In recent years, the use of polymer matrix composites has increased considerably, and its potential demand is expected to grow further. Composite materials currently find their use in applications such as ship frames, electronic devices, parts for helicopters and aircraft, and other items. Their weight savings are quite significant compared to structures made from metal, such as ships and aircraft (Nawaz 2011). The design disadvantages of using composites include high material and production costs, anisotropic properties of the material and low resistance to impact damage. Another problem with using composites instead of metals is their high flammability and low resistance to fire. As stated by Nawaz (2011), when composites are used in structural applications such as aircraft, the combustion process poses a high risk; hence, the US Federal Aviation Administration (FAA) enforces strict fire regulations on materials used in passenger aircraft, particularly within the cabin. Most thermoset and thermoplastic composites do not meet the low flammability and toxicity criteria for smoke in such a way that flame retardant epoxies and polymers with lower flammability can be used, but these bring additional costs and, in most cases, poorer mechanical properties (Mouritz and Gibson 2006).
However, there are some drawbacks to the use of natural-based fillers, including low thermal resilience, high flammability, high moisture absorption, poor mechanical properties, etc. (Mochane et al. 2019), particularly in advanced/technical applications. To address these drawbacks, further researches, to improve the engineering properties of the utilization of natural-based fillers in composites manufacture had been undertaken.
Natural fibres are made from numerous renewable materials, such as animals, plants, and minerals. The chemical composition depends on the source of the fibre and varies between different sections, even though they are of the same family or type (Mochane et al. 2019). Their quality relies on their chemical structure, crystallinity, microfibrillar angle, defects, and physical characteristics. To achieve the highest potential, the data dependent on these criteria are of interest. Natural fibres are known to be prone to deterioration, depending on the individual elements, such as organic, chemical, mechanical, thermal, photochemical, and aqueous (Mochane et al. 2019). For example, lignin is primarily responsible for the degradation of UV and heat, and hemicellulose is responsible for biological and thermal degradation, and high absorption of moisture in fibres (Azwa et al. 2013; Marques et al. 2014). One of the main limitations preventing their technical implementations was an inherited hydrophilic character (Gurunathan et al. 2015; Neher et al. 2016). This results in poor interfacial interaction with polymeric hydrophobic materials that limit the transfer of stress between the composite components (Gupta 2017). However, the handling of natural fibres, when exposed to various conditions, may increase their biodegradation stability (Azwa et al. 2013).
Several variables are dependent on the mechanical properties of hybrid polymer composites. These considerations are the dispersion and distribution of the reinforcements in the polymer matrix selected, the interfacial adhesion between the polymer and the reinforcements, the large surface area, the high aspect ratio of the reinforcements, the mechanical properties of the reinforcements, the loading effect, the adjustment of the surface, the dimension of the fibre and the orientation of the natural fibres (Bisaria et al. 2015). Mechanical properties are commonly documented as a function of loading, duration, and fibre treatment in many experiments (Gupta and Srivastava 2015; Kureemun et al. 2018; Shanmugam and Thiruchitrambalam 2013). Several studies have been published on the development of hybrid polymer composites from both thermosets and thermoplastics using synthetic and natural fibres as well as the combination of nanomaterial fibres and their elucidated mechanical and thermomechanical properties (Akil et al. 2014; Ramana and Ramprasad 2017; Safri et al. 2017).
The need for the use of more than one type of reinforcement is that one type's benefit will complement another's drawback, thus enhancing the properties and efficiency of the resulting material. Besides, demand for the production of such materials is growing as they fulfil the requirements of many goods, such as door panels and car interiors in transport vehicles (Kureemun et al. 2018). The prediction of the mechanical behaviour of hybrid materials depends on the parameters of the material, such as mechanical characteristics of the reinforcement (fibres or particles), mechanical characteristics of the matrix, reinforcement distribution and dispersion, reinforcement volume fractions, and test conditions (Mochane et al. 2019).
In domestic homes, transportation, aerospace, and military applications, there is great demand for fire retardant (FR) products (Boulos et al. 2013). Improving the fire retardation of polymeric materials is a priority and a big challenge too. Appropriate use of FR materials and fire safety devices will greatly reduce the human and economic cost of fire. Developing thermomechanical models that predict accurately the response of a fire-exposed reinforced fibre-polymer composite is critical for engineers in determining the integrity of structural members (Brown and Mathys 1997). Certainly, composites are widely used in aerospace, marine, infrastructure, and chemical processing applications so there is potential for fire events occurring in each of these applications (Eggleston and Turley 1994; Scudamore 1994).
The degradation of the composite material's structural integrity as a result of exposure to fire is a significant safety issue and this decomposition of composite material along with the spread of flames and the release of heat, smoke and toxic fumes is of major concern for safety measures (Tewarson, and Macaione 1993). Invariably, a large amount of research has been done to study the fire reaction behaviour of structural composite materials, and there is plenty of information available regarding their fire reaction properties such as heat release rate, time to ignition, flame spread, gas emissions, smoke density and smoke toxicity (Raju et al. 2012). A loss of stiffness, strength, or creep resistance, however, can cause deformation and the ultimate collapse of a composite structure that could result in injury and death (Ezeh et al. 2020). Therefore, it is not surprising that natural fibre composites have found numerous applications in the engineering industry. This helped to contrive this research work aimed at developing a bio-flame retardant material to improve the thermal properties of polyester-banana peduncle fibre composite using cow horn particles, which is cost-effective and environmentally friendly.