode-I fracture behavior and to measure mode-I fracture toughness under quasi-static loads. Recently, the authors have developed analytical solutions for DCBs under dynamic loads with consideration of structural vibration and wave propagation. There are two methods of beam-theory-based data reduction to determine the energy release rate: (i) using an effective built-in boundary condition at the crack tip, and (ii) employing an elastic foundation to model the uncracked interface of the DCB. In this letter, analytical corrections for a crack-tip rotation of DCBs under quasi-static and dynamic loads are presented, afforded by combining both these data-reduction methods and the authors’ recent analytical solutions for each. Convenient and easy-to-use analytical corrections for DCB tests are obtained, which avoid the complexity and difficulty of the elastic foundation approach, and the need for multiple experimental measurements of DCB compliance and crack length. The corrections are, to the best of the authors’ knowledge, completely new. Verification cases based on numerical simulation are presented to demonstrate the utility of the corrections.

Fracture characterization of overmold composite adhesion

2020 ◽  
pp. 089270572092512
Author(s):  
W Douglas Hartley ◽  
John McCann ◽  
Scott Davis ◽  
Tom Hocker ◽  
Somasekhar Bobba ◽  
...  
Keyword(s):  
Glass Fiber ◽  
Fracture Mode ◽  
Beam Theory ◽  
Theory Model ◽  
Injection Molding Process ◽  
Mode I ◽  
Mode Mixity ◽  
Mode I Fracture ◽  
Polymer Glass ◽  
Fiber Bridging

A general testing approach is presented via a fracture mechanics study on the interfacial delamination behavior in overmolded composite materials using a variant of the double cantilever beam (DCB) geometry. Overmolding, a common injection molding process, is used to fabricate asymmetric DCB test specimens with Lexan™ 3414 resin overmolded onto commercially available TenCate Cetex® FST woven glass fiber/polycarbonate laminates. An analytical beam theory model is employed to partition the planar fracture modes at the overmold interface into mode I and mode II components, which are functions of material properties and relative beam thicknesses. Specimen curvature measurements are integrated into the beam theory model to estimate the residual stress effects on fracture mode mixity. We use the overmold thickness as a tunable variable to control fracture mode mixity, and target near mode I fracture conditions, where we find mode I fracture energy ( G Ic) values of approximately 1 kJ/m2. Fiber bridging across the failure interface is observed, which is not expected at the nominal polymer/polymer overmold interface. Complementary scanning electron microscopy images of the failure surfaces indicate crack initiation at the overmold interface, followed by a change in locus of failure to the nearby polymer/glass fiber interface in the top layer of the composite laminate. Fiber bridging is observed in all specimens tested over a modest range of mode mixity, including specimens modified to the single leg bending geometry, suggesting that the polymer/glass interface is more susceptible to crack propagation than the desired overmold interface, which likely derives its strength from molecular interdiffusion during the overmolding process.

scholarly journals Numerical Investigation of the Fracture Properties of Pre-Cracked Monocrystalline/Polycrystalline Graphene Sheets

Materials ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 263 ◽  
Author(s):  
Xinliang Li ◽  
Jiangang Guo
Keyword(s):  
Fracture Toughness ◽  
Grain Boundary ◽  
Misorientation Angle ◽  
Strain Energy ◽  
Unit Area ◽  
Crack Tip ◽  
Mode I ◽  
Fracture Properties ◽  
Mode I Fracture ◽  
Mode I Fracture Toughness

The fracture properties of pre-cracked monocrystalline/polycrystalline graphene were investigated via a finite element method based on molecular structure mechanics, and the mode I critical stress intensity factor (SIF) was calculated by the Griffith criterion in classical fracture mechanics. For monocrystalline graphene, the size effects of mode I fracture toughness and the influence of crack width on the mode I fracture toughness were investigated. Moreover, it was found that the ratio of crack length to graphene width has a significant influence on the mode I fracture toughness. For polycrystalline graphene, the strain energy per unit area at different positions was calculated, and the initial fracture site (near grain boundary) was deduced from the variation tendency of the strain energy per unit area. In addition, the effects of misorientation angle of the grain boundary (GB) and the distance between the crack tip and GB on mode I fracture toughness were also analyzed. It was found that the mode I fracture toughness increases with increasing misorientation angle. As the distance between the crack tip and GB increases, the mode I fracture toughness first decreases and then tends to stabilize.

Experimental Analysis of the Damage Zone around Crack Tip for Rubberlike Materials under Mode-I Fracture Condition

2013 ◽  
Vol 561 ◽  
pp. 119-124 ◽  
Author(s):  
Xiao Lei Li ◽  
Xiao Jing Li ◽  
Jian Bing Sang ◽  
Yan Hui Qie ◽  
Yao Ping Tu ◽  
...  
Keyword(s):  
Damage Zone ◽  
Crack Tip ◽  
Soft Materials ◽  
Mode I ◽  
Mode I Fracture ◽  
Crack Tip Fields ◽  
Fracture Condition ◽  
Deformation And Fracture ◽  
Digital Moiré ◽  
Rubberlike Materials

Studying the deformation and fracture properties of soft materials can not only provide insight into the physical mechanisms underlying their superior properties and functions but also benefit the design and fabrication of rubberlike materials. In this paper, an application of the experimental digital moire method to determine the damage zone around crack tip for rubberlike material is presented. The measurement principles and the basic procedures of the method are explained in detail. The in-plane defomation distributions of crack tip fields under Mode I fracture condition are measured. In addition, the deformation of crack tip fields in the damage zones is also analyzed using the sector division mode. Finally, an analysis of the damage zone is proposed to describe crack-tip fields in rubber-like materials with large deformation.

The Influence of Thermoplastic Film Interleaving on the Interlaminar Shear Strength and Mode I Fracture of Laminated Composites

1996 ◽  
Vol 118 (3) ◽  
pp. 302-309 ◽  
Author(s):  
L. Li ◽  
P. Lee-Sullivan ◽  
K. M. Liew
Keyword(s):  
Fracture Toughness ◽  
Shear Strength ◽  
Film Thickness ◽  
Beam Theory ◽  
Interlaminar Shear Strength ◽  
Mode I ◽  
Mode I Fracture ◽  
Mode I Fracture Toughness ◽  
Fibre Bridging ◽  
Interlaminar Shear

Results are presented on the interlaminar shear strength (ILSS) and Mode I fracture toughness (GIC) of glass/epoxy laminates interleaved with thermoplastic polyester films using four-point bending and double cantilever beam tests, respectively. The ILSS equation from classical beam theory was modified to account for the increased film thickness. It was found that the ultimate failure load and ILSS could be doubled if a thermoplastic film of high ductility but low glass transition temperature is used. Good film/composite ply adhesion is necessary. Mode I fracture toughness is influenced by film thickness and interleaving with a 0.2 mm thick film increased the GIC by 40 percent. Interleaving with a thinner film (0.1 mm), however, resulted in adhesive failure and reduced fibre bridging.

scholarly journals Dynamic Fracture Toughness of a Unidirectional Graphite/Epoxy Composite

2001 ◽  
Author(s):  
C. Liu ◽  
A. J. Rosakis ◽  
M. G. Stout
Keyword(s):  
Fracture Toughness ◽  
Composite Material ◽  
Crack Propagation ◽  
Epoxy Composite ◽  
Crack Tip ◽  
Dynamic Crack Propagation ◽  
Mode I ◽  
Dynamic Crack ◽  
Mode I Fracture ◽  
Mode I Fracture Toughness

Abstract In this investigation, we studied the process of dynamic crack propagation in a fiber-reinforced composite material using the optical Coherent Gradient Sensing (CGS) technique combined with high-speed photography. The mode-I fracture toughness of the unidirectional graphite/epoxy composite, IM7/8551-7, as a function of the crack-tip speed, was measured quantitatively. It was found that up to the Rayleigh wave speed of the composite material, the mode-I fracture toughness is a decreasing function of the crack-tip velocity. This behavior is similar to that observed in the dynamic crack propagation along interfaces between two homogeneous solids.

Thermosets Toughening by Creation of Residual Compressive Stresses

2006 ◽  
Vol 312 ◽  
pp. 3-8
Author(s):  
Ho Sung Kim ◽  
Nam Ho Kim
Keyword(s):  
Residual Stresses ◽  
Mechanical Behaviour ◽  
Crack Tip ◽  
Mode I ◽  
Mode I Fracture ◽  
Compressive Stresses ◽  
The Creation ◽  
Liquefied Gas ◽  
Compressive Residual Stresses

Toughening of thermosets by creation of residual compressive stresses around microspheres is studied. Expandable hollow micro-spheres containing liquefied gas were used for the creation of residual compressive stresses. Microscopic compressive residual stresses around the micro-spheres in the vicinity of the crack tip were graphically analysed and related to macroscopic mechanical behaviour for mode I fracture. It was confirmed that toughening was due to residual compressive stresses rather post-cure effect.

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