3. Bonding Between Fibers and Matrix

The properties in fiber reinforced geopolymer depend on the performance of fiber, fiber content, precursor of geopolymer and curing environment. However, the interface between the matrix and the fiber plays a key role in the overall mechanical properties of the composites. If the interface is well bonded and the load can be transferred from the matrix to the fiber with a high carrying capacity, fibers with inert surfaces will also result in weak interface contact[31]. Regarding the interface between fiber and matrix, many scholars have studied the interface bonding zone between fiber and geopolymer by establishing mathematical or physical models.
Fiber fracture and pull-out from the matrix are the two main failure mechanisms of geopolymer. At the same time, the fiber will agglomerate if the fiber content in the matrix is too high, thereby resulting in the decrease of the matrix strength. Fig. 2 depicts the interface bonding between different fibers and geopolymers.