Effect of material nonlinearity on the toughness evaluation in quasi-static mode II interlaminar fracture toughness tests of composite laminates. (August 2021)

• Record Type: Journal Article
• Authors: Yashiro, Shigeki; Yamasaki, Tomohiro; Nagai, Hiroto; Yoshimura, Akinori
• Is Part Of: Engineering fracture mechanics. Volume 253(2021)
• Publication Date: 2021-08
• Subjects: Polymer matrix composites -- Toughness testing -- Delamination -- Finite element analysis -- J-integral; Fracture mechanics -- Periodicals; Rupture, Mécanique de la -- Périodiques; Fracture mechanics; Periodicals; 620.112605
• DOI: 10.1016/j.engfracmech.2021.107879
• Languages: English
• ISSNs: 0013-7944

Abstract

Highlights: A new mode II interlaminar fracture toughness test for composite materials is validated. Impact of material nonlinearity on LEFM-based G II evaluation is investigated. An elastoplastic finite-element analysis of unidirectional CFRP is performed. Difference between G II and J in DENT test is smaller than that in flexure-type tests. The compliance calibration method is assessed for the new test method. Abstract: In mode II interlaminar fracture toughness tests of composite laminates, the fracture toughness evaluated based on linear elastic fracture mechanics deviates from the true toughness due to the material nonlinearity of the matrix. In this study, an elastoplastic finite-element analysis was performed on a new quasi-static mode II interlaminar fracture toughness test, i.e., the doubly end-notched tension (DENT) test, to investigate the difference between the perceived energy release rate and the J -integral. The effect of material nonlinearity was compared with other quasi-static mode II interlaminar fracture toughness tests: three- and four-point bend end-notched flexure tests. Analysis of the DENT showed that for a given J -integral loading, the size of the plastic zone at the delamination crack tip was the same regardless of the crack length. The difference between the perceived energy release rate and J -integral in the DENT test with respect to the plastic zone size was independent of the crack length, and was smaller compared with that of flexure-type tests. Furthermore, the compliance calibration method was applied to the elastoplastic analysis results of the DENT test to reduce the evaluation difference of the energy release rate.