scholarly journals Low temperature mixed-mode debond fracture and fatigue characterisation of foam core sandwich

2018 ◽  
Vol 22 (4) ◽  
pp. 1039-1054 ◽  
Author(s):  
Arash Farshidi ◽  
Christian Berggreen ◽  
Leif A Carlsson
Keyword(s):  
Fracture Toughness ◽  
Growth Rate ◽  
Low Temperature ◽  
Mixed Mode ◽  
Room Temperature ◽  
Sliding Mode ◽  
Fatigue Tests ◽  
Mode I ◽  
Foam Core ◽  
Climatic Chamber

This paper experimentally investigates the effects of low temperature on fracture toughness and fatigue debond growth rate in foam core sandwich composites. Mixed-mode bending specimens were statically and cyclically tested inside a climatic chamber at a low temperature (−20°C) and at room temperature (23°C) as a reference. Testing was conducted in mode I (opening) and mixed-mode I/II (opening-sliding) mode mixities. The fatigue tests results are presented according to the modified Paris–Erdogan relation. Results showed substantial fracture toughness reduction due to low temperature. Low temperature furthermore elevated the cyclic crack growth rate.

scholarly journals Enhancement in Interply Toughness of BMI Composites Using Micro-Thin Films

2021 ◽  
Vol 5 (2) ◽  
pp. 49
Author(s):  
Eldho Mathew ◽  
Sunil Chandrakant Joshi ◽  
Periyasamy Manikandan
Keyword(s):  
Thin Films ◽  
Fracture Toughness ◽  
Crack Initiation ◽  
Mixed Mode ◽  
Sliding Mode ◽  
Mode I ◽  
Crack Initiation And Propagation ◽  
Polymeric Thin Films ◽  
Initiation And Propagation ◽  
Automated Fiber Placement

Nowadays, laminated composites are widely used in the aerospace sector. All laminates have interply/interlaminar interfaces even if they are made using automated processes. The interfaces act as the areas of weaknesses and the potential crack initiation regions. Hence, any enhancement in the crack initiation and propagation resistance is always sought after. Usage of polymeric thin films is one of the promising and viable ways to achieve this. It is also easy to incorporate micro-thin films into any automation process. In the present study, different customized thin films that are compatible with Glass/BMI composites are fabricated. Fracture toughness tests in Mode I (opening mode), Mode II (sliding mode) and Mixed Mode I/II are conducted respectively using Double Cantilever Beam (DCB), End Notch Flexure (ENF) and Mixed Mode Bending (MMB) test specimens. This paper discusses the manufacturing of compatible micro-thin films. The various challenges faced during the manufacturing and incorporation of thin films are presented. The results of the various fracture toughness tests are examined. Mechanisms through which the different films help in resisting the crack initiation and propagation are deliberated and discussed. The incorporation of this technique in Automated Fiber Placement (AFP) is also discussed.

Experimental and Numerical Investigation of the Mixed-Mode Delamination of PAN Based Carbon/Epoxy Composite Using Modified Arcan Fixture

2011 ◽  
Vol 471-472 ◽  
pp. 880-885 ◽  
Author(s):  
M. Ziaee ◽  
Naghdali Choupani
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity ◽  
Mixed Mode ◽  
Sliding Mode ◽  
Epoxy Composite ◽  
Mode I ◽  
Mode Ii ◽  
Mixed Mode Fracture ◽  
Pure Mode ◽  
Element Analysis

The present research examines analytically and experimentally the mode-I and mode-II and mixed mode-Interlaminar fracture toughness of PAN based carbon/epoxy composite. A modified Arcan fixture, well-suited for the study of the behavior of used composite assemblies, was developed in order to focus on the analysis of the fracture behavior of the material. The edge effects are minimized by using an appropriate design of the substrates so that experimental results give reliable data. Also the mode-I and mode-II stress intensity factors were computed for different crack lengths and load orientation angles using finite element analysis. The numerical results show that the modified Arcan specimen is able to provide pure mode-I, pure mode-II and any mixed mode loading conditions. It is shown that the results obtained from the fracture tests are consistent very well with mixed mode fracture theories. Obtained results indicated that fracture toughness and stress intensity factor for sliding mode enhanced up when the loading angle increased. Mechanism of fracture and toughening were examined by using scanning electron microscopy.

Determination of Fracture Toughness and K-R Curve for 2524-T3 Aluminum Alloy

2011 ◽  
Vol 291-294 ◽  
pp. 1039-1042
Author(s):  
Wei Xie ◽  
Shao Wei Tu ◽  
Qi Qing Huang ◽  
Ya Zhi Li
Keyword(s):  
Fracture Toughness ◽  
Aluminum Alloy ◽  
Stress Fracture ◽  
Test Data ◽  
Plane Stress ◽  
Crack Extension ◽  
Room Temperature ◽  
Mode I ◽  
Average Value

In the present work, the resistance to crack extension of 2524-T3 aluminum alloy under Mode I loading was studied by using the middle-cracked tension M (T) specimens. The curve, plane-stress fracture toughness and apparent plane-stress fracture toughness were calculated by test data. The average value of measured fracture toughness at room temperature was 161 MPam1/2. The results and conclusions can be referred in airplane skin design.

scholarly journals Mixed-Mode Interlaminar Fracture Toughness of Glass and Carbon Fibre Powder Epoxy Composites—For Design of Wind and Tidal Turbine Blades

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2103
Author(s):  
Christophe Floreani ◽  
Colin Robert ◽  
Parvez Alam ◽  
Peter Davies ◽  
Conchúr M. Ó. Brádaigh
Keyword(s):  
Fracture Toughness ◽  
Carbon Fibre ◽  
Composite Structures ◽  
Mixed Mode ◽  
Epoxy Composites ◽  
Mode I ◽  
Mode Ii ◽  
Pure Mode ◽  
Interlaminar Fracture Toughness ◽  
Interlaminar Fracture

Powder epoxy composites have several advantages for the processing of large composite structures, including low exotherm, viscosity and material cost, as well as the ability to carry out separate melting and curing operations. This work studies the mode I and mixed-mode toughness, as well as the in-plane mechanical properties of unidirectional stitched glass and carbon fibre reinforced powder epoxy composites. The interlaminar fracture toughness is studied in pure mode I by performing Double Cantilever Beam tests and at 25% mode II, 50% mode II and 75% mode II by performing Mixed Mode Bending testing according to the ASTM D5528-13 test standard. The tensile and compressive properties are comparable to that of standard epoxy composites but both the mode I and mixed-mode toughness are shown to be significantly higher than that of other epoxy composites, even when comparing to toughened epoxies. The mixed-mode critical strain energy release rate as a function of the delamination mode ratio is also provided. This paper highlights the potential for powder epoxy composites in the manufacturing of structures where there is a risk of delamination.

scholarly journals Low-temperature degradation resistance and plastic deformation of ATZ ceramics stabilized by CaO

2021 ◽  
Vol 2103 (1) ◽  
pp. 012075
Author(s):  
AA Dmitrievskiy ◽  
DG Zhigacheva ◽  
VM Vasyukov ◽  
PN Ovchinnikov
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Plastic Deformation ◽  
Compressive Strength ◽  
Phase Composition ◽  
Low Temperature ◽  
Uniaxial Compression ◽  
Calcium Oxide ◽  
Tetragonal Phase ◽  
Room Temperature

Abstract In this work, the phase composition (relative fractions of monoclinic m-ZrO2, tetragonal t-ZrO2, and cubic c-ZrO2 phases) and mechanical properties (hardness, fracture toughness, compressive strength) of alumina toughened zirconia (ATZ) ceramics, with an addition of silica were investigated. Calcium oxide was used as a stabilizer for the zirconia tetragonal phase. It was shown that CaO-ATZ+SiO2 ceramics demonstrate increased resistance to low-temperature degradation. The plasticity signs at room temperature were found due to the SiO2 addition to CaO-ATZ ceramics. A yield plateau appears in the uniaxial compression diagram at 5 mol. % SiO2 concentration. It is hypothesized that discovered plasticity is due to the increased t→m transformability.

Experimental and theoretical fracture toughness investigation of PUR foams under mixed mode I+III loading

2018 ◽  
Vol 67 ◽  
pp. 75-83 ◽  
Author(s):  
M.R.M. Aliha ◽  
E. Linul ◽  
A. Bahmani ◽  
L. Marsavina
Keyword(s):  
Fracture Toughness ◽  
Mixed Mode ◽  
Mode I
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