Abstract: The utilisation of oil palm fibre (OPF) and pineapple leaf fibres (PALF) as reinforcement materials for bio-phenolic composites is growing especially in automotive lightweight applications. The major aim of this current study is to investigate the influence of alkali (Ca(OH)2 treatment on pure and hybrid composites. The effects of enhancements in chemical interactions were evaluated by the Fourier-Transform Infrared Spectrometer (FTIR). Dynamic Mechanical Analysis (DMA) and Thermogravimetric Analysis (TGA) performance of untreated reinforcements (OPF and PALF) and treated (OPF/OPF) composites at varying temperature and noted sufficient interfacial bonding contributing towards the improvements in thermal stability. From DMA results, the storage modulus improved with treated composites while the damping factor was reduced. Furthermore, the treated hybrid composites exhibited significant improvements in thermal stability compared to untreated fibre composites. The results indicated that alkali calcium hydroxide (Ca(OH2(:T) incorporation in hybrid composites (OPF/PALF) results in increased tensile strength and modulus among all composites. Similarly, the alkali-treated (Ca (OH)2)-treated pure composite (T/50%PALF), and hybrid composites (T/1OPF.1PALF) exhibited better flexural strength as compared with other composites. In contrast, the T/50% PALF showed higher flexural stress of 78.2 MPa, while the flexural modulus was recorded at 6503 MPa. It can be proposed from the findings of this study that the alkali treatment (5%Ca(OH)2) can be utilised to improve the strength and efficiency of agriculture biomass to be used as reinforcements in composites. Additionally, the hybridisation of bio-fibre composites has the potential as a novel variety of biodegradable and sustainable composites appropriate for several industrial and engineering applications.

Key words: Hybrid fibre composites , · Alkali treatments , · Surface modifications , · Mechanical properties , · Thermal stability