Fatigue Life Prediction for Transverse Crack Initiation of CFRP Cross-Ply and Quasi-Isotropic Laminates.

Atsushi Hosoi,Hiroyuki Kawada

doi:10.3390/ma11071182

Abstract

Carbon fiber reinforced plastic (CFRP) laminates are used as main structural members in many applications. Transverse cracks that form in 90° layers of CFRP laminates are mostly initial damage in the case where tensile loading is vertically applied to the 90° layers of CFRP laminates, and they are the origin of more serious damage of delamination and fiber breakage. It is thus important to predict quantitatively the transverse crack initiation of CFRP laminates subjected to cyclic loading to ensure the long-term reliability of the laminates. The initiation and multiplication behaviors of transverse cracks strongly depend on the laminate configuration, thickness, and thermal residual stress. Therefore, a model based on the Walker model was proposed to predict transverse crack initiation in CFRP cross-ply and quasi-isotropic laminates under cyclic loading in the present study. The usefulness of the proposed model was verified with 10 different CFRP laminates formed from four different prepregs with epoxy resin matrices. The analysis results were in good agreement with experimental results. The fatigue life was expressed with three constants, which related to the fatigue strength reduction, the normalized fatigue strength at N = 1 cycle, and the contribution of stress amplitude to the fatigue life, and they are independent of the laminate configuration.

Highlights

Carbon fiber reinforced plastic (CFRP) laminates are used as the main structural members of aircraft, automobiles, wind turbine blades, tidal turbine blades, and jet-engine fan blades.The damage tolerance strain of CFRP laminates in the design of airplanes is determined based on the compression-after-impact strength
The analytical results obtained using the proposed model are in good agreement with experimental results. These findings indicate that the proposed model successfully considers the the experimental results. These findings indicate that the proposed model successfully considers the effects of the stress ratio, laminate thickness, and laminate configuration on transverse crack initiation effects of the stress ratio, laminate thickness, and laminate configuration on transverse crack initiation under fatigue loading
CFRP laminates under fatigue loading based on the Walker model

Summary

Introduction

Carbon fiber reinforced plastic (CFRP) laminates are used as the main structural members of aircraft, automobiles, wind turbine blades, tidal turbine blades, and jet-engine fan blades.The damage tolerance strain of CFRP laminates in the design of airplanes is determined based on the compression-after-impact strength. Carbon fiber reinforced plastic (CFRP) laminates are used as the main structural members of aircraft, automobiles, wind turbine blades, tidal turbine blades, and jet-engine fan blades. The main forms of the damage mechanism of CFRP laminates are fiber-matrix debonding, intralaminar and interlaminar matrix cracks, and fiber breakage, which propagate while interacting with each other, resulting in the rupture of the laminates [1], and many fatigue life prediction models, which are based on cumulative damage theory [2], strain energy density [3], statistical approach [4], constant fatigue diagram [5], and damage mechanics [6], have been proposed so far. It is essential to evaluate quantitatively the fatigue life to transverse crack initiation of CFRP laminates for the use of the laminates as structural members

Methods

Results

Discussion

Conclusion