Effects of Loading Speed on the Failure Behaviour of FRP Composites

Abstract

The objective of the present work is to ascertain the failure modes under different loading speeds along with change in percentage of constituents of FRP composites. This involves experimental investigation of FRP composites with woven roving fibers and matrix. Different types of composites i.e. Glass : Epoxy, Glass : Polyester and (Carbon + Glass) : Epoxy are used in the investigation with change in percentage of constituents. The variability of fiber content of the composite is in the range of 0.55 to 0.65 weight fractions. The matrix dominated property, like inter laminar shear strength has been studied by three point bend test using INSTRON 1195 material testing machine with increasing five cross head velocities. The variation of inter laminar shear strength of laminates of FRP composites is significant for low loading speed and is not so prominent for high speed. The variation of inter laminar shear strengths are observed to be dependent on the type and amount of constituents present in the composites. The laminates with carbon fiber shows higher inter laminar shear strength than that of glass fiber composites. The laminates with epoxy matrix shows higher inter laminar shear strength than polyester matrix composites for the same fiber. There is no significant variation of inter laminar shear strength beyond loading speed 200 mm/min and this can be used for specifications of testing. Matrix resins such as polyester and epoxy are known to be highly rate sensitive. Carbon fiber are relatively rate independent and E – Glass fibers are rate sensitive. Woven roving Carbon Glass Fiber Reinforced Polymer (CGFRP) shows small rate dependence and woven roving Glass Fiber Reinforced Polymer (GFRP) shows significant rate sensitivity.