Structural integrity and failure in the context of "Funeral"

The World Trade Center, in Lower Manhattan, New York City, was destroyed after a series of terrorist attacks on September 11, 2001, killing almost 3,000 people at the site. Two commercial airliners hijacked by al-Qaeda members were deliberately flown into the complex's Twin Towers, at the time among the five tallest buildings in the world. The plane impacts dealt significant structural damage to the skyscrapers and started large fires in the towers, eventually resulting in both undergoing a total progressive collapse.

The North Tower (WTC 1) was the first building to be hit when American Airlines Flight 11 crashed into it at 8:46 a.m., causing it to collapse at 10:28 a.m. after burning for one hour and 42 minutes. At 9:03 a.m., the South Tower (WTC 2) was struck by United Airlines Flight 175; it collapsed at 9:59 a.m. after burning for 56 minutes.

A hazard is a potential source of harm. Substances, events, or circumstances can constitute hazards when their nature would potentially allow them to cause damage to health, life, property, or any other interest of value. The probability of that harm being realized in a specific incident, combined with the magnitude of potential harm, make up its risk. This term is often used synonymously in colloquial speech.

Hazards can be classified in several ways which are not mutually exclusive. They can be classified by causing actor (for example, natural or anthropogenic), by physical nature (e.g. biological or chemical) or by type of damage (e.g., health hazard or environmental hazard). Examples of natural disasters with highly harmful impacts on a society are floods, droughts, earthquakes, tropical cyclones, lightning strikes, volcanic activity and wildfires. Technological and anthropogenic hazards include, for example, structural collapses, transport accidents, accidental or intentional explosions, and release of toxic materials.

Self-healing materials are artificial or synthetically created substances that have the built-in ability to automatically repair damages to themselves without any external diagnosis of the problem or human intervention. Generally, materials will degrade over time due to fatigue, environmental conditions, or damage incurred during operation. Cracks and other types of damage on a microscopic level have been shown to change thermal, electrical, and acoustical properties of materials, and the propagation of cracks can lead to eventual failure of the material. In general, cracks are hard to detect at an early stage, and manual intervention is required for periodic inspections and repairs. In contrast, self-healing materials counter degradation through the initiation of a repair mechanism that responds to the micro-damage. Some self-healing materials are classed as smart structures, and can adapt to various environmental conditions according to their sensing and actuation properties.

Although the most common types of self-healing materials are polymers or elastomers, self-healing covers all classes of materials, including metals, ceramics, and cementitious materials. Healing mechanisms vary from an instrinsic repair of the material to the addition of a repair agent contained in a microscopic vessel. For a material to be strictly defined as autonomously self-healing, it is necessary that the healing process occurs without human intervention. Self-healing polymers may, however, activate in response to an external stimulus (light, temperature change, etc.) to initiate the healing processes.

A plastic bottle is a bottle constructed from high-density or low-density plastic. They are typically used to store liquids such as water, soft drinks, motor oil, cooking oil, medicine, shampoo or milk. They range from very small bottles to large carboys. Consumer blow molded containers often have integral handles or are shaped to facilitate grasping.

Plastic was invented in the nineteenth century and was originally used to replace common materials such as ivory, rubber, and shellac. Plastic bottles were first used commercially in 1947, but remained relatively expensive until the early 1950s, when high-density polyethylene was introduced. They quickly became popular with manufacturers and customers because, compared to glass bottles, they are lighter, cheaper and easier to transport. However, their greatest advantage over glass bottles is their superior resistance to breakage, in both production and transportation. Except for wine and beer, the food industry internationally has largely replaced glass bottles with plastic bottles.