### Abstract

A detailed investigation has been carried out to determine the effect of local fiber array irregularities and controlling fiber distribution parameters on microscopic interfacial normal stress states for transversely-loaded unidirectional carbon fiber (CF)/epoxy composites. Linear elastic finite element analyses were carried out for two-dimensional image-based models composed of about 70 fibers. The relationship between the geometrical distribution of two adjacent fibers and the interfacial normal stresses (INSs) is investigated for all fibers in different image-based models. Three boundary conditions for loading were selected: Case A involved cooling from the curing temperature (the difference in temperature was -155 K); Case B involved transverse loading of 75 MPa chosen as an example of macroscopic transverse fracture strength; and Case C involved both cooling from the curing temperature and transverse loading of 75 MPa. High compressive INSs due to the difference in the coefficients of thermal expansion are observed at the location of the shortest interfiber distance for Case A (cooling). High tensile INSs are observed at the location of the shortest interfiber distance and where the fiber alignment angle to the loading direction is small for Case B (loading). For Case C (cooling and loading), the high thermal residual compressive INSs and the high mechanical tensile INSs compensate each other, and the INSs at a short interfiber distance are much lower than those for Case B. These results clearly indicate the importance of the contribution of the thermal residual stresses to the transverse tensile failure initiation of CF/epoxy laminates.

Original language | English |
---|---|

Pages (from-to) | 1726-1734 |

Number of pages | 9 |

Journal | Composites Science and Technology |

Volume | 69 |

Issue number | 11-12 |

DOIs | |

State | Published - 2009 Sep 1 |

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### Keywords

- B. Debonding
- C. Finite element analysis (FEA)
- C. Residual stress
- C. Transverse cracking
- Micromechanics

### Cite this

*Composites Science and Technology*,

*69*(11-12), 1726-1734. https://doi.org/10.1016/j.compscitech.2008.08.032

}

*Composites Science and Technology*, vol. 69, no. 11-12, pp. 1726-1734. https://doi.org/10.1016/j.compscitech.2008.08.032

**Effect of fiber array irregularities on microscopic interfacial normal stress states of transversely loaded UD-CFRP from viewpoint of failure initiation.** / Hojo, Masaki; Mizuno, Masaaki; Hobbiebrunken, Thomas; Adachi, Taiji; Tanaka, Mototsugu; Ha, Sung Kyu.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Effect of fiber array irregularities on microscopic interfacial normal stress states of transversely loaded UD-CFRP from viewpoint of failure initiation

AU - Hojo, Masaki

AU - Mizuno, Masaaki

AU - Hobbiebrunken, Thomas

AU - Adachi, Taiji

AU - Tanaka, Mototsugu

AU - Ha, Sung Kyu

PY - 2009/9/1

Y1 - 2009/9/1

N2 - A detailed investigation has been carried out to determine the effect of local fiber array irregularities and controlling fiber distribution parameters on microscopic interfacial normal stress states for transversely-loaded unidirectional carbon fiber (CF)/epoxy composites. Linear elastic finite element analyses were carried out for two-dimensional image-based models composed of about 70 fibers. The relationship between the geometrical distribution of two adjacent fibers and the interfacial normal stresses (INSs) is investigated for all fibers in different image-based models. Three boundary conditions for loading were selected: Case A involved cooling from the curing temperature (the difference in temperature was -155 K); Case B involved transverse loading of 75 MPa chosen as an example of macroscopic transverse fracture strength; and Case C involved both cooling from the curing temperature and transverse loading of 75 MPa. High compressive INSs due to the difference in the coefficients of thermal expansion are observed at the location of the shortest interfiber distance for Case A (cooling). High tensile INSs are observed at the location of the shortest interfiber distance and where the fiber alignment angle to the loading direction is small for Case B (loading). For Case C (cooling and loading), the high thermal residual compressive INSs and the high mechanical tensile INSs compensate each other, and the INSs at a short interfiber distance are much lower than those for Case B. These results clearly indicate the importance of the contribution of the thermal residual stresses to the transverse tensile failure initiation of CF/epoxy laminates.

AB - A detailed investigation has been carried out to determine the effect of local fiber array irregularities and controlling fiber distribution parameters on microscopic interfacial normal stress states for transversely-loaded unidirectional carbon fiber (CF)/epoxy composites. Linear elastic finite element analyses were carried out for two-dimensional image-based models composed of about 70 fibers. The relationship between the geometrical distribution of two adjacent fibers and the interfacial normal stresses (INSs) is investigated for all fibers in different image-based models. Three boundary conditions for loading were selected: Case A involved cooling from the curing temperature (the difference in temperature was -155 K); Case B involved transverse loading of 75 MPa chosen as an example of macroscopic transverse fracture strength; and Case C involved both cooling from the curing temperature and transverse loading of 75 MPa. High compressive INSs due to the difference in the coefficients of thermal expansion are observed at the location of the shortest interfiber distance for Case A (cooling). High tensile INSs are observed at the location of the shortest interfiber distance and where the fiber alignment angle to the loading direction is small for Case B (loading). For Case C (cooling and loading), the high thermal residual compressive INSs and the high mechanical tensile INSs compensate each other, and the INSs at a short interfiber distance are much lower than those for Case B. These results clearly indicate the importance of the contribution of the thermal residual stresses to the transverse tensile failure initiation of CF/epoxy laminates.

KW - B. Debonding

KW - C. Finite element analysis (FEA)

KW - C. Residual stress

KW - C. Transverse cracking

KW - Micromechanics

UR - http://www.scopus.com/inward/record.url?scp=67649126253&partnerID=8YFLogxK

U2 - 10.1016/j.compscitech.2008.08.032

DO - 10.1016/j.compscitech.2008.08.032

M3 - Article

AN - SCOPUS:67649126253

VL - 69

SP - 1726

EP - 1734

JO - Composites Science and Technology

JF - Composites Science and Technology

SN - 0266-3538

IS - 11-12

ER -