Effect Of TPU Nonwoven Fabric On Particle Erosion Resistance And Toughness Properties Of GF/EP Composites

The recent decades have witnessed the rapid development of fiber reinforced plastics（FRP）composites and their increasing applications in the field of engineering.However,with the increased use of FRP in erosive work environments,it has become extremely important to investigate their erosion characteristics intensively.Meanwhile,the delamination damage of FRP restrict their service life.Much attention has been paid to control laminated failure,and improve the delamination resistance in composite materials.Thermoplastic polyurethanes（TPUs）have both plastic processing property and rubber mechanics performance,excellent erosive wear resistance.Melt-blown fabric is more popular because of its simple process and high production efficiency.It has been widely applied in filtration,adsorption,waterproofing and health care and so on.An interleaved fiber laminate system,wherein TPU nonwoven fabric（TNF）was interleaved into fiber ply,has been fabricated by the vacuum-assisted resin transfer molding（VARTM）technique.The TNF can not only enhance composite wear resistance,but also improve composite toughness properties.By this thesis research,exploring the wide spread application prospect of TPU nonwoven fabrics.The main results of the research are as follows:TNF was prepared by the melt-blown（MB）process,and the composites werefabricated by VARTM technique.The interactive influence of various operational variables on specific wear behavior of composite materials has been studied thoroughly.Under air flow pressure of 0.345 MPa,erosion distance of 60 mm and the erosion particle diameter of 300 mm,TNF/GF/EP composites exhibit better erosion resistance than that of conventional GF/EP composites:the erosive wear resistance of TNF/GF/EP composites was improved by 99%,108%,205%and 493%at the impingement angles of 20°,30°,45°and 90°,respectively.On the other hand,compared to neat EP,the erosion rate of TNF/GF/EP composites was decreased by10%,22%,6%and 21%at impingement angles of 20°,30°,45°and 90°,respectively.The 3D network structure of TNF interleaved into the composite can absorb and consume the energy of the impact particles to a larger extent.Meanwhile,TPU fibers were performed as a‘bridging’function.This function certainly helps to protect the‘blocks’from being eroded away.It is believed that TNF coatings absorb additional energy that reduce the erosion of matrix materials.Toughening of GF/EP composites was also achieved by interleaving TNF.It provided the best all-round performance with fracture toughness improvements of78%and 115%for mode-I and mode-Ⅱ,respectively.The higher roughness of TNF/GF/EP fracture surface contributes to increase fracture energy,and is mainly attributed to pulled-off microfiber.Crack path was mainly inside the interphase region for TNF interleaved FRP for mode-I test.The improvement in both G_IC and GⅡ_C is mainly due to enhanced resistance to crack propagation in the interlayer,a process that requires additional energy.To learn how resin flows through the fiber preform and TNF layer,permeabilities of the fiber preform and TNF need to be measured.One time step of the flow front position for the flow through fiber preform in nonrigid mold.After recording the experimental flow front position versus fill time,they were compared with the predicted flow distance.The results showed that the impregnation of the reinforcement is made more difficult by the presence of TNF,as evidenced by the lower permeability values.The decrease of the permeability of fiber perform mainly results from the inhibition of flow of epoxy resin introduced by TNF as structural layers.