Cutting Procedures, Tensile Testing, and Ageing of Flexible Unidirectional Composite Laminates

Engelbrecht-Wiggans, Amy; Krishnamurthy, Ajay; Burni, Faraz; Osborn, William; Forster, Amanda L.

doi:10.3791/58991

Cited by 2 publications

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“…Since the degradation is more prominent in the slower loading rates in the first 100 d than it is for the higher loading rates in the same time period, this leads to the conclusion that there is degradation in the binder resin. In fact, in [35] we included an SEM image showing that the binder resin on the outside of the laminate is disappearing with ageing. After 100 d of ageing, the PPTA fibers may begin to degrade, which could potentially explain why the loading rate versus degradation trend does not continue after 100 d. The specimens tested at the slowest loading rates remain the weakest, even after 100 d, as can be seen in Figure 4.…”

Section: Discussionmentioning

confidence: 99%

“…A non-contacting video extensometer was used to measure strain at three different locations along each specimen's width, and these three strain values were averaged to determine the failure strain. Further details, and rationales, on the specimen ageing, cutting and testing procedure are described in [35]. Scanning Electron Microscopy (SEM) imaging of the unaged fiber laminate was carried out after depositing a nominal (3 nm -5 nm) Au/Pd coating on a small laminate cross-section (less than 0.5 mm by 0.5 mm by 1 mm).…”

Section: Methodsmentioning

confidence: 99%

“…The 'warp' direction is that perpendicular to the axis of the cylindrically-shaped bolt on which the material is rolled, while the 'weft' direction is parallel to the bolt's axis. Clarifying figures to indicate specimen orientation and warp and weft terms are provided in [35].…”

Section: Methodsmentioning

confidence: 99%

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Tensile testing of aged flexible unidirectional composite laminates for body armor

et al. 2019

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Flexible Unidirectional (UD) composite laminates are commonly being used for ballistic-resistant body armor. These laminates comprise UD layers, each constructed by laminating thin layers of high-performance fibers held in place using very low modulus binder resins, with the fibers in each layer oriented parallel to each other. As these materials are used in body armor, it is important to investigate their long-term reliability, particularly with regards to exposure to temperature and humidity as these are known causes of degradation in other commonly used body armor materials. This work investigates the tensile behavior of a poly(p-phenylene terephthalamide), or PPTA flexible UD laminate aged for up to 150 d at accelerated conditions of 70 °C and 76 % relative humidity (RH). Tests were performed at three different crosshead displacement rates and three different gauge lengths. The effect of ageing on the mechanical properties of the material resulted in less than 10 % degradation in tensile strength, with a more significant reduction in longer specimens when tested at slower rates.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Tensile testing of aged flexible unidirectional composite laminates for body armor

et al. 2019

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“…Specimens were cut using a medical scalpel and a straight edge on a self-healing cutting mat, taking care to align the specimens with the fiber direction. The specimen preparation procedure is fully described in [ 33 ]. Specimens were cut with their length nominally perpendicular to the axis of the material roll, i.e., such that they would be along the warp fibers if the material was woven.…”

Section: Methodsmentioning

confidence: 99%

“…These three strain values were averaged to determine the failure strain. Further details and rationales on the specimen aging, cutting, and testing procedure are described in [ 33 ]. Figure 4 shows a specimen before and after mechanical testing.…”

Section: Methodsmentioning

confidence: 99%

Effect of Aging on Unidirectional Composite Laminate Polyethylene for Body Armor

et al. 2023

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The construction of ballistic-resistant body armor is experiencing an increasing use of flexible unidirectional (UD) composite laminates that comprise multiple layers. Each UD layer contains hexagonally packed high-performance fibers with a very low modulus matrix (sometimes referred to as binder resins). Laminates are then made from orthogonal stacks of these layers, and these laminate-based armor packages offer significant performance advantages over standard woven materials. When designing any armor system, the long-term reliability of the armor materials is critical, particularly with regard to stability with exposure to temperature and humidity, as these are known causes of degradation in commonly used body armor materials. To better inform future armor designers, this work investigates the tensile behavior of an ultra-high molar mass polyethylene (UHMMPE) flexible UD laminate that was aged for at least 350 d at two accelerated conditions: 70 °C at 76% relative humidity (RH) and 70 °C in a desiccator. Tensile tests were performed at two different loading rates. The mechanical properties of the material after ageing demonstrated less than 10% degradation in tensile strength, indicating high reliability for armor made from this material.

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Cutting Procedures, Tensile Testing, and Ageing of Flexible Unidirectional Composite Laminates

Cited by 2 publications

References 0 publications

Tensile testing of aged flexible unidirectional composite laminates for body armor

Tensile testing of aged flexible unidirectional composite laminates for body armor

Effect of Aging on Unidirectional Composite Laminate Polyethylene for Body Armor

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