ISO 178 Flexural Properties of Plastics Testing Services

ISO 178 is a three-point bend test where a force is applied on the midpoint of a sample, which is supported at either end.

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ISO 178 Flexural Properties of Plastics Testing Services

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Overview
Scope, Applications, and Benefits
Test Process
Specifications
Instrumentation
Results and Deliverables

Overview

The ISO 178 standard recommends a method to evaluate the flexural strength, flexural modulus, and stress-strain relation of plastic materials when subjected to flexural forces. This method is used to evaluate the ability of plastic materials to resist deformation when subjected to a bending load.

This method is applicable to thermoplastics, thermosets, and reinforced plastics used in structural applications. This method is used to evaluate the flexural properties of materials used in components subjected to flexural forces.

Scope, Applications, and Benefits

Scope

ISO 178 defines procedures for measuring the flexural properties of plastics under controlled bending conditions. The test determines how materials behave when subjected to bending stress and helps evaluate their stiffness and resistance to deformation.

The scope includes:

Determination of flexural strength of plastics
Measurement of flexural modulus (stiffness)
Evaluation of stress–strain behavior during bending
Testing of thermoplastics and thermoset plastics
Support for material comparison and quality control

Applications

Engineering plastic components
Plastic sheets and structural parts
Reinforced polymer materials
Consumer and industrial plastic products
Polymer material development

Benefits

Evaluates bending performance of plastics
Helps select materials for structural applications
Supports design and product development
Enables quality control and material comparison
Improves product durability and reliability

Test Process

Specimen Preparation

Plastic specimens are prepared with standard dimensions and conditioned before testing.

Sample Placement

The specimen is placed on two supports in a three-point bending fixture.

Load Application

A controlled load is applied at the center of the specimen until deformation or failure occurs.

Data Measurement

Flexural strength, modulus, and stress–strain data are recorded and analyzed.

Technical Specifications

Parameter	Details
Test Type	Three-point bending test
Applicable Materials	Thermoplastics, thermosets, reinforced plastics
Specimen Shape	Rectangular bar
Test Equipment	Universal Testing Machine (UTM)
Support Span	Based on specimen thickness
Measured Parameters	Flexural strength, flexural modulus
Output Data	Stress–strain curve and bending properties

Instrumentation Used for Testing

Universal Testing Machine (UTM)
Three-Point Bending Fixture
Extensometer / Deflection Sensor
Vernier Caliper / Micrometer
Data Acquisition System

Results and Deliverables

Flexural strength values
Flexural modulus data
Stress–strain curve
Test conditions and parameters
Compliance evaluation according to ISO 178
Detailed laboratory test report

Why Choose Infinita Lab for ISO 178: Flexural Properties of Plastics?

At the core of this breadth is our network of 2,000+ accredited labs in the USA, offering access to over 10,000 test types. From advanced metrology (SEM, TEM, RBS, XPS) to mechanical, dielectric, environmental, and standardized ASTM/ISO testing, we give clients unmatched flexibility, specialization, and scale. You’re not limited by geography, facility, or methodology—Infinita connects you to the right testing, every time.

Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you. Request a Quote

Frequently Asked Questions

ISO 178 determines the flexural strength, flexural modulus, and deformation behavior of plastic materials when subjected to bending forces. It helps evaluate stiffness and load-bearing performance in applications where plastics experience bending stresses.

ISO 178 applies to rigid and semi-rigid plastics, including thermoplastics, thermosetting plastics, and fiber-reinforced composites. The method is widely used for evaluating materials used in automotive, electrical, construction, and consumer product applications.

The test typically uses rectangular bar specimens prepared with specified dimensions. Proper specimen preparation, uniform thickness, and smooth surfaces are essential to ensure accurate bending behavior and reliable flexural property measurements.

Flexural testing is important because many plastic components experience bending loads in service. ISO 178 helps manufacturers verify structural integrity, material quality, and compliance with product performance requirements.

Factors such as specimen dimensions, span length, loading rate, temperature conditions, and testing machine alignment can influence results. Proper calibration, standardized sample preparation, and controlled testing environments ensure accurate and repeatable measurements.