Effects of porosity on in-plane and interlaminar shear strengths of two-dimensional carbon fiber reinforced silicon carbide composites

Porosity effects on shear properties of 2D C/SiC were investigated based on the corresponding shear damage mechanisms. The results show that as the total porosity increases from 122% to 26.1%, the interlaminar shear strength decreases from 44.58 MPa to 17.80 MPa according to a power law, while the in-plane shear strength decreases linearly from 143.25 MPa to 74.38 MPa. Under interlaminar shear stress, delamination is resulted from matrix cracking and interface debondinglsliding mechanisms. Effects of porosity on interlaminar shear strength is controlled by the volume fraction of the delaminated matrix. Under in-plane shear stress, echelon matrix shear cracking and large scale fiber bridging mechanisms occur. The decreasing of in-plane shear strength depends on the spacing between the echelon cracks. Since the interface debonding/sliding mechanism occurs under both in plane and interlaminar shear stresses, a relationship is obtained that the in-plane shear strength equals the sum of the interlaminar shear strength and the fiber bridging term under the minimum total porosity about 30.5%. (C) 2016 Elsevier Ltd. All rights reserved.