Study of Load Ratio for Mode-I Fatigue Fracture of Wood-FRP-Bonded Interfaces

Abstract

This paper presents the fatigue behavior of interface bond between red maple wood and phenolic FRP substrates. Using linear elastic fracture mechanics concepts, the influence of load ratio on fatigue crack propagation rate is studied. A contoured double cantilever beam (CDCB) specimen is adopted in this study in order to obtain constant strain energy release rate independent of crack length. The compliance method is used for measuring the crack growth rate. A modified Paris Law equation based on strain energy release rate range, ÁG, and mean value of strain energy release rate, G mean , is proposed in this study for efficient evaluation of load ratio effect on fatigue crack propagation of the bonded interfaces. Follow-up environmental effects are being examined by means of the same energy parameters of the present study and without the need to consider crack closure. The proposed approach can further be extended to characterization of other bonded interfaces for dissimilar materials.KEY WORDS: contoured double cantilever beam (CDCB) specimen, crack propagation rate da/dN, load ratio R, crack opening displacement (COD), strain energy release rate.

A fully solar‐powered quadcopter able to achieve controlled flight out of the ground effect

“…CBC composites performed the best in deflection tests per unit weight but were found to be susceptible to torsional vibrations when a motor and propeller were mounted, as were the square cross‐section rods. We thus considered the use of CBC composites for the “×” rods that do not support motors, but fatigue failure due to repeated cyclic loading has been shown to be a significant cause of interface bond failure in fiber‐reinforced composites and wood . Our 124‐cell drone failed during its first and only flight test, when a gust of wind delaminated such a CBC support arm, and CBC was abandoned in later prototypes.…”

“…We thus considered the use of CBC composites for the "×" rods that do not support motors, but fatigue failure due to repeated cyclic loading has been shown to be a significant cause of interface bond failure in fiber-reinforced composites and wood. 15 Our 124-cell drone failed during its first and only flight test, when a gust of wind delaminated such a CBC support arm, and CBC was abandoned in later prototypes.…”

Mode I fatigue and fracture behavior of adhesively-bonded pultruded glass fiber-reinforced polymer (GFRP) composite joints

“…In such cases, FCG curves like the one shown in Figure 6.1 are established to represent the fatigue behavior of the examined joints. 7e33;Shivakumar et al, 2006;Wilkins et al, 1982), mixed Mode I/II (Gustafson & Hojo, 1987;Johnson & Mall, 1985;Kenane, Azari, Benmedakhene, & Benzeggagh, 2011;Mall & Johnson, 1986;Mall et al, 1989;Wilkins et al, 1982), and pure Mode II (Allegri et al, 2011), and for adhesively-bonded structural joints (Curley, Hadavinia, & Kinloch, 2000;Jia & Davalos, 2004a, 2004bMall & Johnson, 1986;Sarfaraz et al, 2011;Zhang et al, 2010). This observation was validated by Mode I experimental data from three independent sources on two aluminum alloys, 2024-T3 and 7075-T6.…”

“…Several models can be found in literature for the simulation of the crack propagation only along the second region of the FCG curve (Andersons et al, 2004;Hojo et al, 1994;Jia & Davalos, 2004a, 2004bWalker, 1970), incorporating the effect of the R-ratio so that all data could be condensed into a single master curve. The crack propagation under constant amplitude (CA) loading at any R-ratio was modeled using the Paris law.…”

Aerodynamic Load Characteristics Evaluation and Tri-Axial Performance Testing on Fiber Reinforced Polymer Connections and Metal Fasteners to Promote Hurricane Damage Mitigation

“…Stating that any of these equations yields satisfactory results for determining the effect of load ratio on crack propagation, authors recommended Eq. (4.3) for use in engineering applications (Jia and Davalos, 2004). and pre-and post-treatment applications have significant negative effects on the FRPtimber bond strength (Tascioglu et al, 2003).…”