Matrix Resin Effects in Composite Delamination: Mode I Fracture Aspects

Hunston, Donald L.; Moulton, Richard J.; Johnston, Norman J.; Bascom, W. D.

doi:10.1520/stp24372s

Cited by 67 publications

(47 citation statements)

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“…On the other hand, the UD GFRP possessed a unidirectional lay-up, with some stitching to hold the fibres in place, which leads to a thinner and less contiguous matrix layer between the fibre plies. In agreement with previous work of Hunston et al [57], the presence of the resin-rich matrix layers in the CFRP and QI GFRP would be expected to typically lead to these materials possessing higher values of G C (composite) compared to the UD GFRP composite, as was indeed observed.…”

Section: Composite Versus Bulk Toughnesssupporting

confidence: 91%

The toughness of epoxy polymers and fibre composites modified with rubber microparticles and silica nanoparticles

et al. 2009

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The present paper investigates the effect of adding silica nanoparticles to an anhydride-cured epoxy polymer in bulk and when used as the matrix of carbon-and glass-fibre reinforced composites. The formation of 'hybrid' epoxy polymers, containing both silica nanoparticles and carboxyl-terminated butadiene-acrylonitrile (CTBN) rubber microparticles, is also discussed. The structure/property relationships are considered, with an emphasis on the toughness and the toughening mechanisms. The fracture energy of the bulk epoxy polymer was increased from 77 to 212 J/m 2 by the presence of 20 wt.% of silica nanoparticles. The observed toughening mechanisms that were operative were (a) plastic shear-yield bands, and (b) debonding of the matrix from the silica nanoparticles, followed by plastic void-growth of the epoxy. The largest increases in toughness observed were for the 'hybrid' materials. Here a maximum fracture energy of 965 J/m 2 was measured for a 'hybrid' epoxy polymer containing 9 wt.% and 15 wt.% of the rubber microparticles and silica nanoparticles, respectively. Most noteworthy was the observation that these increases in the toughness of the bulk polymers were found to be transferred to the fibre composites. Indeed, the interlaminar fracture energies for the fibre-composites materials were increased even further by a fibre-bridging toughening mechanism. The present work also extends an existing model to predict the toughening effect of the nanoparticles in a thermoset polymer. There was excellent agreement between the predictions and the experimental data for the epoxy containing the silica nanoparticles, and for epoxy polymers containing micrometre-sized glass particles. The latter, relatively large, glass particles were investigated to establish whether a 'nanoeffect', with respect to increasing the toughness of the epoxy bulk polymers, did indeed exist.

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Section: Composite Versus Bulk Toughnesssupporting

confidence: 91%

The toughness of epoxy polymers and fibre composites modified with rubber microparticles and silica nanoparticles

et al. 2009

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“…Up to this point where the fibres would restrict the development of the crack tip plastic zone, it is not surprising to find such a basic linear dependence between G Ic,init (comp) and G Ic (bulk) exists, since the toughness at crack initiation in the composite laminates is dependent on the matrix toughness, as no significant fibre-toughening effects have yet had a chance to develop. This effect of the fibres in a composite restricting the development of crack tip plasticity in the matrix between the fibres, and the transition from a 1:1 relationship between G Ic (comp) and G Ic (bulk) below 500 J/m 2 to a shallower gradient above 500 J/m 2 has been previously reported by Hunston et al [56] and subsequent work by Bradley [57] amongst others. In Fig.…”

Section: Toughening Mechanismssupporting

confidence: 60%

Toughened carbon fibre-reinforced polymer composites with nanoparticle-modified epoxy matrices

et al. 2016

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In the current work, the microstructure and fracture performance of carbon fibre-reinforced polymer (CFRP) composites based upon matrices of an anhydride-cured epoxy resin (formulated with a reactive diluent), and containing silica nanoparticles and/or polysiloxane core-shell rubber (CSR) nanoparticles, were investigated. Double cantilever beam tests were performed in order to determine the interlaminar fracture energy of the CFRP composites, while the single-edge-notched bend specimen was employed to evaluate the fracture energy of the bulk polymers. The fracture energy of the bulk epoxy polymers increased from 173 J/m 2 for the unmodified polymer to a maximum of 1237 J/ m 2 with the addition of 16 wt% of CSR nanoparticles. The toughening mechanisms were identified as (a) localised plastic shear yielding and (b) cavitation of the CSR particles followed by plastic void growth of the matrix. The steady-state propagation value of the interlaminar fracture energy of the CFRP composites increased with increasing nanoparticle concentration, from 1246 J/m 2 for the unmodified epoxy matrix to a maximum of 1851 J/m 2 with 4 wt% of silica nanoparticles and 8 wt% of CSR nanoparticles. Crack growth in the CFRP composites was dominated by fibre-bridging toughening mechanisms. The efficiency of the transfer of toughness from the bulk polymers to the carbon fibre composites was considered. The measured fracture energy of both bulk and composite materials decreased at a test temperature of -80°C, compared with room temperature, i.e. 20°C. Nevertheless, the toughening effects of both the silica and CSR nanoparticles on the bulk epoxy polymers and the CFRP composites, compared with the unmodified epoxy polymers, were still evident even at the lower temperature. Indeed, the toughening effect of the silica nanoparticles was greater at -80°C than at room temperature.

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“…12, it is clear that the plastic zone sizes at higher concentrations are large in comparison with the inter-fibre distances, which are in the order of 10 lm. This means that the plastic zone will be inhibited from growing by the presence of the stiff fibres and explains the discrepancy between the CFRP initiation and bulk fracture energies [20,53]. Hunston et al [20] showed that brittle polymers with G IC values less than 200 J/m 2 benefit the most from fibre reinforcement.…”

Section: Fracture Toughnessmentioning

confidence: 99%

“…This means that the plastic zone will be inhibited from growing by the presence of the stiff fibres and explains the discrepancy between the CFRP initiation and bulk fracture energies [20,53]. Hunston et al [20] showed that brittle polymers with G IC values less than 200 J/m 2 benefit the most from fibre reinforcement. In their tests, the tough matrices had incomplete transfer of toughness attributed to the crack tip deformation zone restricted by the closely packed fibres.…”

Section: Fracture Toughnessmentioning

confidence: 99%

“…This poses a problem as fibre composite manufacturers are increasingly moving towards infusion processes to reduce costs, and hence a low resin viscosity is required. Even if the toughness of the epoxy is increased in the bulk, this toughness does not necessarily transfer to high composite toughness due to the fibres restricting the crack tip deformation zone [20]. The issues of reduced modulus and agglomeration with certain modifiers are also a concern.…”

Section: Introductionmentioning

confidence: 99%

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The microstructure and fracture performance of styrene–butadiene–methylmethacrylate block copolymer-modified epoxy polymers

Chong

Taylor

2013

J Mater Sci

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The microstructure and fracture performance of an anhydride-cured epoxy polymer modified with two poly(styrene)-b-1,4-poly(butadiene)-b-poly(methyl methacrylate) (SBM) block copolymers were investigated in bulk form, and when used as the matrix material in carbon fibre reinforced composites. The 'E21' SBM block copolymer has a higher butadiene content and molecular weight than the 'E41'. A network of aggregated spherical micelles was observed for the E21 SBM modified epoxy, which became increasingly interconnected as the SBM content was increased. A steady increase in the fracture energy was measured with increasing E21 content, from 96 to 511 J/m 2 for 15 wt% of E21. Well-dispersed 'raspberry'-like SBM particles, with a sphere-on-sphere morphology of a poly(styrene) core covered with poly(butadiene) particles, in an epoxy matrix were obtained for loadings up to 7.5 wt% of E41 SBM. This changed to a partially phase-inverted structure at higher E41 contents, accompanied by a significant jump in the measured fracture energy to 1032 J/m 2 at 15 wt% of E41. The glass transition temperatures remained unchanged with the addition of SBM, indicating a complete phase separation. Electron microscopy and cross polarised transmission optical microscopy revealed localised shear band yielding, debonding and void growth as the main toughening mechanisms. Significant improvements in fracture energy were not observed in the fibre composites, indicating poor toughness transfer from the bulk to the composite. The fibre bridging observed for the unmodified epoxy matrix was reduced due to better fibre-matrix adhesion. The size of the crack tip deformation zone in the composites was restricted by the fibres, hence reducing the measured fracture energy compared to the bulk for the toughest matrix materials.

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Matrix Resin Effects in Composite Delamination: Mode I Fracture Aspects

Cited by 67 publications

References 0 publications

The toughness of epoxy polymers and fibre composites modified with rubber microparticles and silica nanoparticles

The toughness of epoxy polymers and fibre composites modified with rubber microparticles and silica nanoparticles

Toughened carbon fibre-reinforced polymer composites with nanoparticle-modified epoxy matrices

The microstructure and fracture performance of styrene–butadiene–methylmethacrylate block copolymer-modified epoxy polymers

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