Tensile Initial Damage and Final Failure Behaviors of Glass Plain-weave Fabric Composites in On- and Off-axis Directions

Mechanical properties and failure behavior of glass plain-weave fabric composites under on-axis (i.e. 0 and 90 degrees direction) and off-axis (i.e. =5, 10, 15, 30, 45 and 60 degrees) tensile loading conditions have been experimentally investigated. Acoustic emissions (AE) monitoring and step-by-step optical observation with interrupted tension tests were adopted to study the character and failure mechanisms of various fiber orientations. The experimental results indicate that both off-axis elastic modulus and strength degrade with increasing off-axis angle in all cases. There is a good agreement for the axial modulus E-x between the experimental results and theory results obtained from orthotropic linear elasticity theory. Adoption of the principal shear strength S-45 degrees=28.5 MPa which is evaluated using the tensile strength based on the 45 degrees specimen allows better predictions of the off-axis tensile strengths by means of the Tsai-Hill failure criterion. Off-axis specimens exhibit lower knee point stress than on-axis ones and initial fracture strain monitored by AE (>75 dB) has a good fit to knee-point strain in this study. Tensile strength exhibits an increased tendency toward the delay of initial fracture behavior.