Design of fiber-reinforced polymer damping laminates has been attracting great interest in industrial sectors for lightweight structural damping applications. The present work investigates the impact of skin, core, neutral, and alternate intertwined basalt/flax fabric on the mechanical and vibrational properties of the newly designed polymeric laminate. The designed sequence structure was fabricated using a wet hand lay-up technique with hydraulic compression. Tensile and flexural strength of intertwined multilayer basalt/flax woven composite were studied. An effect of the intertwining on the tensile and flexural strength fractured surface of the composites has been further evaluated. Free vibration technique was used for recording vibration response and the related damping frequencies of intertwining composites. A cantilever mode impact hammer was used for generating periodic signals of the designed composite systems. Damping ratios and damped natural frequencies were calculated with several plies and sequence of flax/basalt woven in the composite. The experimental results revealed that the damped natural frequencies of class II, skin basalt layer intertwined seven core flax layered composite (B2F7) was high, followed by two skin basalt layers intertwined core flax layered composite (B4F5). The addition of the flax layer enhanced the natural frequency to the higher value. It was found that the skin basalt layer with intertwined flax layered B2F7 design structure exhibits maximum damping value with acceptable mechanical properties.

Natural fiber and particulates are being exploited to attain eco-friendly products for construction and automotive sectors. These sectors are moving towards the use of high damping characteristic natural biofibers and particulate-reinforced polymer composite as part of the structural components. In this work, woven flax fiber (0° and 90°) and almond shell particulates were used. They were subsequently treated with alkaline and acetylene chemical solution separately. Polymer composite laminates were prepared using a vinyl ester resin as matrix and by stacking flax fibers and almond particulates interleaved in an alternative sequence using the hand layup technique. This was followed by hydraulic pressing. Composite laminates were fabricated by varying the almond shell particulate weight fraction of 0%, 5%, 10%, and 15%. Mechanical properties such as tensile and flexural strength were experimentally measured. Dynamic thermomechanical analysis was conducted on the alkaline-treated and untreated composites with different frequencies for the assessment of the damping characteristics. The alkaline-treated interleaved almond shell and flax fiber composite showed considerably higher damping characteristics. This could be due to the improved adhesion between the matrix and reinforcements. An addition of almond shell particulate positively increased the strength and stiffness of composites.

The selection of fibers and their stacking sequence, which affect structural integrity and functional properties, are critical parts of polymer composite design. In this work, the influence of various stacking sequences made of basalt and flax fiber layers on the mechanical, thermal, and dynamic mechanical analyses of vinyl ester polymer composites was investigated. The stacking sequence designed by alternate basalt and flax layers showed higher tensile and flexural strengths, with basalt layers in the outer positions. The high‐strength basalt fiber retains considerable stress, particularly in the outer layer, reducing stress transfer to the remaining core layers. The basalt and flax fiber alternative layered sequence with outer basalt layers shows a slightly lower thermal degradation temperature (467°C) than the only basalt layered sequence composite (474°C). Because of the high thermal resistance of the outer basalt layers, heat flow to the next fiber layers is reduced. The dynamic mechanical analysis reveals that the polymer composite intertwined with only basalt fiber was found to have a higher storage modulus. On the other hand, the outer basalt layers intertwined with the core flax layers composite showed a 122% higher damping value than the stacking sequence made of only basalt fiber due to the porous structure of flax fibers dissipating more vibration energy.

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