An Investigation On The Mechanical Properties Of Silk Fabric And Glass Fiber Mat Reinforced Hybrid Composites

As is well known to all, glass fiber, is used as reinforcement in light weight composite for many areas, such as aerospace, architecture, chemical industry, medicine, electronics, agriculture and other military and civilian areas. Silk is favored by consumers because of its soft waxy handle, elegant sense, good skin-touch, good air permeability and moisture absorption, excellent drapability, unique soft and pearly luster. From the viewpoint of sustainable development and economic, countries have worked on recycling discarded textile and apparel for different levels recently. More and more people pay attention to recycling the discarded silk fabric on account of serving as one kind of high quality fabrics.In this research, unused silk fabric is utilized as the first step. Glass fiber mat and silk fabric are employed as reinforcement to fabricate silk fabric and glass fiber mat reinforced hybrid composites(SFGFRP) and glass fiber mat reinforced composites(GFRP) with unsaturated polyester resin by hand lay-up method. The effect of the inserted silk fabric on the mechanical properties of SFGFRP are investigated based on three point bending, low cycle bending fatigue, impact and hydrothermal aging tests.Firstly, the research focuses on three point bending and Izod impact properties of SFGFRP and GFRP. Results show that flexural strength and flexural modulus of hybrid composites with silk fabric in middle layer are 5.7 GPa and 144.2 MPa, respectively, which are highest among three kinds of hybrid composites, 16.3% and 8.1% higher than the values of hybrid composites with silk fabric in the first layer. However, it is obvious that the addition of first-layer or last-layer silk fabric to GFRP have similar flexural modulus and strength. Hybrid composites with silk fabric in the fifth layer have highest flexural deflection, while the value was lowest for silk fabric in the middle layer. It can be concluded that the flexural properties of hybrid composites are affected by the hybrid type. The flexural properties of hybrid composites are similar along the direction of 0° and 90°, even the warp and filling direction of silk fabric are different. Investigations on the impact behavior revealed that the hybrid type of composites and warp and filling direction of silk fabric on impact properties are not significant due to similar impacted surface of hybrid specimens.Secondly, immersion tests, bending tensile and impact tests on immersed specimens are carried out to investigate the degradation of two kinds of composites in hot water from the viewpoint of change in weight and mechanical properties. In terms of GFRP, as the immersion time increased, the flexural properties show a descending trend with the increasing the exposure time after 1 day. Impact strength hardly changes before 30 days and decreased by 58.2% after 90 days. With respect to SFGFRP, flexural and impact properties degrade significantly with the immersion time after 1 day. Neverthless, the inserted silk fabric hardly enhances the effect of hydrothermal aging on GFRP. Besides, flexural and impact properties of hybrid composites with silk fabric in middle layer decrease less compared with those of other two kinds of hybrid composites and GFRP. That is to say, to a certain extent, hybrid composite with silk fabric in middle layer could reduce the effect of hydrothermal aging and protect the silk from hydrothermal aging compared with other two kinds of hybrid composites, because middle-layer silk fabric is less affected by hydrothermal aging.Finally, LCBF tests are carried out to investigate the flexural properties degradation of two kinds of composites at different applied pre-set load from the viewpoint of change in both flexural modulus and strength. It is shown that 55%, 70% and 85% pre-set load low cycle bending fatigue(LCBF) have no significance influence on SFGFRP. In addition, the hybrid type of composites and warp and weft direction of silk fabric on LCBF are not obvious, either. However, GFRP specimens don’t go through more than 85% per-set load LCBF tests. The inserted silk fabric can make a contribution to the anti-fatigue property of GFRP.