FRACTURE ANALYSIS OF RUBBER TOUGHENED ADDITIVELY MANUFACTURED THERMOSETS

This study explores the role of rubber toughening on the dynamic fracture behavior of additively manufactured (AM) high-performance thermosetting polymers formed through digital light processing (DLP). Using DLP to create these polymers allows for rapid, agile manufacturing of prototypes meeting the lightweight and building speed requirements of relevance to military mission applications. This method also provides flexibility in part complexity while maintaining relatively high isotropy compared to traditional AM techniques. Previous work has demonstrated a dependence of these DLP specimens on print layer orientation and loading rate, prompting further investigation into other manufacturing parameters to improve toughness [1]. This study examines the role of rubber toughening on the quasi-static and dynamic fracture behavior of bis-GMA thermosets. Current literature largely reports on quasi-static behavior of DLP specimens, although dynamic conditions are more applicable to many realistic loading scenarios and extreme environments often seen in defense applications. Dynamic experiments leverage a unique long bar striker device that impacts a specimen opposite a pre-crack, sending a stress-wave driven load to initiate a dynamic Mode-I (opening) fracture event. Full-field displacement data ahead of the propagating crack is obtained using ultra high-speed imaging combined with 2D digital image correlation (DIC). An elastodynamic solution following the principles of dynamic fracture mechanics extracts the stress intensity factor (SIF) using a least squares fit at crack initiation and a Newton-Raphson scheme for crack propagation. The rubber toughened thermosets in this study exhibited a rate dependence in fracture toughness with the quasi-static SIF being 1.20 MPa and the dynamic SIF being 0.41 MPa .

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DYNAMIC FACTURE OF HYDROTHERMALLY DEGRADED CARBON-EPOXY COMPOSITES

10.12783/asc36/35805 ◽

2021 ◽

Author(s):

EMILY PITTMAN ◽

STYLIANOS KOUMLIS ◽

LESLIE LAMBERSON

Keyword(s):

Elevated Temperature ◽

Dynamic Fracture ◽

Fracture Behavior ◽

Salt Water ◽

Ambient Condition ◽

Image Correlation ◽

Epoxy Composites ◽

Mode I ◽

Significant Difference

Structures used in naval applications are often subjected to marine or other aqueous environments during their work-life. It has been observed that many composites absorb moisture when exposed to such environments, which can lead to material damage and degradation of mechanical properties. The addition of salt to the water solution may have additional impacts on the material degradation over time. Furthermore, many of these applications require that the material be subject to stresswave loading environments like impact that may cause dynamic fracture. In this experimental study, the effect of water absorption on the Mode-I dynamic fracture behavior of carbon-epoxy composites is investigated. Specifically, the effects of moisture uptake and the role of saline on the critical dynamic SIF are investigated. Samples were hygrothermally soaked in an elevated temperature bath (70 °C) of either ASTM standard sea water or distilled water. The elevated temperature accelerates mass absorption, making experimental observation possible on a more reasonable timeline than natural aging. Soaking durations varied between 3.5 hours to excess of 4 months to explore the role of soak time on dynamic fracture behavior. Pre-cracked specimens were impacted using a unique long-bar striker device at 4 m/s, and the resulting Mode-I (opening mode) fracture behavior investigated. Digital image correlation (DIC) was used in conjunction with ultra-high-speed imaging to track the crack tip surface displacements, and an elastodynamic solution was leveraged to extract the stress intensity factors (SIF) at fracture initiation. The dynamic fracture toughness of the soaked samples was compared with results from a group of unsoaked, ambient condition samples. The results indicated that the ambient condition samples had a consistently higher Mode-I SIF than any of the soaked conditions. The difference between the ambient condition SIF and the soaked conditions was observed to be approximately 60% for the 3.5 hour soaks, 40% for the 2 day soaks, 50% for the 2 week soaks, and 80% for the samples soaked for longer than 4 months. The SIF reduction is thought to be due primarily to matrix and interface degradation. No statistically significant difference in the SIF was observed between samples soaked in DI water versus salt water.

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Tensile and Fracture Characterization of PETI-5 and IM7/PETI-5 Graphite/Epoxy Composites Under Quasi-Static and Dynamic Loading Conditions

Journal of Engineering Materials and Technology ◽

10.1115/1.4003487 ◽

2011 ◽

Vol 133 (2) ◽

Cited By ~ 8

Author(s):

Dongyeon Lee ◽

Hareesh V. Tippur ◽

Brian J. Jensen ◽

Philip B. Bogert

Keyword(s):

Dynamic Loading ◽

Dynamic Fracture ◽

Fracture Behavior ◽

Matrix Material ◽

Image Correlation ◽

Dynamic Crack ◽

Loading Conditions ◽

Fiber Reinforced ◽

Dynamic Loading Conditions ◽

Static And Dynamic Loading

Tensile and fracture responses of the phenylethynyl terminated imide oligomer (PETI-5) are studied. Since this polymer is a candidate aerospace structural adhesive as well as a matrix material in composite systems, neat as well as fiber reinforced forms of PETI-5 are studied under static and dynamic loading conditions. A split-Hopkinson tension bar apparatus is used for performing tensile tests on dogbone specimens. The dynamic fracture tests are carried out using a drop tower in conjunction with 2D image correlation method and high-speed digital photography on edge cracked specimens in three-point bend configuration. A toughened neat epoxy system, Hexcel 3900, is also studied to provide a baseline comparison for neat PETI-5 system. The tensile stress-strain responses show PETI-5 to have excellent mechanical characteristics under quasi-static and dynamic loading conditions when compared with 3900. Fracture behavior of PETI-5 under quasi-static and impact loading conditions also shows superiority relative to 3900. The dynamic fracture behavior of a PETI-5 based graphite fiber reinforced composite, IM7/PETI-5, is also studied and the results are comparatively evaluated relative to the ones corresponding to a more common aerospace composite system, T800/3900-2 graphite/epoxy. Once again, the IM7/PETI-5 system shows excellent fracture performance in terms of dynamic crack initiation and growth behaviors.

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On The Role of Environment on Tensile Response and Fracture Behavior of A High Strength Alloy Steel

Journal of Material Science and Technology Research ◽

10.15377/2410-4701.2016.03.02.1 ◽

2017 ◽

Vol 3 (2) ◽

pp. 1-11

Author(s):

Sunil Gowda ◽

◽

T. Srivatsan ◽

Anil Patnaik

Keyword(s):

Alloy Steel ◽

Fracture Behavior ◽

High Strength ◽

Tensile Response ◽

Strength Alloy

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Experimental Measurement of In-Plane Rolling Nonpneumatic Tire Vibrations Using High-Speed Imaging

Tire Science and Technology ◽

10.2346/tire.18.470101 ◽

2019 ◽

Vol 47 (3) ◽

pp. 196-210

Author(s):

Meghashyam Panyam ◽

Beshah Ayalew ◽

Timothy Rhyne ◽

Steve Cron ◽

John Adcox

Keyword(s):

High Speed ◽

Image Correlation ◽

Dynamic Mode Decomposition ◽

Dynamic Mode ◽

High Speed Imaging ◽

Correlation Algorithm ◽

Mode Decomposition ◽

Series Of Experiments ◽

Plane Deformations ◽

Dominant Frequencies

ABSTRACT This article presents a novel experimental technique for measuring in-plane deformations and vibration modes of a rotating nonpneumatic tire subjected to obstacle impacts. The tire was mounted on a modified quarter-car test rig, which was built around one of the drums of a 500-horse power chassis dynamometer at Clemson University's International Center for Automotive Research. A series of experiments were conducted using a high-speed camera to capture the event of the rotating tire coming into contact with a cleat attached to the surface of the drum. The resulting video was processed using a two-dimensional digital image correlation algorithm to obtain in-plane radial and tangential deformation fields of the tire. The dynamic mode decomposition algorithm was implemented on the deformation fields to extract the dominant frequencies that were excited in the tire upon contact with the cleat. It was observed that the deformations and the modal frequencies estimated using this method were within a reasonable range of expected values. In general, the results indicate that the method used in this study can be a useful tool in measuring in-plane deformations of rolling tires without the need for additional sensors and wiring.

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