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This article presents an alternative manufacturing process for unidirectional tape natural fiber Polypropylene with Maleic Anhydride grafted PolyPropylene (PP + MAPP) thermoplastic composites that could enable large high performance parts to be built, while being recyclable at end of life. The performance target is flax/epoxy composites that are currently manufactured in shipyard. A parametric analysis (time and temperature) of vacuum-bag-only molding of flax unidirectional tapes-reinforced PP + MAPP matrix is conducted to find the best configuration regarding the final composite tensile properties, as no standard procedure exists. The physical phenomena induced by temperature, water sorption/desorption, and pressure during the manufacturing step are investigated. The best parameters for temperature and time are found to be at 180 °C during 45 min, resulting in a fiber volume fraction of 42.2 ± 1.5%, and between 1.9 ± 0.7% and 8.2 ± 1.8% of porosity, depending on the method of determination. Interestingly, tensile properties are in the same order of magnitude as conventionally manufactured continuous flax fiber-reinforced thermoset or thermoplastic composites. The article ends with a discussion of the accessibility and technical concerns of vacuum-bag-only molding, material selection, design, mechanical performance, and end of life.

Ocean racing yachts are mainly manufactured from carbon/epoxy composites similar to those used by the aeronautical industry but, with some exceptions such as masts, these structures are not produced in autoclaves. This leads to the presence of higher porosity levels. This paper will first present the different types of porosity found in traditional racing yacht structures. Difficulties in evaluating defect levels will then be discussed and published work characterizing the influence of defects will be reviewed. Current developments to improve racing yacht composite quality such as thin ply technology, out-of-autoclave processing and automated fibre placement will then be described, and their implications for porosity will be discussed.

This paper describes results from tests to examine the influence of through-thickness pinning on in-plane shear behaviour, measured by tensile loading of +/- 45A degrees specimens. Samples were produced by both aeronautical and marine manufacturing processes. As few previous studies have investigated pinning of marine composites these were also subjected to out-of-plane shear delamination tests. For both carbon/epoxy laminates the pins reduce the apparent in-plane shear modulus and strength. Pins modify the strain field measured by full-field image analysis, and slow damage development. A new damage mechanism, transverse pin cracking, was observed.

Nowadays, the ecological footprint of a material is becoming tremendously important. The Poly l-Lactide Acid (PLLA) matrix composites reinforced by randomly scattered flax fibres have mechanical properties similar to polyester/glass composites [1], lower environmental impacts and can be compost at the end of their lives. In this study, the mechanical characterization of biocomposites has been pushed further with the determination of the compressive and tensile properties. Furthermore, the mechanical properties of single flax fibres have been measured and implemented in a micro-mechanical estimation of the composite elastic modulus. Tensile and compressive stiffness determined by the mechanical analyses show very good correlations with the mathematical estimation.

Delays between lamination of structures and secondary bonding are common in boatbuilding. This paper presents results from an experimental study of the influence of manufacturing procedure on the bond strength of unidirectional glass fibre reinforced polyester composites. Continuously laminated panels are taken as the reference and compared with panels overlaminated after delays of one week with and without peel ply protection. A standard polyester and low styrene DCPD formulation were tested. ILSS testing is shown not to be sensitive to the procedure but crack propagation tests show very large differences in mode I fracture energy. A small drop in fracture energy is measured for a delay of one week between lamination of the first and second halves of the specimen without peel ply. When a nylon peel ply is applied and removed just before overlamination of the second half very large drops in propagation energy, around 75%, are noted for both materials. Surface abrasion after peel ply removal enables fracture energy to be recovered for the standard polyester and to a lesser extent for the low styrene DCPD composite.

Glass fibre reinforced polyester composites are used extensively for hulls and decks of pleasure boats. Boat-builders must optimise manufacturing technology, not only with respect to mechanical properties but also limiting volatile organic compounds (VOC) emissions. One way to achieve this is through modified polyester resin formulations such as low styrene content, low styrene emission or combinations of these. The resin matrix selection procedure is based on design specification (mechanical behaviour) but also manufacturing requirements and cost considerations. For this application post-cure is rarely used so it is important to optimise curing conditions. In this study the influence of the curing cycle on mechanical properties was examined first for two polyester resins. Then for one cycle (16 h at 40 degrees C) the properties of eight resins have been determined. Significant differences in failure strain are observed, from 0.9% to 3.3%. The resins with improved VOC performance are the most brittle. The transverse tensile behaviour of these resins in composites with unidirectional glass fibre reinforcement and the limit of linearity for composites with glass mat both depend on these failure strains. These results are discussed in terms of admissible composite strains for boat design.

The need for improved performance and the development of new composite manufacturing methods require a better understanding of the role of interface phenomena in the mechanical behaviour of these materials. The influence of the cure cycle on the bulk and surface properties of the matrix resin, and of composites based on polyester and epoxy resins reinforced with glass fibres has been studied. While the mechanical properties of the epoxy vary with cure temperature the surface tension is not affected. The increase in interfacial shear strength and interlaminar shear strength with increased cure temperature cannot be simply explained by the wetting of the fibres by the matrix. The importance of thermal stresses, generated at the interface by resin shrinkage and differences in thermal expansion, for the mechanical behaviour of the composite are demonstrated.

This paper gives an overview of the characterization of the interlaminar properties of composites used for marine structures. Composites to be used in marine applications have particular requirements due to their environment, their large dimensions, mechanical loading and cost constraints. Under certain loading conditions (insert loading, impact) there is a risk of delamination as interlaminar strength of these materials is limited. This paper presents an overview of the tests available to measure delamination resistance. The parameters which influence this property, including the constituents (fibre, matrix, interface), specimen geometry, fabrication route and the resulting defects, and aging are reviewed here.