G-control fatigue testing for cyclic crack propagation in composite structures

Carlsson

et al. 2015

Self Cite

This paper presents experimental results from cyclic crack propagation tests performed on sandwich specimens with glass/epoxy face sheets and Poly Vinyl Chloride (PVC) foam cores using the G-controlled cyclic energy release rate (ÁG) test procedure. The face material was tested in tension, compression and shear to determine in-plane and out-of-plane mechanical properties, such as Young's modulus, Poisson's ratio and shear modulus. These properties were then used in an analytical model of the mixed-mode bending sandwich specimen to calculate compliance and energy release rate. Finite element analysis was used to determine the mode-mixity of the crack loading. Experimental crack growth cyclic tests were carried out on pre-cracked mixed-mode bending sandwich specimens with H45, H100 and H160 PVC foam cores under two mode-mixities (mode I and mode II dominant). Post-mortem analysis was performed on tested specimens, highlighting the influence of mode mixity and foam density on the crack path. Crack propagation diagrams showing da/dN versus ÁG curves were obtained to establish the Paris-Erdogan relation for each material combination tested at the two mode-mixities. Results showed constant crack growth rates for all the materials tested and revealed the influence on mode-mixity on crack propagation speed and foam density (higher foam density, slower crack propagation).

Section: Introductionmentioning

confidence: 99%

Fatigue characterization of Poly Vinyl Chloride (PVC) foam core sandwich composite using the G-control method

Manca

Carlsson

et al. 2015

Self Cite

“…The input data for Paris' law were obtained by fatigue experiments conducted on the same bi-material interface configuration as considered in this paper using the Mixed Mode Bending test (MMB) and the G-control method developed and proposed by Manca et al [26]. Parameters c and m are mode dependent meaning that they vary depending on the mode mixity applied.…”

Section: Resultsmentioning

confidence: 99%

Interfacial crack arrest in sandwich beams subjected to fatigue loading using a novel crack arresting device – Numerical modelling

Martakos¹,

Andreasen²,

et al. 2017

A novel crack arresting device is implemented in foam cored composite sandwich beams and tested using the Sandwich Tear Test (STT) configuration. A Finite Element Model of the setup is developed, and the predictions are correlated with observations and results from a recently conducted experimental fatigue test study. Based on a linear elastic fracture mechanics approach, the developed FE model is utilized to simulate crack propagation and arrest in foam cored sandwich beam specimens subjected to fatigue loading conditions. The effect of the crack arresters on the fatigue life is analysed, and the predictive results are subsequently compared with the observations from the previously conducted fatigue tests. The FE model predicts the energy release rate and the mode mixity based on the derived crack surface displacements, utilizing algorithms for the prediction of accelerated fatigue crack growth as well as the strain field evolution in the vicinity of the crack tip on the surface of the sandwich specimens. It is further shown that the developed finite element analysis methodology can be used to gain a deeper insight onto the physics and behavioral characteristics of the novel peel stopper concept, as well as a design tool that can be used for the implementation of crack arresting devises in engineering applications of sandwich components and structures.

“…The Single Cantilever Beam test (SCB) [17][18], the Cracked Sandwich Beam test (CSB) [19], the Mixed Mode Bending test (MMB) [20][21] were used to apply different loading conditions to cracked sandwich beams. Most notably with the MMB test, the mode mixity applied can be constant and independent of the crack length making the test ideal for fatigue crack growth characterization [21][22]. Lastly Berggreen et al [14] introduced the Sandwich Tear Test (STT) to investigate crack propagation paths in different core materials.…”

Section: Developed a Cycle-jumpmentioning

confidence: 99%

“…This behaviour makes the STT test especially interesting for this work, since the objective is to investigate the effect of the novel peel stoppers on the fatigue life of sandwich structural components under generalized loading conditions. In previous works from Berggreen and Moslemian [14], [22,34] testing and simulation of the behaviour of the STT setup were conducted by using FE models both for static and fatigue loading conditions. In those studies though, the propagation of the crack was made in only one predefined bi-material interface to avoid uneven and unpredictable loading of the specimen and generation of moments at the load introduction point, when two cracks are propagating in the specimen.…”

Section: Stt Setupmentioning

confidence: 99%

Experimental investigation of interfacial crack arrest in sandwich beams subjected to fatigue loading using a novel crack arresting device

Martakos

Andreasen

et al. 2017

A recently proposed face-sheet–core interface crack arresting device is implemented in sandwich beams and tested using the Sandwich Tear Test configuration. Fatigue loading conditions are applied to propagate the crack and determine the effect of the crack stopper on the fatigue growth rate and arrest of the crack. Digital image correlation is used through the duration of the fatigue experiment to track the strain evolution as the crack tip advances. The measured strains are related to crack tip propagation, arrest, and re-initiation of the crack. A finite element model is used to calculate the energy release rate, mode mixity and to simulate crack propagation and arrest of the crack. Finally, the effectiveness of the crack arresting device is demonstrated on composite sandwich beams subjected to fatigue loading conditions.