Embedding Vascular Networks into Thick Composite Parts as Thermal Management Tools for Cure Processing: Experimentally Proving its Feasibility. Paper presented at 2018 International Conference on Manufacturing of Advanced Composites (ICMAC), Nottingham, United Kingdom (original) (raw)
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Journal of Composites
Material behaviour of structural components is very important to understand. In fibre reinforced polymer composite materials, this is more difficult in comparison to isotropic materials as they are made up of two constituents: the fibre and the matrix. For aerospace composite materials, the matrix is usually an epoxy resin that cures at a high temperature. This curing regime is known to introduce residual stresses to the composite material as it cools from the high cure temperature. However, how to consider these residual stresses in a structural analysis is still widely debated. In this paper, the authors investigated the offset of thermal residual strains introduced by the cure regime by the swelling of the composite when exposed to moisture.
Stress Relaxation of Thermosetting Prepreg Composites During Cure
This paper presents the experimental results for time-temperature dependent viscoelastic behavior and cure kinetics of two commercial carbon fiber-epoxy prepregs, Cytec IM7/977-2 unidirectional tape (UD) and Cytec IM7/977-2 plain weave fabric (PW). An in-depth study on the oscillatory and transient rheological behavior of prepreg composites is conducted using a dynamic mechanical analyzer (DMA) and the study of cure kinetics is conducted using a differential scanning calorimeter (DSC). A novel experimental methodology is proposed to describe the stress relaxation behavior of prepreg composites during cure. Time- and cure-dependent stress relaxation behavior of prepreg composites is studied in three in-plane directions: 0, 45, and 90 degrees of the laminates. Several other factors, such as the mismatch of fiber orientation of adjoining plies, stacking sequence of the laminate, and relative position of the plies with respect to the neutral axis are considered to study the stress relaxation behavior during cure. The study shows that the relaxation modulus during cure is case dependent. Moreover, when comparing the performance between UD and PW prepregs, it shows that the PW laminate is capable of releasing more stress than the UD laminate.