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 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.

Plain para-aramid/phenolic multiwall carbon nanotubes prepreg/multistiched preform composites: Experimental characterization of mode-I toughness

2018 ◽  
Vol 53 (13) ◽  
pp. 1847-1864 ◽  
Author(s):  
K Bilisik ◽  
E Sapanci
Keyword(s):  
Fracture Toughness ◽  
Multiwall Carbon Nanotubes ◽  
Beam Theory ◽  
Mode I ◽  
Multiwall Carbon Nanotube ◽  
Axial Filament ◽  
Pull Out ◽  
Fiber Bridging ◽  
Nanotube Composites ◽  
Multiwall Carbon

The fracture toughness (mode-I) properties of nanostitched para-aramid/phenolic multiwall carbon nanotube prepreg composites were investigated. The fracture toughness (GIC) of the stitching and nanostitched composites showed 42-fold and 41-fold (beam theory), 18-fold and 21-fold (modified beam theory) increase compared to the control, respectively. The prepreg para-aramid stitching yarn and nanostitched yarn were dominant parameters. The toughness resistance to arrest crack growth in the nanostitched composite was primarily due to nanostitching fiber bridging and pull-out, and was secondarily due to nanotubes and biaxial fiber bridging and pull-out. The failed surfaces of the nanostitched and stitching composites had tensile filament failures in the aramid stitching fibers where filament/matrix/nanotube debonding and axial filament fibrillar splitting were found. The results indicated that stitching yarn and the nanotubes arrested the crack propagation. Therefore, the nanostitched and stitched para-aramid/phenolic composites displayed a better damage resistance performance compared to those of the control or nanotube composites.

Mode I Fracture Toughness of Banana Fiber and Glass Fiber Reinforced Composites

2012 ◽  
Vol 622-623 ◽  
pp. 1320-1324
Author(s):  
V. Santhanam ◽  
M. Chandrasekaran ◽  
N. Venkateshwaran ◽  
A. Elayaperumal
Keyword(s):  
Fracture Toughness ◽  
Glass Fiber ◽  
Volume Fraction ◽  
Fiber Reinforced Polymers ◽  
Mode I ◽  
Fiber Reinforced ◽  
Banana Fiber ◽  
Mode I Fracture ◽  
Mode I Fracture Toughness ◽  
Glass Fiber Reinforced

Although fiber-reinforced polymers (FRP) have until now been largely applied to various fields of engineering, these materials have also been used in many technical applications, especially where high strength and stiffness are required, but with low component weight. Among various natural fibers, banana fiber is of particular interest in that its composites have high tensile strength, high tensile modulus, and low elongation at break beside its low cost and eases of availability. In this study, banana fiber and glass fiber reinforced polyester Resin composites were prepared using hand lay up technique . Experiments are conducted to compare and to find the effect of fiber volume fraction on mode I fracture toughness of both composites.

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.

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