Understanding the Wear Properties of Basalt Fiber Reinforced Polymers

The extent to which the flavor and texture of your food depends on how you break down and combine chains of protein, carbohydrate and fat molecules. This reaction is usually caused using heat, but you can also trigger or accelerate chemical reactions by introducing new enzymes into your food that can change the molecular composition.

Cooking is one of the best examples of composites in our daily lives. A composite material is a combination of two or more constituent materials with different physicochemical properties; the resulting composite has properties that are different from those of the individual elements.

Although composites are ubiquitous, we are often unfamiliar with the original elements used to make them and therefore cannot understand how the combination of materials changes the properties. But in cooking, you can experience the individual elements firsthand as you place them in a bowl and then create a new dish that tastes very different from each of the original ingredients.

Beyond the kitchen, carbon fiber-reinforced polymers are a composite material that promises to have a major impact on our daily lives. This composite material, often referred to as "carbon fiber," has received much attention in recent decades for its potential to replace steel. The combination of carbon fibers in a polymer matrix gives these polymer composites the desired high strength and light weight properties.

However, the high cost of carbon fiber reinforced polymers limits their widespread use, making cost reduction an imperative for manufacturers. Research for this purpose has had some success, but researchers are also considering fibers other than carbon that may help strengthen polymer composites.

Basalt fibers are another material that is considered a reinforcing material. When this inorganic fiber is used to reinforce polymers, the resulting composites have good strength, a high operating temperature range, good chemical resistance, excellent thermal and acoustic insulation, and low water absorption. In addition, basalt fibers are easy to process, environmentally friendly and, most importantly, inexpensive.

To date, basalt fiber-reinforced polymers have not gained mass market acceptance due to technical challenges such as raw material properties and inconsistent regulatory standards. But advances in all the necessary areas - manufacturing efficiency and capacity, global reach, product design and development, regulatory activity - have convinced manufacturers that these materials will play a greater role in the future.

Tribological performance of basalt fiber-reinforced polymers under a variety of operating conditions is one question manufacturers must answer to overcome the regulatory challenges that have prevented these composites from entering certain markets. Tribology is the science of two interacting surfaces in relative motion, including friction, wear, lubrication and related design aspects.

Tribological properties depend on a variety of factors, such as manufacturing processes, operating parameters, and the properties of the polymer matrix and fibers. Therefore, mapping the tribological properties of these composites under various operating conditions requires time and extensive research.

A new open-access study by Malaysian and Brazilian researchers contributes to this effort. They aimed to compare the friction and wear properties of glass or basalt fiber-reinforced epoxy composites to reveal the effects of these different fibers on the tribological properties of epoxy-based composites.

The researchers used the epoxy resin Miracast 1517A, a low-viscosity laminating resin. They fabricated the composites using the traditional filament winding and hand-laminating method, and then tested them in two stages.

1. fixing loads, speeds and distances under adhesion, abrasion and erosion wear conditions.

2. unidirectional and reciprocal adhesive sliding motions against steel counterparts, the former varying at a pressure - velocity factor (0.23 MPa-m/s vs. 0.93 MPa-m/s) and the latter at a mating surface configuration (ball vs. plane vs. cylindrical vs. flat).

The wear performance of the composites was improved by 60% when reinforced with glass or basalt fibers. However, the performance of basalt fiber-reinforced composites was not consistent compared to glass fibers.

The glass fiber-reinforced polymer outperformed the basalt fiber-reinforced polymer in wear resistance under adhesive and abrasive wear conditions, with differences of 18.33 percent and 22.75 percent, respectively. The researchers wrote, "This may be due to the higher stiffness of the [glass fiber-reinforced polymer] composite compared to the [basalt fiber-reinforced polymer] composite, which prevents severe matrix shedding due to adhesive wear." Alternatively, the small diameter size of basalt fibers (9-15 μm compared to 10-17 μm for glass fibers) may affect the fiber-matrix interface strength.

Only under erosive wear conditions did the basalt fiber-reinforced polymer exhibit better wear than the glass fiber-reinforced polymer, with a 9.93% improvement. "This may be attributed to the thermal changes that occur inside the eroded tank. As the distance increases, the sand mixture on the eroded surface creates higher friction. As a result, heating causes changes in the thermal and mechanical properties of the glass fiber reinforced material," they wrote.

In the second phase of testing, the researchers drew several interesting conclusions, including:

that the low coefficient of friction recorded during sliding does not always reflect the low wear rate of the composite, and

✱ Only at high operating parameters, basalt fiber-reinforced polymers exhibited better wear rates and coefficients of friction than glass fiber-reinforced polymers under unidirectional sliding, and

✱ During reciprocal sliding, the basalt fiber-reinforced polymer exhibited an inconsistent pattern of improvement in wear rate and friction coefficient compared to the glass fiber-reinforced polymer.

Ultimately, they concluded that although the friction and wear properties of the composites are highly dependent on the test conditions, "it can be argued that [basalt fibers] have the potential to replace [glass fibers] for tribological applications because the differences between them are still comparable."