Retention of Mechanical Properties After Water Immersion for Glass-Fibre Polymer Composite Laminates with Thermoset & Thermoplastic Infusible Resins

In this work, we conducted an extensive comparative study of the water absorption behavior and retention of mechanical properties of a group of GRP composite laminates manufactured with a range of infusible thermosetting and thermoplastics resins. All laminates were manufactured by Vacuum-Assisted Resin Transfer Moulding (VARTM; the most relevant manufacturing technique in shipbuilding) with a range of state-of-the-art thermosetting resins (Urethane acrylate Crestapol 1210, Epoxy SR1125, Bio-epoxy Supersap CLR, Phenolic Cellobond J2027X) and a novel infusible acrylic thermoplastic resin (Acrylic Elium 150). The reinforcement of choice for each laminate was a unidirectional glass fabric of 996 gsm. Sample preparation for water immersion studies was according to ASTM D5229. This study was part of a comprehensive down-selection of commercially available resins in terms of their suitability for shipbuilding applications, as part of the EU H2020 project FIBRESHIP2 .  A selection of relevant properties of the laminates with different resin systems is presented in this paper including fibre volume fraction, apparent interlaminar shear strength (dry and wet condition), flexural strength (dry and wet condition) and flexural modulus (dry and wet condition)

Bio-based epoxy resin systems as potential alternatives to petroleum based epoxy matrices in marine fibre-reinforced polymer composites

Fibre-reinforced polymers (FRP) are extensively used in the marine industry for the manufacture of lightweight hull structures for vessels up to 50m in length, and for secondary structures and components in larger vessels. The main benefits resulting in the application of FRP in shipbuilding include: significant weight reduction resulting in substantial fuel saving, increase in cargo capacity and subsequent reduction of greenhouse gas emissions, improved life cycle performance and reduced maintenance costs due to corrosion resistance. As the use of thermoset polymers in shipbuilding increases, so too does the interest in finding suitable alternatives to the use of petroleum-based raw materials. Much work has been published on bio-based epoxy resin systems from natural raw materials, such as vegetable oils, however, the mechanical performance of the bio-based resin systems in comparison to equivalent petroleum-based systems is not widely documented. This research focusses on the comparison of petroleum-based and bio-based two-part commercial epoxy resin systems to manufacture glass fibre reinforced polymers (GFRP) for marine applications. Laminates were manufactured using the Vacuum Assisted Resin Transfer Moulding (VARTM) manufacturing process. Specimens were mechanically characterised in order to evaluate fibre volume fraction, density, apparent inter-laminar shear strength, flexural modulus and strength. The effect of water ingress on the mechanical properties of laminates was also studied by soaking samples in water at 35°C for 28 days. Specimen quality and fracture surfaces were assessed using optical and scanning electron microscopy. Initial results have shown that the average apparent inter-laminar shear strength of the petroleum-based samples was almost identical to the bio-based samples (within 1%), while the flexural strength and modulus of the petroleum-based samples was only 6% and 7% higher than the bio-based samples. Despite the comparatively good mechanical performance of the bio-based laminate, the high viscosity of the resin resulted in higher infusion temperatures and longer infusion times than for the petroleum-based epoxy

Numerical and experimental procedure for material calibration using the serial/parallel mixing theory, to analyze different composite failure modes

This work proposes a calibration procedure to obtain the material parameters required by the Serial/Parallel Mixing Theory for the analysis of composites. A set of experimental tests are defined to obtain the main composite failure modes. Then, it is proposed to calculate the parameters required by the formulation using the experimental results. The procedure proposed is validated by comparing the numerical results, with those obtained from the experimental campaign. This comparison shows that the Serial/Parallel mixing theory is capable of representing the failure modes of the composite for different loading scenarios as well as the material toughnes

Development of the Usability of Sleep Apnea Equipment – Positive Airway Pressure (USE-PAP) questionnaire

BACKGROUND: A growing number of positive airway pressure (PAP) device users will develop physical/sensory impairments such as arthritis. For these individuals, the usability of their PAP devices (eg, efficiency and satisfaction) may impact the frequency and safety of device usage. Questionnaires to assess PAP usability are unavailable; therefore, we developed the Usability of Sleep Apnea Equipment – Positive Airway Pressure (USE-PAP) questionnaire. METHODS: Questionnaire development included in-depth interviews to identify relevant content areas, a technical advisory panel to review/edit items, cognitive interviews to refine items, and a cross-sectional survey of Veterans Affairs sleep clinic patients assessing PAP device usability overall (one multi-item scale), usability of PAP components (multi-item scales for machine controls, mask/headgear, tubing, and humidifier), frequency of usability-related issues (one multi-item scale), PAP device characteristics, and demographics. RESULTS: After conducting 19 in-depth interviews, a panel meeting, and 10 cognitive interviews, we administered the survey to 100 PAP device users (67% ≥60 years; 90% male). The items assessing machine control usability received the least favorable ratings. Twenty percent of respondents reported difficulty getting equipment ready for use, and 33 percent had difficulty cleaning equipment. The six multi-item scales had excellent internal consistency reliability (alpha ≥0.84) and item–rest correlations (≥0.39). CONCLUSIONS: This study provides initial support for the USE-PAP for measuring PAP device usability. Studies that include large samples are needed to further evaluate the psychometric properties of the USE-PAP. In addition, comparisons of USE-PAP responses with direct observations of PAP-related tasks and objectively measured PAP adherence are needed to fully evaluate the questionnaire