Today's KNOWLEDGE Share: Fiber properties:

Today's KNOWLEDGE Share:

Fiber properties:

As you may already know, fibers and their properties are very important to the performance of the final composite material being developed! 

Not only that, but the material price also needs to be in accordance with the business case of the project! 

That said, how does the most common high performance reinforcements fare against each other when it comes to Specific Fiber Toughness, Compressive Modulus, Tensile Modulus, Compressive Strength, Tensile Strength, Density and Cost? 

This graph offers an easy way to compare and select the best option between them! 

Bibliographical Reference:

Structural Composite Materials - Page 35

Source:#managingcomposites #thenativelab

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#composites #fiber #tensile #compression #toughness #materialsscience #polymerscience

Today's KNOWLEDGE Share: Strength of fibers

Today's KNOWLEDGE Share:

Strength of fibers

Fibers generally exhibit much higher strengths than the bulk form of the same material. The probability of a flaw per unit length present in a sample is an inverse function of the volume of the material. Since fibers have a very low volume per unit length, they are much stronger on average than the bulk material, which has a high volume per unit length. On the other hand, because a bulk material has a much higher content of weakening flaws, it exhibits much lower variability in strength. Thus, the smaller the fiber diameter and the shorter its length, the higher the average and maximum strength but the greater the variability. Therefore, fibers have higher strength than their bulk counterparts, but they have greater scatter in their strength. The variability in the strength of fibers is a function of the flaws they contain and, in particular, the flaws they contain on the surface. 

Flaws can be minimized by careful manufacturing processes and the application of coatings to protect them from mechanical and environmental damage. Precursors used in fiber manufacturing processes must be of high purity and free of inclusions. Many fiber manufacturing processes involve drawing or spinning operations that impose very high degrees of orientation parallel to the fiber axis, thus producing a more favorable orientation in the crystalline or atomic structure. In addition, some processes involve very high cooling rates that produce ultrafine-grained structures, which are not achievable in most bulk materials. 

That said, how do commercially important fibers fair against each other when it comes to specific strength and specific modulus? Check out this graph to discover! 

Bibliographical Reference:

Structural Composite Materials - Page 32

Source:#managingcomposites #thenativelab

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#fibers #strength #mechanical #composites #manufacturing

Today's KNOWLEDGE Share:Fatigue Striations (PC HEADLIGHT LENS)

Today's KNOWLEDGE Share:

Fatigue Striations

I completed a failure analysis on a polycarbonate automobile headlight lens. Cracking was identified within the lens during inspection conducted after completion of performance testing. This testing included exposure of the lens to vibratory stress.

The external macro examination indicated that the cracking lacked characteristics associated with micro ductility, and displayed features associated with brittle fracture. The crack was completed and the fracture surface was examined with the aid of a scanning electron microscope (SEM). The SEM examination revealed a single crack origin, positioned immediately adjacent to a threaded boss design feature. The origin corresponds to a design corner, which acted as a point of stress concentration, multiplying the applied vibratory load.

A characteristic feature present on the fracture surface was the presence of radiating band features. The bands presented features indicative of arrest markings associated with dynamic crack propagation. At high magnification, the bands displayed characteristics of fatigue striations, corresponding to crack propagation through alternating cycles of cracking and arrest. This was consistent with the stated stress loading which precipitated the failure.

The fatigue striations on this project were textbooks for plastic materials. Fatigue cracking generally initiates at inhomogeneities within the microstructure, particularly at points of stress concentration, as was the case in this instance. The imposed stresses typically produce a complex process of both interactions of the defects, resulting in the initiation of microscopic cracks. The presence of the crack under load creates a further condition of stress concentration around the crack tip. When the stress maximum within this region exceeds the yield strain, a zone of damage is formed immediately in front of the crack tip, resulting in craze formation. Continued cyclic stresses lead to disentanglement of polymer molecules chains through cumulative rupture of the craze fibrils and coalescence of micro voids. Ruptured crazes are evident in the images below representing the headlight lens project. This process represents crack propagation and corresponds to the formation of bands of fatigue striations, as indicated below.

Once again, fractography clearly tells the story of how the component failed.

Source:The Madison group

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Today's KNOWLEDGE Share: Pressure Relief Valve:

Today's KNOWLEDGE Share:

Pressure Relief Valve:
A pressure Relief Valve is a safety device designed to protect a pressurized vessel or system during an overpressure event. An overpressure event refers to any condition which would cause pressure in a vessel or system to increase beyond the specified design pressure or maximum allowable working pressure (MAWP). The primary purpose of a pressure Relief Valve is protection of life and property by venting fluid from an overpressurized vessel. Many electronic, pneumatic and hydraulic systems exist today to control fluid system variables, such as pressure, temperature and flow. Each of these systems requires a power source of some type, such as electricity or compressed air in order to operate.

A pressure Relief Valve must be capable of operating at all times, especially during a period of power failure when system controls are nonfunctional. The sole source of power for the pressure Relief Valve, therefore, is the process fluid. Pressure Relief Valve Once a condition occurs that causes the pressure in a system or vessel to increase to a dangerous level, the pressure Relief Valve may be the only device remaining to prevent a catastrophic failure.The importance of adding Pressure relief device in gas storage systems in the recent years get more priority than the others in the safety aspects of whole process.

Source:Technical Engineering portal

Today's KNOWLEDGE Share: The main properties of composite materials

 Today's KNOWLEDGE Share:

The main properties of composite materials

As you may know, the characteristics/properties of composite materials resulting from the combination of reinforcement and matrix depend on: the proportions of reinforcements and matrix, the form of the reinforcement, and the fabrication process. 

But what are the most remarkable properties of these materials? 

- Composite materials generally possess very high specific mechanical properties.

- Composite materials do not yield: their elastic limits correspond to the rupture limit.

- Composite materials have high strength under fatigue loads.

- Composite materials age under the action of moisture and heat.

- Composite materials do not corrode, except in the case of contact aluminum with carbon fibers in which galvanic phenomenon creates rapid corrosion.

- Composite materials are not sensitive to the common chemicals used in engines: grease, oils, hydraulic liquids, paints and solvents, petroleum. However, cleaners for paint attack the epoxy resins.

- Composite materials have medium- to low-level impact resistance (inferior to that of metallic materials).

- Composite materials have excellent fire resistance as compared with the light alloys with identical thicknesses. However, the smoke emitted from the combustion of certain matrices can be toxic.

Bibliographical Reference:

Composite Materials Design and Applications - Page 16

Source:#managingcomposites/#thenativelab

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#composites #carbonfiber #carbonneutral #fatigue #mechanical

#corrosionprotection #materials #materialsscience



Hydrogen engines to be mass produced by Hyundai by 2025

 

After the completion of its H2 internal combustion engines (ICE) design and rolling out the prototype, Hyundai Doosan Infracore (HDI) is revving up the development of its hydrogen engines, with the aim to mass produce these engines by 2025.

HDI’s H2 ICE is an 11-litre class engine

The hydrogen-powered internal combustion engine can produce a power output of 300 kW (402 HP) and a torque of 1700 NM at 2000 RPM. Fulfilling Tier 5/Stage 5/Euro7 regulation, the engine satisfies the emission requirements to be 90% decreased to the current level to meet Zero CO2 (below 1g/kwh) and Zero Impact Emission.

Low-purity hydrogen is used to power the hydrogen engines. This makes the engines not only strong, energy-dense and economical, but the most suitable engine system for mid-to-large-size vehicles and vehicles traveling long distances. Just one charge of 10 minutes allows for a distance up to 500 km (310.6 miles), meanwhile the H2 internal combustion engines are 25-30% more economical than battery packs or fuel cells when vehicle price and maintenance costs are factored in.

The new hydrogen engines will be installed in commercial vehicles.

To both accelerate commercialization and lower costs, HDI plans to leverage its current engine technology and facilities. The new hydrogen engines that will be produced will be installed on commercial vehicles, including large buses, trucks and construction equipment. HDI will unveil its prototype hydrogen-powered ICE power unit this year (2023), with plans for full-scale testing slated for 2024, and full-scale mass production planned for the following year in 2025.

Hydrogen internal combustion engines will be used in mid-to-large-sized commercial vehicles such as trucks, buses and construction equipment and mid-to-large-sized power generators,” said Kim Joong-soo, HDI’s Head of the Engine Department. “We will put in the utmost effort to realize carbon neutrality in response to the eco-friendly market by developing green hydrogen-related technologies in line with increasingly strict carbon emission regulations.

Source:Hydrogenfuelnews

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