The optimal combination of processing parameters for achieving maximum tensile strength was determined using the Taguchi optimisation technique with an L18 orthogonal array. The study evaluated the effects of three main factors:

• Reinforcement composition (varied combinations of cow bone and cassava cortex),
• NaOH chemical treatment (0%, 2%, and 4% alkali treatment),
• Particle size (100 µm, 250 µm, and 500 µm).

Through signal-to-noise (S/N) ratio analysis and ANOVA, the optimal configuration was identified as:

• Reinforcement Composition (R4): 20% cow bone and 20% cassava cortex,
• Treatment (T4): 4% NaOH chemical treatment,
• Particle Size (PS100): 100 µm particle size.

This combination (denoted as R4T4PS100) produced the highest tensile strength of 91.80 MPa, indicating a well-balanced hybrid reinforcement with enhanced fiber–matrix adhesion and improved stress transfer. The 4% NaOH treatment removed surface impurities and hemicellulose, increasing the availability of cellulose for bonding with the epoxy resin. Meanwhile, the finer particle size (100 µm) provided greater surface area and aspect ratio, contributing to better dispersion and mechanical interlocking.

Statistical validation from ANOVA confirmed:

• Reinforcement composition had the highest influence on tensile strength (98.22% contribution),
• Followed by NaOH treatment (1.06%),
• While particle size had a minimal effect (0.81%).

The results confirm that the Taguchi method is highly effective for identifying optimal processing conditions with fewer experimental runs, and the combination R4T4PS100 is ideal for producing strong, lightweight, and sustainable composites suitable for automotive applications.

Based on Taguchi method optimization (using an L18 orthogonal array), the optimal processing parameters to achieve maximum tensile strength in a hybrid composite typically include:

• Reinforcement content: An intermediate or higher weight percentage of reinforcement (often around 9 wt.%) is found to optimize tensile strength by balancing load transfer and avoiding agglomeration.
• NaOH treatment concentration: Moderate alkali treatment, commonly at 2% NaOH, improves fiber surface roughness and bonding with the matrix, enhancing tensile properties. Higher concentrations tend to damage fibers, reducing strength.
• Particle size: Finer particle sizes, usually around 0.25 µm, promote better dispersion and interfacial adhesion, contributing to higher tensile strength.

These parameters are statistically optimized via the Taguchi approach, which identifies the best combination by analyzing the influence of each factor on tensile strength with minimal experimental runs. Reinforcement content is generally the most influential factor, followed by NaOH treatment and particle size. This combination maximizes interfacial bonding and composite integrity, leading to superior mechanical performance.

For precise details, the specific study referenced would provide exact parameter settings and tensile strengths obtained, but this overview aligns with the common findings from Taguchi-based optimization of hybrid composites.