Effects of Fibrous Layer Structure on Tensile Behavior and Fracture Toughness of E-Glass/Epoxy Composites: A Comparison Between Angle Plied and Woven Layers

The fibrous layer structure plays a pivotal role in determining the mechanical performance of fiber reinforced polymer composites (FRPCs). Studying the influence of fibrous layer structure on fracture behavior of FRPCs, as one of the key mechanical characteristics, is crucial to improve safety and complex load bearing capacity of advanced structures. Therefore, the main objective of this research is to compare the tensile behavior and crack growth in two types of E-glass/epoxy composites and to examine how the structure of fibrous layers influences the mechanical properties of the composite. Samples were produced in a four-layer configuration using vacuum infusion process (VIP). The first sample consisted of four layers of woven fabric arranged at ±45o, while the second sample was made from four angle plied layers with a fiber orientation of ±45o. Before conducting tensile and fracture tests, microbond tests were performed to explore any possible differences between the fiber/matrix interfacial properties within the two composite samples. Physical characteristics including thickness, density, fiber volume fraction and void content in the two composite samples were also evaluated. Then, the composite samples were subjected to tensile tests. To investigate mode I fracture toughness, the samples were single-edge notched and then subjected to tensile tests. Results indicated that the composite reinforced with woven layers exhibited high tensile strength and stiffness but was more sensitive to crack growth. The composite with angle plied layers, despite being thicker, showed 28.47% higher stress intensity factor and 56.63% higher critical energy release rate, compared with the woven counterpart.