Energetic materials are conventionally ignited by the application of heat to some part of an explosive target. This is most often provided by a flame or by electrical heating using a resistive wire. The material responds by thermally heating and starting a burning zone, which spreads out from the ignition point generating gas. In some cases this zone can accelerate (due to the effect of this gas) into a reactive shock wave, termed detonation. Lasers are used in a variety of applications to thermal heat a range of materials, and thus seem an obvious candidate to trigger chemical reaction in energetic ones. A light pulse offers several advantages over an electrical one, since it may be delivered down a path both immune to electrical effects and chemically stable. Thus, the triggering of safety apparatus (such as the firing of bolts on aircraft exits) represents a major thrust in the development of laser–triggered explosive devices. The energy of the pulse may be used in one of two ways to achieve these effects. In the first, the laser is shone directly upon the chemical medium, which absorbs the light at discrete wavelengths. In the second, it is used to vaporize a metallic flyer that is launched to impact on a target creating a high–pressure zone. Either mechanism starts the required reaction. However, when the pulse is delivered directly to the material, detonation is found to proceed immediately with no transition via burning. This makes the process inexplicable using present concepts. This review will address a range of the experiments conducted and theories developed for this novel field. However, it should be emphasized that the fundamental mechanisms remain to be fully explained making the application both academically stimulating as well as industrially important.

On the laser ignition and initiation of explosives

micro/nano-energetic materials(NEM) have been highly attended by many researchers for improved performance in terms of safety, energy release, ignition, and mechanical properties. Multifarious preparation techniques and methods have been developed, solvent- nonsolvent crystallization method is an important route, this article reviews the recent progress of NEM preparation research through solvent- nonsolvent crystallization method, various factors for affecting NEM size and shape are provided, such as mixed mode, solvent, liquid concentration and crystallization temperature, anti-aggregation measures.

https://iopscience.iop.org/article/10.1088/1757-899X/382/2/022030/pdf

Preparation Progress of micro/nano-energetic materials

The large area and short‐pulse shock initiation experiments on the plastic bonded mixed explosive of TATB(80%) and HMX(15%) have been performed with an electric gun where a Mylar flyer of 10–19 mm in diameter and 0.05∼0.30 mm in thickness was launched by an electrically exploding metallic bridge foil. The cylindrical explosive specimens (Φ16 mm×8 mm in size) were initiated by the Mylar flyers in thickness of 0.07∼0.20 mm, which induced shock pressure in specimen was of duration ranging from 0.029 to 0.109 μs. The experimental data were treated with the DRM(Delayed Robbins‐Monro) procedure and to provide the initiation threshold of flyer velocities at 50% probability are 3.398∼1.713 km/s and that of shock pressure P 13.73∼5.23 GPa, respectively for different pulse durations. The shock initiation criteria of the explosive specimen at 50% and 100% probabilities are yielded. In addition, the 30° wedged sample was tested and the shock to detonation transition (SDT) process emerging on its inclined surface was ...

Large Area and Short-Pulse Shock Initiation of a Tatb/hmx Mixed Explosive

Review of Laser Initiation

At LLNL we have been evaluating shock-initiation thresholds for various explosives for a number of years, using thin flyer plates accelerated by an electric gun as the shock stimulus (1 to 3). It is advantageous in time and expense to minimize the number of test specimens required for a threshold determination. We have recently improved our velocity calibrated and our experimental protocol in selecting firing voltages so that we can usually obtain a good estimate of the threshold using only 8 to 10 samples.

R.C. Weingart

Papers

Improvements in thin-pulse shock initiation threshold measurements