---
title: "Define toughness in brief"
subject: "Civil Engineering Materials"
chapter: 1
key: "semester_3/civil_engineering_materials:property-toughness"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/property-toughness
site: BCT Engineering
---

# Define toughness in brief

Civil Engineering Materials · Chapter 1: Introduction to Civil Engineering Material

- Asked in: 2066 Shrawan (old course), 2 marks; 2068 Baisakh (asked 2 times)
- Video: [Understanding Material Strength, Ductility and Toughness](https://www.youtube.com/watch?v=WSRqJdT2COE) — The Efficient Engineer
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/property-toughness
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-1

## Question

Define toughness as a property of materials.

## Short answer

Toughness is the ability to absorb energy and deform plastically before fracturing, represented by the total area under the stress-strain curve. Mild steel is tough and resists shock; brittle glass and cast iron have low toughness, tested by Charpy and Izod tests.

## Answer

**Toughness** is the ability of a material to absorb energy and deform plastically before it fractures. It is the total area under the stress-strain curve up to fracture (modulus of toughness), measured in $\text{N/mm}^2$ or J/m$^3$.

A tough material (mild steel) resists shock and impact loads, whereas a brittle material (glass, cast iron) has low toughness even if it is strong. Toughness is tested by Charpy and Izod impact tests.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Toughness is the ability to
   A. resist scratching
   B. store energy only in the elastic range
   C. carry maximum stress
   D. absorb energy and deform plastically before fracture
   Answer: D. Toughness is energy absorbed up to fracture. (Key point: Definition)

2. Modulus of toughness is
   A. the total area under the stress-strain curve up to fracture
   B. the slope of the elastic line
   C. the stress at yield
   D. the area up to the elastic limit only
   Answer: A. Area under elastic part only is resilience. (Key point: Measure)

3. A brittle material such as glass has
   A. high toughness
   B. low toughness even if strong
   C. high ductility
   D. high impact resistance
   Answer: B. Brittle materials absorb little energy. (Key point: Brittle vs tough)

4. Toughness is tested by
   A. Brinell test
   B. Vicat test
   C. Charpy and Izod impact tests
   D. Slump test
   Answer: C. Impact tests measure absorbed energy. (Key point: Tests)

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- [Hardness, toughness and strength compared](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Ahardness-toughness-strength-difference) — Civil Engineering Materials, chapter 1
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