The PLA + PHB composite exhibited the lowest flexural strength (76 MPa) attributed to the poor mechanical properties of PHB in Table 2. Similar to the tensile strength, no real improvements of flexural strength were observed with the addition of CNF with a PHB carrier system when compared with neat PLA + PHB matrix. Flexural strength of PLA was 82 MPa and increased to a value of 90 MPa with the addition of 10 wt.% CNF. The reason for the improvement in flexural strength can be attributed to a well-formed interface that allows better stress transfer from the PLA matrix to the CNFs
Table 2 shows that the flexural modulus of elasticity (FMOE) of PLA nanocomposites increased linearly with increasing CNF content. The PLA + PHB composite exhibited the lowest FMOE (2.55 GPa) and FMOE increased by 11% up to 5 wt.% CNF with a PHB carrier system. On the other hand, FMOE of PLA was 2.93 GPa and increased to a value of 3.43 GPa with
the addition of 10 wt.% CNF. The stiffness of CNF could explain the significantly enhanced FMOE of PLA nanocomposites, and increased composite stiffness depends on the CNF content and uniformity of reinforcement dispersion