Assessment of cure residual strains through the thickness of carbon-epoxy laminates using FBGs, Part I: Elementary specimen

M. Mulle; F. Collombet; P. Olivier; Y. H. Grunevald

doi:10.1016/j.compositesa.2008.10.008

Assessment of cure residual strains through the thickness of carbon-epoxy laminates using FBGs, Part I: Elementary specimen

M. Mulle^*, F. Collombet, P. Olivier, Y. H. Grunevald

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

95 Scopus citations

Abstract

Variability of thermo-mechanical properties within a composite part is a well known issue. It is problematic at the early stage of structural design. This variability being generated during the processing phases, the characterisation of the initial state of a structure becomes a crucial operation. A first step to this objective is presented in this paper. It deals with the assessment of autoclave cure induced strains in carbon epoxy laminates. Distribution and amplitude are considered through the thickness of carbon/epoxy elementary and technological specimens thanks to a series of FBGs embedded at different levels of the ply stack. Part I of this work concerns the analysis of unidirectional reinforced specimens. It begins with an overview of the various phenomena that cause the presence of residual stresses after cure and how they can be measured in experiments. Their development being closely related to the rheology of the matrix, an analysis of the M21 resin is given and assumptions are made to justify the following assessment procedures. A discussion leads to select the onset of gelation as the key point to start measuring residual cure stresses. The autoclave cure monitoring of the [0₈] specimen is then carried out and analyzed. Depending on their location through the laminate thickness, the FBG sensors give different information highlighting the effects of interaction between the laminate and the tool/plate.

Original language	English (US)
Pages (from-to)	94-104
Number of pages	11
Journal	Composites Part A: Applied Science and Manufacturing
Volume	40
Issue number	1
DOIs	https://doi.org/10.1016/j.compositesa.2008.10.008
State	Published - Jan 2009
Externally published	Yes

Bibliographical note

Funding Information:
The authors wish to thank DDL Consultants Company for its technical support and for financing a thesis concerning this project, the DGA (Direction Générale de l’Armement) for its financial support through the upstream program AMERICO and Hexcel Composites Company for providing us with HexPly ® prepreg.

Keywords

A. Laminates
B. Residual/internal stress
D. Process monitoring
E. Autoclave

ASJC Scopus subject areas

Ceramics and Composites
Mechanics of Materials

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10.1016/j.compositesa.2008.10.008

Cite this

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title = "Assessment of cure residual strains through the thickness of carbon-epoxy laminates using FBGs, Part I: Elementary specimen",

abstract = "Variability of thermo-mechanical properties within a composite part is a well known issue. It is problematic at the early stage of structural design. This variability being generated during the processing phases, the characterisation of the initial state of a structure becomes a crucial operation. A first step to this objective is presented in this paper. It deals with the assessment of autoclave cure induced strains in carbon epoxy laminates. Distribution and amplitude are considered through the thickness of carbon/epoxy elementary and technological specimens thanks to a series of FBGs embedded at different levels of the ply stack. Part I of this work concerns the analysis of unidirectional reinforced specimens. It begins with an overview of the various phenomena that cause the presence of residual stresses after cure and how they can be measured in experiments. Their development being closely related to the rheology of the matrix, an analysis of the M21 resin is given and assumptions are made to justify the following assessment procedures. A discussion leads to select the onset of gelation as the key point to start measuring residual cure stresses. The autoclave cure monitoring of the [08] specimen is then carried out and analyzed. Depending on their location through the laminate thickness, the FBG sensors give different information highlighting the effects of interaction between the laminate and the tool/plate.",

keywords = "A. Laminates, B. Residual/internal stress, D. Process monitoring, E. Autoclave",

author = "M. Mulle and F. Collombet and P. Olivier and Grunevald, {Y. H.}",

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Assessment of cure residual strains through the thickness of carbon-epoxy laminates using FBGs, Part I: Elementary specimen

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

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