Repeatable Fatigue Life Improvement of Thermoset CFRP Composites by In-Situ Thermoplastic Healing of Mode-I Fatigue Crack

2022 ◽  
Author(s):  
Nilesh J. Vishe ◽  
Sameer B. Mulani ◽  
Samit Roy
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Mode I ◽  
Cfrp Composites ◽  
Life Improvement

MODE-I FATIGUE CRACK HEALING IN CFRP COMPOSITES USING THERMOPLASTIC HEALANT

2021 ◽  
Author(s):  
NILESH J. VISHE ◽  
SAMEER B. MULANI ◽  
SAMIT ROY
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Carbon Fiber ◽  
Crack Growth ◽  
Fatigue Loading ◽  
Mode I ◽  
Crack Healing ◽  
Delamination Crack ◽  
Dcb Specimen

Mode-I fatigue crack healing in carbon fiber-reinforced polymer (CFRP) composites subjected to fatigue loading is investigated in this study. Laminated composites are highly susceptible to delamination, and delamination due to fatigue loading is one of the most critical damage modes in composite structures that may lead to a catastrophic failure. Hence, it is paramount to investigate and quantify the delamination crack growth behavior due to fatigue loading and explore methods to heal the delamination. Therefore, double cantilever beam (DCB) specimens of a carbon fiber-reinforced thermoset polymer (CFRP) composite containing thermoplastic healants were manufactured. Mode- I fatigue delamination experiments were carried out for virgin (initial case) and up to seven repeated healing cycles. The main objective of using thermoplastic healants, i.e., polycaprolactone (PCL) and shape memory polymer (SMP), was to close and then heal the cracks formed during fatigue loading and retain the fatigue life of the DCB specimen. The in-situ healing was achieved by activating macro fiber composite (MFC) actuators bonded to the DCB specimen, where the high frequency vibration of the actuator provides the heat necessary to close the cracks using thermoplastic healants. The insitu healing was triggered using MFCs after 5000 cycles of initial loading to allow initial crack extension. The DCB specimen was then loaded up to half a million cycles to study the effect of healing on fatigue life. From the experimental data of the virgin and healed specimens, the Paris law parameters were extracted, and the results obtained were repeatable. Significant increase in maximum Mode-I strain energy release rate (G ) observed after in-situ healing is likely due to the increase in the bond stiffness of the DCB specimen material of the healed zone. More research is needed to investigate the exact mechanism for the increase of G . Mode-I fatigue life improvement of up to a factor of 2 was observed after in-situ healing for the same delamination crack growth with respect to the virgin cycle prior to healing. We envision that these findings will be helpful in extending the service life of composites and result in significant repair cost savings.

Experimental Research on Crack Propagation in U71Mn and U75V Rail Steels

2006 ◽  
Vol 324-325 ◽  
pp. 807-810
Author(s):  
Jing Jing Li ◽  
Ya Fang Guo ◽  
Yue Sheng Wang ◽  
Chang Hai Tian
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Rail Steel ◽  
Mode I ◽  
Static Loads ◽  
In Situ Observations ◽  
Electronic Microscope ◽  
Better Than

In this paper, the continuous in-situ observations of the fatigue crack growth in U71Mn and U75V rail steel are made by using the scanning electronic microscope (SEM). The microstructure patterns of cracks under the mode I fatigue loads and quasi-static loads are presented. The results indicate that the short fatigue crack growth in rail steel is a quasi-cleavage fracture. The ductility and the performance of fatigue resistance of U71Mn rail steel are better than those of U75V rail steel.

scholarly journals Comparison of Fatigue Life Cycle of Different Aluminium Alloy AA 5083 - AA6062

2019 ◽  
pp. 283-288
Author(s):  
Sunit Yadav ◽  
Kamal Kanaujia ◽  
Ravi Shukla
Keyword(s):  
Wear Resistance ◽  
Fatigue Crack ◽  
Life Cycle ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Comparative Study ◽  
Aluminium Alloy ◽  
Fatigue Testing ◽  
Mode I ◽  
Loading Mode

Fatigue failure is one of the main reasons for the mechanical failure in engineering materials. To improve the fatigue strength of the material one of the most used method is surface treatment of the materials in which hardness, wear resistance and aesthetics is improved. In this paper a comparative study of fatigue of two different aluminium alloy [AA 5083-AA6062] was conducted. CT specimen of both the alloys was formed as per ASTM-E647 Standard. The result shows that the fatigue life of AA5083 greater than AA6062. In this paper fracture that occur in material during fatigue testing and effect of fatigue life on material is studied. The main purpose of the research presented herein was to study the fatigue crack propagation under loading mode I.

Factors Influencing the Fatigue Behavior of Ferrous Laminates

1987 ◽  
Vol 109 (3) ◽  
pp. 244-251 ◽  
Author(s):  
J. Wittenauer ◽  
O. D. Sherby
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Carbon Steel ◽  
Fatigue Behavior ◽  
Layered Material ◽  
Factors Influencing ◽  
Ultrahigh Carbon Steel ◽  
Processing History ◽  
Crack Blunting ◽  
Similar Processing

Laminates based on ultrahigh carbon steel were prepared and found to exhibit enhanced fatigue life as compared to a monolithic reference material. This result was achieved through the insertion of weak interlaminar regions of copper into the layered material during preparation of the laminates. The presence of these regions allowed for the operation of a delamination mechanism in advance of the propagating fatigue crack. The result was interlaminar separation and associated crack blunting. Stress-life curves show that an increase in life by as much as a factor of four is achieved for these materials when compared to monolithic specimens of similar processing history.

scholarly journals Fatigue Crack Growth Analysis with Extended Finite Element for 3D Linear Elastic Material

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 397
Author(s):  
Yahya Ali Fageehi
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Mixed Mode ◽  
Propagation Path ◽  
Loading Conditions ◽  
Extended Finite Element ◽  
Linear Elastic

This paper presents computational modeling of a crack growth path under mixed-mode loadings in linear elastic materials and investigates the influence of a hole on both fatigue crack propagation and fatigue life when subjected to constant amplitude loading conditions. Though the crack propagation is inevitable, the simulation specified the crack propagation path such that the critical structure domain was not exceeded. ANSYS Mechanical APDL 19.2 was introduced with the aid of a new feature in ANSYS: Smart Crack growth technology. It predicts the propagation direction and subsequent fatigue life for structural components using the extended finite element method (XFEM). The Paris law model was used to evaluate the mixed-mode fatigue life for both a modified four-point bending beam and a cracked plate with three holes under the linear elastic fracture mechanics (LEFM) assumption. Precise estimates of the stress intensity factors (SIFs), the trajectory of crack growth, and the fatigue life by an incremental crack propagation analysis were recorded. The findings of this analysis are confirmed in published works in terms of crack propagation trajectories under mixed-mode loading conditions.

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