Stitched shape memory alloy wires enhance damage recovery in self-healing fibre-reinforced polymer composites

A major issue in composite technology is matrix micro-cracking due to low-velocity impact damage, which may severely limit service lifetimes of composite parts. In a novel approach, remarkable levels of healing of impact damage are obtained using shape memory alloy (SMA) wires to close longitudinal cracks in woven glass fibre-reinforced polymer plates with an epoxy-polycaprolactone (EP-PCL) matrix that shows dual-phase continuity. Thermal actuation of SMA wires stitched through the thickness of the stacked glass fibre plies introduces compressive loads to the cracks thanks to anchoring of the SMA loops at the fabric surfaces and debonding of the intervening threads, which prevents local deformation of the SMA, so that crack closure by about 200 μm is achievable. Concomitant expansion of the vascular network formed by the molten PCL fills the compressed cracks, resulting in highly effective healing on cooling, as demonstrated by C-scan images. Specimens stitched with SMA wires hence show almost complete healing, i.e. damage area recovery of 85%, after low-velocity impact at up to 17 J followed by heat treatment at 150 °C. This represents a 55% improvement over previous results for unstitched EP-PCL composites, and hence significantly greater degrees of healing than so far reported for this range of impact energies and this type of system

Healing of a glass fibre reinforced composite with a disulphide containing organic-inorganic epoxy matrix

We report the development of an intrinsic healing glass fibre reinforced polymer (GFRP) composite based on a disulphide-containing organic-inorganic thermoset matrix. Thermomechanical experiments showed that the newly developed matrix has a combination of a Young's modulus value in the range of (800-1200 MPa), the ability to multiple thermally induced healing delamination (70-85 degrees C), and processability by conventional vacuum infusion process that is not yet reported in literature. The composite mechanical properties and the extent of healing were determined by flexural, fracture and low-velocity impact testing. Small sized (cm(2)) damage, by increasing the healing pressure provided the location of the primary damage is concentrated within the matrix phase. The polymer matrix composite introduced here represents a significant step forward from the often mechanically inferior intrinsically self-healing composites towards structural self-healing composites. (C) 2017 Elsevier Ltd. All rights reserved

Healing of a glass fibre reinforced composite with a disulphide containing organic-inorganic epoxy matrix

We report the development of an intrinsic healing glass fibre reinforced polymer (GFRP) composite based on a disulphide-containing organic-inorganic thermoset matrix. Thermomechanical experiments showed that the newly developed matrix has a combination of a Young's modulus value in the range of (800–1200 MPa), the ability to multiple thermally induced healing delamination (70–85 °C), and processability by conventional vacuum infusion process that is not yet reported in literature. The composite mechanical properties and the extent of healing were determined by flexural, fracture and low-velocity impact testing. Small sized (<cm2) damage could be partially healed multiple times using a minimal healing pressure to ensure a good alignment of the damaged interfaces. The level of healing can be enhanced, even for large (>cm2) damage, by increasing the healing pressure provided the location of the primary damage is concentrated within the matrix phase. The polymer matrix composite introduced here represents a significant step forward from the often mechanically inferior intrinsically self-healing composites towards structural self-healing composites.Novel Aerospace Material

Out-of-plane permeability measurement for reinforcement textiles: A benchmark exercise

The out-of-plane permeability of two glass fibre fabrics was measured by 26 institutions using silicone oil as a test fluid. Participants in this study were free to select the test procedure, specimen dimensions and data analysis method, provided that testing was carried out at three target fibre volume fractions, 46 %, 50 % and 54 %. While results showed a variability of two orders of magnitude between participants, most values were within a significantly narrower band. A majority of participants used 1D saturated test method. A few selected 1D unsaturated and 3D unsaturated flow method which gave very similar results. Focusing on analysis of data and results of 1D saturated flow measurements, results are not conclusive, but they are consistent with number of layers in a specimen, fibre volume fraction, injection pressure and sealing of specimen edges all having an effect on the measured permeability. Specifying limits for these parameters is expected to result in reduced scatter in measured permeability.ISSN:1359-835XISSN:1878-584

Out-of-plane permeability measurement for reinforcement textiles: A benchmark exercise

The out-of-plane permeability of two glass fibre fabrics was measured by 26 institutions using silicone oil as a test fluid. Participants in this study were free to select the test procedure, specimen dimensions and data analysis method, provided that testing was carried out at three target fibre volume fractions, 46%, 50% and 54%. While results showed a variability of two orders of magnitude between participants, most values were within a significantly narrower band. A majority of participants used 1D saturated test method. A few selected 1D unsaturated and 3D unsaturated flow method which gave very similar results. Focusing on analysis of data and results of 1D saturated flow measurements, results are not conclusive, but they are consistent with number of layers in a specimen, fibre volume fraction, injection pressure and sealing of specimen edges all having an effect on the measured permeability. Specifying limits for these parameters is expected to result in reduced scatter in measured permeability