Damage sensing in multi-functional glass fiber composites under mode-I fracture loading

2020 ◽  
Vol 54 (30) ◽  
pp. 4821-4829
Author(s):  
Jacob O’Donnell ◽  
Vijaya Chalivendra ◽  
Asha Hall ◽  
Yong Kim
Keyword(s):  
Carbon Fiber ◽  
Crack Initiation ◽  
Glass Fiber ◽  
Carbon Fibers ◽  
Mode I ◽  
Initiation Toughness ◽  
Mode I Fracture ◽  
Conductive Composites ◽  
Damage Sensing ◽  
Conductive Glass

A detailed experimental study is performed for piezo resistance damage sensing on conductive glass fiber/epoxy composites under mode-I fracture conditions. The conductive composites are fabricated by homogeneously dispersing carbon nanotubes (CNTs) within the epoxy matrix and electro-flocking short carbon fibers onto the laminates along with a vacuum infusion process. A parametric study is done on the in-situ damage sensing properties by varying the carbon fiber lengths (150 µm and 350 µm) and the carbon fiber areal densities (500, 1000, 1500, and 2000 fibers/mm2). The change in resistance is captured with a four-point probe measuring methodology by measuring the resistance through the thickness of the composite. The crack initiation toughness value of the composites containing carbon fibers showed improvement over control composites. Composites containing 350 µm length carbon fibers and 2000 fiber/mm2 not only showed the best crack initiation toughness but also provided sensitive network for detecting crack growth.

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.

Layup Analyzing of a Carbon/Glass Hybrid Composite Wind Turbine Blade Using Finite Element Analysis

2011 ◽  
Vol 87 ◽  
pp. 49-54 ◽  
Author(s):  
Hai Chen Lin
Keyword(s):  
Finite Element ◽  
Carbon Fiber ◽  
Wind Turbine ◽  
Glass Fiber ◽  
Turbine Blade ◽  
Carbon Fibers ◽  
Fiber Composite ◽  
Wind Turbine Blade ◽  
Fiber Reinforced ◽  
Carbon Fiber Composite

This thesis use AOC15/50 blade as baseline model which is a composite wind turbine blade made of glass/epoxy for a horizontal axis wind turbine. A finite element modeling of composite wind turbine blade was created using the SHELL element of ANSYS. Then we study how to use the carbon fiber material replaces the glass fiber to make the hybrid blade, and find a suitable layup to improve the performance of the blade. The hybrid blade was made through introducing carbon fibers. Different models, with introducing different number of carbon fibers, 75% carbon fibers replace unidirectional glass fibers in spar cap of blade model which can achieve best structure performance. The wind turbine blades are often fabricated by hand using multiple of glass fiber-reinforced polyester resin or glass fiber-reinforced epoxy resin. As commercial machines get bigger, this could not to meet the demands. The advantages of carbon fiber composite materials are used by blade producer. Studies show that carbon fiber has high strength-to-weight ratio and resistance fatigue properties. Carbon fiber is mixed with epoxy resin to make into carbon fiber-reinforced polymer. Carbon fiber-reinforced polymer is the one of best blade materials for resistance bad weather. The stiffness of carbon fiber composite is 2 or 3 times higher than glass fiber composite [1], but the cost of carbon fiber composite is 10 times higher than glass fiber composite. If all of wind turbine blades are made of carbon fiber composite, it will be very expensive. Therefore carbon/glass fiber hybrid composite blade has become a research emphasis in the field of blade materials. This paper gives an example of finite element modeling composite wind turbine blade in ANSYS by means of the medium-length blade of AOC 15/50 horizontal axis wind turbine. This model can be directly used in dynamics analysis and does not need to be imported from the CAD software into finite element program. This finite element modeling of composite wind turbine blade was created using the SHELL element of ANSYS. Then we study how to use the carbon fiber material replaces the glass fiber to make the hybrid blade, and find a suitable lay-up to improve the performance of the blade.

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