Damage Tolerance Estimation of Advanced Composite Materials

1st Report : Study on Interlaminar Fracture Toughness Test

Abstract

Characterization of interlaminar fracture toughness will play an important role in the establishment of a damage-threshold/fail-safe approach to composite materials and structures. Double cantilever beam (DCB) and end notched flexure (ENF) tests are reviewed and revised methods are proposed for accurate and easy estimation of mode I and II interlaminar fracture toughness. Thickness normalized crack length versus cube root of compliance plots are used for data reduction of DCB test. CSD measurement technique is introduced to ENF test and stabilized ENF test is proposed. Mode II interlaminar fracture toughness can be estimated directly from load versus CSD diagram without measuring crack length. Applicability of proposed protocols are well confirmed by experiments of four kinds of carbon fiber composite systems, T300/2500, T800H/3631, APC-2 and Celion6000/PMR-15.