An Experimental Study On Fibre Reinforced PDMS

Polydimethylsiloxane(PDMS)is a kind of high molecular polymer widely used in the field of stretchable electronics due to its unique optical transparency,good flexibility,chemical inertness and shape replication ability.PDMS has a good elasticity,but its fracture toughness is pretty low,which indicates that it is vulnerable to defects(such as cracks).The low fracture toughness of PDMS greatly limits its engineering applications.In this thesis,two kinds of high-tenacity plain weft-knitted fabric,which are composed of nylon and spandex core-spun yams respectively,are selected as the toughening materials in PDMS to enhance the fracture toughness of PDMS.The direct-coating method is used to fabricate the fabric/PDMS composites.The unidirectional tensile tests are carried out on the plain weft-knitted fabric and the corresponding composites along the transverse and longitudinal directions of the fabric structure.The mechanical properties of the composites in the transverse and longitudinal directions are compared with the PDMS specimens.The experimental results show that the elastic modulus,breaking force,breaking strength and elongation at the break of the two kinds of fabric/PDMS composites are improved to some extent compared with PDMS.It is shown that the nylon fabric composite in the transverse direction has the best mechanical stability.When it refers to crack propagation,unidirectional notched tensile specimens of unreinforced PDMS,two kinds of fabrics and the corresponding composites are manufactured.The uniaxial tensile tests of notched specimens are carried out.The experimental results show that both transverse and longitudinal specimen of the nylon fabric and the longitudinal specimen of the spandex fabric are able to resist the crack propagation.For the composites,the fracture toughness of all four composites is much higher than that of the PDMS.The transverse nylon composite has the highest fracture toughness,with its enhancement ratio as high as 700%.In addition,the loading and unloading tests of the composites with pre-crack are analyzed.These results provide the experimental basis for the preparation of crack-insensitive flexible substrates.