High-Performance Transparent Laminates Based on Highly Oriented Polyethylene Films

Advanced composite materials reinforced with high-performance fibers like carbon, glass, aramid, or ultra-high-molecular-weight polyethylene are widely used as lightweight materials in the fields of automotive, aerospace, sports, and protection. However, nearly always these composites are opaque and/or absorb light, which greatly limits their application in areas where high optical transparency is desired such as impact-resistant windows and visors. In this work, composite laminates that combine high optical clarity with high mechanical properties are reported for the first time using highly oriented high-density polyethylene (HDPE) films as the reinforcing phase. A high optical transparency with a far-field light transmittance of around 85% was achieved for four-layer HDPE-reinforced laminates sandwiched between glass or polycarbonate (PC) sheets with either unidirectional (UD) or bidirectional (BD) orientations. In combination with outer layers of glass or PC, the fabricated transparent composite laminates show high tensile strength and also high penetration energy absorption, outperforming existing transparent materials like glass, laminated glass, or PC. These transparent composites combine both high mechanical performance and high optical clarity, providing great potential for future applications in structural glazing, automotive glazing, safety shields, visors, and displays for portable electronics

Prepreg tack: A review of mechanisms, measurement, and manufacturing implication

The stickiness of prepregs (tack) is considered a decisive material property for the success of high‐quality composite manufacturing by automated lay‐up processes such as automated fiber placement (AFP) or automated tape laying (ATL). Adverse control of prepreg tack can easily result in laminate defects or machine breakdown, which are highly undesirable considering the tremendous machinery and material costs of these processes. Prepreg tack is governed by a complex interaction of adhesive and cohesive phenomena that are influenced by machine and environmental parameters of the production process as well as by intrinsic properties of the prepreg material itself. This review aims at providing a condensed insight into the current state of research on prepreg tack. Therefore, experimental studies including the discussion of utilized tack measurement methods as well as model approaches to prepreg tack are reviewed. The findings are discussed against the background of fundamental mechanisms, the strong interdependency of influencing parameters and the challenge of translating measured tack data into an enhanced AFP/ATL process stability by process adjustment