Enhancing the Mechanical Properties of Carbon Fiber Reinforced Polymer With Carbonized Coconut Shell Particles

Carbon Fiber Reinforced Composites and other Fiber Reinforced Composites are increasingly being utilized in structural applications as a result of their superior in-plane characteristics, such as high specific strength and stiffness (strength and stiffness to weight ratio).  Nonetheless, they possess poor and unpredictable off-axis properties that translates into weak crack resistance and delamination, thereby making them susceptible to failure in the event of out-of-plane or multi-axial loading, particularly, impact or blast. One of the ways to circumvent these shortcomings is to toughen the polymer matrix with organic or inorganic particulates to develop a multiscale and multifunctional composite. This study involves using Carbonized particles from coconut shells to modify an epoxy matrix and utilize it in producing a hybrid carbon fiber-multiscale bio-composite.   The mechanical properties of this hybrid composite will be investigated. Natural fillers like coconut fibers have recently gained much research interest in the production of bio-composites for their low cost, ease of accessibility, lightweight, toughness, and biodegradability. Carbonized Coconut Shell Particles (CCSP) were synthesized by heating the coconut shells at a high temperature in a controlled environment to avoid burning of the sample into ash. Scanning Electron Microscopy (SEM) analysis was performed on the carbonized particle, revealing an ordered structure and pore formation. The final product from the pyrolysis was then milled into finer particles using a high speed vibrating ball miller. Two different forms of Carbon Fiber Reinforced Polymer (CFRP) composite with different matrices were fabricated using the hand lay-up method. Each composite material consisted of four plies of woven carbon fibers. Neat epoxy was used as the control and compared with the composite having 3wt% of carbonized coconut shell particles. The axial properties of both composites were investigated by tensile test, it was observed that the failure strength and strain of the hybrid bio-composite was increased considerably compared to the control. The failure strain for the hybrid composite was 4.2% compared to the control which was 3.5%. The elastic modulus and tensile strength of CFRP also increased by 23% and 41% respectively with the addition of carbonized shell particles. The impact response was investigated using drop weight impact test and it was observed that incorporating of CCSP improves the resistance to impact load. The resistance to deformation under flexural load was also analyzed using a 3-point bending test according to ASTM D790. The flexural strength and flexural modulus of CFRP was improved with the addition of carbonized particulates. Hybrid composites with varying weight composition will be fabricated and the mechanical properties investigated. Dynamic Mechanical Analysis and hardness test will also be performed to evaluate the damping effect and resistance to abrasion or wear, respectively of the bio-composites.

Keywords: Carbonized filler, coconut shells, bio-composite, carbon fiber, mechanical properties