M.S. Found

Single and multiple impact behaviour of a CFRP laminate

Single and repeated impact tests have been conducted on a thin (0, 45, 0) CFRP laminate using an instrumented dropweight impact rig. For single impacts the data suggest that the initiation of failure is governed by the impact force rather than the impact energy and a limiting maximum force of 570 N was observed for our circularly clamped plates. Changes in the rate of increase in impact force could be related to change in damage with increasing impact energy. Damage caused by repeated impacts at energies of 0.54 and 0.73 J did not produce changes in the peak impact force. However a second impact at 0.93 J produced a significant reduction in the peak force and an increase in impact duration.

Evaluation of CFRP panels with scarf repair patches

The scarf patch repair of CFRP panels has been evaluated using a test rig to statically load the panels in a square frame, clamped at the edges and loaded diagonally through pin joints. Three repair systems were used, two wet lay-ups and one prepreg system. The most consistent results were obtained with one of the wet lay-up repairs whilst the prepreg system appears to offer the greatest potential increase in load to failure. The failure load appears to be governed by the amount of buckling the repair is subjected to. Because of the buckling it was not possible to predict the failure load of repaired panels using standard test coupons. Studies on unrepaired panels containing a central hole indicated that buckling identified using photoelastic and strain gauge techniques could be predicted using finite element and empirical methods.

Interpretation of signals from dropweight impact tests

A spring-mass model has been developed to describe the dropweight impact response of CFRP panels. The model separates the effects of the main impact impulse, high frequency oscillations and free vibrations and can be used as a reliable guide for effective digital filtering of signals from dropweight impact tests. Whilst the model at present does not account for damage, the onset of high frequencies towards the peak impact force indicate the onset of damage in the panel. The oscillations become larger and extend over a wider plateau as the perforation threshold energy is approached.

The influence of FRP inserts on the energy absorption of a foam-cored sandwich panel

Abstract This paper describes an experimental investigation into the energy absorption properties of a foam-cored sandwich panel with integral fibre-reinforced plastic (FRP) tubes and frusta. The panels were tested under quasi-static flatwise compression and a number of different insert geometries were examined. By using X-ray analysis it was found that those panels with inserts which failed by stable progressive brittle fracture exhibited-the best specific energy absorptions. Inserts which failed catastrophically led to much lower values. Conical inserts were found to offer the most repeatable performance as their geometry assisted in ensuring consistency of manufacture.

Impact behaviour of stiffened CFRP sections

Dropweight impact tests have been performed on thin CFRP panels stiffened with blade or T-stiffeners and comparisons made with similar plain panels. The change in structural response of the panels is governed by the amount of damage sustained during impact. The increase in panel stiffness is associated with the suppression of backface cracking but larger areas of delamination.

Static indentation and impact behaviour of GRP pultruded sections

Static indentation and dropweight impact tests have been performed on three pultruded sections of glass fibre/polyester resin laminates using an instrumented test rig. Damage in the form of cracking of the lower surface has been related to permanent indentation of the contact surface. This damage relationship is independent of flexural stiffness for static loading but dependent on flexural stiffness for impact conditions. Backface cracking has been assessed in terms of residual compression and the results indicate that static loading is more severe than impact.

Impact perforation of thin stiffened CFRP panels

Static indentation and dropweight impact tests have been performed on thin CFRP panels stiffened with three T-blade stiffeners and comparisons made with similar tests on plain panels. The impact perforation threshold energy may be estimated from the work done by the indentor during a static indentation test for both plain and stiffened panels. For impacts conducted in-line with the stiffener the perforation energy is significantly increased and the maximum damage levels occur at higher energies than for other panel loading conditions.

Size effects in thin CFRP panels subjected to impact

The static indentation and impact behaviour of three- and nine-ply CFRP panels circularly clamped with rings of 100 and 300 mm diameter have been evaluated. The maximum static force is similar for small and large panels for both three- and nine-ply laminates. Increasing the panel size of the three-ply laminates subjected to impact only appears to affect the threshold of perforation. For the nine-ply laminates an increase in panel size produced a reduction in delamination area and backface cracking. Interpretation of energy maps is suggested as a means of identifying when the peak impact force has occurred and the threshold of perforation.

Design of composite driving end structures for structural use in UK passenger rolling stock

ABSTRACT The use of composites in rolling stock is increasing rapidly and one area of significant potential is in vehicle end structures. The paper examines the major technical requirements composite driving end structures must meet if they are to feature for future use in UK passenger rolling stock applications. The research being undertaken at ARRC to design and develop such structures is described and the key challenges that designers will face in producing composite end structures capable of satisfying current industry criteria are discussed.

Energy Absorption Characteristics of a Foam-Cored Sandwich Panel with Fibre-Reinforced Plastic Inserts

This paper describes an experimental investigation into the energy absorption properties of a foam-cored sandwich panel with integral fibre-reinforced plastic tubes and frusta. The panels were tested under both quasi-static flatwise and edgewise compression. Under flatwise compression, it was found that the panels with inserts which failed by stable progressive brittle fracture exhibited the best energy absorption characteristics. Under edgewise compression, the panels with inserts which prevented separation of the face plates offered the most predictable and repeatable performance. Particular insert geometries which achieve these ideals are identified.