Q1: A material lacking in toughness is usually termed as

ANS:C - brittle

Brittle is a term used to describe the property of a material that fractures or breaks with little or no plastic deformation when subjected to stress. Here's an explanation of the term "brittle":

1. Fracture Behavior: Brittle materials exhibit a tendency to fail suddenly and catastrophically without warning when stressed beyond their strength limit. Unlike ductile materials, which undergo significant plastic deformation before fracturing, brittle materials typically fracture with little or no visible deformation.
2. Lack of Plasticity: Brittle materials lack the ability to undergo plastic deformation, meaning they cannot change shape or deform permanently under stress without fracturing. Instead, they retain their original shape until they reach their breaking point.
3. Characteristics: Some characteristics of brittle materials include:
   • Low Energy Absorption: Brittle materials have limited ability to absorb energy before fracture. This results in sudden, high-energy releases upon fracture, which can lead to catastrophic failure.
   • High Stiffness: Brittle materials tend to have high stiffness or modulus of elasticity, meaning they exhibit little elasticity and deform elastically only up to a point before fracturing.
   • Sharp, Clean Fracture Surfaces: Fracture surfaces of brittle materials typically exhibit sharp, clean breaks with little evidence of plastic deformation or necking.
   • Low Toughness: Brittle materials generally have low toughness, which is a measure of a material's ability to resist fracture under stress.
4. Examples: Common examples of brittle materials include:
   • Ceramics: Materials such as glass, porcelain, and certain types of ceramics are highly brittle and prone to sudden fracture under stress.
   • Some Metals at Low Temperatures: While most metals are ductile at room temperature, some become brittle at low temperatures. For example, steel can transition from a ductile to a brittle state at low temperatures, leading to brittle fracture.
   • Brittle Polymers: Certain polymers, particularly those with high molecular weight or crystallinity, can exhibit brittle behavior under certain conditions.

In summary, brittle materials are characterized by their tendency to fracture without significant deformation when subjected to stress. They lack plasticity and have low toughness, making them prone to sudden and catastrophic failure. Understanding the brittleness of materials is important for engineering design and material selection to prevent unexpected failures in structures and components.