Glass fibre reinforced plastic (GFRP) has been widely used in many applications, including chemical plants, marine vehicle and automobile structures, aerospace components and electronic components (e.g printed circuit boards). Apart from the elementary considerations of the mechanical properties of the composite constituents, appropriate interfacial properties between fibre and matrix are absolutely necessary to provide adequate strength, stiffness and fracture toughness of the composites. A strong interface bond between the fibre and matrix is often desirable, but under many circumstances it promotes catastrophic failure of the composite with cracks propagating right through the fibre and matrix. In sharp contrast, a weak interfacial bond may encourage unique toughening mechanisms to t...[ Read more ]

Glass fibre reinforced plastic (GFRP) has been widely used in many applications, including chemical plants, marine vehicle and automobile structures, aerospace components and electronic components (e.g printed circuit boards). Apart from the elementary considerations of the mechanical properties of the composite constituents, appropriate interfacial properties between fibre and matrix are absolutely necessary to provide adequate strength, stiffness and fracture toughness of the composites. A strong interface bond between the fibre and matrix is often desirable, but under many circumstances it promotes catastrophic failure of the composite with cracks propagating right through the fibre and matrix. In sharp contrast, a weak interfacial bond may encourage unique toughening mechanisms to take place more extensively, giving rise to high fracture toughness of the composite.

In the present study, the interfacial properties of E-glass woven fabric vinylester matrix composites affected by fibre surface treatment were characterized by static and dynamic loading conditions. The effects of temperature and hygrothermal ageing on mechanical performance of composites were studied. In light of the distinct properties imparted by fibre surface treatment with different silane coupling agents, composite laminates consisting of fabric layers with different combinations of coupling agents were fabricated. The mechanical properties of these hybrid composites were measured and compared with non-hybrid composites. The results showed significant improvements in tensile and bending strengths when the laminates consisted of hybrid layers with low and high silane concentrations. Significant improvements in crack growth stability in mode I interlaminar fracture were also highlighted for similar combinations of hybrid layers. Furthermore, previous studies recognised the importance of the mechanical properties and size of the interphase of finite thickness created between fibre and matrix. Lack of adequate experimental techniques in the past did not allow accurate prediction of these properties to be made for a given fibre reinforced composite. An attempt is successfully made in this study to characterize the size and modulus of the fibre-matrix interphase based on novel nanoindentation and nanoscratch tests, and thermal capacity measurements. Although there still exist uncertainties on how the observed measurements reflect the actual performance of the composites, it is highlighted that the variations of the obtained interphase thickness were consistent with the changes in fibre surface treatments.

Keywords: E-glass woven fabric laminates, silane coupling agent, interfacial properties, interphase thickness